Biology NCERT Class 11 Solutions

NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption

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NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption.

Question 1.
Choose the correct answer among the following:
(a) Gastric juice contains
(i) pepsin, lipase, and rennin
(ii) trypsin, lipase, and rennin
(iii) trypsin, pepsin, and lipase
(iv) trypsin, pepsin, and rennin
(b) Succuss enterics is the name given to:
(i) a junction between the ileum and large intestine
(ii) intestinal juice
(iii) swelling in the gut
Solution:
(a) (i) Pepsin, lipase, and rennin
(b) (ii) Intestinal juice

Question 2.
Match column I with column II
Column I                                         Column II
(a) Bilirubin and biliverdin           (i) Parotid
(b) Hydrolysis of starch                (ii) Bile
(c) Digestion of fat                        (iii) Lipases
(d) Salivary gland                            (iv) Amylases
Solution:
Column I                                 Column II
(a) Bilirubin and biliverdin     (ii) Bile
(b) Hydrolysis of starch          (iv) Amylases
(c) Digestion of fat                 (iii) Lipases
(d) Salivary gland                   (i) Parotid

Question 3.
Answer briefly:
(a) Why are villi present in the intestine and not in the stomach?
(b) How does pepsinogen change into its active form?
(c) What are the basic layers of the wall of the alimentary canal?
(d) How does bile help in the digestion of fats
Solution:
(a) Villi increases surface area for absorption and maximum absorption takes place in the intestine.
(b) Coming in contact with hydrochloric acid in stomach proenzyme pepsinogen convert to its active form pepsin, the proteolytic enzyme of the stomach.
(c) There are four basic layers in the wall of alimentary canal i.e. serosa, muscularis, submucosa and mucosa.
(d) Bile helps in the emulsification of fats i.e. breakdown the fats into very small micelles. Bile also activates lipases.

Question 4.
State the role of pancreatic juice in the digestion of proteins.
Solution:
Pancreatic juice contains inactive enzymes like trypsinogen, chymotrypsinogen, procarboxypeptidases. Trypsinogen is activated by an enzyme enterokinase secreted by the intestinal mucosa into active trypsin which in turn activates other enzymes in the pancreatic juice. Proteins, proteases, and peptones in the chyme are digested by the proteolytic enzymes of pancreatic juice.

Question 5.
Describe the process of digestion of protein in the stomach.
Solution:
The mucosa of the stomach has gastric glands that secrete mucus, proenzyme pepsinogen, HCl, and intrinsic factor. Intrinsic factor is essential for the absorption of vitamin B12. The food mixes thoroughly with acidic gastric juice of the stomach and called the chyme. The proenzyme pepsinogen on exposure to HC1 gets converted to active enzyme pepsin. Pepsin converts proteins into proteases and peptones. Renin found in the gastric juice of infants also helps in the digestion of milk protein.

Question 6.
Give the dental formula of human beings.
Solution:
Dental formula of human beings is 2123/2123.

Question 7.
Bile juice contains no digestive enzymes, yet it is important for digestion. Why?
Solution:
The bile juice released into the duodenum contains bile pigments (bilirubin and biliverdin), bile salts, cholesterol, and phospholipids but no enzymes. Bile helps in the emulsification of fats i.e. break down the fats into very small micelles. Bile also activates lipases. Bile is alkaline (pH about 8). Bile pigments are excreted in faeces. In absence of HCl, the above-mentioned functions will not occur and digestion of food will be affected.

HCl of the gastric juice may cause gastric or duodenal ulcers and damage, the underlying blood vessels. These cause hemorrhage inside. Strong HCl is produced in stress conditions also. Parental or oxyntic cells which secrete HCl and intrinsic factor (Intrinsic factor is essential for the absorption of vitamin B2)

Question 8.
Describe the digestive role of chymotrypsin. Which two other digestive enzymes of the same category are secreted by their source gland?
Solution:
Chymotrypsin changes proteins into peptides and also milk protein, changes into paracasein (curd). The pancreatic juice contains inactive enzymes, trypsinogen, chymotrypsinogen, procarboxypeptidases, amylases, lipases and nucleases. Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into active trypsin, which in turn activates the other enzymes in the pancreatic juice.

Trypsin changes proteases and peptones into peptides and amino acids. Procarboxypetidases change peptides into small peptides and amino acids. Amylases change starch into maltose. Lipases change emulsified fat into fatty acids and glycerol. Nucleases changes nucleotides into phosphate, sugar and nitrogen bases.

Question 9.
How are polysaccharides and disaccharides digested?
Solution:
(a) Digestion of carbohydrates starts in the mouth cavity with the help of enzymes salivary amylase.
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 1

Question 10.
What would happen if HCl were not secreted in the stomach?
Solution:
HCl is secreted by oxyntic cells in the stomach wall and performs five functions:

  1. Kill bacteria and germs
  2. Loosens fibrous material of food.
  3. Activates proenzyme pepsinogen to its active form pepsin.
  4. Gives an acidic medium for action by pepsin.
  5. Curdles milk.  Pepsin changes proteins into proteases and peptones.

Question 11.
How does butter in your food get digested and absorbed in the body?
Solution:
Butter is a kind of fat. Fats are broken down by lipases with the help of bile into di- and monoglycerides:
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 2

Question 12.
Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal.
Solution:
(a) In the stomach the proenzyme pepsinogen, on exposure to HC1 converted into active pepsin that converts proteins into proteases and peptones.
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 3
(b) Proteins, proteases and peptides in the chyme reaching the intestine are acted upon by proteolytic enzymes of pancreatic juice and converted to dipeptides.
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 4
(c) The enzymes in succuss entericus act on the end product to form amino acids.
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 5

Question 13.
Explain the terms thecodont and diphyodont.
Solution:
Thecodont: In human beings, teeth are
embedded in pits, the sockets of the jawbones. Such teeth are called the thecodont.
Diphyodont: The teeth that appear in two sets, i. e., milk-teeth which are later replaced by permanent teeth. This condition is called diphyodont.

Question 14.
Name different types of teeth and their number in an adult human.
Solution:
Incisors – 8
Canines – 4
Premolars – 8
Molars – 12

Question 15.
What are the functions of the liver?
Solution:

  • Secretion of bile
  • Synthesis of blood clotting factors
  • Regulating carbohydrate, protein, and lipid metabolism.
  • Synthesis of amino acids, plasma proteins, cholesterol, etc.
  • Stores glycogen, fats, fat-soluble vitamins, etc.
  • Detoxifies toxic substances
  • Elimination of foreign bodies
  • Produces heat through metabolism
  • Produces anticoagulant heparin
  • Synthesis of urea from ammonia.

VERY SHORT ANSWER QUESTIONS

Question 1.
What is digestion?
Solution:
Digestion is the mechanical, enzymatic, and biochemical transformation of complex (polymers) food molecules into simple molecules (monomers) which are suitable for absorption.

Question 2.
Which is the food constituent that bile helps to digest and absorb?
Solution:
Fats.
Question 3.
What is the function of enterokinase?
Solution:
Enterokinase of intestinal juice activates the inactive trypsinogen into trypsin which digests protein in the duodenum.

Question 4.
Which is a nondigestive activating enzyme?
Solution:
Enterokinase.

Question 5.
Mention the role of bile salt in the digestion of fats.
Solution:
Bile salts emulsify fat particles and reduce the surface tension of fat droplets to increase the action of enzyme lipase.5. Bile salts emulsify fat particles and reduce the surface tension of fat droplets to increase the action of the enzyme lipase.

Question 6.
What is the role of HCl in protein digestion?
Solution:
Role of HCl:

  • It activates pepsinogen into active pepsin.
  • It provides a suitable acidic medium for the action of proteases in the stomach.

Question 7.
Name the hardest substance in the body.
Solution:
Enamel.

Question 8.
What is a cystic duct?
Solution:
Duct of gall bladder.

Question 9.
Mention two functions of mucus.
Solution:
Role of mucus:
(a) Acts as a lubricant.
(b) Protects the epithelial surface of the stomach from the corrosive effect of hydrochloric acid and digestion by pepsin.

Question 10.
Name the secretion of goblet cells in the human stomach.
Solution:
Goblet cells secrete mucus.

Question 11.
Where the taste buds located?
Solution:
Taste buds are located in the papillae on the upper surface of the tongue.

Question 12.
What is the ‘Pancreatic Enzyme’ which acts on starch? (Oct. 83, 01)
Solution:
The pancreatic amylase(Amylopsin).

Question 13.
What is the function of epiglottis?
Solution:
Epiglottis prevents the entry of food into the trachea, by closing its opening called the glottis.

Question 14.
Which part of the stomach continues into the duodenum?
Solution:
Pyloric region

Question 15.
What name is given to the major lymph vessel present in the intestinal villi?
Solution:
Lacteal

Question 16.
Where are the crypts of Leiberkuhn located?
Solution:
Crypts of Lieberkuhn are located in between the bases of the villi in the intestine.

Question 17.
Name the structural and functional unit of the liver.
Solution:
Hepatic lobules

Question 18.
Mention the secretion of Goblet cells.
Solution:
Mucin (Mucus) (April 93)

Question 19.
What is a bolus?
Solution:
When the thoroughly masticated food mixes with the saliva, the food particles become adhered together by the mucus known as bolus.

Question 20.
What is chyme?
Solution:
After partial digestion in the stomach, the form of food is called chyme.

Question 21.
What is the meaning of deglutition?
Solution:
The act of swallowing is called deglutition.

Question 22.
Name the enzyme involved in the breakdown of nucleotides into sugars and bases.
Solution:
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 6

SHORT ANSWER QUESTIONS

Question 1.
Mention the juice secreted by the liver. State its function indigestion. (April 1985)
Solution:
The liver cells secrete a juice called the ‘Bile juice’. ‘Bile salts’ are one of the components of Bile juice. These are very important in digesting lipids or fats. Specifically ‘Bile salts’ aid in digestion than bringing about digestion of fat by emulsifying fats and making the fat molecules accessible to the action of the pancreatic Lipase (or Lipid digesting) enzyme. Apart from this the bile juice also creates an alkaline medium in the intestine so that food particles can be actively acted upon by the pancreatic enzymes.

