CBSE Class 12

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 11 Biotechnology: Principles and Processes. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 11 Important Extra Questions Biotechnology: Principles and Processes

Biotechnology: Principles and Processes Important Extra Questions Very Short Answer Type

Question 1.
What is genetic engineering?
Answer:
Genetic engineering. It is a technique for artificially and deliberately modifying DNA (genes) to suit human needs. It is also called recombinant DNA technology or DNA splicing. It is a kind of biotechnology.

Question 2.
Define recombinant DNA.
Answer:
Recombinant DNA. They are molecules of DNA that are formed through genetic recombination methods.

Question 3.
What is the role of restriction endonuclease?
Answer:
Restriction endonucleases are specific enzymes which can cleave double-stranded DNA at the specific site.

Question 4.
What are BACs and YACs? (CBSE 2016)
Answer:
BACs and YACs are artificial chromosomes from bacteria and yeast efficient for gene transfer. They are vectors.

Question 5.
Name the soil bacterium which contains the gene for production of endotoxins.
Answer:
Agrobacterium tumefaciens.

Question 6.
Name a technique by which DNA fragments can be separated. (CBSE Delhi 2008)
Answer:
Gel electrophoresis.

Question 7.
What is the principle of Gel electrophoresis?
Answer:
DNA fragments are negatively charged so they move to anode under electric field through the matrix (usually agarose). This matrix gel acts as sieve and DNA fragments resolve according to their size.

Question 8.
Name the compound used for staining DNA to be used in Recombinant Technology. What is the colour of such stained DNA?
Answer:
The compound used for staining DNA is ethidium bromide. Stained DNA becomes orange.

Question 9.
Name the technique for vector less direct gene transfer.
Answer:
Gene gun.

Question 10.
What is the role of ‘Ori’ in any plasmid?
Answer:
The plasmid is prokaryotic circular DNA which has a sequence of nucleotides from where the replication starts. This is called the origin of replication.

Role of Ori is to start replication. Also, the copy number of linked DNA is controlled by Ori.

Question 11.
Do normal £. coli cells have any gene resistance against antibiotics?
Answer:
No.

Question 12.
What is the function of TPA?
Answer:
TPA (Tissue plasminogen activator) dissolves blood clots after a heart attack and stroke.

Question 13.
Give an example in which recombinant DNA technology has provided a broad range of tool in the diagnosis of diseases.
Answer:
Construction of probes, which are short segments of single-stranded DNA attached to a radioactive or fluorescent marker.

Question 14.
Give the full form of PCR. Who developed it? (CBSE Delhi 2013)
Answer:
PCR is a polymerase chain reaction. It was developed by Kary Mullis in 1985.

Question 15.
What is the source of DNA polymerase, i.e. Taq polymerase? (CBSE Outside Delhi 2013)
Answer:
Taq polymerase is isolated from the bacterium Thermus Aquaticus.

Question 16.
Define “melting of target DNA”.
Answer:
The target DNA containing the sequence to be amplified is heat-denatured (around 94° C for 15 seconds) to separate its complementary strands. This process is called melting of target DNA.

Question 17.
Expand ELISA. Write one application. (CBSE Delhi 2013)
Answer:
ELISA-Enzyme Linked ImmunoSorbent Essay. Importance-lt is used for the diagnosis of AIDS.

Question 18.
What are transgenic animals? Give one example. (CBSE Outside Delhi 2016)
Answer:
Transgenic animals: The animals obtained by genetic engineering containing transgenes are known as transgenic animals.
Example. Transgenic cow ‘Rosie’.

Question 19.
How many PCR cycles are adequate for proper amplification of DNA segment?
Answer:
20-30 cycles.

Question 20.
Define gene therapy.
Answer:
Gene Therapy: It is the replacement of a faulty gene by normal healthy functional gene.

Question 21.
What is the importance of gene bank?
Answer:
It provides a stock from which genes can be obtained for improving the varieties or used in genetic engineering.

Question 22.
What can be the source of thermostable DNA?
Answer:
Thermostable DNA is obtained from a bacterium Thermus Aquaticus.

Question 23.
What are selectable markers?
Answer:
Genes which are able to select transformed cell from the non-recombinant cells are called selectable markers.

Question 24.
Why is enzyme cellulase used for isolating genetic material from plant cells and not from animal cells? (CBSE 2010)
Answer:
Cellulase is used for breaking the cell wall of plant cells whereas animal cells lack a cell wall. The cell wall is made of cellulose which can be broken down by cellulase.

Question 25.
Give one example each of transgenic plant and transgenic animal.
Answer:

1. Transgenic tomato plant called Flavor Savr.
2. A transgenic mouse called Supermouse.

Question 26.
What would be the molar concentration of human DNA in a human cell?
Answer:
Humans have 3 M of DNA per cell, i.e. the molar concentration is 3.

Question 27.
Do eukaryotic cells have restriction endonucleases?
Answer:
Yes, eukaryotic cells possess restriction endonucleases. They are involved in editing (Proofreading) and DNA repairs during DNA replication.

Question 28.
Name a technique by which DNA fragments can be separated. (CBSE Delhi 2008)
Answer:
Get electrophoresis.

Question 29.
Biotechnological techniques can help to diagnose the pathogen much before the symptoms of the disease appear in the patient. Suggest any two such techniques. (CBSE Outside Delhi 2019)
Answer:
PCR – Polymerase chain reaction
ELISA – Enzyme-linked immunosorbent assay

Question 30.
Why is it not possible for an alien DNA to become part of chromosome anywhere along its length and replicate? (CBSE 2014)
Answer:
For multiplication of any alien DNA, it needs to be a part of a chromosome which has a specific sequence known as the origin of replication.

Question 31.
Mention the type of host cells suitable for the gene guns to introduce an alien DNA. (CBSE Delhi 2014)
Answer:
Plant cells.

Question 32.
Name the enzymes that are used for isolation of DNA from bacterial and fungal cells for rDNA technology. (CBSE 2014)
Answer:
Lysozyme for bacterial cell and chitinase for the fungal cell.

Question 33.
What is EcoRI? How does EcoRI differ from an exonuclease? (CBSE Outside Delhi 2015)
Answer:
EcoRI is an endonuclease restriction enzyme which cut both the stands of palindromic DNA at a specific position of nitrogen base 5′ (GAATTC) 3′ while exonuclease removes nucleotides from terminals of DNA strands.

Biotechnology: Principles and Processes Important Extra Questions Short Answer Type

Question 1.
(i) While cloning vectors, which of the two will be preferred by biotechnologists, bacteriophages or plasmids. Justify with reason.
Answer:
Biotechnologists prefer bacteriophages for cloning over plasmids because they have very high copy numbers of their genome within the bacterial cells whereas some plasmids may have only one or two copies per cell and others may have 15-100 copies per cell. Phage vectors are more efficient than plasmids for cloning large DNA fragments.

(ii) Name the first transgenic cow developed and state the Improvement In the quality of the product produced by it. (CBSE Sample paper 2018-19)
Answer:
Transgenic cow Rosie produced human protein-enriched milk (2.4 grams per litre).

Question 2.
What are the two core techniques that enabled the birth of biotechnology?
Answer:
The two core techniques that enabled the birth of modern biotechnology are:

1. Genetic engineering techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism.
2. Maintenance of sterile (microbial contamination-free) ambience in chemical engineering processes to enable the growth of only the desired microbe/eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc.

Question 3.
Make a list of tools of recombinant DNA technology. (CBSE Delhi, 2011)
Answer:
Key tools of recombinant DNA technology:

1. Restriction enzymes
2. Polymerase enzymes
3. Ligases
4. Vectors
5. Host organism.

Question 4.
What does EcoRI signify? How its name is derived?
Answer:
EcoRI signifies the name of restriction endonuclease:

1. First capital letter of the name that comes from the genus Escherichia is ‘E’.
2. Second two small letters come from the species Coli of prokaryotic cells from which they are isolated, i.e. ‘co’.
3. Letter R is derived from the name of the strain, i.e. Escherichia coli Ry 13.
4. The Roman number indicates the order in which enzymes were isolated from that strain of bacteria.

Question 5.
What are recognition sequences or recognition sites?
Answer:
The sites recognised by restriction endonucleases are called recognition sites. The recognition sequences are different and specific for the different restriction endonucleases. These sequences are palindromic in nature.

Question 6.
Define vector. Give the properties of a “Good Vector”.
Answer:
A vector is a DNA molecule that has the ability to replicate in an appropriate host cell, and into which the DNA fragment to be cloned is integrated for cloning.

A good vector must have the following properties:

• It should have an origin of replication so that it is able to replicate autonomously.
• It should be easy to isolate and purify.
• It should get easily introduced into the host cells.

Question 7.
What is the difference between cloning and expression vectors?
Answer:
All vectors that are used for propagation of DNA inserts in a suitable host are called cloning vectors. When a vector is designed for the expression of, i.e. production of the protein specified by, the DNA insert, it is termed as an expression vector.

Question 8.
What do you understand by the term selectable marker?
Answer:
Selectable marker:

1. A marker is a gene which helps in selecting those host cells which contain the vector (transformant) and eliminating the non-transformants. It selectively permits the growth of transformants.
2. Common selectable markers for E. coli include the genes encoding resistance to antibiotics such as ampicillin. chloramphenicol tetracycline and kanamycin or the gene for (i-galactosidase which can be identified by a colour reaction. Normal E.Coli do not carry resistance against any of these antibodies.

Question 9.
Explain the principle that helps in separation of DNA fragments in Gel electrophoresis. (CBSE Delhi 2009 C)
Answer:
Get electrophoresis is a technique of molecules such as DNA/RNA/protein on the basis of their size under the influence of the electric field so that they migrate in the direction of electrode bearing the opposite charge. Positively charged molecules move towards cathode (-ve electrode) and vice versa. These molecules move through a medium or matrix and can be separated on the basis of their size.

Question 10.
Give the applications of PCR technology. (CBSE, Delhi 2013)
Answer:

1. Amplification of DNA and RNA.
2. Determination of orientation and location of restriction fragments relative to one another.
3. Detection of genetic diseases such as sickle cell anaemia, phenylketonuria and muscular dystrophy.

Question 11.
Why is “Agrobacterium-mediated genetic transformation” in plants described as natural genetic engineer of plants? (CBSE Delhi 2011)
Answer:
Agrobacterium tumefaciens is a plant pathogenic bacterium which can transfer part of its plasmid DNA because it infects host plants. Agrobacterium produces crown gall in most of the dicotyledonous plants. These bacteria contain large tumours inducing plasmid (Ti-plasmids) which pass on their tumour causing gene into the genome of the host plant. Thus gene transfer is happening in nature without human involvement hence Agrobacterium-mediated genetic transformation is described as natural genetic engineering in plants.

Question 12.
Differentiate gene therapy and gene cloning.
Answer:
Differences between gene therapy and gene cloning:

Question 13.
From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
Answer:
DNA molecules are bigger in size as compared to the molecular size of enzymes. Enzymes are proteins. Protein synthesis occurs from a small portion of DNA called genes.

Question 14.
How does restriction endonuclease work? (CBSE Delhi 2013, 2014, Outside Delhi 2019)
Or
What are molecular scissors? Explain their role. (CBSE 2009)
Answer:
Restriction endonuclease enzymes are called molecular scissors which can cut double-stranded DNA at specific sites.

Role of restriction endonuclease:

• Restriction endonuclease inspects the length of DNA sequence.
• It finds specific recognition sequence, i.e. palindromic nucleotide sequence in DNA.
• These enzymes cut the strand of DNA a little away from the centre of palindromic sites.
• Thus restriction endonucleases leave overhanging stretches called sticky ends on each strand.

Question 15.
How and why is the bacterium Thermus Aquaticus employed in recombinant DNA technology? Explain. (CBSE Delhi 2009)
Answer:
Thermus Aquaticus bacterium is employed in recombinant DNA technology because it has thermostable DNA polymerase (Taq. Polymerase) that remains active during high temperature-induced denaturation of a step of PCR.

This enzyme is employed during amplification of gene using PCR (Polymerase Chain Reaction). The amplified fragment can be used to ligate with a vector for further cloning.

Question 16.
Name the source of Taq polymerase. Explain its advantages. (CBSE Outside Delhi 2009)
Answer:
Taq Polymerase is extracted from Thermostable bacteria, namely Thermus Aquaticus. It remains active at a higher temperature and is used for denaturation of DNA during PCR.

Question 17.
What are recombinant proteins? How do bioreactors help in their production? (CBSE Outside Delhi 2009, 2015)
Answer:
Recombinant proteins. When any protein-encoding gene is expressed in a heterologous host, it is called recombinant protein. Bioreactors help in the production of recombinant proteins on large scale. A bioreactor provides optimal conditions for achieving the desired recombinant protein by biological methods.

Question 18.
What is meant by gene cloning?
Answer:
Formation of multiple copies of a particular gene is called gene cloning. A gene is separated and ligated to a vector-like plasmid. The recombinant plasmid is introduced into a plasmid-free bacterium through transformation. The transformed bacterium is made to multiply and form a colony. Each and every bacterium of the colony has a copy of the gene.

Question 19.
Both the wine marker and a molecular biologist who has developed a recombinant vaccine claim to be biotechnologist. Who in your opinion is correct?
Answer:
Both are considered biotechnologists. Wine marker utilises a strain of yeast which produces wine by fermentation. The molecular biologist uses a cloned gene for the antigen. The antigen is used as a vaccine. This permits the formation of antigen in huge quantity. Both generate products and services using living organisms useful to mankind.

Question 20.
You have created a recombinant DNA molecule by ligating a gene to a plasmid vector. By mistake, your friend adds an exonuclease enzyme to the tube containing the recombinant DNA. How will your experiment get affected as you plan to go to the transformation now?
Answer:
The experiment is not likely to be affected as the recombinant DNA molecule is circular and closed, with no free ends. Hence, it will not be a substrate for exonuclease enzyme which removes nucleotides from the free ends of DNA.

Question 21.
Explain the work carried out by Cohen and Boyer that contributed immensely to biotechnology. (CBSE2012)
Answer:
Work of Cohen and Boyer:

1. Discovery of restriction endonuclease, an enzyme of E.coli which cut DNA at palindromic sequence.
2. Preparation of recombinant DNA (Plasmid and DNA of interest.)
3. Their work established recombinant DNA (rDNA) technology also called genetic engineering.

Question 22.
How are ‘Sticky ends’ formed on a DNA strand? Why are these so-called? (CBSE Delhi 2014)
Answer:
1. Restriction enzymes cut the strand of DNA a little away from the centre of palindrome site, but between the same two bases on opposite strands. As a result, single-stranded portions are left at each end. These overhanging stretches of DNA are called ‘Sticky ends’.

2. The Sticky ends are named so because they form hydrogen bonds with their complementary cut counterparts. The stickiness helps in the action of DNA ligase.

Question 23.
How is a continuous culture system maintained in bioreactors and why? (CBSE Delhi 2019)
Answer:
In order to maintain a continuous culture system, the used medium is drained out from one side of the bioreactor and the fresh medium is added from one side. This type of culturing method produces larger biomass leading to higher yields of the desired product.

Question 24.
Galactosidase enzyme is considered a better selectable marker. Justify the statement. (CBSE Delhi 2019)
Answer:
Recombinant strains can be differentiated from the non-recombinants ones easily by using this selectable marker. The selection is done on the basis of the colour change. All are grown on a chromogenic substance. Non-recombinants will change from colourless to blue while in recombinants insertional inactivation of galactosidase gene occurs.

Hence, recombinants showed no colour change. This is a single step, an easy method for selection.

Biotechnology: Principles and Processes Important Extra Questions Long Answer Type

Question 1.
What is genetic engineering? Explain briefly the distinct steps common to all genetic engineering technology.
Or
With the help of diagrams show the different steps in the formation of recombinant DNA by the action of restriction endonuclease. (CBSE 2011)
Answer:
Genetic engineering: It is a technique for artificially and deliberately modifying DNA (genes) to suit human needs. It is also called recombinant DNA technology or DNA splicing.

It is a kind of biotechnology:

1. Isolation of genetic material which has the gene of interest.
2. Cutting of gene of interest from genome and vector with the same restriction endonuclease enzyme. Amplifying gene of interest (PCR).
3. Ligating gene of interest and vector using DNA ligase forming rDNA.
4. Transformation of rDNA into the host cell.
5. Multiplying host cell to create clones.

Diagram showing various steps Involved in DNA recombinant technology for the production of a recombinant protein.

Question 2.
List three important features necessary for preparing a genetically modifying organism.
Answer:
Conditions necessary for preparing:

1. Identification of DNA with desirable genes.
2. Introduction of the identified DNA into the host.
3. Maintenance of introduced DNA in the host and transfer of the DNA to its progeny.

Question 3.
How are restriction endonuclease enzymes named? Write examples. (CBSE 2014
Answer:
The naming of restriction enzymes is as follows:

1. The first letter of the name comes from the genus and the next two letters from the name of the species of the prokaryotic cell from which they are isolated.
2. The next letter comes from the strain of the prokaryote.
3. The roman numbers following these four letters indicate the order in which the enzymes were isolated from that strain of the bacterium.

Examples:

1. EcoR I is isolated from Escherichia coli RY 13.
2. Hind II is from Haemophilus influenza.
3. Bam H I is from Bacillus amylotiquefaciens.
4. Sal I is from Streptomyces Albus
5. Pst I is from Providencia stuartii.

Question 4.
Explain any three methods of vector less gene transfer. (CBSE Outside Delhi 2013)
Answer:
Vectors of gene transfer. Following are common methods of vectors gene transfer.

1. Microinjection: Microinjection is the process/technique of introducing foreign genes into a host cell by injecting the DNA directly into the nucleus by using microneedle or micropipette.
2. Electroporation: Electroporation is the process by which transient holes are produced in the plasma membrane of the (host) cell to facilitate entry of foreign DNA.
3. Gene Gun: Gene gun is the technique of bombarding microprojectiles (gold or tungsten particles) coated with foreign DNA with great velocity into the target cell.

Question 5.
Write a note on the cloning vector.
Answer:
Cloning vectors:

1. Plasmids and bacteriophages are the commonly used vectors
2. Presently genetically engineered/ synthetic vectors are also used for easily linking the foreign DNA and selection of recombinants from non-recombinants.
3. The following features are required to facilitate cloning in a vector:
   (a) Origin of replication (Ori)
   (b) Selectable marker
   (c) Cloning (Recognition) site
   (d) Small size of the vector.