Question 2.
Name the organs which secret carboxypeptidases and aminopeptidases respectively. Give the function performed by these enzymes
Solution:
Carboxypeptidases are secreted by the pancreas. Aminopeptidases are secreted by the intestine. Both the enzymes act on the terminal peptide bonds and release the terminal/last amino acids of the peptide chain.

Question 3.
State the Role of HCI indigestion. (Oct. 88, April 93, 98)
Solution:
The main role of HCI is to convert the inactive enzyme pepsinogen to pepsin which in turn helps in the digestion of proteins. It also creates an acidic medium in the stomach for the activity of pepsin.

Question 4.
What is succus entericus? Mention any two carbohydrate digesting enzymes present in it? (April 2006)
Solution:
Succus entericus intestinal juice is the secretion of intestinal glands in the ileum of the small intestine. The carbohydrate digesting enzymes are maltase, lactase, and sucrase.

Question 5.
Differentiate between micelles and chylomicrons.
Solution:
The differences between micelles and chylomicrons are
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 7

Question 6.
How is our gut lining protected from its own secretion of proteases?
Solution:
(i) Protease is secreted in an inactive form and poses no threat to the gut lining.
(ii) The mucus provides protection to the epithelial lining.

Question 7.
Name the organs which secrete carboxypeptidases and aminopeptidases respectively. Give the functions performed by these enzymes.
Solution:
Carboxypeptidases are secreted by the exocrine part of the pancreas. Aminopeptidases are secreted by the intestinal mucosa. These enzymes act on the terminal peptide bonds and release the last amino acid from the polypeptide chain, thereby progressively shortening the peptide chain.

Question 8.
Where is the ileocaecal valve present? What is its function?
Solution:
The ileo-caecal valve is present at the junction of the ileum of the small intestine and the caecum of the large intestine.
It prevents the backflow of the matter from the caecum into the ileum.

Question 9.
How does the nervous system control the activities of the gastro-intestinal tract?
Solution:
The sight, smell and presence of food in the oral cavity can stimulate the secretion of saliva. Gastric and intestinal secretions are also stimulated by similar neural signals. Muscular activities of the alimentary canal are coordinated by both local and CNS neural mechanisms. Hormonal control of secretion of digestive enzymes is carried out by local hormones.

Question 10.
Name the final products of the digestion of proteins. How and where are they absorbed from the alimentary canal?
Solution:
The final products of digestion of proteins are amino acids They are absorbed by an active process utilising energy against the concentration gradient in the ileum.

Question 11.
What is the pancreas? Mention the major secretions of the pancreas that are helpful in digestion.
Solution:
The pancreas is a carrot-shaped soft greyish pink gland that lies transversely below the stomach between the duodenum and spleen, which secretes digestive enzymes from its exocrine parts and hormones from its endocrine parts.
The pancreas secretes three enzymes in inactive proenzyme or zymogen state and three in active enzyme state.
Proenzymes. Trypsinogen, chymotrypsinogen, and procarboxypeptidases.
Active Enzymes. Amylase, lipase, and nucleases.

LONG ANSWER QUESTIONS

Question 1.
What is meant by vernalization? Explain the significance of vernalization.
Solution:
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 8

Question 2.
Write short notes on
(a) Liver
(b) Layers of the alimentary canal
Solution:
(a) Liver: The liver is the largest gland of the body. It is situated in the abdominal cavity, just below the diaphragm and has two lobes. The hepatic lobules are the structural and functional units of the liver containing hepatic cells arranged in the form of cords. Each lobule is covered by a thin connective tissue sheath called the Glisson’s capsule. The bile secreted by the hepatic cells passes through the hepatic ducts and is stored and concentrated in a thin muscular sac called the gall bladder. The duct of gall bladder (Cystic duct) along with the peptic duct from the liver forms the common bile duct. The bile contains pigments like bilirubin and biliverdin, bile salts, cholesterol and phospholipids but no enzymes. Bile helps in the emulsification of fats and activates lipases.

(b) Layers of the alimentary canal:
The wall of the alimentary canal possesses four layers namely serosa, muscularis, sub-mucosa, and mucosa. The serosa is the outermost layer and is made up of a thin mesothelium with some connective tissues. Muscularis is formed by smooth muscles usually arranged into an inner circular and an outer longitudinal layer. An oblique muscle layer may be present in some regions.

The sub-mucosal layer is formed of loose connective tissues containing nerves, blood, and lymph vessels. In the duodenum, glands are also present in the sub-mucosa. The innermost layer lining the lumen of the alimentary canal is the mucosa. This layer forms irregular folds in the stomach and small finger-like foldings called villi in the small intestine. The cells lining the villi produce numerous microscopic projections called microvilli giving a brush border appearance.

Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal. The mucosal epithelium has goblet cells which secrete mucus that help in lubrication. Mucosa also forms glands in the stomach and crypts in between the bases of villi in the intestine (crypts of lieberkuhn).

Question 3.
Describe the major disorders of the human digestive system.
Solution:
Disorders of the digestive system:
(i) Indigestion:

  • It is the condition in which the food is not properly digested leading to a feeling of fullness.
  • It is caused by inadequate secretion of digestive enzymes, food poisoning, overeating or spicy food.

(ii) Constipation

  • It refers to the condition where the faeces are retained in the rectum for longer periods as the bowel movements occur irregularly.

(iii) Diarrhoea:

  • It refers to the abnormal frequency of bowel movement and increased liquidity of the faecal discharge; absorption of food is impaired.

(iv) Vomiting:

  •  It is the ejection of stomach contents through the mouth; this reflex action is controlled by the vomit centre in the medulla.
  • It is due to viral infection, where liver is affected and digestion of fats is impaired.
  • The eyes and skin turn yellow due to the deposit of bile pigments.

Question 4.
How is the DNA content in our diet digested in the body?
Solution:
DNA content is digested in the intestinal part of our alimentary canal by the enzymes present in pancreatic juice and succus entericus.
NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption 9
DNAase is found in pancreatic juice while nucleotidase and nucleosidase occur in succus entericus and hydrolyse the DNA content in our diet.

We hope the NCERT Solutions for Class 11 Biology at Work Chapter 16 Digestion and Absorption, help you. If you have any query regarding NCERT Solutions for Class 11 Biology at Work Chapter 16 Digestion and Absorption, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom

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NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom.

Question 1.
What is the basis of the classification of algae?
Solution:
Classification of Algae: The algae are divided into three main classes: Chlorophyceae, Phaeophyceae, and Rhodophyceae.

  1. Chlorophyceae: The members of Chlorophyceae are commonly called green algae.
  2. Phaeophyceae: The members of Phaeophyceae or brown algae, are found primarily in marine habitats.
  3. Rhodophyta is commonly called red algae. (See Table on the opposite page)

Question 2.
When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?
Solution:
I. Liverwort – The main part of the body of liverwort is thalloid. Haploid gametes are produced from the male and female sex organs garnets fuses to form zygote. Zygote develops in the form of sporophytes. These sporophytes are further differentiated into foot, seta and capsule. As a result of reduction division many haploid spores are produced in capsule.
II. Moss – In the first stage in moss primary protonema develops into secondary ’ protonema. Both these stages are haploid. Zygote formed by the fusion of gametes further produce sporophytes.
III. Fern – Leaves of sporophyte bear sporangia in which spores are produced by reduction division in meiosis.
IV. Gymnosperm – In microsporophylls and megasporophylls that bear microsporangia and megasporangia respectively, reduction division occurs to produce microspores (pollen grains) and megaspore.
V. Angiosperm – Main part of the body is sporophytic and bears flowers. Reduction division takes place in anthers of stamen i.e. haploid pollen grains and in the ovary of pistil producing eggs.

Question 3.
Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Solution:

Archegonia is the female reproductive organ of

  1. Bryophytes
  2. Pteridophytes and
  3. Gymnosperms groups of plants.

The life cycle of gymnosperms: The gymnosperms are heterosporous, they produce haploid microspores and megaspores. The two kinds of spores are produced within sporangia that are borne oil sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones.
The strobili bearing microsporophylls and microsporangia are called microsporangia or male strobili. The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells. This reduced gametophyte is called pollen-grain. The development of pollen- grains takes place within the microsporangia.

The cones Rearing megasporophylls with ovules or megasporangia are called microsporangia or female strobili. The male or female cones or strobili may be borne on the same tree or on different trees. The megaspore mother cell is differentiated from one of the cells of the nucellus. The nucellus is protected by envelopes and the composite structure is called an ovule.

The ovules are borne on megasporophylls which may be clustered to form the female cones. The female cones are borne on the main plant body of the sporophyte. The megaspore mother cell divides meiotically to form four megaspores. One of the megaspores enclosed within the megasporangium (nucleus) develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs. The multicellular female gametophytes are also retained within megasporangium.

Three groups of plant that bear archegonia are
1. Bryophyta,
2. Pteridophyta and
3. Gymnosperm.

  1. Life cycle of gymnosperms: The gymnosperms are heterosporous, they produce haploid microspores and megaspores.
  2. The two kinds of spores are produced within sporangia that are borne on sporophyll which are arranged spirally along an axis to form strobili or cones.
  3. The strobili bearing microsporophylls and microsporongia are called microsporangiate or male strobili.
  4. The microspores develop into a male gametophytic generation which is highly reduced, and confined to only limited number of cells. The reduced gametophyte is called pollen grain.
  5. The development of pollen grain takes place within microsporangia.
    The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili.
  6. The male or female cones or strobili may be borne on the same tree or different trees. The megaspore mother cell is differentiated from one of the cells of the nucellus.
  7. The nucellus is protected by envelopes and the composite structure is called an ovule. The ovules are borne on megasporophylls which may be clustered to form the female cones.
  8. The females cones are borne on the main plant body of the sporophyte. The megaspore mother cell divides meiotically to form four megaspore.
  9. One of the megaspore enclosed within the megasporangium develops into a multicellular female gametophyte that bears 2 or more archegonia or female sex organs.
  10. The multicellular female gametophyte is also remaining within megasporangium.

Question 4.
Mention the ploidy of the following: protonemal cells of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a fern; gemma cell in Marchantia; Meristem cells of monocot, ovum of liverwort and zygote of a fern.
Solution:
Protonemal cells of a moss – Haploid (n) Primary endosperm nucleus in dicot – Triploid (3n)
Leaf cell of a moss – Haploid (n)
Prothallus cell of a fem – Haploid (n)
Gemma cell in Marchantia – Haploid (n) Meristem cells of monocot – Diploid (2n) Ovum of liverwort – Haploid (n)
Zygote of a fem – Diploid (2n)

Question 5.
Write a note on economic importance of algae and gymnosperms.
Solution:

  1. Algae like Chlorella, Gelidium (produce agar- agar) are used as food. Many algae like diatoms (used in manufacture of glass, polish, etc), algin (used in vulcanisation, artificial fibres, etc.), are used in industry.
  2. Nos toe, Anabaena, etc., are useful in increasing fertility of soil. Antibiotic chlorellin is extracted from Chlorella.
  3. Many algae have harmful effect also, for example, Microcystis, Chlrococcus, Oscillatoria cause water blooms and Cephaleuros species of algae are parasitic on tea leaves and cause harm to tea industry.
  4. v Alginic acid are extracted from the members Phaeophycea such as laminaria, Macrocystis and carrageenin is extracted from red algae chondris Crispos.

Economic importance of gymnosperms :

  1. Gymnosperms helps in checking soil erosion.
  2. Seeds of Pinns gerardiana, Gnetnm gnemon and Ginkgo biloba are eaten.
  3. Conifers like Pinus longifolia, Cedrus deodara, Picea, Tsngo, etc., produce soft wood. Bark of Tsugo yields tannins for making inks, seeds and bark of Cycas are used as poultica for wounds and sores.
  4. Ephedra, Gnetum, Taxus baccata, Cycles rumphii are used for medicinal purposes.

Question 6.
Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
Solution:
Gymnosperms are ‘naked seeded’ plants because their seeds are not enclosed in fruit wall whereas angiosperm are ‘enclosed seeds’ as seeds (ovules) are found enclosed in the ovary wall.

Question 7.
What is heterospory? Briefly comment on its significance. Give two examples.
Solution:

  1. Genera like Selaginella and Salvinia which produce two kinds of spores macro and microspores are known as heterosporous.
  2. The megaspore and microspores germinate and give rise to female and male gametophytes, respectively.
  3. The female gametophytes in these plants are retained on the parent sporophyte for variable periods.
  4. The development of the zygotes into young embryo takes place within the female gametophytes.
  5. This event is considered as an important step in evolution leading to seed habit. Heterospory is considered as the first step towards seed habit. Selaginella and Marsilea, show seed habit.

Question 8.
Explain briefly
(i) Protonema
(ii) Antheridium
(iii) Archegonium
(iv) Diplontic
(v) Sporophyll
(vi) Isogamy
Solution:
(i) Protonema: The predominant stage of moss gametophyte which directly develops from spore is known as protonema.
(ii) Antheridium: The male sex organ in bryophytes, pteridophytes and gymnosperms is called antheridium. It bears male gamete.
(iii) Archegonium : It is the female sex organ found in bryophytes, pteridophytes and gymnosperms. It bears a female gamete.
(iv) Diplontic: In the life cycle of plants when their diploid stage is dominant for long time then this is called diplontic.
(v) Sporophyll: The sporophyte bears sporangia that are subtended by leaf-like appendages called sporophylls.
(vi) Isogamy: When the gametes involved in sexual reproduction are morphologically similar then this is called isogamy. These gametes are physiologically different.

Question 9.
Differentiate between the following:-
• Red algae and brown algae
• Liverworts and moss
• Homosporous and heterosporous pteridophyte
• Syngamy and triple fusion 
Solution:

Differences between red algae and brown algae are as follows
NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom 1
NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom 2

Question 10.
How would you distinguish monocots from dicots?
Solution:
Dicots are characterized by having two cotyledons in their seeds while the monocotyledons have only one.

Question 11.
Match the following content of column I with column II
Column I Column II
(a) Chlamydomonas (i) Moss
(b) Cycas (ii) Pteridophyta
(c) Selaginella (iii) Algae
(d) Sphagnum (iv) Gymnosperm
Solution:
(a) Chlamydomonas  (iii) Algae
(b) Cycas                    (iv) Gymnosperm
(c) Selaginella            (ii) Pteridophyta
(d) Sphagnum           (i) Moss

Question 12.
Describe the important characteristics of gymnosperms.
Solution:
The seed forming vascular plants which produce seeds but no fruits are called gymnosperms. General characters of gymnosperm are as follows:

  • Fertilization does not require water.
  • Leaves may be of two kinds: foliage leaves and scale leaves.
  • The ovules are orthotropus.
  • Most primitive seed-bearing plants.
  • Mostly these plants are evergreen.
  • Have no ovary wall, seeds are naked.
  • Exhibit polyembryony. Sexual reproduction oogamous type.
  • Large, tall and woody trees.

VERY SHORT ANSWER QUESTIONS

Question 1.
Which group of plants are commonly called “Amphibians of Plant Kingdom”?
Solution:
Bryophytes

Question 2.
Which pigment does provide red colour to red algae?
Solution:
Phycoerythrin.

Question 3.
Which alga does reproduce sexually by conjugation?
Solution:
Spiro gym

Question 4.
Name the organ that fixes the Plant body of Riccia to the soil.
Solution:
Hepaticopsida.

Question 5.
Which plant group is called vascular cryptograms?
Solution:
Pteridophytes.

Question 6.
Which plant is commonly called as walking fern?
Solution:
Adiantum

Question 7.
Which group of plants produces seed but not fruits?
Solution:
Gymnosperm.

Question 8.
Which part of ovule is haploid in gymnosperm?
Solution:
Endosperm

Question 9.
What is name of megasporophyll bearing ovules of angiosperm?
Solution:
Carpel.

Question 10.
Why do gymnosperms fail to produce fruits?
Solution:
Fruits are formed from ovaries. Since the gymnosperm ovules are not enclosed inside the ovaries, they do not produce fruit.

Question 11.
Why life cycle of angiosperm is called diplontic?
Solution:
Life cycle of angiosperm is called diplontic because the diploid (sporophytic) phase is more prominent and long-lived whereas the haploid (gametophytic) phase is short-lived.

Question 12.
Which algae is known as Rolling alga?
Solution:
Volvox

Question 13.
Which are the specialized structures in selaginella which bear adventitious roots?
Solution:
Rhizophores

Question 14.
What is the number of cells and nuclei present in the embryo sac of angiosperm?
Solution:
7 cells and 8 nuclei

Question 15.
Which plant is known as a living fossil?
Solution:
Cycas

SHORT ANSWER QUESTIONS

Question 1.
What are the salient features of pteridophyte?
Solution:
Pteridophytes are vascular cryptogams i.e., plants of this group possess vascular tissue (i. e., xylem, and phloem) for the conduction of water and minerals and for the translocation of foods. They are flowerless and seedless plants.
The general characters of pteridophytes are as following.
I. Primary root is short-lived. It is replaced by adventitious roots.
II. All vegetative parts possess vascular tissues. A cambium is altogether absent. In xylem trachea are absent and in phloem companion cells are absent.
III. Pteridophytes show origin and evolution of stele {i.e., vascular tissue, pericycle, and if present the pith).
IV. Pteridophytes are characterized by having only tracheids in their xylem and only sieve tube in their phloem.
V. The main plant body is the sporophyte (diploid), usually differentiated into true roots, true stems, and true leaves. A stem is usually an underground rhizome or an erect trunk as in tree ferns. Leaves are large (megaphyllous) and variously shaped.

Question 2.
What is the Alternation of Generation?
Solution:
gametophytic and sporophytic generations alternate in the life cycle, it is called the Alter-nation of generation. Or vice versa gametophyte produces gametes and their fusion product zygote or Oospore. Oospore produces sporophyte. The sporophyte produces spores. Spores germinate and produce gametophyte.

Question 3.
What are gemmae? Name two plants that produce gemmae.
Solution:
Gemmae are green, multicellular asexual buds, which develop in small receptacles, called gemmae cups, on the thallus.
The gemmae become detached from the parent thallus and germinate to form new individuals. e.g., Marchantia, Riccia.

Question 4.
Differentiate between cytotaxonomy and chemotaxonomy.
Solution:
Cytotaxonomy that is based on cytological information like chromosome number, structure, behaviour and chemotaxonomy that uses the chemical constituents of the plant to resolve confusions, are also used by taxonomists these days.

Question 5.
Differentiate between monocotyledon and dicotyledons.
Solution:
NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom 3

Question 6.
Mention four types of Placentation with suitable examples.
Solution:

  • Marginal placentation: Example members of the family fabaceae (Crotalaria)
  • Axile placentation: Example members of the family Malvaceae (Hibiscus)
  • Parietal placentation. Example: Cucumber.
  • Basal placentation Example: Sunflower.

Question 7.
What are the features of Gemmae found in bryophytes?
Solution:
Gemmae are the means of asexual reproduction found in many bryophytes (ex-Liverworts). They are one to many-celled, specially produced clonal plant fragments. They are green multicellular, asexual buds which develop in small receptacles called “gemma cups” located on the thalli. Gemmae become detached from the parent body and germinate to form a new individual

Question 8.
What is the basis of the classification of the phylogenetic system?
Solution:
It indicates evolutionary as well as the genetic relationship among organism, it is based on the fossil record, biochemical, anatomical, morphological, embryological, physiological, genetics, Karyotype, and other studies.

Question 9.
What are the main features of Anthocerotopsida?
Solution:
These are also known as hornworts because typical horn-like appearances are present of their sporophyte. These contain thalloid gametophyte, distinctly dorsiventral, rhizoids are present, Thalloid do not possess air chambers and scales. Each cell of thallus has a single large chloroplast with a pyrenoid.