Question 6.
What is PCR? List the three main steps. Show the steps with a diagrammatic sketch.
Answer:

1. PCR. Polymerase Chain Reaction.
2. Three steps of PCR.
   (a) Denaturation
   (b) Primer annealing and
   (c) Extension of primers.

The three steps of PCR

Question 7.
Name the various cloning vectors and explain how a plasmid can be used for genetic engineering.
Answer:
Cloning vectors:

• Plasmids
• Bacteriophages
• Plant and animal vectors
• Jumping genes (Transposons)
• Artificial chromosomes of bacteria, yeast and mammals (BAC, YAC).

Use of plasmid as genetic material Plasmids are obtained from bacteria. They are treated with a restriction endonuclease enzyme to obtain the fragments of the desired genome. They are allowed to fuse with the help of a DNA ligase enzyme. The recombinant plasmids thus formed are used as genetic material.

Question 8.
Give various means by which a competent host is formed for recombinant DNA technology. Why and how bacteria can be made ‘competent’? (CBSE Delhi 2013)
Answer:
A host cell should be competent enough to take the DNA molecule for the transformation as the following methods can be used.

1. Using divalent cations: Bacteria are treated with Ca²⁺, etc. so that DNA enters the bacterium through pores in its cell wall.
2. Heat shock: Cells can be incubated on ice and then at 42°C for a heat shock and then again put on ice.
3. Microinjection: Recombinant DNA is directly injected into the nucleus of an animal cell.
4. Biolistic. Cells bombarded with high- velocity micro-particles of gold or tungsten coated with DNA is known as a gene gun.

Question 9.
How is recombinant DNA transferred to host?
Answer:
Transfer of recombinant DNA into the host:

1. The bacterial cells must be made competent to take up DNA; this is done by treating them with a specific concentration of calcium, that increases the efficiency with which DNA enters the cell through the pores in its cell wall.
2. Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice followed by placing them at 42°C and then putting them back on ice (heat shock treatment),
3. Microinjection is a method in which the recombinant DNA is directly injected into the nucleus of the animal cell with the help of microneedles or micropipettes.
4. Gene gun or biolistics is a method suitable for plant cells, where cells are bombarded with high-velocity microparticles of gold or tungsten coated with DNA.
5. Disarmed pathogens are used as vectors; when they are allowed to infect the cell, they transfer the recombinant DNA into the host.

Question 10.
Why DNA cannot pass through the cell membrane? How can the bacteria be made competent to take up a plasmid? Explain a method for the introduction of alien DNA into a plant host cell. Name a pathogen that is used as a disarmed vector. (CBSE Outside Delhi 2019)
Answer:
DNA is a hydrophilic molecule thus it cannot pass through the cell membrane.

Bacterial cells are made ‘competent’ by treating them with a specific concentration of divalent cation such as calcium in order to take up the plasmid. The divalent cation increases the efficiency with which DNA enters the bacterium through the pores of the cell wall.

Procedure: Recombinant DNA is forced into ‘competent’ bacterial host cells by incubating them on the ice. It is followed by placing them briefly at 42°C. It is termed ‘heat stock’ treatment. Again they are placed back on ice. This process allows bacteria to take up the recombinant DNA.

Gene gun or biolistic method is used for the introduction of alien DNA into a plant host cell. Here, the plant cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA. Agrobacterium tumefaciens or Retroviruses can be used as a disarmed vector.

Question 11.
Write a note on vectors used during recombinant DNA technology. (CBSE Delhi 2008)
Answer:
A vector or vehicle DNA is used as a carrier for transferring selected DNA into cells. A plasmid with its small DNA from a bacterium is a good choice for indirect gene transfer because it can move from one cell to another and make several copies of itself. However, artificial chromosomes from bacteria and yeast called BACs and YACs respectively are more efficient for eukaryotic gene transfers.

Plasmid and Yeast Artificial Chromosome

Question 12.
(i) Identify A and B illustrations in the following:
(a)
(b)
Answer:
A= 5′ GAATTC 3′
B marks for ORI (origin of replication).

(ii) Write the term given to A and C and why?
Answer:
A represents a nucleotide palindromic sequence. C-sticky end.

(iii) Expand PCR. Mention its importance in biotechnology. (CBSE Delhi 2011)
Answer:
PCR, Polymerase chain reaction. It helps in gene amplification.

Question 13.
Write the role of the following sites in pBR322 cloning vector:
(a) rop
Answer:
Role of rop, ori and selectable marker in pBR322 cloning vector.

Role of rop: Rop gene regulates copy number. Rop process is involved in stabilising the interaction between RNA I and RNA II which in turn prevents replication of pBR322.

(b) ori
Answer:
Origin of replication (Ori):

• It is a specific sequence of DNA bases, which is responsible for initiating replication.
• An alien DNA for replication should be linked to the origin of replication.
• A prokaryotic DNA has normally a single origin of replication, while eukaryotic DNA may have more than one origin of replication.
• The sequence is responsible for controlling the copy number of linked DNA.

(c) selectable marker (CBSE Delhi 2019 C)
Answer:
Selectable marker:

• A marker is a gene which helps in selecting those host cells which contain the vector (transformant) and eliminating the non-transformants.
• Common selectable markers for E. coli include the genes encoding resistance to antibiotics such as ampicillin. Chloramphenicol, tetracycline and kanamycin or the gene for B-galactosidase can be identified by a colour reaction.

Question 14.
(i) Explain the significance of palindromic nucleotide sequence in the formation of recombinant DNA.
Answer:
The palindromic sequences, i.e. the sequence of base pairs read the same on both the DNA strands when the orientation of reading is kept the same, e.g.
5’ — GAATTC — 3’
3’ — CTTAAG — 5’

Every endonuclease inspects the entire DNA sequence for palindromic recognition sequence.

(ii) Write the use of restriction endonuclease in the above process. (CBSE 2017)
Answer:
On finding the palindrome, the endonuclease binds to the DNA. It cuts the opposite strands of DNA, but between the same bases on both the strands and forms sticky ends. This sticky ends facilitate the action of enzyme DNA ligase and help in the formation of recombination DNA.

Question 15.
Describe the roles of heat, primers and the bacterium Thermus Aquaticus in the process of PCR. (CBSE 2017)
Answer:
Role of heat: Heat helps in the denaturation process in PCR. The double-stranded DNA is heated in this process at very high temperature (95°C) so that both the strands separate.

Role of primers: Primers are chemically synthesised small oligonucleotides of about 10-18 nucleotides. These are complementary to a region of template DNA and helps in the extension of the new chain. Rote of Bacterium Thermus

Aquaticus: A thermostable Taq DNA polymerase is isolated from this bacterium, which can tolerate high temperatures and forms new strand.

Question 16.
How has the use of Agrobacterium as vectors helped in controlling Meloidogyne incognita infestation in tobacco plants? Explain in the correct sequence. (CBSE 2018, Outside Delhi 2019)
Or
(a) Write the mechanism that enables Agrobacterium tumefaciens to develop tumours in their host dicot plant.
(b) State how Agrobacterium tumefaciens and some retroviruses have been modified as useful cloning vectors. (CBSE Delhi 2019 C)
Answer:
(a) Cloning
(b) A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield.

To prevent this infestation a novel strategy was adopted which was based on the process of RNA interference (RNAi).

Nematode-specific genes were introduced into the host plants using Agrobacterium vectors. The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two RNAs, being complementary to each other, formed a double-stranded RNA (dsRNA) that initiated RNAi and thus, silenced specific mRNA of the nematode. Due to this the parasite could not survive in a transgenic host by expressing specific interfering RNA. The transgenic plant, therefore, got itself protected from the parasite.

Question 17.
Explain the roles of the following with the help of an example each in recombinant DNA technology:
(i) Restriction Enzymes
Answer:
Restriction enzymes :
(a) Restriction enzymes belong to nucleases class of enzymes which breaks nucleic acids by cleaving their phosphodiester bonds.
(b) Since restriction endonucleases cut DNA at a specific recognition site, they are used to cut the donor DNA to isolate the desired gene.
(c) The desired gene has sticky ends which can be easily ligated to cloning vector cut by same restriction enzymes having complementary sticky ends to form recombinant DNA.
(d) An example is EcoR1 which is obtained from E.coli bacteria “R” strain which cuts DNA at specific palindromic recognition site.
5‘ GAATTC 3‘
3‘ CTTAAG 5‘

(ii) Plasmids (CBSE 2018)
Answer:
Plasmids: Plasmids are autonomous, extrachromosomal circular double-stranded DNA of bacteria. They are used as cloning vectors in genetic engineering because they are small and self-replicating. Some plasmids have antibiotic resistance genes which can be used as marker genes to identify recombinant plasmids from non-recombinant ones.

To obtain the desired products, plasmids are cut and ligated with desired genes and transformed into a host cell for amplification. An example of artificially modified plasmids is pBR322 (constructed by Bolivar and Rodriguez) or pUC (constructed at University at California).

Question 18.
When the gene product is required in large amounts, the transformed bacteria with the plasmid inside the bacteria are cultured on a large scale in an industrial fermenter which then synthesises the desired protein. This product is extracted from the fermenter for commercial use.
(a) Why is the used medium drained out from one side while the fresh medium is added from the other? Explain.
Answer:
In the bioreactor used medium is drained out and the fresh medium is added to maintain the cells in their physiologically most active log / experimental phase,

(b) List any four optimum conditions for achieving the desired product in a bioreactor. (CBSE Sample Paper 2020)
Answer:
Condition for obtaining the desired product in a bioreactor:

• Temperature
• Substrates
• SaLts
• pH
• Oxygen

Question 19.
List the steps in the formation of rDNA.
Answer:
Steps in formation of rDNA:
Recombined DNA technology involves the following steps:

1. Isolation of DNA.
2. Fragmentation of DNA by restriction endonucleases.
3. Isolation of the desired DNA fragment.
4. Amplification of the gene of interest.
5. Ligation of the DNA fragment into a vector using DNA ligase.
6. Transfer of DNA fragment into the vector using DNA ligase.

Question 20.
How is the isolated gene of interest amplified? (CBSE Delhi 2019, 2019 C)
Answer:
Amplification of the DNA/gene of interest:

1. Amplification refers to the process of making multiple copies of the DNA segment in vitro.
2. It employs the polymerase chain reaction (PCR).
3. The process was designed by K. Mullis,
4. This technique involves three main steps:
   (a) Denaturation
   (b) Primer annealing and
   (c) Extension of primers.
5. The double-stranded DNA is denatured by subjecting it to high temperatures.
6. Two sets of primers are used; primers are the chemically synthesised short segments of DNA (oligonucleotides), that are complementary to the segment of DNA (of interest).
7. DNA polymerase enzyme (Taq polymerase) is used to make copies of DNA making use of genomic template DNA and primer.

Question 21.
List the features required to facilitate cloning into a vector. Show with a sketch the E. coli cloning vector showing restriction sites.
Or
Sketch pBR322. (CBSE 2012, Outside Delhi 2019)
Answer:
Features required to facilitate cloning vector.

1. Origin of replication (Ori)
2. Selectable marker
3. Cloning sites
4. Vectors for cloning genes in plants and animals
   Sites of cloning vector

E. coli Cloning Vector pBr322 showing restriction sites (Hindlll, EcoRI, BamHI, Sal I, Pvu II, Pst I, ClaI), oriV and antibiotic resistance genes (ampR and tetR). Rop codes for the proteins involved in the replication of the plasmid.

Question 22.
With the help of simple sketch show the action of restriction enzyme (EcoR1).
Answer:
The action of restriction enzyme.

Ecol cuts the DNA between bases G and A only when the sequence GAATTC is present in the DNA.

Question 23.
Explain the importance of (a) ori, (b) ampR and (c) rop in the E. colt vector. (CBSE Outside Delhi 2009, Outside Delhi 2019)
Answer:

1. Importance of ori: This is a sequence from where replication starts and any piece of DNA, when linked to this sequence, can be made to replicate within the host cells, it allows multiple copies per cell.
2. Importance of ampR: It is the antibiotic resistance gene for ampicillin. It helps in the selection of transformer cells.
3. Importance of rop: It codes for the proteins involved in the replication of plasmid.

Question 24.
Name any two cloning vectors. Describe the features required to facilitate cloning into a vector. (CBSE Sample Paper)
Answer:
Plasmids and bacteriophages are two examples of the cloning vector. A vector is a DNA molecule that has the ability to replicate in an appropriate host cell and into which the DNA fragment to be cloned is integrated for cloning.

A good vector must have the following properties:

• It should be able to replicate autonomously.
• it should be easy to isolate and purify,
• It should be easily introduced into the host cells.

Cloning vectors: All vectors that are used for propagation of DNA inserts in a suitable host are called cloning vectors. When a vector is designed for the expression of, i.e. production of the protein specified by, the DNA insert, it is termed as an expression vector.

Question 25.
What are bioreactors? Sketch the two types of bioreactors. What is the utility? Which is the common type of bioreactors? (CBSE Delhi 2013)
Or
How do bioreactors help in the production of recombinant proteins? (CBSE Outside Delhi 2009)
Or
(i) How has the development of bioreactor helped in biotechnology?
(ii) Name the most commonly used bioreactor and describe its working. (CBSE Delhi 2018, 2019 C)
Answer:
Small volume cultures cannot yield appreciable quantities of products. To produce these products in large quantities the development of ‘bioreactors’ was required where large volumes (100-1000 litres) of culture can be processed. Thus bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products, using microbial, plant, animal or human cells or individual enzymes.

Role. A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions (temperature, pH, substrate, salts, vitamins, oxygen).

One of the most commonly used bioreactors is of stirring type.

A stirred tank reactor is cylindrical or a container with a curved base which facilitate the mixing of the reactor contents. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor. Alternatively, air can be passed through the reactor. It consists of agitator system, an oxygen delivery system, a foam control system, a temperature control system, pH control system and sampling ports so that small volumes of the culture can be withdrawn periodically.

(a) Simple stirred-tank bioreactor (b) Sparged stirred-tank bioreactor through which sterile air bubbles are sparged

Question 26.
Describe briefly the following:
(i) Origin of replication (Ori).
Answer:
(a) It is a specific sequence of DNA bases, which is responsible for initiating replication.
(b) An alien DNA for replication should be linked to the origin of replication.
(c) A prokaryotic DNA has normally a single origin of replication, while eukaryotic DNA may have more than one origin of replication.
(d) The sequence is responsible for controlling the copy number of linked DNA.

(ii) Bioreactor.
Answer:
(a) They are vessels in which raw materials are biologically converted into specific products using microbial, plant or human cells.
(b) A bioreactor provides optimal conditions for achieving the desired product by providing optimum growth conditions, pH, substrate salts, vitamins, oxygen, etc.
(c) The commonly used bioreactors are of stirring type.
(d) A stirred-tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the contents.
(e) The stirrer facilitates the even-mixing and oxygen availability throughout the bioreactor.
(f) The bioreactor has the following components:

• An agitator system.
• An oxygen delivery system.
• A foam control system.
• A temperature control system.
• pH control system and
• Sampling ports.

(iii) Downstream processing.
Answer:
(a) It refers to the series of processes, to which a genetically modified product has to be subjected before it is ready to be marketed.
(b) The processes include two processes:

1. separation and
2. purification.

(c) The product has to be formulated with suitable preservatives.
(d) Such formulation has to undergo thorough clinical trials in the case of drugs. Strict quality control testing is also required.
(e) A proper quality controlled testing of each product is also required.

Question 27.
Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors to have over shake flasks?
Answer:
Shake flasks are the conventional flasks for fermentation studies during secondary screening or laboratory process development. So, stirred-tank bioreactors are used to produce the product in large quantities.

Besides aeration and mixing:

1. it also helps in providing optimum growth conditions (temperature, pH, substrate, salts, vitamins, oxygen) to achieve the desired product.
2. cost-effective
3. due to baffles, the oxygen transfer rate is very high
4. the capacity of fermenters is more.

Question 28.
Explain briefly the following
(i) PCR
(ii) Restriction enzymes and DNA
(iii) Chitinase. (CBSE 2012)
Or
Explain the three steps involved in a polymerase chain reaction. (CBSE Delhi 2018C)
Answer:
(i) PCR-Polymerase Chain Reaction; It is the process in which multiple copies of the gene or segment of DNA of interest are synthesised in vitro using primers and DNA polymerase.

Working Mechanism of PCR: A single PCR amplification cycle involves three basic steps: denaturation, annealing and extension (polymerisation).
(a) Denaturation. In the denaturation step, the target DNA is heated to a high temperature (usually 94°C), resulting in the separation of the two strands. Every single strand of the target DNA then acts as a template for DNA synthesis.

(b) Annealing (Anneal = Join). In this step, the two oligonucleotide primers anneal (hybridize) to each of the single-stranded template DNA since the sequence of the primers is complementary to the 3’ ends of the template DNA. This step is carried out at a lower temperature depending on the length and sequence of the primers.

(c) Primer Extension (Polymerisation): The final step is an extension, wherein Taq DNA polymerase (of a thermophilic bacterium Thermus aquatics) causes synthesis of the DNA region between the primers, using dNTPs (deoxynucleoside triphosphates) and Mg²⁺. It means the primers are extended towards each other so that the DNA segment lying between the two primers is copied.

The optimum temperature for this polymerisation step is 72°C. To begin the second cycle, the DNA is again heated to convert all the newly synthesised DNA into single strands, each of which can now serve as a template for synthesis of more new DNA. Thus the extension product of one cycle can serve as a template for subsequent cycles and each cycle essentially doubles the amount of DNA from the previous cycle. As a result, from a single template molecule, it is possible to generate 2ⁿ molecules after n number of cycles.

Applications of PCR:

• Diagnosis of pathogen
• Diagnosis of the specific mutation
• DNA fingerprinting
• Detection of plant pathogens
• Cloning of DNA fragments from mummified remains of humans and extinct animals.