LONG ANSWER QUESTIONS

Question 1.
Enumerate distinguishing characters of Bryophytes.
Solution:

  • Bryophytes are called “Amphibians of the plant kingdom” They grow in moist shady places. They require water for their sperms to swim towards eggs, hence the term ‘amphibians’.
  • The plant body is gametophyte so that it produces garnets.
  • The gametophyte is nonvascular so that xylem and phloem tissues are absent.
  • The gametophyte is thalloid in structure or it may be differentiated into stem-like, root-like and leaf-like organs.
  • Gametophyte reproduces sexually. The male sex organs are antheridia and the female sex organs are archegonia. Antheridia produce flagellated motile sperms. Archegonia produce female gamete or egg.
  • Fertilization results in the formation of diploid oospore. It produces diploid sporophyte Sporophyte reproduces asexually and produces haploid spores. They germinate and produce haploid gametophyte. The sporophyte is dependant on the gametophyte.
  • In the life cycle, there is an alternation of generation between haploid gametophyte and diploid sporophyte.
  • Bryophytes also show vegetative reproduction by fragmentation, gemmae formation etc.

Question 2.
Write short notes on the following :
(a) Peristomial teeth of moss
(b) Protonema of moss
(c) Archegonia of moss
Solution:
(a) Peristomal teeth are located just below the operculum. It helps in the dispersal of spores by the hygroscopic movement of its outer ring while the inner ring does not show the hygroscopic movements.
(b) Each spore produces a filamentous juvenile stage called protonema. Protonema has two types of branches, subterranean nongreen rhizoidal, and green Mediterranean branches. Buds develop on green prostrate branches which grow to form new moss plants.
(c) Female reproductive organ of moss is called archegonium.
NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom 4

 

Question 3.
Explain the general characters of the Gymnosperm plant body. (Tumkur 2008)
Solution:

  • Gymnosperm plant body is sporophyte.
  • Sporophyte consists of stem, root and leaves. Stem is unbranched in cycas. the stem bears crown of leaves at the tip.
  • The foliage leaves are pinnately compound in cycas and needle-like in conifers. Brown small non-photosynthetic leaves called scale leaves/cataphylls are present in cycas.
  • In cycas, the cataphylls are thickly covered with brown hairs called ramenta.
  • The foliage leaves are green. The pinnae are tough, leathery and has only midrib without veins.
  • Young leaves show circinate vernation.
  • The roots are inhabited by blue-green algae like Nostoc help the plant in nitrogen fixation
  • The sporophyte produces two types of spores so it is heterosporous.

Question 4.
Give a comparative account of gymnosperms and angiosperms.
Solution:
Comparison of gymnosperms and angiosperms
NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom 5

Question 5.
Describe major features of Plant kingdom.
Solution:
Features of Plant Kingdom:

  • Plants are autotrophic, except for some carnivorous, plants. They trap photo energy from sunlight and convert it to chemical energy through I photosynthesis. Because of this plants are the main channel for supplying energy in the food chain on earth.
  • Reproduction in plants can be by any of the following modes: Vegetative or Asexual, and Sexual Reproduction.
  • Plant cell is unique because of presence of cell wall and large vacuoles. Green parts of plant contain chlorophyll, which helps them in trapping the photo energy.
  • Sizes of plants can vary from microscopic to a very large tree. Plants are mainly divided into Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.
  • Lower plants, like algae and bryophytes, have thalloid structures, while higher plants, like gymnosperms and angiosperms, have clearly defined roots and stems.
  • In higher plants root gives a means to anchor in the soil and helps the plant in taking minerals and water from the soil. Green leaves on the stem help them in photosynthesis.
  • Most of the plant growth as a result of photosynthesis. After photosynthesis, extra food is utilized to facilitate growth.
  • Usually in higher plants growth is unlimited and some taller trees can live a life of more than 1000 years.
  • Being the main carbon fixation agent, plants are very important for the whole ecology.
  • The whole food basket for humans is being filled by the plant kingdom. Even animal products, like milk and poultry, are indirect results of a plant’s carbon fixation.
  • Plants supply raw materials for a majority of economic activities. Wood for furniture and building materials comes from plants. The whole paper industry is dependent on the plant kingdom. Think of life if there was no paper and you may understand the larger impact on human civilization.
  • Angiosperms have special organs, called flowers, to bear sexual parts. Flowers are a helpful tool in facilitating variations and further evolution of the plant kingdom.

NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom 6

We hope the NCERT Solutions for Class 11 Biology at Work Chapter 3 Plant Kingdom, help you. If you have any query regarding NCERT Solutions for Class 11 Biology at Work Chapter 3 Plant Kingdom, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 11 Biology Chapter 8 Cell: The Unit of Life

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NCERT Solutions for Class 11 Biology Chapter 8 Cell: The Unit of Life

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 8 Cell: The Unit of Life.

Question 1.
Which of the following is not correct?
(a) Robert brown discovered the cell.
(b) Schleiden and Schwann formulated the cell theory.
(c) Virchow explained that cells are from pre¬existing cells.
(d) A unicellular organism carries out its life activities within single cell.
Solution:
(a) Robert brown discovered the cell.

Question 2.
New cells generate from
(a) bacterial fermentation
(b) regeneration of old cells
(c) pre-existing cells
(d) abiotic material
Solution:
(c) pre-existing cells

Question 3.
Match the following
Column A Column B
(a) Cristae (i) Flat membranous sac in stroma
(b) Cisternae (ii) Infoldings in mitochondria
(c) Thylakoids (iii) Disc-shaped sacs in Golgi apparatus
Solution:
(a) Cristae (ii) Infoldings in mitochondria
(b) Cisternae (iii) Disc-shaped sacs in Golgi apparatus
(c) Thylakoids (i) Flat membranous sac in stroma

Question 4.
Which of the following is correct
(a) Cells of living organisms have a nucleus.
(b) Both animals and plant cells have a well defined cell wall.
(c) In prokaryotes, there are no membrane bound organelles.
(d) Cells are formed de novo from abiotic materials
Solution:
(c) In prokaryotes, there are no membrane-bound organelles.

Question 5.
What are mesosomes in a prokaryotic cells? Mention the function that it performs.
Solution:
A special membranous structure is a mesosome that is formed by the extensions of the plasma membrane into the cell. These extensions are in the form of vesicles, tubules, and lamellae. They help in cell wall formation, DNA replication, and distribution to daughter cells. They also help in respiration, in the secretion process increase plasma membrane surface and enzymatic content.

Question 6.
How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
Solution:
Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient i.e. from higher concentration to the lower. Water may also move across this membrane from higher to lower concentrations. The movement of water by diffusion is called osmosis. As the polar molecules cannot pass through the non-polar lipid bilayer, they require a carrier protein of the membrane to facilitate their transport across the membrane.

A few ions or molecules are transported across the membrane against their concentration gradient i.e. from lower to the higher concentration. Such transport is an energy-dependent process, in which ATP is utilized and is called active transport. e,g., Na’/K* Pump.

Question 7.
Name two cell-organelles that are double membrane-bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
Solution:
Two double membrane-bound cell organelles:
(a) Mitochondria: It has finger-like folds in the inner membrane called cristae. Mitochondria is the place for aerobic respiration.
NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 1
(b) Chloroplast: Chloroplast is responsible for converting light energy into chemical energy. Chloroplast contains stacked thylakoid in its matrix.
NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 2
Functions of mitochondria: The double membrane mitochondria are actively associated with aerobic respiration and the release of energy for cellular activity. The biological oxidation of the fats and carbohydrate release much amount of energy which is utilised by mitochondria for ATP synthesis. The required energy is released from ATP molecules for various cell processes in cells so they are termed as “the powerhouse of the cell”
Functions of chloroplast :
(i) Their main function of the chloroplast is to trap the sun’s energy and to convert it into chemical energy of food by photosynthesis.
(ii) Storage of starch.
(iii) Chloroplast in fruits and flowers changes into chromoplasts.

Question 8.
What are the characteristics of prokaryotic cells?
Solution:
The prokaryotic cells are represented by bacteria, blue-green algae, mycoplasma, and PPLO (Pleuro Pneumonia-like organisms). They are generally smaller and multiply more rapidly than the eukaryotic cells. They may vary greatly in shape and size. The four basic shapes of bacteria are bacillus (rod-like), coccus (spherical), vibrio (comma-shaped), and spirillum (spiral).

The organization of the prokaryotic cell is fundamentally similar even though prokaryotes exhibit a wide variety of shapes and functions. All prokaryotes have a cell wall surrounding the cell membrane. The fluid matrix filling the cell is the cytoplasm. There is no well-defined nucleus. The genetic material is basically naked being not enveloped by a nuclear membrane.

In addition to the genomic DNA (the single chromosome/ DNA circle), many bacteria have small DNA circles outside the genomic DNA. These smaller DNA circles are called plasmids, The plasmid DNA confers certain unique phenotypic to antibiotics. Prokaryotes have something unique in the form of inclusions.

A specialised differentiated form of the cell membrane called mesosome is the characteristic of prokaryotes. They are essentially infoldings of the cell membrane.

Question 9.
Multicellular organisms have a division of labour. Explain.
Solution:
In unicellular organisms, there is no division of labour.

  1. The single cell of the organisms is capable of performing all the vital activities of life i.e., respiration, movement, digestion and reproduction, etc. Respiration, nutrition, and excretion in most of these unicellular organisms takes place through the general body surface.
  2. No special organs for these are present in them because they are too small to need them. Most of these unicellular organisms reproduce by simple binary division, to maintain their continuity.
  3. However, in some, sexual reproduction has also been observed.

Question 10.
Cell is the basic unit of life. Discuss in brief.
Solution:
Cell: The Basic Unit of life: All living organisms are composed of small, tiny structures or compartments called cells. These cells are called the ‘building blocks’ of life.

  1. The cells in true sense are considered as the basic unit of life because all the life processes i.e., metabolism, responsiveness, reproduction are carried out by the cells.
  2. Respiration, nutrition, release of energy for the body are carried out within the cells only.
  3. Even the animals and plants reproduce because the cells reproduce individually.
  4. Growth occurs because cell grow and multiply.
    In Amoeba all the life processes are performed within the boundaries of the single cell.
  5. This is true of all other multicellular organisms. The only difference in the multicellular organisms is that the body of these organisms is made up of many cells.
  6. In these organisms, the cell do not behave independently but get organized into tissues. Each tissue is specialized to perform specific functions. Different tissues then get organised into tissues.
  7. Each tissue is specialized to perform specific functions. Different tissues then get organised into organs which perform certain specific functions.
  8. Different organs are finally organised to form organ systems. Now it must be very clear that the basic structure to tissues, organs and organ system are the cells only.
  9. These tissues, organs and organ system of the organisms work because the cells work.
  10. Thus “the cells are structural and functional unit of the living beings” hence it is the basic unit of life.

Question 11.
What are nuclear pores? State their function.
Solution:
At a number of places, the nuclear envelope is intercepted by minute pores which are called nuclear pores. These are formed by the fusion of two nuclear membranes. These nuclear pores are the passages through which the movement of RNA and protein molecules takes place in both directions between the nucleus and the cytoplasm.

Question 12.
Both lysosomes and vacuoles are * endomembrane structures, yet they differ in
terms of their functions. Comment.
Solution:
Lysosomes are filled with hydrolytic enzymes that are capable of digesting carbohydrates, proteins, lipids and nucleic acids whereas vacuoles contain water, sap, excretory product and other materials not useful for cell.

Question 13.
Describe the structure of the following with the help of labelled diagrams.
(i) Nucleus
(ii) Centrosome
Solution:
NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 3
(i) Nucleus:

    1. The nucleus is a large organelle controlling all the activities of the eukaryotic cells. Some cells have more than one nucleus.
    2. Binucleate cells have 2 nuclei per cell eg. Paramoecium. Multinucleate cells have many nuclei e.g. Ascaris.
    3. Some cells lack nucleus (anucleate) at maturity. Examples: mammalian RBCs and sieve tube cells in vascular plants.
    4. The nucleus is bounded by two membranes, which make the nuclear envelope.
    5. The outer and inner membranes are separated by a narrow space, perinuclear space.
    6. The outer membrane remains in continuation with endoplasmic reticulum (ER) and the inner one surrounds the nuclear contents.
    7. At some points, the nuclear evelope is interrupted by the presence of small structures called nuclear pores.
    8. These pores help in exchange of materials between nucleoplasm and cytoplasm. Nuclear membrane dissappears during cell division. It reappears during nuclear reorganization in stage.
    9. The nucleoplasm contains chromatin and nucleolus. The nucleolus is a rounded structure. It is not separated from the rest of the nucleoplasm by membrane.
    10. It is associated with a specific nucleolar organizing region (NOR) of some chromosomes. Nucleolus is the “site for ribosomal RNA synthesis”.
    11. The cells which remain engaged in protein synthesis have larger and more numerous nuclei in their nucleoplasm.

NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 4

(ii) Centrosome:

  1. Under the electron microscope, each centriole is seen to be formed of nine sets of tubular structures arranged in a circular fashion.
  2. Each of these sets is a triplet composed of three microtubules. Each microtubule has a diameter of about 250A. The triplets are found in the matrix.
  3. Sometimes delicate strands appear to connect sets of the triplet to each other.
  4. Also can be seen radiating from the central core of the cylinder, delicate strands which connect sets of the triplets to each other giving a cartwheel appearance.
  5. Basal bodies are structures similar to the centrioles. They produce cilia and flagella.

Question 14.
What is a centromere? How does the position of the centromere form the basis of the classification of chromosomes? Support your answer with a diagram showing the position of the centromere on different types of chromosomes.
Solution:
Eukaryotic chromosomes: The chromosomes are uncoiled in a loose, indistinct network called the chromatin that contains DNA, RNA and protein in interphase.

The types of proteins present and associated with DNA are histone and non-histone proteins.

Chromosomes are thread-like structures. They become visible (under light microscope) during cell division.

In higher organisms, the well-developed nucleus contains a definite number of chromosomes of definite size and shape.
NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 5
The shape of a chromosome is usually observable at metaphase and anaphase when the position of primary constriction {centromere) is clearly seen. Based on the position of the centromere, chromosomes are of 3 types:

  • telocentric – with terminal centromere,
  • the acrocentric – terminal centromere is capped by a telomere
  • submetacentric – the centromere is subterminal in position
  • metacentric – these have median centromere.

VERY SHORT ANSWER QUESTIONS

Question 1.
Who discovered the Golgi body?
Solution:
Camillo Golgi (1898).

Question 2.
Give the location of 70S ribosomes.
Solution:
Prokaryotic cells, plastids, and mitochondria

Question 3.
Name the cell organelle rich in acid hydrolases.
Solution:
Lysosomes

Question 4.
Who proposed the cell theory?
Solution:
Schleiden and Schwann.

Question 5.
Expand PPLO.
Solution:
PPLO (Pleuro Pneumonia Like Organisms)

Question 6.
Name the organelle responsible for protein synthesis in a cell.
Solution:
Ribosome

Question 7.
Give the full form of SER and RER.
Solution:

  • SER – Smooth endoplasmic reticulum.
  • RER – Rough endoplasmic reticulum.

Question 8.
Name the membrane which surrounds the vacuole in the cell.
Solution:
Tonoplast

Question 9.
Name two types of constituents of the plasma membrane.
Solution:
Proteins and lipids.

Question 10.
Name two processes of passive transport.
Solution:

  • Osmosis
  • Diffusion

Question 11.
What is plasmodesmata? What is its function?
Solution:
Plasmodesmata: Adjoining the cells and the linking gap of cytoplasmic protoplasmic presence is called Plasmodesmata. It links the neighbouring cells together.

SHORT ANSWER QUESTIONS

Question 1.
Why fluid-mosaic model is more accepted than other models of the plasma membrane?
Solution:
The fluid mosaic model explains
(i) quasifluid state of the plasma membrane,
(ii) It differentiates two 6. types of proteins
(iii) It explains functional specificity and variability in two surfaces of PM.

Question 2.
Name three types of elements in the Golgi body. List two major functions of the Golgi body.
Solution:
Three types of elements in golgi body are cistemae, vesicles and vacuoles. The main function of golgi bodies are cellular secretion and acrosome formation.

Question 3.
What is peculiar about mitochondrial DNA?
Solution:
Mitochondrial DNA is circular double-stranded and not associated with histone proteins.

Question 4.
How does cytokinesis take place in plant and animal cells?
Solution:
In plant cell cytokinesis take place by cell plate formation and in animal cells it occurs by constriction

Question 5.
Differentiate between prokaryotic and eukaryotic cells.
Solution:
The main differences between prokaryotic cell and eukaryotic cell are
NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 6

Question 6.
Differentiate between active and passive transport across the membrane.
Solution:
The main differences between active transport and passive transport are
NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 7

Question 7.
Describe the different methods of transport of nutrients in cell.
Solution:
Different methods of transport of nutrients in the cell are:
(i) Simple diffusion : It is the movement of ions/ molecules of any substance from a region of higher concentration to ‘the region of lower concentration, until equilibrium is reached. Many neutral solutes move by diffusion.
(ii) Osmosis : It is the movement of solvent molecules across a semipermeable membrane, from the region of higher concentration to the region of lower concentration, until equilibrium is reached. Water moves by osmosis from one cell to the other.
(iii) Facilitated diffusion : It refers to the movement of ions/molecules across the membrane with the help of transmembrane proteins.

Question 8.
Why are ribosomes of prokaryotes different from eukaryotes?
Solution:
The type of ribosomes of prokaryotes is different from eukaryotes because the prokaryotes were primitive, simpler and have remained intact during evolution while at the base level eukaryotes have adapted with the environment and are retaining their kind of entities for the complex structure. Prokaryotes have 70S ribosomes with 30S and 50S subunit and eukaryotes have 80S ribosome with 40S subunit and 60S sub unit.

Question 9.
What is the function of
(1) Nuclear Pores
(2) Slimy Capsule in Bacteria
(3) Golgi Bodies:
(4) Centrosome with Centrioles
Solution:
(1) Nuclear Pores: There is exchange of RNA and proteins through the nuclear pores
(2) Slimy Capsule in Bacteria : A slimy capsule is the outer covering of cell wall of bacteria and is an additional protection for the bacteria.
(3) Golgi Bodies :
(i) It takes part in packaging materials delivered either to the intra-cellular targets or secteted outside the cell.
(ii) It is also a important site of formation of glycoproteins and glycolipids.
(4) Centrosome with Centrioles
(i) Centrioles help in organising the spindle fibres and astral rays during cell division.
(ii) It also provides basal bodies which give rise to cilia and flagella.

LONG ANSWER QUESTIONS

Question 1.
Describe the structure of cell wall.
Solution:

  • A non-living rigid structure called the cell wall forms an outer covering for the plasma membrane of fungi and plants.
  • Cell wall does not only give shape to the cell and but protect the cell from mechanical damage and infection.
  • It also helps in cell-to-cell interaction and provides barrier to undesirable macromolecules.
  • Algae have cell wall, made of cellulose, galactans, mannans and minerals like calcium carbonate, while in other plants it consists of cehulose, hemicellulose, pectins and proteins.
  • The cell wall of a young plant cell, the primary wall is capable of growth, which gradually diminishes as the cell matures and the secondary wall is formed on the inner side of the cell.
  • The middle lamella is a layer mainly of calcium pectate which holds or glues the different neighbouring cells together.
  • The cell wall and middle lamellae may be transferred by plasmodesmata which connect the cytoplasm of neighbouring cells.

Question 2.
Give an account of prokaryotic cells.
Solution:

  • The prokaryotic cells are represented by bacteria, blue green algae, mycoplasma and PPLO (Pleuro Pneumonia Like Organisms). They are generally smaller and multiply more rapidly than the eukaryotic cells.
  • They may vary greatly in shape and size. The four basic shapes of bacteria are bacillus (rod like), coccus (spherical), vibrio (comma shaped) and spirillum (Spiral).
    The organisation of the prokaryotic cell is fundamentally similar even though prokaryotes exhibit a wide variety of shapes and functions. All prokaryotes have a cell wall surrounding the cell membrane.
  • The fluid matrix filling the cell is the cytoplasm. There is no well defined nucleus.
  • The genetic material is basically naked, not enveloped by a nuclear membrane.
  • In addition to the genomic DNA (the single chromosome/circular DNA), many bacteria have small circular DNA outside the genomic DNA. These smaller DNA is called plasmids.
  • The plasmid DNA confers certain unique phenotypic characters to such bacteria. One such character is resistance to antibiotics. Nuclear membrane is found in eukaryotes.
  • No organelles, like the ones in eukaryotes, are found in prokaryotic cells except ribosomes.
  • Prokaryotes have something unique in the form of inclusions. A specialised differentiated form of cell membrane called mesosome is the characteristic of prokaryotes which helps in respiration process.
  • They are essentially infoldings of cell membrane.