(ii) Restriction enzymes:
(a) They are called “molecular scissors” or chemical scalpels.
(b) Restriction enzymes, synthesised by micro-organisms as a defence mechanism, are specific endonucleases, which can cleave double-stranded DNA.
(c) Restriction enzymes belong to a class of enzymes called nucleases.
(d) They are of two kinds:

• Exonucleases, which remove nucleotides from the ends of DNA.
• Endonucleases, which cut the DNA at specific positions anywhere in its length (within).

(e) The recognition sequence is a palindrome, where the sequence of base pairs reads the same on both the DNA strands when the orientation of reading is kept the same, i.e. 5′ → 3′ direction or 3′ → 5′ direction.
e.g. 5′ – GAATTC – 3′
3′ – CTTAAG – 5′

(f) Each restriction endonuclease functions by inspecting the length of a DNA sequence and binds to the DNA at the recognition sequence.
(g) It cuts the two strands of the double helix at specific points in their sugar-phosphate backbones, a little away from the centre of the palindrome sites, but between the same two bases on both the strands.
(h) As a result, single-stranded portions called sticky ends are produced at the ends of the DNA; this stickiness of the end facilitates the action of enzyme DNA ligase.

1. When cut by the same restriction endonuclease, the DNA fragments (of the donor as well as the host/ recipient) yield the same kind of ‘sticky ends’ which can be joined end-to-end by DNA ligases.
2. Chitinase. This cell wall in fungi is made of chitin. The enzyme is used in fungi to break open the cell to release DNA along with their macromolecules like RNA proteins, lipids and polysaccharides.

Question 29.
Discuss with your teacher and find out how to distinguish between
(i) Plasmid DNA and chromosomal DNA
Answer:
Differences between plasmid DNA and chromosomal DNA:

(ii) Exonuclease and Endonuclease (CBSE, Delhi 2013)
Answer:
Differences between Exonuclease and Endonuclease:

Question 30.
Collect the examples of palindromic sequences by consulting your teacher. Better try to create a palindromic sequence by following base pair rules.
Answer:

Question 31.
Can you list 10 recombinant proteins which are used In medical practice? Find where they are used as therapeutics (use the Internet).
Answer:

Question 32.
How is DNA isolated in a purified form? (CBSE Outside Delhi 2009)
Answer:
Isolation of DNA in the purified form:

1. DNA has to be isolated in pure form for the action of restriction enzymes.
2. DNA can be released from the cells by digesting the cell envelope by the use of enzymes like lysozyme for bacterial cells, chitinase for fungal cells and cellulase for plants cells.
3. Since DNA is intertwined with histone proteins and RNAs, proteins are removed by treatment with proteases and RNAs by ribonucleases.
4. Other impurities are removed by employing suitable treatments.
5. The purified DNA is precipitated by the addition of chilled ethanol. It is seen as fine threads in suspension.

Question 33.
How is isolation and Fragmentation of DNA of interest carried out in recombinant DNA technology? (CBSE Outside Delhi 2009, 2019)
Answer:
1. Fragmentation DNA: Fragmentation of DNA is carried out by incubating the purified DNA molecules with suitable restriction enzymes at optimal conditions of temperature and pH.

2. Isolation of DNA (gene) of Interest:
(a) The fragments of DNA are separated by a technique called gel electrophoresis.
(b) The DNA is cut into fragments by restriction endonucleases.
(c) These fragments are separated by a technique called gel electrophoresis.
(d) Agarose, the natural polymer obtained from seaweeds, is used as the matrix.
(e) DNA fragments being negatively charged are separated by forcing them to move through the matrix towards the anode under an electric field.
(f) The DNA fragments separate/ resolve according to their size.
(g) The separated molecules are stained by ethidium bromide and visualised by exposure to UV radiation, as bright orange coloured bands.
(h) The separated bands of DNA (on the gel) are cut from the gel and extracted from the gel piece (elution).
(i) Such DNA fragments are purified and used for constructing recombinant DNA by joining them with cloning vectors.

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 10 Microbes in Human Welfare. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 10 Important Extra Questions Microbes in Human Welfare

Microbes in Human Welfare Important Extra Questions Very Short Answer Type

Question 1.
Which bacterium Is responsible for the formation of curd from milk?
Answer:
Lactobacillus but Agaricus (Lactic acid bacteria).

Question 2.
What is brewing?
Answer:
Brewing is a complex fermentation process, which involves the production of malt beverages such as beer, ale, porter, and stout with the help of strains of Saccharomyces cerevisiae.

Question 3.
Name the type of association that genus Glomus exhibits with the higher plant. (CBSE2014)
Answer:
Mycorrhiza- Symbiotic association.

Question 4.
Which one of the following is the baker’s yeast used in fermentation-Saccharum Barberi, Saccharomyces cerevisiae or Sonalika? (CBSE2009)
Answer:
Saccharomyces cerevisiae.

Question 5.
Milk starts to coagulate when Lactic Acid Bacteria (LAB) is added to milk as a starter. Mention two benefits that LAB provides. (CBSE 2009)
Answer:

1. LAB checks the growth of disease-causing microbes.
2. LAB converts milk into curd and also increases nutritional quality by increasing vitamin B12.

Question 6.
Give the scientific name of the source organism from which the first antibiotic was produced. (CBSE Sample paper 2018-19)
Answer:
Penicillium Notatum

Question 7.
Name the different vitamins which are produced by micro-organisms.
Answer:

1. Riboflavin or Vitamin B2 is produced by yeast and bacteria.
2. Vitamin B12 or cobalamine is produced by bacteria and actinomycetes.

Question 8.
Name the original wild strain of the mold by which vitamin B2 is produced.
Answer:
Ashbya Gossypii.

Question 9.
What is a single-cell protein (SCP)?
Answer:
Single-cell protein (SCP) refers to any microbial biomass produced by uni and multi-cellular organisms and can be used as food or feed additives.

Question 10.
Name a microbe used for statin production. How do statins lower blood cholesterol levels?
Answer:
Microbe:
Monascus Purpureus Mechanism: Statins are competitive inhibitors of enzymes required for cholesterol synthesis. Therefore, play role in decreasing cholesterol level in the body.

Question 11.
‘Swiss cheese’ is characterized by the presence of large holes. Name the bacterium responsible for it. (CBSE Delhi Outside 2019)
Answer:
Propionibacterium sharmanii

Question 12.
What for Nudeopolyhedra viruses (NVP) are being used nowadays? (CBSE, Delhi 2014, 2019C)
Answer:
Nudeopolyhedro viruses are being used to kill insects and other arthropods pests of crops. The viruses have no effect on plants and non-target animals. Thus used in biological control of pests.

Question 13.
How has the discovery of antibiotics helped mankind in the field of medicine?
Answer:
Antibiotics have helped mankind in treating most of the deadly bacterial and fungal diseases of humans.

Question 14.
Why is distillation required for producing certain alcoholic drinks?
Answer:
For increasing the alcohol strength or concentration of the drinks.

Question 15.
What is the primary sludge?
Answer:
All the solids that settle from the sewage on primary treatment constitute primary sludge.

Question 16.
What is the relationship between BOD and organic matter in sewage?
Answer:
The greater the BOD of wastewater more is the amount of organic matter in sewage.

Question 17.
Name two gases produced during secondary treatment by sewage.
Answer:

1. Carbon dioxide and
2. Hydrogen sulfide.

Question 18.
What are bioreactors?
Answer:
In the pilot plant, the glass vessels are replaced by stainless steel vessels. They are called bioreactors.

Question 19.
Name the bacteria which can be used for yogurt formation.
Answer:

1. Lactobacillus bulsaricus.
2. Streptococcus Thermophilus.

Question 20.
What is Bacitracin?
Answer:
It is an antibiotic obtained from Bacillus Licheniformis.

Question 21.
Name the group of organisms and the substrate they act on to produce biogas. (CBSE 2009)
Answer:
Methanogens such as Methanol bacterium act on activated sludge to produce biogas.

Question 22.
WrIte the scientific name of the microbe used for fermenting malted cereals and fruit juices. (CBSE 2011)
Answer:
Saccharomyces cerevisiae

Question 23.
Write an alternate source of protein for animal and human nutrition. (CBSE 2014)
Answer:
Single-cell proteins.

Question 24.
How are the members of the genus Glomus useful to organic farmers? (CBSE Delhi Outside 2019)
Answer:
Many members of the genus Glomus form mycorrhizae- symbiotic associations with roots of higher plants. The fungal component of these associations helps in the absorption of phosphorus from soil. It also makes the plant drought-resistant.

Microbes in Human Welfare Important Extra Questions Short Answer Type

Question 1.
Expand the ‘LAB’. How are LABs beneficial to humans? (Write any two benefits) (CBSE 2019 C)
Answer:
LAB-Lactic Acid Bacteria Benefits:

• Found in curd. They improve the nutritional quality of food.
• Yogurt is prepared from milk by Lactobacillus Bulgaricus.

Question 2.
What is cyclosporin A? What is its importance?
Answer:
Cyclosporin A. It is an eleven-membered cyclic oligopeptide obtained through the fermentative activity of fungus Trichoderma Polysporum.

Importance. It has antifungal, anti-inflammatory, and immunosuppressive properties. It inhibits the activation of T-cells and therefore, prevents rejection reactions in organ transplantation.

Question 3.
How do antibiotics act?
Answer:
Antibiotics do not have identical effects on all harmful microbes. All of them inhibit growth or destroy bacteria, viruses, and fungi. Actually, antibiotic molecules should disrupt a vital link in the microbe’s metabolism and this link is their target or point of impact.

Question 4.
Write the various steps of fermentation.
Answer:
The major steps of fermentation are:

1. Sterilization of the fermenter and medium in steam. It is carried out under pressure and high temperature.
2. Inoculation of a selected strain of the yeast.
3. Recovery of the product.

Question 5.
What are the two ways by which micro-organisms can be grown in bioreactors?
Answer:
Micro-organisms can be grown in the bioreactors in two ways:

1. As a layer or film on the surface of the nutrient medium. It is known as a support growth system.
2. By suspending cells or mycelia in a liquid medium contained in the growth vessel. It is known as a suspended growth system.

Question 6.
What is sewage? In which way can this be harmful?
Answer:
Sewage is used and wastewater consisting of human excreta, wash waters, industrial and agricultural wastes that enter the sewage system. In general, sewage contains 95.5% water and 0.1 to 0.5% organic and inorganic matter. They are very harmful to us due to the presence of a variety of micro¬organisms in them, most of which are highly pathogenic. Sewage has a high BOD value, which develops anaerobic conditions in water resulting in the death of water animals and emitting foul smell due to incomplete oxidation of organic materials in the sewage.

Question 7.
What is the key difference between primary and secondary sewage treatment?
Answer:
Primary treatment of wastes is the screening and removal of insoluble particulate materials, by addition of alum and other coagulants. It is the physical removal of 20-30% of organic materials present in sewage in particulate form. Secondary treatment of waste is the biological removal of dissolved organic matter through trickling filters, activated sludge, lagoons, extended aeration systems, and anaerobic digestors.

Question 8.
Draw a simple diagram to show an anaerobic sludge digester.
Answer:

Anaerobic sludge digester.

Question 9.
GIve the full form of Bt. Name the insects killed by It.
Answer:
The full form of Bt is Bacillus Ttiuringiensis. It kills a wide range of Insects Like moths, beetles, mosquitoes, aphids, and termites.

Question 10.
Why are biofertilizers or biopesticides preferred to chemical fertilizers or pesticides? (CBSE Delhi 2011)
Answer:
Biofertilizers or biopesticides are preferred to chemical fertilizers or pesticides because

• They are safe to use and are biological in origin.
• They do not spoil the quality of the soil and are target-specific.
• They do not pollute the atmosphere and are non-poisonous.
• They are less expensive and are biodegradable.

Question 11.
Name the blank spaces a, b, c, and d from the table given below: (CBSE 2008)

Answer:
(a) Trichoderma polypore
(b) Organ transplantation (Immunosuppressant)
(c) Yeast
(d) Blood cholesterol-lowering agent

Question 12.
How does the addition of a small amount of curd to fresh milk help the formation of curd? Mention a nutritional quality that gets added to the curd. (CBSE Delhi 2010 and Outside Delhi 2019)
Answer:

1. Curd is prepared from milk.
2. Microorganisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd.
3. During growth, the LAB produces acids that coagulate and partially digest the milk proteins.
4. A small amount of curd added into the fresh milk as inoculum or starter contains millions of LAB which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12.
5. In our stomach too, the LAB plays a very beneficial role in checking disease-causing microbes.

Question 13.
Name a free-living and symbiotic bacterium that serves as a biofertilizer. Why are they called so? (CBSE Outside Delhi 2016)
Answer:
Free-living nitrogen-fixing bacteria Azotobacter and Bacillus Polymyxa Symbiotic nitrogen-fixing bacteria. Rhizobium.

These micro-organisms enrich the soil by fixing nitrogen. They enhance the availability of nutrients to crops, thus called biofertilizers.

Question 14.
(i) Why are fruit juices bought from the market clearer as compared to those made at home?
Answer:
Bottled juices are clarified by the use of pectinases and proteases.

(ii) Name the bioactive molecules produced by Trichoderma Polysporum and Monascus Purpureus. (CBSE Delhi 2013)
Answer:
(a) Bioactive molecules produced by Trichoderma polypore are cyclosporin A. It is used as an immunosuppressive agent in organ- transplant patients.
(b) Bioactive molecules produced by Monascus Purpureus are statins. It is a blood cholesterol-lowering agent.

Question 15.
Your advice is sought to improve the nitrogen content of the soil to be used for the cultivation of a non-leguminous terrestrial crop.
(i) Recommend two microbes that can enrich the soil with nitrogen.
Answer:
Azospirillum, Azotobacter, Anabaena, Oscillatoria (Any two)

(ii) Why do leguminous crops not require such enrichment of the soil? (CBSE 2018)
Answer:
Leguminous crops do not require such enrichment of the soil because they have a symbiotic association with Rhizobium bacteria which traps nitrogen directly from the atmosphere and provides it to the plant and in turn gets food and shelter.

Question 16.
What are ‘floes’, formed during secondary treatment of sewage? (CBSE Delhi 2019)
Answer:
Floes are masses of bacteria, associated with fungal filaments to form mesh-like structures.

Question 17.
Write any two places where methanogens can be found. (CBSE Delhi 2019)
Answer:
Methanogens can be found in the following places:

1. In anaerobic sludge (digester) of a sewage treatment plant
2. In rumen (gut/stomach) of cattle or ruminants
3. Marshy areas
4. Flooded paddy fields
5. Biogas plant Methane, H₂S, and C0₂ are produced during microbial digestion of organic compounds in case of secondary treatment of sewage.
6. The dung of the cattle produces methane gas in the biogas plants.

Microbes in Human Welfare Important Extra Questions Long Answer Type

Question 1.
Give examples to prove that microbes release gases during metabolism.
Answer:

1. Large holes in ‘Swiss Cheese’ are due to the production of a large amount of C0₂ by a bacterium named Propionibacterium shamanic.
2. The puffed-up appearance of dough is due to the production of C0₂ gas by yeast, Saccharomyces cerevisiae.
3. Methane, H₂S, and CO₂ are produced during microbial digestion of organic compounds in the case of secondary treatment of sewage.
4. The dung of the cattle produces methane gas in the biogas pLants.

Question 2.
Make a table showing industrial products obtained from activities of bacteria.
Answer:
industrial products obtained from use activities of Bacteria:

Question 3.
What are Baculo viruses? Write their significance.
Answer:
Baculoviruses are those viruses, which attack insects and other arthropods, e.g. Nuclepolyhedrovirus.

Significance:

• Baculoviruses are species-specific and narrow-spectrum insecticides.
• They have no negative impacts on plants, birds, mammals, or even other non-target insects.
• The desirable aspect In conservation of beneficial insects in overall integrated pest management (IPM) program as in an ecologically sensitive area.

Question 4.
Which nitrogen fixers are available on a commercial basis In the market? Also, name the beneficial crop.
Answer:

Question 5.
Distinguish between the roles of floes and anaerobic sludge digester in sewage treatment. (CBSE Delhi 2016)
Answer:
Floes are masses of bacteria associated with fungal filaments to form mesh-like structures. These microbes digest a lot of organic matter, converting it into microbial biomass and releasing a lot of minerals. Anaerobic sludge digester is a large tank in which anaerobic microbes digest the anaerobic mass as well as aerobic microbes of sludge. Biogas is produced by methanogens. It is inflammable and a source of energy.

Question 6.
Tabulate the list of common antibiotics, organisms producing them, and organisms sensitive to these antibiotics.
Answer:

Question 7.
Give a flow chart of sewage treatment.
Answer:
Flow chart of sewage treatment:

Flow chart of sewage treatment

Question 8.
List the events that lead to the production of biogas from wastewater whose BOD has been reduced significantly. (CBSE Dethi 2016)
Answer:

1. During secondary treatment of wastewater, sewage fungus forms focus.
2. BOD decreases. As it decreases to 10-15% of originaL sewage, the wastewater Is taken to a Large settling tank where the focus of sewage fungus settles down.
3. The supernatant can be passed into water bodies or treated further.
4. The organic sediment is passed into an anaerobic sludge digester where anaerobic microbes methanogens decompose organic matter.
5. It is accompanied by the production of blogs and the formation of manure or compost.

Question 9.
Explain the basis of biological control of weeds.
Answer:
Basis of biological control of weeds:

1. Biological control of weeds involves breeding of insects that would feed selectively a weed or use of certain micro-organisms which will produce diseases in the weeds and eliminate them.
2. Certain crop plants do not allow the growth of weeds nearby. They are called smoother plants such as Barley, Rye, Sorghum, Millet, etc. They eliminate weeds through chemicals.
3. In some cases, specially tailored plants called transgenic plants have been introduced which have tolerance against weeds.
4. In India and Australia, the overgrowth of cacti was checked by the introduction of the cochineal insect (Cactoblastis cactorum).
5. The latest technique is to use fungal spores to control weeds. These are suitable because they can be kept for a long time and also resist adverse conditions.

Question 10.
What are biofertilizers? What are the main sources of biological nitrogen fixation? Name two organisms that fix nitrogen symbiotically and two organisms that fix symbiotically.
Answer:
Biofertilizers are organisms that can bring about soil nutrient enrichment by their biological activity.

• Sources of biofertilizers: Bacteria, cyanobacteria, and fungi.
• Biological nitrogen fixation: The conversion of atmospheric nitrogen into nitrogenous compounds through the agency of living organisms is called biological nitrogen fixation.