Question 3.
Give an ultrastructure of mitochondria.
Solution:

  • Mitochondria, unless specifically stained, are not easily visible under the microscope.
  • The number of mitochondria per cell is variable depending on the physiological activity of the cells.
  • In terms of shape and size also, considerable degree of variability is observed.
  • Typically it is sausage shaped or cylindrical having a diameter of 0.2-1.0 ft m (average 0.5 film) and length (1.0 -4.1 ft).
  • Each mitochondrion is a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments, i.e. the outer compartment and the inner compartment.
  • The inner compartment is called the matrix. The outer membrane forms the continuous limiting boundary of the organehe.
  • The inner membrane forms a number of infoldings called the cristae. The cristae increase the surface area.
  • The two membranes have their own specific enzymes associated with the mitochondrial function. Mitochondria are the sites of aerobic respiration.
  • They produce cellular energy in the form of ATP, hence they are called. “Power houses” of the cell.
  • The matrix also possesses single circular DNA molecule, a few RNA molecules, ribosomes (70s) and the components required for the synthesis of proteins. The Mitochondria divide by fission.
    NCERT Solutions for Class 11 Biology Chapter 8 Cell The Unit of Life 8

Question 4.
Describe the fluid mosaic model of membrane.
Solution:
The characteristic features of fluid mosaic model
• This model was proposed by Singer and Nicholson.
• According to this model, there is a central bilipid layer (of phospholipids) with their polar head group toward the outside and the non-polar tails pointing inwards.
• Some proteins which are embedded in the lipid layer are called integral proteins and they cannot be separated from the membrane easily.
• Some large globular integral proteins which project beyond the lipid layer on both the sides are believed to have channels through which water soluble materials can pass across.
• Those proteins which are superficially attached are called peripheral (extrinsic) proteins and they can be easily removed.
• Some membrane lipids and integral proteins remain bound to oligosaccharides; such oligosaccharides project into the extracellular fluid and they influence the manner in which cells interact with the other cell.
• There are also certain specific proteins called membrane receptors, which mediate the flow of materials and information into the cell.

Question 5.
What are plastids? How are they classified on the basis of the type of pigments? Name them and their pigments and mention their functions.
Solution:
Plastids are double-membrane bound organelles
of different shapes, that are found only in plant
cells and contain pigments and storage products.
They are of three types :
(i) Leucoplasts
These are the oval, spherical, rod-like or filamentous colourless plastids which are found in storage organs. Their main function is to store reserve materials like starch (amyloplasts), proteins (aleuroplasts) and fats (elaioplasts).
(ii) Chromoplasts
• These are coloured plastids containing mainly the yellow, red and orange pigments (carotene and xanthophyll).
• These are found in petals of flowers and skin of fruits.
• They attracts agents for pollination and dispersal of fruits/seeds.
(iii) Chloroplasts
• These are the green plastids containing mainly chlorophylls and very little carotene and xanthophyll.
• Their main function is photosynthesis and the formation of starch.

We hope the NCERT Solutions for Class 11 Biology at Work Chapter 8 Cell: The Unit of Life, help you. If you have any query regarding NCERT Solutions for Class 11 Biology at Work Chapter 8 Cell: The Unit of Life, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division

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NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division.

Question 1.
What is the average cell cycle span for a mammalian cell?
Solution:
It is significant to note that in the 24-hour average duration of the cell cycle of a human cell or mammalian cells, cell division proper lasts for only about an hour.

Question 2.
Distinguish cytokinesis from karyokinesis.
Solution:

  1. Karyokinesis is a division of the nucleus (mitosis or meiosis) while cytokinesis is a division of the cytoplasm.
  2. Cytokinesis in an animal cells is achieved by the appearance of a furrow in the plasma membrane.
  3. The furrow gradually deepens and ultimately joins in the center dividing the cell cytoplasm into two.
  4. In-plant cell cell wall formation starts in the center of the cell and grows outward to meet the existing lateral walls.
  5. The formation of a new cell wall begins with the formation of a simple precursor, called the cell plate that represents the middle lamella between the walls of two adjacent cells.
  6. It is the time of cytoplasmic division, organelles like mitochondria and plastids get distributed between the two daughter cells.
  7. In some organisms, karyokinesis is not followed by ”cytokinesis as a result of which multinucleate condition arises leading to the formation of syncytium (liquid endosperm of coconut).

Question 3.
Describe the events taking place during the interphase.
Solution:
The interphase though called the resting phase is the time during which the cell is preparing for division by undergoing both cell growth and DNA replication in an orderly manner. The interphase is divided into three further phases :

  • G1 phase (Gap)
  • S phase (Synthesis)
  • G2 phase (Gap2)

G1 phase corresponds to the interval between mitosis and initiation of DNA replication. During G1 phase the cell is metabolically active and continuously grows but does not replicate its DNA. S or synthesis phase marks the period during which DNA synthesis or replication takes place. During this time the amount of DNA per cell doubles. If the initial amount of DNA is denoted as 2C then it increases to 4C. However, there is no increase in the chromosome number; if the cell had diploid or 2n number of chromosomes at G1 even after the S phase the number of chromosomes remains the same i.e. 2n.

In animal cells, during the S phase, as DNA replication begins in the nucleus, the centrioles, initiate replication in the cytoplasm. Dumping the G2 phase proteins are synthesized in preparation for mitosis while cell growth continues.

Question 4.
What is the G0 (quiescent phase) of the cell cycle?
Solution:
Some cells in adult animals do not appear to exhibit division (e.g., heart cell, nerve cell). These cells become inactive and become specialized by differentiating and do not further exit the G1 phase, and enter a stage but divide occasionally called the quiescent stage (G0) of the cell cycle.
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 1
A cell in this stage remains metabolically active but no longer proliferate unless called to do so depending on the requirement of the organism.

Question 5.
Why is mitosis called equational division?
Solution:
M phase is the most dramatic period of the cell cycle involving a major reorganization of virtually all components of the cell. Since the number of chromosomes in the parent and progeny cells is the same it is also called equational division. Though for convenience mitosis has been divided into four stages of nuclear division, it is very essential to understand that cell division is a progressive process and very clear-cut lines cannot be drawn between various stages.
Mitosis is divided into the following four stages:

  • Prophase
  • Meta phase
  • Anaphase
  • Telophase

Question 6.
Name the stage of the cell cycle at which one of the following events occur:
i. Chromosomes are moved to the spindle equator.
ii. Centromere splits and chromatids separate.
iii. Pairing between homologous chromosomes takes place.
iv. Crossing over between homologous chromosomes takes place.
Solution:
i. Metaphase
ii. Anaphase II
iii. Zygotene
iv. Pachytene

Question 7.
Describe the following:
(a) synapsis
(b) bivalent
(c) chiasmata
Draw a diagram to illustrate your answer.
Solution:
(a) During zygotene of prophase I of meiosis homologous chromosomes pair together. This pairing is called synapsis.
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 2
(b) Bivalent: The complex formed by homologous chromosomes during zygotene is called a bivalent.
(c) Chiasmata: During diplotene, the paired chromosomes make an X-shaped structure. This is called chiasmata.

Question 8.
How does cytokinesis in plant cells differ from that in animal cells?
Solution:
In animal cells, cytokinesis is achieved by the appearance of a furrow in the plasma membrane. The furrow gradually deepens and ultimately joins in the centre dividing the cell cytoplasm into two.

Due to the presence of cell walls, cytokinesis is different in plants. In plants, wall formation starts in the centre of the cell and grows outward to meet the existing lateral walls. The formation of the new cell wall begins with the formation of a simple precursor, called the cell plate that represents the middle lamella between the walls of two adjacent cells. Organelles like mitochondria and plastids get distributed between the two daughter cells during this process.

Question 9.
Find examples where the four daughter cells from meiosis are equal in size and where they are found unequal in size.
Solution:
The four daughter cells produced may be equal in size in the sperm of animals. They may be unequal in size as gametes in plants-pollen grains and egg in ovules.

Question 10.
Distinguish anaphase of mitosis from anaphase I of meiosis.
Solution:
The main difference between anaphase of mitosis and anaphase I of meiosis are as follows:
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 3

Question 11.
List the main differences between mitosis and meiosis.
Solution:
The main differences between mitosis and meiosis are as follows :
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 4

Question 12.
What is the significance of meiosis?
Solution:
1. Meiosis ensures the production of the haploid phase in the life cycle of sexually reproducing organisms whereas fertilization restores the diploid phase. We come across meiosis during gametogenesis in plants and animals. This lead to the formation of haploid gemotes.

2. Crossing over takes place during the Pachytene stage of meiosis, in which an exchange of genetic matter occurs. This produces variation, the raw material for evolution.

3. Meiosis has an impact on the genetic consequences due to pairing, crossing over, recombination, and segregation of homologous chromosomes.

Question 13.
Discuss with your teacher about

  1. haploid insects and lower plants where cell-division occurs and
  2. some haploid cells in higher plants where cell-division does not occur.

Solution:

  1. Some insects like honey bee drones are haploid. They are not fertile.
  2. In lower plant, main plant body is haploid produces haploid microspores by mitosis. The gametes of Chlamydomonas fuse to form diploid zygotes. Meiosis take place at this stage in lower plants forming haploid spous which give rise to the new plant.

Question 14.
Can there be mitosis without DNA replication in S-phase?
Solution:
S or synthesis phase marks the period during which DNA synthesis or replication takes place. During this time the amount of DNA per cell doubles. If the initial amount of DNA is denoted as 2C then it increases to 4C. However, there is no increase in the chromosome number; if the cell had diploid or 2n number of chromosomes at G, even after the S phase the number of chromosomes remains the same i.e. 2n.

Question 15.
Can there be DNA replication without cell division?
Solution:
DNA replication takes place in order to prepare cells for division. Cell division is the next logical step after DNA replication.