Symbiotically nitrogen-fixing organisms:

• Rhizobium leguminosarum, Frankia Bacillus radicicola.
• Free-living/Asymbiotic nitrogen-fixing organisms-Cyanobacteria, Azotobacter.

Question 11.
(a) What is biogas? What are its components? What is the calorific value of biogas? (CBSE Outside Delhi 2013)
Answer:
Biogas is a methane-rich fuel gas produced by anaerobic breakdown or digestion of biomass with the help of methanogenic bacteria.

Components of biogas: Methane, Carbon dioxide, Hydrogen sulfide, hydrogen, and nitrogen.
Calorific value 23-28 MJ/m³.

(b) Why is a slurry of cattle dung (gobar) added to bio-wastes in the tank of a gobar gas plant for the generation of biogas? (CBSE Delhi 2019 C)
Answer:
Slurry consisting of excreta dung of cattle commonly called gobar is rich in methanogen bacteria. It is used for the generation of biogas. These bacteria called methane bacterium grow anaerobically and break down the cellulose of dung to liberate gases such as methane, C0₂, and H₂.

Question 12.
(?) Name the toxin produced by B. Thuringiensis.
Answer:
∝-exotoxin, β-exotoxin, γ-exotoxin, and louse factor

(ii) Nitrogen fixers are available on a commercial basis in the market? Also, name the beneficial crop and microbes used in the following table.

Answer:
A. Rhizobium B. Legume C. Legume

(iii) Expand BOD and COD
Answer:
BOD- Biological Oxygen Demand COD- Chemical Oxygen Demand

Question 13.
By a flow chart showing the stages in anaerobic digestion during the production of biogas.
Answer:

Stages in Anaerobic Digestion during biogas formation

Question 14.
Given below is a list of six microorganisms. State their usefulness to humans.
(i) Nucleopolyhedrovirus
(ii) Saccharomyces cerevisiae
(iii) Monascus Purpureus
(iv) Trichoderma polypore
(v) Penicillium Notatum
(vi) Propionibacterium shamanic. (CBSE Delhi 2016)
Answer:

Question 15.
Explain the different steps involved in the secondary treatment of sewage. (CBSE Sample paper 2018—19)
Or
Secondary treatment of sewage is also called biological treatment. Justify this statement and explain the process. (CBSE 2018)
Answer:

1. Secondary treatment of sewage is a biological process that employs the heterotrophic bacteria naturally present in the sewage.
2. The effluent from the primary treatment is passed into large aeration tanks, where it is constantly agitated and the air is pumped into it.
3. This allows the rapid growth of aerobic microbes into ‘floes’ which consume the organic matter of the sewage and reduce the biological oxygen demand (BOD). The greater is the BOD of wastewater, the more is its polluting potential.
4. When the BOD of sewage is reduced significantly, the effluent is passed into a settling tank, where the ‘floes’ are allowed to sediment forming the activated sludge.
5. A small part of the activated sludge is pumped back into the aeration tanks.
6. The remaining major part of the sludge is pumped into anaerobic sludge digesters, where the anaerobic bacteria digest the bacteria and fungi in the sludge-producing methane, hydrogen sulfide, and carbon dioxide,
   i. e. biogas. This is why secondary treatment of sewage is also called biological treatment.
7. The effluent after secondary treatment is released into water-bodies like streams or rivers.

Question 16.
Microbes can be used to decrease the use of chemical fertilizers. Explain how this can be accomplished. (CBSE Delhi 2019)
Answer:

1. Rhizobium bacteria present in the root nodules of leguminous plants (pea family) forms a symbiotic association and fixes atmospheric nitrogen into organic forms as nitrates/nitrites which are used by the plant as nutrient.
2. Free-living bacteria in the soil Azospirillum and Azotobacter can fix atmospheric nitrogen thus enriching the nitrogen content of the soil.
3. Many members of the genus Glomus (Fungi) form mycorrhizal symbiotic associations with higher plants. In these, the fungal symbiont absorbs phosphorus from soil and passes it to the plant.

Question 17.
(?) Organic farmers prefer biological control of diseases and pests to the use of chemicals for the same purpose. Justify.
Answer:
Chemical methods often kill both useful and harmful living beings indiscriminately. The organic farmer holds the view that the eradication of the creatures that are often described as pests is not only possible but also undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive. Thus, the use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides.

(ii) Give an example of a bacterium, a fungus, and an insect that are used as biocontrol agents. (CBSE 2018)
Answer:
Insects = Ladybird and Dragonflies. Bacteria = Bacillus thuringiensis. Fungus = Trichoderma

Question 18.
The three microbes are listed below. Name the product produced by each one of them and mention their use.
(i) Aspergillus niger
(ii) Trichoderma polypore
(iii) Monascus Purpureus (CBSE Delhi 2018C)
Or
(i) A patient had suffered myocardial infarction and clots were found in his blood vessels. Name a ‘clot buster’ that can be used to dissolve clots and the microorganism from which it is obtained.
(ii) A woman had just undergone a kidney transplant. A bioactive molecular drug is administered to oppose kidney rejection by the body. What is the bioactive molecule? Name the microbe from which this is extracted.
(iii) What do doctors prescribe to lower the blood cholesterol level in patients with high blood cholesterol? Name the source organism from which this drug can be obtained. (CBSE Outside Delhi 2019)
Answer:
(i) Aspergillus niger produces citric acid. Citric acid is used as a flavoring agent and as a food preservative.
(ii) Trichoderma Polysporum produces a bioactive molecule cyclosporin A. It is used as an immunosuppressive agent in organ transplant patients.
(iii) Monascus Purpureus produces statins. Statins are capable of competitive inhibition of enzymes required for cholesterol synthesis. Hence, it is used as blood cholesterol-lowering agents.
Or
(i) Streptokinase-‘Clot buster’ can be used to dissolve clots. It is obtained from the bacteria Streptococcus.
(ii) The bioactive molecule is Cyclosporin A which is used as an immunosuppressive agent in organ transplantation. It is produced by the fungus Trichoderma Polysporum.
(iii) Doctors prescribe Statins to lower blood cholesterol. It is obtained from the fungus Monascus Purpureus.

Question 19.
Baculoviruses are good examples of biocontrol agents. Justify giving reasons. (CBSE Delhi 2018C)
Answer:
Baculoviruses kill insects and other arthropods, hence they are used as biocontrol agents especially Nucleopolyhedrovirus.

Reasons for their use:

• These viruses are species-specific and have narrow spectrum insecticidal applications.
• They do not harm non-target organisms like other harmless insects, birds, animals, etc.
• It is very useful in integrated pest management programs or treatment of ecologically sensitive areas.

Question 20.
Describe the primary and secondary treatment of domestic sewage before it is released for reuse. (CBSE, 2014)
Answer:
Treatment of domestic sewage. The municipal wastewaters are treated in Effluent Treatment Plant (ETP) prior to disposal in water bodies.

It consists of 3 steps: primary, secondary, and tertiary.
1. Primary treatment. It includes physical processes, such as sedimentation, floatation, shredding (fragmenting and filtering). These processes remove most of the large debris.

2. Secondary treatment. It is a biological method. Activated sludge method. Sewage, after primary treatment, is pumped into aeration tanks or oxidation ponds. Here, it is mixed with air and sludge containing algae and bacteria. Bacteria consume organic matter. The process results in the release of C02 and the formation of sludge or biosolid. Algae produce oxygen for the bacteria. The water, which is now almost clear of organic matter, is chlorinated to kill microorganisms.

3. Tertiary treatment. It involves. removal of nitrates and phosphates. The water, after the above treatment, is then released. It can be reused.

Question 21.
Explain biological control of pests and plant pathogens with examples.
Answer:
The very familiar beetle with red and black markings the Ladybird, and Dragonflies are useful to get rid of aphids and mosquitoes, respectively.

Role of Bacillus Thuringinesis:
Bt Coming to microbial biocontrol agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (often written as Bt). These are available in sachets of dried spores which are mixed with water and sprayed onto vulnerable plants such as Brassica and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed.

The bacterial disease will kill the caterpillars, but leave other insects unharmed. Because of the development of the methods of genetic engineering in the last decade or so, scientists have introduced B. thuringiensis toxin genes into plants. Such plants are resistant to attack by insect pests. Bt-cotton is one such example which is being cultivated in some states of our country.

Biological control of plant pathogens: A biological control developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma sp. are free-living fungi that are very common in soil and root ecosystems. They are effective biocontrol agents of several plant pathogens.

Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications.

They have been shown to have no negative impacts on plants, mammals, birds, fish, or even on non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall IPM (integrated pest management) program, or when an ecologically sensitive area is being treated.

Question 22.
How do biofertilizers enrich the soil?
Answer:
Biofertilizers play a vital role to solve the problems of soil fertility and soil productivity.

1. Anabaena azollae, a cyanobacterium, lives in symbiotic association with the free-floating water fern, Azolla. The symbiotic system Azolla-Anabaena complex is known to contribute 40-60 mg N ha-1 per rice crop. In addition to this, cyanobacteria add organic matter, secretes growth-promoting substances like auxins and vitamins, mobilizes insoluble phosphate, and thus improves the physical and chemical nature of the soil.
2. Rhizobium Leguminoserum and Azospirillum fix atmospheric nitrogen as nitrates and nitrites.
3. Mycorrhizae formed by an association of bacteria and roots of higher plants increase soil fertility.

Question 23.
Discuss the role of Microbes as Biofertilizers. (CBSE Delhi 2011, 2015, 2019)
Answer:
Role of microbes as biofertilizers:
Bacteria, cyanobacteria, and fungi (mycorrhiza) are the three groups of organisms used as biofertilizers.
1. Bacteria:
(a) Symbiotic bacteria Rhizobium.
(b) Free-living bacteria Azospirillum and Azotobacter.
(c) They fix the atmospheric nitrogen and enrich soil nutrients.

2.  Cyanobacteria, e.g. Anabaena, Nostoc, Aulosira, Oscillatoria, etc.
(a) They function as biofertilizers by fixing atmospheric nitrogen and
(b) Increasing the organic matter of the soil through their photosynthetic activity.

3. Fungi/mycorrhizae:
(a) Fungi form a symbiotic association with roots of higher plants (mycorrhizae), e.g. Glomus.
(b) The fungus absorbs phosphorus and passes it on to the plant.
(c) Other benefits of mycorrhizae are :

• resistance to root-borne pathogens.
• tolerance to salinity.
• tolerance to drought.
• the overall increase in the plant growth and development

Question 24.
You have been deputed by your school principal to train local villagers in the use of biogas plants. With the help of a labeled sketch explain the various parts of the biogas plant. (CBSE Outside Delhi 2013)
Answer:
Biogas plant:

Biogas plant

1. The plant consists of a well-like underground tank made of bricks. This tank is called a digester.
2. The roof of the digester is dome-shaped made of cement and bricks. The dome of the digester tank acts as a gas holder (or storage tank for biogas). Thus, the gas holder in this type of gas-plant is fixed.
3. There is a gas outlet at the top of the dome for the supply of biogas.
4. On the one side of the digester tank, there is a slopping inlet tank and on the other side, there is a rectangular outlet tank or overflow tank. Both these tanks are made of cement and bricks.
5. The mixing tank is connected with a slopping inlet chamber (or tank) while the outflow tank is connected with a rectangular outlet chamber (or tank).
6. The inlet-chamber is for introducing fresh dung slurry into the main digester tank whereas the outlet chamber is for taking out spent dung slurry after extraction of biogas.

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 9 Strategies for Enhancement in Food Production. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 9 Important Extra Questions Strategies for Enhancement in Food Production

Strategies for Enhancement in Food Production Important Extra Questions Very Short Answer Type

Question 1.
Define the livestock.
Answer:
Domesticated animals reared to provide milk, hide, flesh, etc.

Question 2.
What do you mean by the white revolution?
Answer:
Increased production of milk.

Question 3.
Who is called the Father of the White revolution?
Answer:
Dr. V. Kurien.

Question 4.
Give one example of each of the indigenous and exotic milch breeds of cow.
Answer:
Indigenous breed: Sahiwal; Exotic breed: Brown swiss.

Question 5.
Name one bacterial and one viral disease of cattle.
Answer:
Bacterial disease: Anthrax ;
Viral disease: foot and mouth disease.

Question 6.
What are the main advantages of cross-breeds of fowls over indigenous breeds?
Answer:
These consume less feed and produce more eggs.

Question 7.
Name two high-yielding cross-breeds of fowls.
Answer:
“B-77” and “HH-260”.

Question 8.
What is meant by ‘hidden hunger’?
Answer:
It is the consumption of food that is deficient in some essential nutrients like micronutrients, proteins, and vitamins.

Question 9.
Why are plants obtained by protoplast culture called somatic hybrids?
Answer:
Plants obtained from protoplast culture are called somatic hybrids because they are formed from hybrid cells developed through the fusion of genetically different somatic cells.

Question 10.
A person who is allergic to pulses was advised to take a capsule of Spirulina daily. Give the reasons for the advice.
Answer:
Spirulina is rich in proteins. Thus it overcomes the protein deficiency due to non-eating of pulses.

Question 11.
Give examples of some microorganisms working for SCP.
Answer:
Spirulina maxima, Methylophilus methylotrophs, Candida utilize, Paecilomyces variety.

Question 12.
What is the importance of male sterility in plant breeding?
Answer:
Plant breeders use male-sterile plants in artificial hybridization to avoid self-pollination.

Question 13.
Give the significance of superovulation.
Answer:
It increases the production of eggs (6-8) per cycle. Thus it helps in increasing herd size in a short time.

Question 14.
What is the economic value of Spirulina? (CBSE 2008, 2009)
Answer:
Spirulina can be grown on easily available cheap materials like wastewater from potato processing plants, molasses, and even sewage. They provide a large quantity of protein-rich food. Hence it also minimizes pollution.

Question 15.
List the products obtained from bee-keeping. (CBSE Delhi 2008)
Answer:
Honey, wax, royal jelly, and bee venom.

Question 16.
What is the importance of MOET? (CBSE Delhi 2013)
Answer:
MOET is multiple ovulation embryo transfer technologies.

Importance:

1. It is used to increase herd size in short term.
2. It is also meant for the successful production of hybrids.

Question 17.
Name any two diseases the ‘Himgiri’ variety of wheat is resistant to. (CBSE Outside Delhi 2013)
Answer:

1. Leaf and stripe rust
2. Hill bunt.

Question 18.
Name the following:
(a) The semi-dwarf variety of wheat is high-yielding and disease-resistant.
Answer:

1. Sonalika and
2. Kalyan Sona

(b) Anyone inter-specific hybrid mammal. (CBSE 2012)
Answer:
Mule.

Strategies for Enhancement in Food Production Important Extra Questions Short Answer Type

Question 1.
What is animal breeding? Name two main methods.
Answer:
Animal breeding: The main aim of animal breeding is to produce more milk-yielding cows with longer lactation periods and sturdier work animals. So animal breeding is an important aspect of animal husbandry. Two main methods are inbreeding and outbreeding.

Question 2.
A farmer was facing the problem of low yield from his farm. He was advised to keep a beehive in the vicinity. Why? How would the beehive help in enhancing yield?
Answer:
The honeybee is the major pollinator of several crop plants. Keeping a beehive near the farm will ensure proper pollination of crop plants. Therefore, crop yield will be ensured.

Question 3.
List three scientific approaches to obtain a high yield of crops.
Answer:

1. Crop production management
2. Crop improvement for higher yield through genetic manipulation
3. Crop protection management.

Question 4.
List the main steps of plant breeding. (CBSE2014)
Answer:

1. Collection of variability.
2. Evaluation and selection of parents.
3. Cross-hybridisation among selected parents.
4. Selection and testing of superior recombinations.
5. Testing, release, and commercialization of new cultivars.

Question 5.
Suggest two features of plants that will prevent insect and pest infestation.
Answer:

1. Increasing hair growth on aerial parts of plants.
2. Rendering the flowers nectar less.
3. Enabling plants to secrete insect-killing chemicals (toxins).

Question 6.
Briefly explain hybridization. Give one example.
Answer:
For the process of hybridization, selected parents are crossed to combine useful characters in the progeny. Heterosis is exploited in augmenting yields in several commercial crops. A high-yielding variety of wheat is a classical example of hybridization in crop evolution.

Question 7.
How is a disease-resistant plant selected for successful breeding? (CBSE Delhi 2013)
Answer:
Successful breeding for disease resistance depends mainly on two factors:

1. A good source of resistance.
2. A dependable disease test.

Question 8.
Define germplasm. How is it maintained? (CBSE Delhi 2014)
Answer:
Germplasm is the sum total of all the alleles of the genes present in a crop and its related species. Germplasm collections are usually maintained at low temperatures in the form of seeds. In the case of fruit trees, the germplasm is maintained as trees grown in the field.

Question 9.
Name any five varieties of crop plants that have been developed in India.
Answer:

1. Himgiri variety of wheat.
2. Pusa Swarnim variety of Brassica.
3. Pusa Shubhra variety of Cauliflower.
4. Pusa Komal variety of Cowpea.
5. Pusa Sadabahar variety of Chilli.

Question 10.
What is inbreeding depression and how is it caused in organisms? Write any two advantages of inbreeding. (CBSE Delhi 2011)
Or
Explain inbreeding depression. (CBSE Delhi 2011)
Answer:
Inbreeding depression. Continued inbreeding especially close inbreeding, usually reduces fertility and even productivity. It is termed inbreeding depression.

Advantages of inbreeding:

1. Evolve and maintain a pure line in any animal.
2. It helps in the accumulation of superior genes and the elimination of less desirable genes.

Question 11.
List the four objectives with which bio-fortification has been carried out to improve public health. (CBSE Delhi 2019 C)
Answer:
The method of breeding crops with higher levels of vitamins and minerals or higher protein and healthier fats is called biofortification. It is one of the most important methods for improving public health.

Objective:

• In the recent past, many varieties of crop plants such as rice, carrots, spinach, pumpkin, and bathua have been developed which possess several times more nutritive value and vitamins as compared to existing varieties.
• High protein content and quality
• High oil content and quality
• Micronutrient and minerals content.