Question 16.
Analyze the events during every stage of the cell cycle and notice how the following two parameters change
i. Number of chromosomes (N) per cell
ii. Amount of DNA content (C) per cell
Solution:
Cell division is a very important process in all living organisms. During the division of a cell, DNA replication and cell growth also take place. Although cell growth is a continuous process, DNA synthesis occurs only during one specific stage in the cell cycle. The replicated chromosomes (DNA) are then distributed to daughter nuclei by a complex series of events during cell division. These events are themselves under genetic central.

The cell cycle is divided .nto two basic phases: The M phase starts with the nuclear division, corresponding to the separation of daughter chromosomes (Kaiyokinesis), and usually ends with the division of cytoplasm (Cytokinesis’). The interphase though called the resting phase is the time during which the cell is preparing for division by undergoing both cell growth and DNA replication in an orderly manner. The interphase is divided into three further phases:

  • G1 phase (Gap)
  • S phase (Synthesis)
  • G2 phase (Gap2)

VERY SHORT ANSWER QUESTIONS

Question 1.
What is karyokinesis?
Solution:
Division of nucleus is Known as karyokinesis.

Question 2.
Name the phase in which chromatids move apart.
Solution:
Anaphase.

Question 3.
Name the synthetic phase of interphase.
Solution:
S phase

Question 4.
Name the cell divisions which help recombination of genes.
Solution:
Meiosis.

Question 5.
Which type of cell division occurs in the meristematic cell of the root apex?
Solution:
Mitosis

Question 6.
Name the stage during which astral and spindle fibres disappear and nuclear membrane and nucleoli reappear.
Solution:
Telophase.

Question 7.
Name the sub-phases of prophase-I of Meiosis.
Solution:
Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis.

Question 8.
In which stage, the actual reduction of chromosome number occurs in meiosis?
Solution:
Anaphase I

Question 9.
What is Synapsis? (Bijapur, Belgaum, Shimoga 2004)
Solution:
The process of pairing homologous chromosomes is called Synapsis.

Question 10.
What is the peculiarity of zygotene?
Solution:
In the zygotene phase pairing of homologous chromosomes or synapsis takes place.

Question 11.
Define crossing over. Give its significance.
Solution:
It is an exchange of genes between non-sister chromatids of homologous chromosomes. It produces new combination of genes and variation.
Question 12.
Why mitosis is an equational division called?
Solution:
Mitosis is a process of cell division, in which chromosomes are equally distributed into two daughter cells so it is equational division.

SHORT ANSWER QUESTIONS

Question 1.
Differentiate between:
(a) S-phase and G2 phase.
(b) G1 and G2 phase
Solution:
(a) Difference between S-phase and G2 phase:
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 5
(b) Difference between Gj and G2 phase
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 6

Question 2.
Write the significance of Mitosis / Meiosis. (Udupi 2006, D.Kannada 2010)
Solution:
Significance of Mitosis:

  • The distribution of an equal number of chromosomes to the daughter cells maintains a constant chromosome number.
  • Mitosis increases the number of cells so it contributes to growth.

Significance of Meiosis:

  • Meiosis brings genetic crossing over and random distribution of paternal and maternal chromosomes to daughter cells.
  • Recombination produces variations and variations are the sources of organic evolution.

Question 3.
Mention the significance of mitosis.
Solution:

  • In multicellular organisms, the growth of the body is due to the mitotic division of cells.
  • Replacement of worn-out cells and repair of the damaged cells is by mitosis.
  • In unicellular organisms, mitosis results in the asexual reproduction of cells.
  • In plants, vegetative propagation involves only mitotic divisions.

Question 4.
When and why does a reduction in the number of chromosomes take place in meiosis?
Solution:
The actual reduction in the number of chromosomes takes place in anaphase I.
This is because in anaphase I, one member from each homologous pair moves to one pole; the two chromatids of the chromosomes do not separate as the centromeres do not divide at this stage.

Question 5.
Differentiate between prophase I and prophase of mitosis.
Solution:
Difference between prophase I and prophase of mitosis are :
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 7

Question 6.
Imagine a situation if there was no meiosis. Then what would have happened to the next generation?
Solution:
In the absence of meiosis, the next generation would have double the number of chromosomes after the fusion of gametes. This would have resulted in the birth of an altogether new species. The maintenance of characters’ sets would have been possible only through asexual reproduction.

Question 7.
Which stage in meiosis is marked with genetic recombination? How
Solution:
In the pachytene stage of meiosis I the chromosomes appear as tetrads of homologous chromosomes and cross as the genetic material exchange takes place. Thus this stage is marked with genetic recombination.

Question 8.
What is Synapsis and Synaptonemal Complex? In which stage do these occur?
Solution:
The pairing of chromosomes is called Synapsis.
In the chromosomal synapsis, a complex structure is made known as the Synaptonemal complex These occur in the zygotene stage of meiosis.

Question 9.
Describe the events in the prophase of animal cells.
Solution:

  • Chromosomal material condenses to form compact mitotic chromosomes.
  • Chromosomes are seen to be composed of two chromatids attached together at the centromere.
  • The centrioles formed in interphase start moving to the opposite poles of the cell.
  • Initiation of the assembly of the mitotic spindle, the microtubules, the proteinaceous components of the cell cytoplasm help in the process.
  • By the end of the prophase, the nuclear membrane and nucleolus disappear.

Question 10.
Diagrammatically shows the cell cycle and answers the following questions.
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 8
(a) Which is the resting stage.
(b) Which is the stage where replication takes palce.
(c) Which is the stage where mitosis takes place.
(d) Which is the post cell synthetic but pre-cell division stage.
Solution:
(a) Go Phase
(b) S Phase
(c) M Phase
(d) G2 Phase

Question 11.
Define cytokinesis. How is it accomplished in animal and plant cells?
Solution:
The process by which the cytoplasm of the cell divides resulting in the formation of two daughter nuclei is called cytokinesis.

In an animal cell, this is achieved by the appearance of a furrow in the plasma membrane. The furrow gradually deepens and ultimately joins in the centre dividing the cell cytoplasm into two.

In-plant cells, wall formation starts in the centre of the cell and grows outward to meet the existing lateral walls. The formation of a new cell wall begins with the formation of a simple precursor, called the cell plate that represents the middle lamella between the walls to two adjacent cells.

LONG ANSWER QUESTIONS

Question 1.
Describe briefly cytokinesis in animal cells and plant cells.
Solution:
(a) Cytokinesis in animal cells: In the animal cells, the cytoplasm divides by constriction. It appears on the equator and slowly deepens. The constriction converges on all the sides and pinches off the parent cell into 2 daughter cells. Constriction is the result of a peripheral band of microfilaments. This constriction divide the cytoplasm finally,

(b) Cytokinesis in plant cells: Plant cells have a rigid cell wall and this cannot undergo cytokinesis by invaginating cleavage furrow. Therefore, in them, the cytokinesis is accomplished by the formation of phragmoplast from carbohydrate and lipid-containing vesicles of Golgi apparatus and endoplasmic reticulum vesicles. A cell plate at the equator of the dividing cell is formed and divides the cytoplasm.

Question 2.
Mention the significance of mitosis.
Solution:
Significance of mitosis: Mitosis or the equational division is usually restricted to the diploid cells only.

  • However, in some lower plants and in some social insects haploid cells also divide by mitosis.
  • It is very essential to understand the significance of this division in the life of an organism.
  • Mitosis results in the production of diploid daughter cells with identical genetic complement usually.
  • The growth of multicellular organisms is due to mitosis. Cell growth results in disturbing the ratio between the nucleus and the cytoplasm.
  • It, therefore, becomes essential for the cell to divide to restore the nucleo- cytoplasmic ratio. A very significant contribution to mitosis is cell repair.
  • The cells of the upper layer of the epidermis, cells of the lining of the gut, and blood cells are being constantly replaced.
  • Mitotic divisions in the meristematic tissues – the apical and the lateral cambium, result in the continuous growth of plants throughout their life.

Question 3.
Describe meiosis II with the help of suitable diagrams.
Solution:
Meiosis II is divided into four phases.

Prophase II. Meiosis II is initiated immediately after cytokinesis, usually, before the chromosomes have fully elongated. In contrast to meiosis I, meiosis II resembles a normal mitosis. The nuclear membrane disappears by the end of prophase II. The chromosomes again become compact.

Metaphase II- At this stage, the chromosomes align at the equator and the microtubules from opposite poles of the spindle get attached to the kinetochores of sister chromatids. Anaphase II- It begins with the simultaneous splitting of the centromere of each chromosome (which was holding the sister chromatids together), allowing them to move toward opposite poles of the cell.

Telophase II- Meiosis ends with telophase II, in which the two groups of chromosomes once again get enclosed by a nuclear envelope; cytokinesis follows resulting in the formation of a tetrad of cells i.e., four haploid daughter cells.
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division 9

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NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals

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NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals.

Question 1.
Answer in one word or one line.
(i) Give the common name of Periplaneta americana.
(ii) How many spermathecae are found in earthworms?
(iii) What is the position of ovaries in cockroach?
(iv) How many segments are present in the abdomen of the cockroach?
(v) Where do you find malpighian tubules?
Solution:
(i) Cockroach
(ii) Four pairs of spermathecae are found in the 6“ to 9th segments (one pair in each segment).
(iii) Cockroach includes a pair of ovaries, that lies laterally in the 2nd to 6th abdominal segments of the abdomen.
(iv) Ten
(v) At the junction of midgut and hindgut. 100-150 yellow coloured thin filamentous ring is present in earthworm, which is called malpighian tubules.

Question 2.
Answer the following :
(i) What is the function of nephridia?
(ii) How many types of nephridia are found in earthworms based on their location?
Solution:
(i) Nephridia is the excretory organ of the earthworm or pheretima.
(ii) There are three types of nephridia –
(i) Septal nephridia – Present on both the sides of intersegmental septa of segment 15 to the last that open into the intestine.
(ii) Integumentary nephridia – Attached to the lining of the body wall of segment 3 to the last that opens on the body surface.
(iii) Pharyngeal nephridia – Present as three paired tufts in the 4th, 5th, and 6th segments.
These three different types of nephridia are almost similar in structure.