Question 12.
Why is animal husbandry essential?
Or
What are the objectives of animal breeding? (CBSE 2014)
Answer:

• To increase milk production.
• To increase egg production.
• To increase meat production.
• To increase fish production.
• For proper utilization of animal wastes.

Question 13.
(a) What is the breeding of crops for enhancing their nutritional value called? Why is the need felt for enhancing the nutritional value of the crops?
Or
How have these grains improved in their nutritional value in comparison to their conventional varieties? (CBSE Outside Delhi 2019)
Answer:
Iron-fortified rice variety contains over five times as much iron as compared to commonly consumed rice.

(b) Rice, wheat, and maize are the most commonly used food grains the world over.
Answer:

1. Iron-fortified rice variety contains over five times as much iron as compared to commonly consumed rice.
2. Wheat variety Atlas-66 has huge protein content.
3. Maize hybrids have twice the amount of lysine and tryptophan amino acid.

Question 14.
Name any two common Indian millet crops. State one characteristic of millets that has been improved as a result of hybrid breeding to produce high-yielding millet crops. (CBSE Delhi 2015)
Answer:
Hybrid varieties of maize, Jower, and Bajra have been developed in India by plant breeders. Hybrid breeding has led to the development of several high-yielding varieties resistant to water stress.

Question 15.
Enumerate four objectives for improving the nutritional quality of different crops for the health benefits of the human population by the process of “Biofortification.” (CBSE Delhi 2015)
Answer:
Objectives:

• Protein content and quality.
• Oil content and quality.
• Vitamin content.
• Micronutrient and mineral content.

Question 16.
(i) Why are the plants raised through
micropropagation termed as some clones 1(CBSE Outside Delhi 2015)
Answer:
Plants raised by the tissue culture method are genetically identical to the original plant from which they were grown hence called some clones.

(ii) Mention two advantages of their technique.
Answer:
(a) Plants can be produced on a commercial scale.
(b) Recovery of healthy plants from diseased plants.

Question 17.
(i) Name any two fowls other than chicken reared in a poultry farm.
Answer:
Fowls other than chickens :

1. Turkeys,
2. Geese,
3. Swans,
4. Guinea fowls,
5. Peafowls.

(ii) Enlist four important components of poultry farm management. (CBSE Delhi 2016)
Answer:
Important components of poultry farm management:
(a) Selection of disease-free and suitable breeds.
(b) Brood house should be crowd-free.
(c) Sanitation and hygiene. The brooding house should be cleaned, disinfected, and with the proper drainage system.
(d) Care of chicken during brooding.

Question 18.
Explain the process of artificial hybridization to get improved crop variety in
(i) plants bearing bisexual flowers and
Answer:
In plants bearing bisexual flowers, the anthers are removed from the flower before they dehisce. This is called emasculation. The emasculated flowers are covered with a bag of butter paper to prevent contamination of stigma with unwanted pollen. This process is called bagging. When this stigma attains receptivity, mature pollen grains are dusted on the stigma and the flowers are rebagged to allow the fruits to develop.

(ii) female parent producing unisexual flowers. (CBSE Outside Delhi 2010)
Answer:
If the female parent produces unisexual flowers, emasculation is not done. The flower buds are bagged before the flowers open. When the stigma becomes receptive, pollen is dusted on the stigma and the flower is rebagged.

Question 19.
(i) Mention the property that enables the explants to regenerate into a new plant.
Answer:
Totipotency is the ability of a cell to grow or generate the whole plant.

(ii) A banana herb is virus-infected. Describe the method that will help in obtaining healthy banana plants from this diseased plant. (CBSE Outside Delhi 2010, Delhi 2019)
Answer:
Healthy banana plants can be obtained from diseased plants by meristem culture. Although the plant is virus-infected, the apical and axillary meristems are free of virus. The meristem is removed from the plant and is grown in vitro by micropropagation. The plants produced are virus-free.

Question 20.
You have obtained a high-yielding variety of tomatoes. Name and explain the procedure that ensures retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop. (CBSE Delhi 2018)
Answer:
The retention of the desired characteristics in a large population of crops can be done by micropropagation, which is a type of vegetative propagation.

In this process, a small part of the plant is excised and grown under a sterile condition in a special nutrient medium to obtain many such plants that would be genetically identical to the original plants.

Question 21.
A herd of cattle is showing reduced fertility and productivity. Provide one reason and one suggestion to overcome this problem. (CBSE Delhi 2017)
Answer:
The cattle’s productivity is decreased due to inbreeding depression. A single outcross, i.e. breeding with animals of the same breed but should not have a common ancestor on either side up to 4-6 generations, can restore its fertility.

Question 22.
Why are microbes like Spirulina being produced on a commercial scale? Mention its two advantages. (CBSE Delhi 2018C)
Answer:
25% of the human population suffers from hunger and malnutrition. Single-cell protein (SCP) is the solution to this problem. Spirulina is a rich source of protein, so it is grown on a commercial scale for SCP production.

Advantages:

1. It utilizes cheap substrate like raw material like animal manure, wastewater from potato processing plants, straw molasses, and even sewage, therefore incidentally cleaning the environment and reducing pollution.
2. A small amount of microbe can produce a huge quantity of protein.

Question 23.
“Modern methods of breeding animals and plants can alleviate the global food shortage”. Comment on the statement and give suitable examples.
Answer:
Several new techniques like inbreeding, outbreeding, artificial insemination, MOET, somatic hybridization, and tissue culture are playing important role in enhancing global food production. Because all these techniques aim at increasing productivity.

Strategies for Enhancement in Food Production Important Extra Questions  Long Answer Type

Question 1.
What is apiculture? How is it important in our lives? (CBSE Delhi 2019 C)
Or
Beekeeping practice is a good income-generating industry. Write the different points to be kept in mind for successful beekeeping. Write the scientific name of the most common Indian species used for the purpose. (CBSE Delhi 2019)
Answer:
Apiculture is the maintenance of hives of honeybees for commercial purposes. It is also called Beekeeping. Apiculture is very important in our lives because it produces products of high economic and nutritive value:

1. The main product of beekeeping is honey which is a highly nutritious edible product. It replaces the use of sugar in many industries.
2. Honey is used as a part of many indigenous medicines.
3. Another product called beeswax is also produced which is used in the cosmetic and polish industry.
4. Honeybees are chief pollinating agents so helpful in improving the plant yield.
5. The most commonly used species in the wild state is Apis Indica and in the domestic state Apis mellifera.

Question 2.
What is plant breeding? (CBSE Delhi 2013)
Answer:
Plant breeding is the genetic improvement of the crop in order to create desired plant types that are better suited for cultivation, give better yields, and are disease resistant. Conventional plant breeding is in practice from 9,000 to 11,000 years ago. Most of our major food crops are derived from domesticated varieties.

But now due to advancements in genetics, molecular biology, and tissue culture, plant breeding is being carried out by using molecular genetic tools. Classical plant breeding includes hybridization (crossing) of pure lines, artificial selection to produce plants with desirable characters of higher yield, nutrition, and resistance to diseases.

Question 3.
What is a hybrid? Explain the procedure of obtaining a hybrid.
Answer:
Hybrid: A progeny obtained by crossing two varieties or species having desired genes thus showing required characters.

Process of hybridization:
This technique involves the following steps:

1. Removal of undehisced anthers from the bisexual flower of a plant to be used as female. This is called emasculation.
2. The emasculated flowers are covered by butter paper to avoid pollination by an undesirable pollen grain. It is also termed bagging.
3. Pollen grains from known seeds of desirable plants are used to pollinate these emasculated flowers.
4. They are collected, multiplied and their desirable characters are determined.

Question 4.
(i) Give the scientific name of the soil bacterium which produces crystal (Cry) proteins.
Answer:
A soil bacterium Bacillus thuringiensis (Bt) produces a crystal (Cry) protein.

(ii) How are these proteins useful in agriculture?
Answer:
A crop expressing cry gene is usually resistant to a group of insects for which the concerned Cry protein is toxic.

(iii)What do the different written terms “Cry” and “cry” represent respectively?
Answer:
The first letter of the protein symbol is always capital and always written in roman letters, i.e. Cry. However, the gene symbol usually has small letters and written in italics, i.e. cry. So Cry represents protein and cry represents a gene.

Question 5.
Differentiate between inbreeding and outbreeding in cattle. State one advantage and one disadvantage for each one of them. (CBSE Delhi 2013)
Or
How is inbreeding advantageous as well as disadvantageous in cattle breeding programs? (Mention any two advantages and two disadvantages.) (CBSE Sample Paper 2019-20)
Answer:
Differences between inbreeding and outbreeding:

Question 6.
What are superovulation and embryo transfer?
Or
Explain the strategy used for herd improvement in cattle. (CBSE Delhi 2019 C)
Or
Expand MOET. Explain the procedure of this technology in cattle improvement. (CBSE Delhi 2008, 2012, Outside Delhi 2019)
Answer:
MOET (Multiple Ovulation and Embryo Transplantation Technique). It is the latest technique to produce super milch cows.

1. Superovulation: It involves the stimulation of high milk-producing cows to ovulate more eggs by hormonal stimulation. Fertilization is done by artificial insemination. In this way, 4 to 10 embryos are developed in such cows.
2. Embryo transfer: In this, embryos are collected from superovulated cows. Each embryo is transplanted in the uterus of surrogate cows of inferior quality to produce a large number of calves with good germplasm. It can also be done in sheep, goats, and other livestock animals as well.

Question 7.
Why does a beekeeper keep beehives in crop fields during the flowering periods? State any two advantages. (CBSE Sample Paper)
Or
Honey collection improves when beehives are kept in crop fields during the flowering season. Explain. (CBSE 2010)
Answer:

1. Bees act as pollinating agents.
2. Bees bring about cross-pollination. Thus the productivity of crops increases. This in turn is beneficial to bees too as they get nectar to make honey.

Question 8.
Give a brief account of the cultivation of sugarcane and millets. (CBSE Delhi 2011, 2015)
Or
Write the scientific name of the sugarcane variety that was originally grown in North India. Why was this variety hybridized with the tropical variety of sugarcane grown in South India? (CBSE Delhi 2019 C)
Answer:
Cultivation of sugarcane:

1. Saccharum Barberi, originally grown in North India, had poor sugar content.
2. Saccharum officinarum, grown in South India, has thicker stems and higher sugar content but could not grow properly in North India.
3. A cross has been made between these species and the hybrid variety, combining the desirable qualities like thick stem, high sugar content, and higher yield is being grown in North India.

Cultivation of millets:

1. Several hybrid varieties of maize, bajra, and Jowar have been developed in India.
2. These breeding programs have resulted in the development of high-yielding varieties that are resistant to water stress.

Question 9.
Explain out-breeding, out-crossing, and cross-breeding practices in animal husbandry. (CBSE Delhi 2018)
Or
Differentiate between out-crossing and cross breeding. (CBSE Delhi 2018C)
Answer:
Out-breeding: Out-breeding is the breeding of unrelated animals, which may be between individuals of the same breed but having no common ancestors for 4-6 generations or between different breeds or different species.

Out-crossing: Out-crossing is the practice of mating animals within the same breed, but having no common ancestors on either side of their pedigree, up to 4-6 generations. It is the best breeding method for animals that are below average in milk productivity.

Cross-breeding: Cross-breeding allows the desirable qualities of two different breeds to be combined. In this method, superior males of one breed are mated with superior females of another breed. The progeny hybrid animals may be used for commercial production or they may be subjected to some form of inbreeding and selection to develop new stable breeds that may be superior to the existing breeds. Many new animal breeds have been developed by this approach.

Question 10.
(i) Write the desirable characters a farmer looks for in his sugarcane crop,
Answer:
The desirable characters that should be present in the sugarcane crop are:
(a) High yield,
(b) thick stem,
(c) high sugar content and
(d) ability to grow in North India.

(ii) How did plant breeding techniques help north Indian farmers to develop cane with desired characters? (CBSE Delhi 2017)
Answer:
Cultivation of sugarcane:

1. Saccharum Barberi, originally grown in North India, had poor sugar content.
2. Saccharum officinarum, grown in South India, has thicker stems and higher sugar content but could not grow properly in North India.
3. A cross has been made between these species and the hybrid variety, combining the desirable qualities like thick stem, high sugar content, and higher yield is being grown in North India.

Cultivation of millets:

1. Several hybrid varieties of maize, Bajra, and Jowar have been developed in India.
2. These breeding programs have resulted in the development of high-yielding varieties that are resistant to water stress.

Question 11.
(i) Lifestyle diseases are increasing alarmingly in India. We are also dealing with large-scale malnutrition in the population. Suggest a process by which we can address both these problems.
Answer:
These problems can be addressed by the process termed biofortification,

(ii) Give any three examples to support your answer. (CBSE Sample Paper 2018-19)
Answer:
Biofortification can be done:
(a) by enhancing food quality with respect to protein, e.g. improved wheat, maize varieties, etc.
(b) by cultivating vitamin-enriched vegetables, e.g. vitamin A enriched carrots, spinach, pumpkin, etc
(c) by enriching micronutrient and mineral content in vegetables, e.g. iron and calcium-enriched spinach and bathua

Question 12.
What is biofortification? Mention the contribution of the Indian Agricultural Research Institute towards it with the help of any two examples. (CBSE Delhi 2018C)
Answer:
It is an improvement in the nutritional quality of food crops by breeding. Through this, levels of vitamins, minerals, proteins, and healthier fats are enriched in crops. Indian Agricultural Research Institute released several vitamin and mineral enriched vegetable crops like vitamin A enriched carrots and spinach; Vitamin C enriched bitter guard, mustard, tomato; iron and calcium-enriched spinach and bathua; protein-enriched broad lablab, French and garden peas.

Question 13.
(i) What is artificial insemination? Give its significance.
Answer:
Artificial insemination:

• It is the process in which the semen collected from a superior quality male is injected into the reproductive tract of the selected female by the breeder.
• The advantages of artificial insemination are as follows:
• Semen can be used immediately or stored/frozen and used at a later date when the female is in the right reproductive phase.
• Semen can be transported in the frozen form to a distant place where the selected female animals are present.
• Semen from one selected male animal can be used on a number of female animals.
• The disadvantage is that the success rate is fairly low.

(ii) Write a note on MOET. (CBSE Delhi 2008)
Answer:
Multiple Ovulation Embryo Transfer Technology (MOET):

1. It is a method to improve the herds and their size.
2. The steps in the method are as follows:
3. A cow is administered hormones (like FSH) to induce follicular maturation and superovulation, i.e. production of 6-8 ova in one cycle.
4. The cow is mated with the selected bull or artificially inseminated.
5. The fertilized eggs at 8-32 celled stages are recovered and transferred to surrogate mothers.
6. This technology has been used for cattle, rabbits, mares, etc.
7. High milk-yielding breeds of females and high-quality meat-yielding bulls have been bred successfully to increase the herd size in a short time.

Significance:

• Several cows (up to 3,000) can be inseminated by the semen of a single pedigree bull of good quality.
• Avoid the transportation of animals,
• The quality and quantity of progeny can be improved.
• New characters can be introduced in the progeny.
• It is economical.

Question 14.
What are the practices adopted to improve crop production?
Answer:
The practices adopted to improve crop production are as follows:

1. Addition of fertilizers to the soil.
2. Selective breeding.
3. Weed control.
4. Control of plant diseases.
   (a) Fertilisers: These are the chemical compounds that are added to the soil to increase fertility. They make up for the deficiency of the required nutrients and help in increasing crop production.
   (b) Selective breeding: Disease-resistant seeds are produced by selective breeding. Regular use of high yield variety results in better crop production.
   (c) Weed control: The unwanted plants or weeds are controlled by using certain chemicals called weedicides.
   (d) Control of plant diseases: Crops should be protected from insects, fungi, animals, and other diseases. It is very useful for increasing crop production. Insects are very harmful to crops. So insecticides should be used to kill insects.

Question 15.
Discuss the role of plant tissue culture in increasing food production. (CBSE Delhi 2011)
Answer:
Applications of tissue culture technique:

1. This technique is applied for the rapid multiplication of desirable and rare plants.
2. By this technique, an indefinite number of plants can be produced.
3. From the culturing of virus-free tissues of the shoot apex of an infected plant, it becomes possible to obtain virus-free plant in sufficient stock. The tissue culture technique has been used to obtain virus-free potatoes and sugarcane.
4. The technique (Embryo culture) is useful in overcoming seed dormancy, but also in producing viable plants from the crosses which normally fail due to the death of immature embryos.
5. The technique has been applied for obtaining a large number of haploid and homozygous diploids.
6. Somatic hybridization helps the fusion of cells belonging to different families.
7. This technique is also useful for the genetic improvement of useful plants.

Question 16.
“The benefits of a new variety can be achieved only if farmers grow the variety”. Explain.
Answer:
The seed of new variety must be multiplied and made available to the farmers. In-plant breeding, seed means any plant part that is used to grow a crop. Thus ‘seed’ would include grains of wheat, rice, etc. tubers of the potato, stems of sugarcane, etc., provided they are used for producing new plants.

Therefore, wheat grains used as food cannot be termed as seeds, whereas those used for raising a crop are called seeds. A seed of a variety with superior traits is called an improved seed, which must be of high purity and have a high germination percentage. It must also be free from weed seeds and from diseases.

Question 17.
(a) What is mutation breeding? Give an example of a crop and disease to which resistance was induced by this method.
Answer:
(a) Mutation breeding involves the following steps:

1. Inducing mutation(s) through various methods/ mutagens.
2. Screening the plant materials for disease resistance.
3. Multiplication of these selected plants for direct use or for use inbreeding.
4. Hybridization of the selected plant materials.
5. Selection for disease resistance, testing, and release as a variety.
6. Through mutation breeding, varieties of mung bean have been developed that are resistant to yellow mosaic virus and powdery mildew.

(b) Differentiate between pisciculture and aquaculture. (CBSE Sample Paper 2020)
Answer:

Question 18.
How can crop varieties be made disease resistant to overcome the food crisis in India? Explain. Name one disease-resistant variety in India of:
(i) Wheat to leaf and stripe rust
Answer:
Mutation breeding involves the following steps:
(a) Inducing mutation(s) through various methods/mutagens.
(b) Screening the plant materials for disease-resistance.
(c) Multiplication of these selected plants for direct use or for use inbreeding.
(d) Hybridisation of the selected plant materials.
(e) Selection for disease resistance, testing, and release as a variety.
(e) Through mutation breeding, varieties of mung bean have been developed that are resistant to yellow mosaic virus and powdery mildew.

(ii) Brassica to white rust (CBSE 2011)
Answer:
(a) Himgiri variety of wheat
(b) Pusa swarm of Brassica

Question 19.
(i) Name the technology that has helped the scientists to propagate on a large scale the desired crops in a short duration. List the steps carried out to propagate the crops by the said technique.
(ii) How are somatic hybrids obtained?
Or
Scientists tried to develop a single plant exhibiting the characteristic of tomato and potato by using cells from tomato and potato plants respectively. Name the procedure and list the steps to achieve this. (CBSE Delhi 2014, Outside Delhi 2019, Sample Paper 2020)
Answer:
1. Tissue culture:
(a) It is the technique of regeneration of whole plants from any part of a plant by growing it on a suitable culture/nutrient medium under aseptic/sterile conditions in vitro.
(b) The culture medium must supply the energy, inorganic nutrients, vitamins, amino acids, and growth regulators like cytokinins and auxins.
(c) By this method, called micropropagation, thousands of plants can be grown in a short period of time.

The advantages of micropropagation are:
(a) The plants produced are genetically identical and constitute some clones.
(b) A number of plants can be grown in a short period of time.
(c) Healthy, disease-free plants can be grown by meristem culture.
(d) Somatic hybrids can be raised by tissue culture, where sexual hybridization is not possible.

2. Somatic Hybridization: Fusion of isolated protoplasts from two different plant varieties each having desirable characters is called somatic hybridization. The resultant hybrid is called somatic hybrids. This somatic hybrid can be grown into a new plant carrying all desirable qualities.

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 8 Human Health and Disease. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 8 Important Extra Questions Human Health and Disease

Human Health and Disease Important Extra Questions Very Short Answer Type

Question 1.
What is health?
Answer:
It is a state of complete physical, mental and social well-being of a person.

Question 2.
What is a disease?
Answer:
Malfunctioning of one or more organs characterised by signs and symptoms is called disease.

Question 3.
Write the role of interferons. (CBSE Delhi 2019(C))
Answer:
Role of interferon. These are glycoprotein released by virus-infected cells. They protect the adjoining cells from the attack of the virus.

Question 4.
Define autoimmunity.
Answer:
It is an abnormality which sometimes occurs in the immune system and instead of destroying foreign molecules, it attacks the body’s own cells.

Question 5.
A boy of ten years had chickenpox. He is not expected to have the same disease for the rest of his life. Mention how it is possible. (CBSE 2009)
Answer:
The body will acquire active immunity as the antibodies formed will protect him from the attack of microbes of chickenpox.

Question 6.
What is it that prevents a child to suffer from a disease he/she is vaccinated against? Give one reason. (CBSE 2010)
Answer:

1. Antibodies
2. These antibodies neutralise the action of antigens.

Question 7.
Name the pathogen which causes Typhoid. Name the test that confirms the disease. (CBSE Delhi 2019 (C))
Answer:
Causative pathogen: Salmonella typhi Test: Widal test

Question 8.
Name two types of cells in which the HIV multiplies after gaining entry into the human body. (CBSE 2008)
Answer:

1. T-Lymphocytes
2. White Blood Corpuscles (Macrophages).

Question 9.
Why is a secondary immune response more intense than the primary immune response in human? (CBSE 2014)
Answer:
It is because the human body appears to have more memory of the first encounter.

Question 10.
When does a human body elicit an anamnestic response? (CBSE (Outside Delhi) 2013)
Answer:
The primary immune response is of low intensity; a subsequent encounter with the same pathogen elicits a highly intensified anamnestic or secondary response.

Question 11.
Name the two intermediate hosts which the human liver fluke depends on to complete its life cycle so as to facilitate parasitisation of its primary host. (CBSE Delhi 2014)
Answer:

1. Freshwater Snail
2. Fish

Question 12.
Indiscriminate use of X-rays for diagnoses should be avoided. Give reason. (CBSE (Delhi) 2015)
Answer:
X-rays cause mutation thus may lead to cancer.

Question 13.
Give the scientific name of the source organism from which the first antibiotic was produced. (CBSE Sample paper 2018-19)
Answer:
Penicillium Notatum

Question 14.
Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes. (CBSE 2018)
Answer:
Dengue and chikungunya

Question 15.
How do cytokine barriers provide innate immunity in humans? (CBSE 2018)
Answer:
Cytokine barriers: Cytokines inhibit viral replication. Virus-infected cells secrete proteins called interferons which protect non-infected cells from virus.

Question 16.
Name two recent incidences of wide-spread diseases caused by Aedes mosquitoes. (CBSE Delhi 2008)
Answer:

1. Dengue
2. Chikungunya

Question 17.
How does the human body respond when haemozoin produced by Plasmodium is released in its blood? (CBSE Delhi 2019 (C))
Answer:
As haemozoin is released in the blood, the patient shows symptoms of malaria such as restlessness, sleeplessness, muscular pain and chilliness. In response to chill, the body temperature rises.

Question 18.
How does saliva act in body defence? (CBSE Delhi 2004)
Answer:
Human saliva contains lysozyme, a lytic enzyme, which kills the germs in the food.

Question 19.
Name the type of cells that produce antibodies. (CBSE 2004)
Answer:
Lymphocytes which is a form of leucocytes (white blood cells) produce antibodies.

Question 20.
Why sharing injection needles between two individuals is not recommended? (CBSE Delhi 2013)
Answer:
Sharing of injection needles between two individuals may cause the transmission of AIDS and Hepatitis B.

Question 21.
How do monocytes act as a cellular barrier in humans to provide innate immunity? (CBSE Delhi 2018C)
Answer:
Monocytes kill bacteria by the process of phagocytosis.

Human Health and Disease Important Extra Questions Short Answer Type

Question 1.
Make a list of common infectious diseases.
Answer:
Common infectious diseases: Depending on the pathogen, infectious diseases are as follows:

Question 2.
Given below are pairs of pathogens and diseases caused by them. Which of these is not a matching pair and why?
(i) Virus Common Cold
(ii) Salmonella Typhoid
(iii) Microsporum Filariasis
(iv) Plasmodium Malaria
Answer:

1. (iii) is not matching.
2. Microsporum is a fungus which causes ringworm disease. Filariasis is caused by Wuchereria bancrofti and W. Malayi (roundworm).

Question 3.
Differentiate between antibodies and interferons.
Answer:
Differences between antibodies and interferons:

Question 4.
(i) Name the source plants of heroin drug. How is it obtained from the plants?
Answer:
Papaver somniferum is the source plant of heroin drug. It is obtained by acetylation of morphine, which is extracted from the latex of poppy plant (Papaver somniferum).

(ii) Write the effects of heroin on the human body. (CBSE 2018)
Answer:
Heroin is depressant and slows down body functions.

Question 5.
Mention one application for each of the following:
(i) Passive immunisation
Answer:
(i) Passive Immunisation: When ready¬made antibodies are introduced into the body, it is called passive immunisation. Passive immunisation provides a quick immune response in the body.

(ii) Antihistamine
Answer:
Anti-Histamines: Anti-Histamines are the chemicals which are given against allergic reactions.

(iii) Colostrum (CBSE 2017, 2019)
Answer:
Colostrum: Colostrum is the yellow fluid produced during the initial days of lactation. It is rich in antibodies and is essential to develop resistance in a newborn baby.

Question 6.
What is a vaccine? (CBSE Delhi 2019 C)
Answer:
Vaccine: It is a preparation of dead or altered (weakened) germs of a disease which on entry into the body of a healthy person provide temporary or permanent active/passive immunity by inducing antibody formation. Thus antibody provoking agents are called vaccines. The vaccine provides artificial active immunity.

Question 7.
Name the primary and secondary lymphoid organs. (CBSE Delhi 2019 C)
Or
State the function of primary and secondary lymphoid organs. (CBSE Delhi 2011)
Answer:
Primary lymphoid organs:

• Bone Marrow
• Thymus.

Secondary lymphoid organs:

• Spleen
• Lymph nodes
• Tonsils
• Peyer’s Patches of the small intestine.

Or

Primary lymphoid organs are the sites where immature lymphocytes differentiate and become antigen-sensitive mature lymphocytes.

However, secondary lymphoid organs provide site/location for mature lymphocyte & antigen interaction.

Question 8.
Explain what is meant by metastasis. (CBSE 2009)
Answer:
Metastasis. Small pieces of primary tumour break off and are carried to other body parts by the blood or lymph where these form the secondary tumours. This process is called metastasis. So metastasis is the process of transference of cancerous cells from the site of origin to distant parts of the body. The most frequent sites of metastasis are lymph nodes, lungs, long bones, liver, skin and brain. Metastasis is the most feared property of malignant tumours.

Question 9.
A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions?
Answer:
The condition is called allergy. Mast cells are responsible for such reactions. To avoid such reactions, the following precautions must be taken:

• Use of drugs like antihistamine, adrenalin and steroids quickly reduces the symptoms.
• Avoid contact with substances to which a person is hypersensitive.

Question 10.
What are the symptoms of allergic reactions?
Answer:
Symptoms of allergic reactions.
The following are the symptoms of allergies:

• The person may suffer from high fever
• The mucous membrane of the lower part of the respiratory tract gets affected which leads to cough and asthma.
• Reddening of the skin, the appearance of blisters on the skin.
• Accumulation of tissue fluid below the skin.
• Watering of eyes and inability to breathe.
• Sneezing, running nose, etc.

Question 11.
In the metropolitan cities of India, many children are suffering from allergy asthma. What are the main causes of this problem? Give some symptoms of allergic reactions.
Answer:

1. Allergy is the exaggerated (hypersensitive) response of the immune system to certain antigens present in the environment. These certain antigens are called allergens. Our immune system responds to it by releasing histamines and serotonin from mast cells. Common allergens are mites in the dust, pollens and animal dander (material shed from animals),
2. Lifestyle in metro cities is making them sensitive to allergens.
3. The symptoms are sneezing, watery eyes, running nose and difficulty in breathing.

Question 12.
Drugs and alcohol give short-term ‘high’ and long-term ‘damages’. Discuss.
Answer:
Mostly stimulant drugs (caffeine) and alcohol (depressant) give a feeling of intoxication and euphoria for only a brief period soon after use. However, prolonged use for long-term causes permanent damage to vital body parts like liver, kidneys, lungs, cardiovascular system, etc.

Question 13.
List any two adaptive features evolved in parasites enabling them to live successfully on their hosts. (CBSE Delhi 2008)
Answer:
Adaptations of parasites:

1. Presence of adhesive organs or suckers to cling to the host.
2. Loss of unnecessary sense organs.

Question 14.
What is dengue fever? List two symptoms.
Answer:
Dengue fever: Dengue fever is caused by an RNA containing arbovirus of flavivirus group which also causes yellow fever (not found in India). Thus, the virus which causes dengue fever is a mosquito-borne flavi-ribo virus. The virus of dengue fever is transmitted by the bite of Aedes aegypti (mosquito). The incubation period is 3-8 days.

Symptoms:

• Abrupt onset of high fever.
• Severe frontal headache and pain behind eyes which worsens with eye movement.

Question 15.
Why is the structure of an antibody molecule represented as H₂L₂? Name any two types of antibodies produced in humans. (CBSE Delhi 2018C)
Answer:

• The antibody molecule is made up of four peptide chains-two small chains are called light chains and two longer chains are called heavy chains. Hence it is represented as H₂L₂.
• Ig G, Ig A, Ig M. and Ig E are the antibodies produced in humans.

Question 16.
What are the preventive measures of dengue fever? Is there any vaccine available?
Answer:
Prevention and treatment:

1. Mosquitoes and their eggs should be eliminated. Put wire mesh on doors and windows.
2. No specific treatment is available.
3. Symptomatic care including bed rest, intake of adequate fluid and pain killer medicines are recommended.
4. Do not take Aspirin and Aspirin. Give plenty of liquids to the patient.
5. No vaccine for Dengue fever is available.

Question 17.
Differentiate between the roles of B-lymphocytes and T-lymphocytes in generating immune responses. (CBSE Delhi 2019)
Answer:
Role of B-lymphocytes and T-lymphocytes in the immune response:

1. B-cells (B-lymphocytes) and T-cells (T lymphocytes) comprising the immune system are produced in the bone marrow. T-cells differentiate in the thymus.
2. B-lymphocytes produce antibodies in response to foreign substances (antigens) such as pathogens and pollen. Antibodies are immunoglobulins. They are specific for each antigen. There is more than one antibody for an antigen. Antibodies bind antigens but do not destroy them. This is attacked through other mechanisms. Allergens which are weak antigens cause allergy.
3. T-cells respond to pathogens by producing three types of cells: killer T-cells, helper T-cell and suppressor T-cells. T lymphocytes either help B-lymphocytes to produce antibodies or kill the pathogen directly (killer T-cells). Both B- and T-cells produce memory cells when stimulated. These have long lives and form the basis of acquired immunity.

Question 18.
Why is tobacco smoking associated with rising in blood pressure and emphysema? Explain. (CBSE Outside Delhi 2019)
Answer:
Nicotine, an alkaloid present in tobacco, stimulates the adrenal gland to release adrenaline and nor-adrenaline into blood circulation. Both these hormones increase blood pressure and heart rate.

Smoking causes emphysema. Tobacco smoke damages the air sacs (alveoli) of the lungs. Thus surface area for exchange of gases becomes less and disorder emphysema is caused.

Question 19.
Write the scientific names of the causal organisms of elephantiasis and ringworm in humans. Mention the body parts affected by them. (CBSE DeLhi 2012)
Answer:

Human Health and Disease Important Extra Questions Long Answer Type

Question 1.
(i) How and at what stage does Plasmodium enter a human body?
Answer:
Sporozoite stage enters human body aLong with saLiva of female anopheLes mosquito as ii
bites to suck bLood.

(ii) With the help of a flow chart only shows the stages of asexual reproduction in the life cycle of the parasite in the infected human.
Answer:
Asexual phases of the life history of plasmodium in the body of a human

(iii) Why does the victim show symptoms of high fever? (CBSE Delhi 2008, 2013)
Answer:
When the parasite attacks red blood cells, it leads to its rupture with the release of haemozoin, which is a toxin. As the haemozoin is released into blood, symptoms (high fever) of malaria appear.

Question 2.
What is Immune system? Mention the two types of the immune system. (CBSE Delhi 2011)
Answer:
The system which protects our body from pathogens and other foreign invaders is called the immune system. It is of two types.

1. Innate
2. Acquired

Innate immunity is non-specific and is present by birth. It includes physical barriers, physiological barriers, cellular and cytokinin barriers.

Acquired immunity is pathogen-specific and is obtained with experience. It is of two types- Humoral and cell-mediated

Question 3.
Distinguish between B-cells and T-cells.
Answer:
Differences between B-cells and T-cells:

Question 4.
(i) Name the infective stage of Plasmodium which Anopheles mosquito takes in along with the blood meal from an infected human.
Answer:
Gametocytes

(ii) Why does the infection cause fever in humans?
Answer:
Due to the release of haemozoin toxin in the blood.

(iii) Give a flow chart of the part of the life cycle of this parasite passed in the insect. (CBSE (Delhi) 2008, 2011)
Answer:

Question 5.
(i) Why do the symptoms of malaria not appear immediately after the entry of sporozoites into the human body when bitten by female Anopheles? Explain.
Answer:
As the sporozoites enter the human body along with saliva of female anopheles mosquito, these parasites pass through hepatic schizogony in liver cells and erythrocytic schizogony in RBCs. Haemozoin present in unused cytoplasm of RBC is released, followed by the appearance of malarial symptoms. This period is also called the incubation period.

(ii) Give the scientific name of the malarial parasite that causes malignant malaria in humans. (CBSE 2009)
Answer:
Plasmodium falciparum. Causes malignant malaria in human.

Question 6.
Give the scientific name of the parasite that causes malignant malaria in humans. At what stage does this parasite enter the human body? Trace its life cycle in the human body. (CBSE 2009, 2012)
Answer:

• Plasmodium falciparum
• Sporozoites enter the human body along with saliva of the female anopheles mosquito.
• The life cycle of Plasmodium in the human body

Life Cycle of Plasmodium

Question 7.
A 17-year-old boy is suffering from high fever with profuse sweating and chills. Choose the correct option from the following diseases which explains these symptoms and rule out the rest with adequate reasons.
(i) Typhoid
Answer:
If the boy is suffering from typhoid, then he should have sustained high fever (39° to40°C), weakness, stomach pain, constipation and headache. So it cannot be typhoid.

(ii) Viral Fever
Answer:
If the boy is suffering from viral fever, he will suffer from high fever, joint pain, weakness and headache. So it cannot be a viral fever.

(iii) Malaria (CBSE Sample paper 2018-19)
Answer:
If the boy is suffering from malaria, he should have high fever recurring with profuse sweating every three to four days associated with chills and headache. There is a possibility that he is suffering from malaria because high fever associated with chills is possible with malaria.

Question 8.
Medically it is advised to all young mothers that breastfeeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer. (CBSE 2018)
Answer:
Yes, I do agree with the fact that breastfeeding is the best for newborn babies. Mammary glands start producing milk at the end of pregnancy. The milk produced during the initial few days of lactation is called colostrum which contains several antibodies. It helps in developing resistance for newborn baby against diseases. It helps the baby fight off viruses and bacteria. Thus breast milk is packed with a disease-fighting substance that protects newborn babies from illness. Breast milk also naturally contains many of the vitamins and minerals that a newborn requires. It is easily digested as well. There is no constipation, diarrhoea and upset stomach.

Question 9.
Name a human disease, its causal organism, symptoms (any three) and vector, spread by intake of water and food contaminated by human faecal matter. (CBSE 2017)
Answer:

• Amoebic dysentery [Amoebiasis]
• Causal Organism: Entamoeba historlytica, protozoa.

Symptoms:

• Abdominal pain
• Constipation
• Cramps.

Vector: Housefly.

Question 10.
(i) Why is there a fear amongst the guardians that their adolescent wards may get trapped in drug/alcohol abuse?
Answer:
Reasons for alcohol abuse in adolescents:
(a) Curiosity for adventure, excitement and experiment
(b) Social pressure
(c) To escape from stress, depression and frustration
(d) To overcome hardships of life
(e) Unstable or unsupportive family structure, etc.

(ii) Explain ‘addiction’ and dependence’ in respect of drug/alcohol abuse in youth. (CBSE 2017)
Answer:
Addiction is the psychological attachment to certain effects such as euphoria and a temporary feeling of well-being, associated with drugs and alcohol. The addicted person cannot manage him/herself without drug or alcohol.

Dependence: Dependence is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome on abrupt discontinuation of a regular dose of drug/alcohol.

Question 11.
What is the basic principle of vaccination? How do vaccines prevent microbial infections? Name the organism from which the hepatitis B vaccine is produced.
Or
Principle of vaccination is based on the property of “memory” of the immune system. Taking one suitable example, justify the statement. (CBSE Delhi 2019)
Answer:
Principle of vaccination is based on the property of ‘memory’ of the immune system.

In vaccination, a preparation of antigenic proteins of pathogens or inactivated/live but weakened pathogens is introduced into the body. The antigens generate a primary immune response by producing antibodies along with forming memory B-cells and T-cells. When the vaccinated person is attacked by the same pathogens, the existing memory B-cells and T-cells recognise the antigen and overwhelm the invaders with massive production of lymphocytes and antibodies. The hepatitis-B vaccine is produced from yeast.

Question 12.
Prior to a sports event blood and urine samples of sportspersons are collected for drug tests.
(i) Why is there a need to conduct such tests?
Answer:
Drugs are consumed by sportspersons to enhance their performance. It is necessary to test the blood and urine of sportspersons to analyse the presence of any performance-enhancing drug.

(ii) Name the drugs the authorities usually look for.
Answer:
Narcotic analgesics, anabolic steroids, diuretics.

(iii) Write the generic names of two plants from which these drugs are obtained. (CBSE Delhi 2016)
Answer:
(a) Cocaine is obtained from Erythroxylum coca
(b) Caffeine is obtained from Coffea arabica and narcotics from Papaver somniferum.

Question 13.
Explain the following terms:
(i) Benign tumour
Answer:
A benign tumour (Non-malignant tumour). Such tumours grow slowly but become quite large. It remains restricted to the place of origin and does not spread to other areas of the body. Most tumours are of this type and do not give rise to cancer.

(ii) Cancerous tumour
Answer:
A cancerous tumour (Malignant tumour): It begins as a small tumour growth at first, grows slowly in the starting and more rapidly later on. The tumour ultimately spreads to the neighbouring tissue like the roots of a tree. Later on, cancerous cells separate off from the original site and migrate through the blood to the other sites and they divide and redivide to form a secondary tumour.

(iii) Metastasis.
Answer:
Metastasis: The stage when the secondary tumour is formed and accumulated by repeated division, is called metastasis. This stage is fatal and causes death sooner or later.

Question 14.
Why cannabinoids are banned in sports and games?
Answer:
Cannabinoids are hallucinogenic chemicals obtained from leaves, resins and inflorescence of Hemp plant, Cannabis sativa. They are used by sportspersons to increase their athletic performance. Intake of cannabinoids results in rapid heartbeat decreased vital capacity of the lung. But their misuse is associated with a number of problems in both sportsmen and sportswomen, e.g. these cause masculinisation, increased aggressiveness, mood swings, abnormal menstrual cycles, enlarged clitoris in sportswomen, while their misuse in sportsmen is known to cause acne, mood swings, reduced testicular size, decreased spermatogenesis, enlarged breasts and prostate gland, dysfunctioning of liver and kidney, etc.

Question 15.
The outline structure of a drug is given below:
1. Which group of drugs does this represent?
2. What are the modes of consumption of these drugs?
3. Name the organ of the body which is affected by the consumption of this drug.

Answer:

1. Cannabinoids.
2. By smoking or oral ingestion.
3. Cannabinoids generally affect the cardiovascular system of the body.

Question 16.
What is cannabis? List its main derivatives.
Answer:
Cannabis: It is the most ancient drug and is obtained from hemp plants.
The following three kinds of drugs are obtained from these plants (Derivative of Cannabis indica):

1. Hashish or Charas is obtained from flowering tops of female plants.
2. Bhang is obtained from dry leaves.
3. Ganja is obtained from small leaves and bracts of inflorescence.

Marijuana is another drug obtained from Cannabis sativa. The common reaction of these drugs is relaxation, euphoria, laughing tendency and rise in blood sugar level.

Question 17.
Why is using tobacco in any form injurious to the health? Explain. (CBSE Delhi 2008, Outside Delhi 2011)
Answer:
Tobacco is injurious to health:

1. Nicotine present in tobacco is toxic and addictive. It causes coronary diseases.
2. Heat irritants and carcinogens cause mouth cancer and lung cancer.
3. Tobacco leads to male infertility.
4. in pregnant women, nicotine causes decreased foetal growth and development.
5. Tobacco addiction often leads to gastric and duodenal ulcers.
6. It is an expensive habit causing staining of teeth and fingers and making breath unpleasant.
7. Swelling of respiratory tract leads to chronic bronchitis.

Question 18.
Give reasons for the following:
(a) Antibody-mediated immunity is called humoral immunity.
Answer:
(a) Antibodies produced by plasma cells are present in the blood, the response is called humoral, immunity response. Thus it is termed humoral immunity.

(b) How is a child protected from a disease for which he/she is vaccinated?
Answer:
The principle of vaccination is based on the property of the ‘memory’ of the immune system. As during vaccination, antigens are introduced in the body. In response to antigens, antibodies are produced in the body against them. They neutralise the pathogen during actual infection.

(c) Name the type of cells the AIDS virus enters after getting into the human body. (CBSE Outside Delhi 2019)
Answer:
HIV enters macrophages. Simultaneously HIV enters T helper- Lymphocytes.

Question 19.
(a) Write the scientific names of the source plants from where opioids and cannabinoids are extracted.
Answer:
Opioids are obtained from the opium plant Papaver somniferous. Cannabinoids are extracted from Cannabis sativa.

(b) Write their receptor sites in the human body. How do these drugs affect human beings? (CBSE Outside Delhi 2019)
Answer:
Receptors of opioids are present on the central nervous system and gastrointestinal tract. They are a depressant and slow down the body functions. Receptors of cannabinoids are present in the brain. They affect the cardiovascular system of the body.

Question 20.
Briefly describe the life history of the malarial parasite.
Answer:

1. Malarial parasite (Plasmodium) completes its life cycle in two hosts., i.e. female anopheles mosquito and humans.
2. Sporozoites are the infective stage.
3. The sporozoites enter the human body, reach the liver through blood and multiply within the liver cells.
4. Such liver cells burst and release the parasites (Cryptomerozoites) into the blood.
5. Then they attack RBCs, multiply and cause their rupture.
6. The rupture of RBCs is associated with the release of a toxin called haemozoin, which is responsible for the high recurring fever and the chill/ shivering and causing malaria.
7. Sexual stages (gametocytes) develop in the red blood cells.
8. The parasite then enters the female Anopheles mosquito along with the blood when it bites the infected person.
9. Further development occurs in the stomach wall of the mosquito.
10. The gametes fuse to form a zygote. It takes the worm-like shape called ookinete as it pierces the wall of the stomach.
11. The zygote undergoes further development in the body of the mosquito to form sporozoites.
12. Sporozoites are transported to and stored in the salivary glands of mosquitoes and are transferred to a human body during the bite of the mosquito.
13. Female mosquito sucks human blood because it requires blood proteins for the development of its eggs.

Question 21.
Describe the effects of drug and alcohol abuse.
Answer:
Effects of drug/alcohol abuse:

1. The immediate effects of drugs/ alcohol abuse are manifested as reckless behaviour, vandalism and violence.
2. Excess doses can lead to coma and death due to cerebral haemorrhage, respiratory and heart failure.
3. A combination of drugs or their intake of alcohol leads to death.
4. The most common warning signals of drug/alcohol abuse include:
   (a) Drop in academic performance.
   (b) Lack of interest in personal hygiene.
   (c) Withdrawal and isolation from family and friends.
   (d) Aggressive and rebellious behaviour.
   (e) Lack of interest in hobbies.
   (f) Change in sleeping and eating habits.
   (g) Fluctuations in weight, etc.

Question 22.
Name the type of immunity that is present at the time of birth in humans. Explain any two ways by which it is accomplished. (CBSE 2008)
Answer:
Innate immunity: It is also called inborn or non-specific immunity. It is the first line of defence. It is composed of the following steps:
1. Anatomic barriers: The skin and mucous membranes secrete certain chemicals which dispose of pathogens. Specific cases of this defence are cited below: The oil and sweat secreted by sebaceous and sudoriferous glands contain lactic acid and fatty acids, which make the skin surface acidic (pH 3 to 5). This does not allow the microorganisms to establish.

2. Physiological barrier: Body temperature, pH and various body secretions like saliva prevent the growth of many pathogenic microorganisms. Pyrogens and interferons aid in fighting infections.

Question 23.
On what basis diagnosis of cancer is made?
Answer:
Diagnosis of cancer:

1. Blood and bone marrow tests are done for increased cell counts in case of leukaemia.
2. Histopathological study or biopsy: In a biopsy, a piece of the suspected tissue cut into thin sections is stained and examined under a microscope by a pathologist.
3. Radiography: X-rays are used to detect cancer of the internal organs
4. Computed tomography: It uses X-rays to generate a three-dimensional internal image of an object.
5. Resonance imaging: Non-ionising radiation and strong magnetic field are used in MRI to accurately detect pathological and physiological changes in the living tissue.
6. Monoclonal antibodies: Antibodies against cancer-specific antigens are also used for the detection of certain cancers.

Question 24.
Explain with the help of sketch the action of HIV in the body. (CBSE Delhi 2011)
Or
Name the cells HIV (Human Immuno Deficiency Virus) gains entry into after infecting the human body. Explain the events that occur in these cells. (CBSE Outside Delhi 2016)
Or
Trace the events that occur in the human body to cause immunodeficiency when HIV gains entry into the body. (CBSE 2011, 2014)
Answer:
The action of HIV in the body. After getting into the body of the person, the virus enters into macrophages where RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase. This viral DNA gets incorporated into the host cell’s DNA and directs the infected cells to produce virus particles. The macrophages continue to produce virus and in this way acts as an HIV factory.

Simultaneously, HIV enters into helper (Th) T-lymphocytes (a type or subset of T-lymphocytes about which you have read above, in the immune system), replicates and produces progeny viruses. The progeny viruses released in blood attack other helper T-lymphocytes. This is repeated leading to a progressive decrease in the number of helper T-lymphocytes in the body of the infected person.

During this period, the person suffers from bouts of fever, diarrhoea and weight loss. Due to the decrease in the number of helper T-lymphocytes, the person starts suffering from an infection due to bacteria such as Mycobacterium, viruses, fungi and even parasite Toxoplasma. The patient becomes so much immunologically deficient and unable to fight against such infections.

The action of HIV in the body cells.

Question 25.
(a) If a patient is advised anti-retroviral drug, name the possible infection he/ she is likely to be suffering from. Name the causative organism.
Answer:
The person may be suffering from AIDS. It is caused by HIV (Human Immunodeficiency Virus).

(b) How do vaccines prevent subsequent microbial infection by the same pathogen?
Answer:
Antibody-provoking agents are called a vaccine. They prevent microbial infection by initiating production of antibodies to act against antigens to neutralise the pathogenic agents during later actual infection.
The vaccine also generates memory B-cells and T-cells that actually recognise the pathogen quickly in case of infection at later stages of life.

(c) How does a cancerous cell differ from a normal cell?
Answer:
Differences between the cancerous cell and normal cell:

(d) Many microbial pathogens enter the gut of humans along with food. Name the physiological barrier that protects the body from such pathogens. (CBSE Sample Paper 2020)
Answer:
The acid present in the stomach and saliva kills the microbial pathogens that enter along with food.

Question 26.
Write the source and the effect on the human body of the following drugs:
(i) Morphine
(ii) Cocaine
(iii) Marijuana (CBSE Delhi 2011)
Answer:

Here we are providing Class 12 Biology Important Extra Questions and Answers Chapter 7 Evolution. Important Questions for Class 12 Biology are the best resource for students which helps in Class 12 board exams.

Class 12 Biology Chapter 7 Important Extra Questions Evolution

Evolution Important Extra Questions Very Short Answer Type

Question 1.
When did life appear on earth?
Answer:
Life originated sometimes 3600 million years ago.

Question 2.
Arrange the following substances in a proper sequence with regard to the formation of chemical constituents at the time of origin of life: Sugar, methane, nucleic acid, and amino acid.
Answer:
Methane-sugar-amino acid-nucleic acid.

Question 3.
Mention the type of nutrition in the cells that originated first during the origin of life.
Answer:
Heterotrophic nutrition.

Question 4.
Which group of organisms were responsible for the appearance of free oxygen in the atmosphere of the primitive earth?
Answer:
Oxygenic photosynthetic bacteria resembling the present-day blue-green algae or cyanobacteria.

Question 5.
Give the three key factors of the modern concept of evolution.
Answer:
Genetic variations, natural selection, and isolation.

Question 6.
What is the ultimate source of organic variation?
Answer:
Genetic variations due to mutations, recombination, and polyploidy.

Question 7.
What is proved by the phenomenon of resistance to DDT in mosquitoes?
Answer:
Natural selection.

Question 8.
Attempt giving a clear definition of the term species.
Answer:
The members of a species that resemble structurally and functionally are able to interbreed freely and produce fertile offspring of their own kind and share a common gene pool.

Question 9.
What causes speciation according to Hugo de Vries? (CBSE Delhi 2008)
Answer:
Mutations.

Question 10.
How did Charles Darwin express ‘fitness’? (CBSE Delhi 2019)
Answer:
Charles Darwin expressed ‘fitness’ as reproductive fitness. The adaptive ability of an organism is inherited. The best-adapted species increase their population by reproduction.

Question 11.
Name the scientist who disproved spontaneous generation theory. (CBSE 2010)
Answer:
Louis Pasteur.

Question 12.
Mention the type of evolution that has brought the similarity as seen in potato tuber and sweet potato. (CBSE 2009)
Answer:
Convergent evolution.

Question 13.
Briefly explain the theory of biogenesis. (CBSE 2012)
Answer:
According to this theory, life originated from pre-existing life forms.

Question 14.
Write the probable difference in eating habits of Homo habilis and Homo erectus. (CBSE Outside Delhi 2016)
Answer:
Homo habilis was carnivorous. Homo erectus was omnivorous.

Question 15.
How do we compute the age of a living tree?
Answer:
By determining the number of annual rings in the lower part of its trunk, called dendrochronology.

Evolution Important Extra Questions Short Answer Type

Question 1.
What are we referring to when we say “simpler organisms” or “complex organisms”?
Answer:
By “simpler organisms”, we mean those organisms which are primitive with simple organization and simple metabolic pathways, structural and functional. “By complex organisms”, we mean those organisms which are more evolved, have a complex level of structural and functional organization and complex metabolic pathways.

Question 2.
Louis Pasteur’s experiments, if you recall, proved that life can arise from only pre-existing life. Can we correct this as life evolves from pre-existent life or otherwise we will never answer the question as to how the first forms of life arose? Comment.
Or
State the two principal outcomes of the experiments conducted by Louis Pasteur on the origin of life. (CBSE Delhi 2019)
Answer:

1. Dismissed theory of spontaneous generation of life.
2. Yes, we can correct this as life evolves from pre-existent life.

The first life that appeared on the earth was apparently the result of chemical evolution, i.e. the life originated from inorganic molecules that formed organic molecules, further forming complex compounds.

This finally resulted in simple cells and then simple organisms, where-in complexity developed with time. However, once life originated, abiogenesis could not follow, and hence, life evolved further only through biogenesis, i.e. pre-existent life gave rise to new life.

Question 3.
What is convergent evolution?
Answer:
Convergent evolution. When adaptation for survival in similar habitats is similar, then this form of evolution is called convergent evolution or parallel evolution. Examples: Some of the marsupials of Australia resemble placental mammals that live in similar habitats to other continents. Australia separated about 50 million years ago. Marsupials arrived here before the separation from Antarctica and evolved in isolation earlier than placental mammals.

Question 4.
What are analogous organs? Give examples. (CBSE 2016)
Answer:
Analogous organs: The organs which are similar in appearance and perform the same function but differ in their fundamental structure and origin are called analogous organs.

Examples:

1. Wings of birds and insects.
2. Leaves of a plant and cladodes of Ruscus are also analogous organs.

Question 5.
What are vestigial organs? Give examples.
Answer:
Vestigial organs are non-functional organs in an organism that are functional in related animals and were functional in the ancestors. There are 90 vestigial organs in the human body and mainly include coccyx (tail bone); nictitating membrane (3rd eyelid); caecum and vermiform appendix; canines; wisdom teeth; body hair; auricular muscles; mammary glands in male; etc. Vestigial organs are also present in some other animals, e.g. splint bones in the horse; hind-limbs and pelvic girdles in python; wings and feathers in flightless birds; etc.

Question 6.
Write the significance of vestigial organs.
Answer:
Significance of vestigial organs. Organic evolution states that these vestigial organs were functional in the ancestral forms but have become non-functional due to changes in their function and may finally disappear. So the presence of vestigial organs is convincing evidence of organic evolution and is supported by Lamarck’s theory of use and disuse of organs.

Question 7.
What are fossils?
Answer:
Fossils. The remnants or impressions of living organisms from the remote past may be regarded as fossils. Fossil formation involves the burial of dead organisms. Layer after layer of sediment is laid above the dead organisms. It is only on this account that the oldest fossils are found in the deepest layers of the earth’s surface, while the fossils of recent origin are found in the upper layers. Thus by examining the various layers of the earth from the deepest to the most superficial strata for the fossil record, the story of life in the correct historical sequence can be known.

Question 8.
Why is Archaeopteryx called a connecting link between reptiles and birds?
Or
What is the significance of Archaeopteryx in the study of organic evolution?
Answer:
Importance of Archaeopteryx as connecting link. The fossil forms representing the characters of the two distinct groups of living animals are known as missing links. The best example of connecting link is afforded by a fossil bird, Archaeopteryx. It was the size of a crow. Archaeopteryx is decidedly a bird as it has feathers and a beak. But like reptiles, it has a long tail, jaws full of teeth, claws on forefingers, and keelless sternum. Thus it represents a stage between reptiles and birds through Archaeopteryx-like intermediate form.

Question 9.
What is adaptive radiation? (CBSE Delhi 2016)
Or
Describe one example of adaptive radiations. (CBSE Delhi 2008 S, 2010, 2015, 2019 C, Outside Delhi 2014)
Or
How did Darwin explain the existence of different varieties of finches on the Galapagos Islands? (CBSE Outside Delhi 2009, Delhi 2010)
Answer:
Adaptive radiation: It is the process of divergent evolution in which members of the same ancestral species of a large taxonomic group are evolved along different lines in different habitats of the same geographical area.

Example: Darwin’s Finches are an example of adaptive radiation.

There were many varieties of small blackbirds in the Galapagos Islands. Darwin reasoned that after originating from a common seed-eating stock, the finches must have radiated to different geographical locations in the same island and undergone adaptive changes, especially in the type of beak. Living in isolation for long, the new kinds of finches emerged that could survive and function in the new habitats.

Question 10.
List the main points of Lamarck’s theory.
Answer:
Lamarck’s theory of evolution:

1. Effect of environment.
2. Effect of use and disuse of organs.
3. The inheritance of acquired characters.
4. The origin of new species.

Question 11.
Give the main points of Darwin’s Theory of Evolution. (CBSE Outside Delhi 2019)
Answer:
Darwin’s Theory of Evolution may be summed up as follows:

1. Rapid multiplication/overproduction
2. Struggle for existence.
3. Variations.
4. Natural selection or survival of the fittest.
5. Inheritance of useful variations.
6. Origin of new species.

Alfred Wallace also arrived at the same conclusion as that of Charles Darwin.

Question 12.
Name the following:
(i) Who conceived the idea of the chemosynthetic hypothesis of the origin of life on earth?
Answer:
Oparin and Haldane

(ii) Who proved that spontaneous generation does not occur?
Answer:
Francesco Redi, Spallanzani, and Louis Pasteur

(iii) Who experimentally proved that life develops from pre-existing life only?
Answer:
Pasteur

(iv) Who gave the theory of organic evolution? (CBSE 2010)
Answer:
Charles Darwin.

Question 13.
Describe De Vries Mutation theory. (CBSE Delhi 2011)
Answer:
De Vries Mutation Theory: Hugo de Vries (1848-1935) was a Dutch Botanist. He performed experiments on the Evening Primrose (Oenothera Lamarckian). According to this theory, new species arise suddenly showing abrupt deviations in characters from the normal forms. These sudden deviations are because of mutation. Thus evolution is not a slow and gradual process but a sudden discontinuous and jerky process.

Question 14.
State a reason for the increased population of dark-colored moths coinciding with the loss of lichens (on tree barks/during industrialization period in England). (CBSE Delhi 2015)
Answer:
Soot evolved from coal-based industries deposited on tree bark of oak plants and darkened it, which is called industrial melanism. Dark-colored moth (Bistort Carbonaria) had more chances of survival so increased in number. Before industrialization, white-colored thick lichens grew on tree barks. In that background, white-winged moths survived but dark moths were picked out by predators.

But post-industrialization, lichens disappeared and tree trunks became dark due to the deposition of soot evolved from coal-based industries. Now white moths became easy prey compared to dark ones. Thus dark moths survived and increased their population.

Question 15.
Select the homologous structures from the combinations given below:
1. Fore-limbs of whale and bats
2. A tuber of potato and sweet potato
3. Eyes of Octopus and Mammals
4. Thorn of Bougainvillea and Tendril of Cucurbita. (CBSE Outside Delhi 2015)
Answer:

1. Because both of them share similarities in the pattern of bones of forelimbs, though they perform different functions like forelimb of whale helps in swimming, while that in bats it helps in flying.
2. Because both are modified stem branches (axillary buds) but are differently modified to perform different functions, e.g. thorns for protection from grazing animals and tendrils for climbing.

Question 16.
According to Hardy-Weinberg’s principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population? (CBSE 2009)
Answer:
Disturbances in genetic equilibrium or Hardy-Weinberg equilibrium lead to a change of frequency of alleles in a population which results in evolution.

Question 17.
With the help of two suitable examples, explain the effect of anthropogenic actions on organic evolution. (CBSE Delhi 2013)
Answer:
Effect of anthropogenic actions on organic evolution:

1. Creation of breeds by artificial or selective breeding programs.
2. (a) Excess use of herbicides, pesticides, etc. has resulted in the selection of resistant varieties in a much lesser time.
   (b) Selection of drug-resistant microbes.
3. Survival of dark-winged (melanized) moths after industrialization in England.

Question 18.
Can we call human evolution adaptive radiation?
Answer:
No, we cannot call human evolution adaptive radiation. It is the case of descent with modification in which more advanced types are evolved from the simple forms. In the case of human evolution, there appears to be parallel evolution of the human brain and language.

Question 19.
State two postulates of Oparin and Haldane with reference to the origin of life. (CBSE Delhi 2017)
Answer:
Oparin and Haldane proposed that:

1. life originated from pre-existing non¬living organic molecules.
2. the diverse organic molecules were formed from inorganic constituents by chemical evolution.

Question 20.
Write the names of the following:
(i) A 15 mya primate that was ape-like
Answer:
Dryopithecus

(ii) A 2 mya primate that lives in East African grasslands (CBSE Delhi 2018)
Answer:
Australopithecus

Question 21.
(i) Write two differences between Homo erectus and Homo habilis.
Answer:
Differences between Homo erectus and Homo habilis:

(ii) Rearrange the following from early to late geologic periods: Carboniferous, Silurian, Jurassic. (CBSE Delhi 2019)
Answer:
Silurian, Carboniferous, Jurassic.

Evolution Important Extra Questions Long Answer Type

Question 1.
What are homologous organs? Give similar or different functions are catted examples. (CBSE 2016) homologous organs.
Answer:
Homologous organs: Organs that have a common origin, embryonic development, and the same fundamental structure but perform similar or different functions are catted homologous organs.

Examples of homologous organs:
1. The wings of bird and bat, flipper embryonic development, and same (fin) of whale and human forearm are fundamental structures but perform differently in forms because these have to perform different functions. Studies of the bones forming the skeleton of these organs would reveaL similarity in construction. In fact, these are the forms of forearms that have originated from pentadactyl forms and due to the different functions they are performing, they transformed into different forms.

2. In plants, the homologous organs may be a thorn of Bougainvillea or a tendriL of Cucurbita both arising in axillary position. Both have different forms depending on their function to perform.

Question 2.
How has the study of fossils helped in convincing scientists that organisms have come into existence through evolution? (CBSE Outside Delhi 2019)
Answer:
Fossils are important for man because of many reasons:

1. They provide evidence of past life.
2. They furnish direct and most convincing proofs in favor of organic evolution.
3. They afford some information of ancient environment and climate.
4. The most primitive forms of life are in the oldest rocks.
5. Ancient forms were simpler than those found today.
6. None of the plants and animals of the past were exactly similar to those found today.
7. A complete fossil record has been found in the evolution of horses.

Question 3.
Explain antibiotic resistance observed in light of Darwinian selection theory.
Answer:
Antibiotics were considered to be very effective against diseases caused by bacteria. But within two or three years of the introduction of antibiotics, new antibiotic-resistant bacteria appeared in the population. Sometimes a bacterial population happens to contain one or a few bacteria having mutations that make them resistant to the antibiotic. Such resistant bacteria survive and multiply quickly as the competing bacteria have died.

Soon the resistance-providing genes become widespread and the entire bacterial population becomes resistant. Some hospitals harbor antibiotic-resistant bacteria due to the extensive use of antibiotics.

Question 4.
How does natural selection operate according to Darwin’s theory of natural selection? (CBSE Delhi 2016, 2019 C)
Answer:
Natural selection operates in the following ways according to Darwin’s theory:

1. All plants and animals reproduce in a geometrical pattern. The number of organisms produced is much more than that can survive due to limited space and food.
2. Due to the same basic requirement, competition between organisms takes place and those who are better adapted to the environment survive while the rest die.
3. The individuals having useful variation overpower those without such variations. These variations are transmitted to future generations.

Question 5.
Distinguish between microevolution and macroevolution. Narrate the significance of population genetics in evolution.
Answer:
Evolution on the grand scale of geological time is called macroevolution, while evolution at the genetic level is microevolution. Microevolution is actually operative at genetic level change within a population. Significance of population genetics.

The gene frequency of a population is called population genetics. Evolution occurs within populations as the relative frequencies of different variations of DNA change over time. If genes change, then enzymes automatically change and represent two different forms of individuals and definitely result in evolution.

Question 6.
Compare and contrast the theories of evolution proposed by Darwin and Hugo De Vries. (CBSE Sample Paper 2018-19, Outside Delhi 2019)
Answer:

Question 7.
How would the gene flow or genetic drift affect the population in which either of them happens to take place? (CBSE Delhi 2019)
Answer:
Gene flow is the transfer of genetic variations from one population to another. As a result of gene flow, the gene frequencies change in the original as well as in the new population. New genes or alleles are added to the new population and lost from the old population. If such a change in genes/alleles happens by chance, it is called genetic drift. In this case, the allelic frequency of the population will be affected. Such changes in allelic or gene frequencies lead to evolution, speciation, or founder effect.

Question 8.
Using the Internet and discussing with your teacher, trace the evolutionary stages of any one animal, say, a horse.
Answer:
The major evolutionary trend of horses:

1. General increase (with occasional decrease) in size.
2. The progressive loss of toes.
3. Lengthening of toes that are retained.
4. Lengthening of limbs in general.
5. Enlargement of the brain (especially cerebral hemisphere).
6. Increase in height.
7. Increase in the complexity of molar teeth and an enlargement of the last two and, eventually, the last three premolars until they came to resemble molars.

Question 9.
Summarise Milter’s simulation experiment for organic synthesis. Comment on its efficacy. (CBSE Delhi 2012)
Answer:
Miller’s experiment. Milter (1953) made the first successful simulation experiment to assess the validity of the claim for the origin of organic molecules. Miller sealed in a spark chamber a mixture of water, methane, ammonia, and hydrogen gas. He made arrangements for boiling water.

The trap in turn was connected with the flask for boiling water. After 18 days, a significant amount of simple major organic compounds, such as amino acids, such as glycine, alanine, and aspartic acid, and peptide chains, began to appear. Simple sugars, urea, and short-chain fatty acids were also formed. In the atmosphere, this spark is provided by U.V. light or other energy sources.

Stanley Miller’s Experiment in the artificial production of organic compounds.

Question 10.
With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations? (CBSE Delhi 2018)
Or
Explain Hardy-Weinberg’s principle. (CBSE Delhi 2019 C)
Answer:
In a given population, one can find out the frequency of occurrence of alleles of a gene or a locus. This frequency is supposed to remain fixed and even remain the same through generations. Hardy-Weinberg’s principle stated it using algebraic equations. According to this principle, allele frequencies in a population are stable and are constant from generation to generation. The gene pool (total genes and their alleles in a population) remains constant. This is called genetic equilibrium.

Sum total of all the allelic frequencies is 1. Individual frequencies, for example, can be named as p, q, etc. In a diploid, p and q represent the frequency of allele A and allele a, respectively. The frequency of AA individuals in a population is simply p². This is simply stated in another way, i.e. the probability that an allele A with a frequency of p appears on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e. p². Similarly of aa is q², of Aa 2pq. Hence, p² + 2pq + q² = 1. This is a binomial expansion of (p + q)². When the frequency measured is different from expected values, the difference (direction) indicates the extent of evolutionary change.

Disturbance in genetic equilibrium, or Hardy-Weinberg equilibrium, i.e. change of frequency of alleles in a population, would then be interpreted as resulting in evolution.

Question 11.
(i) Differentiate between analogous and homologous structures.
Answer:

(ii) Select and write analogous structures from the list given below:
(o) Wings of butterfly and birds
(b) Vertebrate hearts
(c) Tendrils of Cucurbita and thorns of Bougainvillea
(d) Tubers of sweet potato and potato (CBSE Delhi 2018)
Answer:
(a) Wings of butterflies and birds.
(b) Tubers of sweet potato and potato.

Question 12.
Write thecharacteristicsofRamapithecus, Dryopithecus, and Neanderthal man. (CBSE Delhi 2017)
Answer:
Characteristics of Ramapithecus:

• They evolved around 15 mya.
• They were more man-like, walked more erect, and had teeth like modern men.

Characteristics of Dryopithecus:

• They evolved around 5 mya.
• They were ape-like, having hairy arms and legs of the same length, large brains. They used to eat soft fruits and leaves and walked like gorillas and chimpanzees.

Characteristics of Neanderthal Man:

• They evolved around 1,00,000-40,000 years ago.
• Fossil found in east and central Asia had brain size 1400 cc. They used hides to protect their body. They buried their dead.

Question 13.
How does the process of natural selection affect Hardy-Weinberg equilibrium? List the other four factors that disturb the equilibrium. (CBSE Outside Delhi 2013)
Or
Write Hardy-Weinberg principle.
Or
How can Hardy-Weinberg equilibrium be affected? Explain giving three reasons. (CBSE Delhi 2018C)
Answer:
Hardy-Weinberg Principle states that the sum of allelic frequencies in a population is stable and is constant from generation to generation, i.e. the gene pool (total genes and their alleles) in a population remains constant. This is called genetic equilibrium. The sum total of all the allelic frequencies is

Hardy-Weinberg’s Equilibrium p²+ q² + 2pq =

Five factors that influence these values are:
The five factors which affect Hardy- Weinberg’s equilibrium is as follows:

1. Gene migration: When some individuals of a population migrate to other populations or when certain individuals come into a population (i.e. migration and immigration), some genes are lost in the first case and added in the second.
2. Genetic drift: Random changes in the allele frequencies of a population occurring only by chance constitute genetic drift. The change in allele frequency may become so drastically different that they form a new species.
3. Mutations: The mutations are random and directionless. They are sufficient to create a considerable genetic variation for speciation to occur.
4. Recombination: New combinations of genes occur due to crossing over in meiosis during gametic formation.
5. Natural selection: It is the most critical evolutionary process that leads to changes in allele frequencies
   and favors adaptation as a product of evolution.

Question 14.
Define genetic drift. How does it produce the founder effect and genetic bottleneck?
Or
How does the original drifted population become a founder? (CBSE 2019 C)
Answer:
Genetic drift: Random change occurring in the allele frequency by chance alone is called genetic drift. It is due to habitat fragmentation, isolation, natural calamities, or any epidemics.

Founder effect: When a section of the population gets separated from the original population, then this section becomes genetically different from the original population due to a change in alleles frequency. The original population becomes the founder of the new population. This is called the founder effect which is the result of genetic drift, i.e. by chance. Genetic bottleneck.

When in a season one population died leaving few individuals of the population which become the founder of the new population, then it will produce only a few genes by selection only, i.e. by chance new population is emerged and it is similar to a bottle in which only certain population is allowed to flow as in the neck of a bottle.

Bottleneck effect

Question 15.
How does Darwin’s theory of natural selection explain new forms of life on earth? (CBSE 2008, 2016)
Answer:
Darwin’s Theory of evolution may be summed up as follows:
Darwin’s Theory of natural selection. Charles Darwin (1809 – 1882), a naturalist, proposed a theory to explain the process of evolution. His theory was published in his famous book “Origin of Species” published in 1858.

His theory of natural selection is termed Darwinism:

• Rapid multiplication
• Struggle for existence
• Variations
• Natural selection or survival of the fittest
• Inheritance of useful variations
• Origin of new species.

Evidence in favor of Darwin’s theory: Darwin’s theory is supported by natural selection, phenomena of mimicry and protective coloration, and the correlation between nectaries of flowers and proboscis of pollinating insects.

Darwin’s theory fails to explain the perpetuation of vestigial organs and over-specialization of organs.
Darwin’s theory has since been modified in the light of progress in genetics.

Question 16.
Describe the present-day concept of evolution.
Answer:
1. Modern concept of evolution: The modern concept of evolution is a modified form of Darwin’s theory of natural selection and is often called Neo-Darwinism. It comprises genetic variation, natural selection, and isolation.
(a) Mutations: These have been recognized as the ultimate source of biological changes and hence the raw material of evolution. The mutation in chromosomes may be due to changes in structure, number, or gene.

(b) Gene Recombination takes place during crossing over in meiosis. New combinations of genes produce new phenotypes.

(c) Hybridisation is the intermingling of the genes of the members of closely related species.

(d) Genetic drift is the elimination of the genes of some original characteristics of a species by extreme reduction due to different reasons.

In Monoparental reproduction, only chromosomal and gene mutation are sources of genetic variation,

2. Natural Selection: If differential reproduction (i.e. some individuals produce abundant offspring, some only a few, and some organisms none) continues for many generations, genes of the individuals which produce more offspring will become predominant in the gene pool of the population. Thus natural selection occurs through differential reproduction in successive generations. The migration of individuals from one to another population is an accessory factor for speciation (origin of new species).

3. Isolation: By selecting the most suitable genotypes, natural selection guides different populations into different adaptive channels. The reproductive isolation between the populations due to certain physical barriers or others leads to the formation of new species. Isolation plays a significant role in evolution.

Question 17.
(i) Name the primates that lived about 15 million years ago. List their characteristic features.
Answer:
Primates Dryopithecus and Ramapithecus lived about 15 mya.

Features:
(a) Hairy and walked like gorillas and chimpanzees. Height up to 4 feet but walked upright.

(ii) (a) Where was the first man-like animal found?
Answer:
Ethiopia and Tanzania

(b) Write the order in which Neanderthals, Homo habilis, and Homo erectus appeared on the earth. State the brain capacity of each one of them.
Answer:

• Homo habilis – 700 cc
• Homo erectus – 900 cc
• Neanderthals man – 1300-1600 cc

(c) When did modern Homo sapiens appear on this planet ? (CBSE Delhi 2011)
Answer:
Homo sapiens appeared about 34000 years ago.

Very Importance Figures:

(A) Foretimbs of vertebrates as homologous organs.
(B) AnaLogous organs. Wings of insect and bird.

Darwin finches

Adaptive radiations of Australian marsupials

Kinds of selection