Question 3.
Draw a labelled diagram of the reproductive organs of an earthworm.
Solution:
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 1

Question 4.
Draw a labelled diagram of the alimentary canal of a cockroach
Solution:
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 2

Question 5.
Distinguish between the followings :
(a) Prostomium and peristomium
(b) Septal nephridium and pharyngeal nephridium
Solution:
(a) The main difference between prostomium and peristomium are :
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 3
(b) The main difference between septal nephridium and pharyngeal nephridium are:
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 4
Question 6.
What are the cellular components of blood?
Solution:
Red blood cells and white blood cells are the cellular components of blood.

Question 7.
What are the following and where do you find them in an animal body.
1. Chondrocytes
2. Axons
3. Ciliated epithelium
Solution:
1. Chondriocytes: The intercellular material of cartilage is solid and pliable and resists compression. Cells of this tissue (Chondriocytes) are enclosed in small cavities within the matrix secreted by them. Most of the cartilages in vertebrate embryos are replaced by bones in adults. Cartilage is present in the tip of the nose, outer ear joints, between adjacent bones of the. vertebral column, limbs, and hands in adults.

2. Axons: It is found in the nervous system neuron. It is a long fiber, the distal end of which is branched. The main function of axons is the transmission of impulses by means of neurotransmitters.

3. Ciliated epithelium: If the columnar or cuboidal cells bear cilia on their free surface they are called the ciliated epithelium. They are found in the lining of the stomach and intestine and help in secretion and absorption, their function is to move particles or mucus in a specific direction over the epithelium. They are mainly present in the inner surface of hollow organs like bronchioles and fallopian tubes.

Question 8.
Describe various types of epithelial tissues with the help of labelled diagrams.
Solution:
Epithelial tissues
Epithelial tissues provide covering to the inner and outer lining of various organs. The cells of epithelial tissues are compactly packed with a little intercellular matrix.
There are two types of epithelial tissues:
(i) Simple epithelium
(ii) Compound epithelium
(i) Simple epithelium :
Composed of a single layer of cells and functions as a lining for body cavities ducts and tubes. It is further divided into three types on the basis of structure modifications-
(a) Squamous epithelium – It is made of a single layer of flattened cells with irregular boundaries.
It is found as a lining for body cavities, ducts, and tubes such as in the walls of blood vessels and air sacs of lungs.
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 5
Functions – It helps in forming a diffusion boundary.
(b) Cuboidal epithelium – It is made of a single, layer of cube-like cells. It is commonly found in the ducts of glands and tubular parts of nephrons in kidneys. Specialized cuboidal cells are capable of producing gametes found in gonads called the germinal epithelium.
Functions- It helps in secretion and absorption and also in moving particles or mucus in a specific direction over the epithelium.
(c) Columnar epithelium – It is composed of a single layer of tall and slender cells. Nuclei are located at the base.
Its free surface may have microvilli.
It is found inlining of the stomach and intestine.
Functions – It helps in secretion and absorption.
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 6

Question 9.
Distinguish between
(a) Simple epithelium and compound epithelium
(b) Cardiac muscle and striated muscle
(c) Dense regular and dense irregular connective tissues
(d) Adipose and blood tissue
(e) Simple gland and compound gland
Solution:
(a) The main difference between simple epithelium and compound epithelium are as following.
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 7
The main difference between Cardiac muscles and striated muscle are as following.
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 8
The main difference between dense regular connective tissues and dense irregular connective tissues are as following.
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 9
The main difference between adipose tissue and blood tissue are as following.
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 10
The main difference between simple gland and compound gland are as following
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 11

Question 10.
Mark the odd one in each series:
(a) Areolar tissue; blood; neuron; tendon
(b) RBC; WBC; platelets; cartilage
(c) Exocrine: endocrine; salivary gland;ligament
(d) Maxilla; mandible; labrum; antennae
(e) Protonema; mesothorax; metathorax; coxa
Solution:
(a) Neuron
(b) Cartilage
(c) Ligament
(d) Antennae
(e) Protonema

Question 11.
Match the terms in column I with those in column II:
Column I Column II
(a) Compound epithelium – (i) Alimentary canal
(b) Compound eye – (ii) Cockroach
(c) Septal nephridia – ( iii) Skin
(d) Open circulatorysystem – (iv) Mosaic vision
(e) Typhlosole – (v) Earthworm
(f) Osteocytes – (vi) Phallomere
(g) Genitalia – (vii) Bone
Solution:
(a) Compound epithelium ( iii) Skin
(b) Compound eye – (iv) Mosaic vision
(c) Septal nephridia – (v) Earthworm
(d) Open circulatory system – (ii) Cockroach
(e) Typhlosole – (i) Alimentarycanal
(f) Osteocytes – (vii) Bone
(g) Genitalia – (vi) Phallomere

Question 12.
Mention briefly the circulatory system of earthworms.
Solution:
Pheretima exhibits a closed type of blood vascular system, consisting of blood vessels capillaries, and heart. Due to the closed circulatory system, blood is confined to the heart and blood vessels. Contractions keep blood circulating in one direction. Smaller blood vessels supply the gut, nerve cord, and body wall. Blood glands are present on the 4th, 5th, and 6th segments. They produce blood cells and hemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature. Earthworms lack specialized breathing devices. Respiratory exchange occurs through moist body surfaces into their bloodstream.

Question 13.
Draw a neat diagram of the digestive system of the frog.
Solution:
The digestive system of frog:
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 12

Question 14.
Mention the function of the following:
(a) Ureters in frog
(b) Malpighian tubules
(c) Body wall in earthworm
Solution:
Functions:
(1) Ureters in frog:

  • They carry the urine from the kidneys to the cloaca.
  • In males, it also conducts the sperm as it is the urinogenital duct.
  • In females, the ureters and oviduct open- separately in the cloaca.

(2) Malpighian tubules:

  1. They are the excretory organs of a cockroach.
  2. They collect the nitrogenous wastes from the haeomolymph and send them into the intestine.
  3. Each tubule is lined by glandular and ciliated cells. They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut.

(3) Body wall of earthworm:
The body wall of the earthworm is covered externally by a thin non-cellular cuticle

VERY SHORT ANSWER QUESTIONS

Question 1.
Name the protein found in white fibres.
Solution:
Collagen.

Question 2.
State the function of setae.
Solution:
It helps in locomotion by gripping the earth.

Question 3.
What is the functional unit of the cockroach eye?
Solution:
Ommatidium.

Question 4.
Name the unit of neural or nervous system.
Solution:
Neurons.

Question 5.
What is worm casting ?
Solution:
It is the insoluble and undigested food that is given out along with soil through anus.

Question 6.
Which cell covers the exposed surfaces of the body (skin) and internal passage ways (digestive tract and glands) ?
Solution:
Squamous epithelium

Question 7.
Name the type of epithelium that lines the inner surface of stomach.
Solution:
Columnar epithelium

Question 8.
Name the type of epithelium that lines the buccal cavity.
Solution:
Stratified squamous epithelium.

Question 9.
N ame of type of tissue that is the most abundant in animal body.
Solution:
Connective tissue.

Question 10.
What is the other name given to the gizzard of cockroach?
Solution:
Proventriculus.

Question 11.
Name the larva of a frog.
Solution:
Tadpole.

Question 12.
What is the scientific name of Indian (bull) frog?
Solution:
Rana tigrina.

SHORT ANSWER QUESTIONS

Question 1.
What are the neuroglia cells?
Solution:
Cells which holds the neuron together are known as neuroglia cells.

Question 2.
What is vermicompositing?
Solution:
The process of increasing soil fertility by earthworms is known as vermicomposting.

Question 3.
What are exocrine glands? Name any two secretions of them.
Solution:
Exocrine glands : Those glands which have ducts to pour their secretion(s) into the respective site of action, are called exocrine.
(i) Salivary glands secrete saliva into the buccal cavity.
(ii) Liver secretes bile into the duodenum.

Question 4.
Write four functions of bones.
Solution:
Functions of bones:
(i) They provide place for attachment of muscles and help in movement and locomotion.
(ii) Bone marrow is the site of manufacture of blood cells.
(iii) Bones provide protection to the internal organs.
(iv) The long bones of the limbs serve the weight-bearing function.
(v) They act as the depot of calcium and phosphorus.

Question 5.
Describe the three types of cell junctions present in the epithelium and other tissues.
Solution:
Cell junctions
(i) Tight junctions – They check leaking of substances across a tissue.
(ii) Adhering junctions – They help in cementing the neighbouring cells together.
(iii) Gap junctions – They facilitate the cells to communicate with each other by cytoplasmic connections, for rapid transfer of ions, small molecules, etc.

Question 6.
How is the gizzard in the alimentary canal of a cockroach suitable for grinding the food?
Solution:
Gizzard of cockroach has following characteristics:
(i) The gizzard has an outer layer of thick circular muscles.
(ii) The inner thick layer of cuticle forms six plate like teeth.
(iii) The movement with the help of muscles and the teeth-like structures help in grinding the food.

Question 7.
What is a typhlosole in an earthworm? Where is it found? What is its function?
Solution:
Typhlosole: It is an internal median fold of the dorsal wall of the intestine. It is found in the intestine between 26th and 35th segments of the body.
It increases the effective area of absorption.

LONG ANSWER QUESTIONS

Question 1.
Describe the female reproductive organs of frog.
Solution:
The female reproductive organs include a pair of ovaries. The ovaries are situated near kidneys and there is no functional connection with kidneys. A pair of oviduct arising from the ovaries opens into the cloaca separately. A mature female can lay 2500 to 3000 ova at a time.
Fertilisation is external and takes place in water. Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult.

NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 13

Question 2.
Describe with examples, various types of connective tissues.
Solution:
Connective tissues are most abundant and widely distributed in the body of complex animals. They are named connective tissues because of their special function of linking and supporting other tissues/C ••gans of the body. Connective tissues are classified into three types:
(i) Loose connective tissue,
(ii) Dense connective tissue and
(iii) Specialised connective tissue.
(i) Loose connective tissue:

  • It has cells and fibres loosely arranged in a semi-fluid ground substance, for example, areolar tissue present beneath the skin.
  • Often it serves as a support framework for epithelium. It contains fibroblasts (cells that produce and secrete fibres), macrophages and mast cells.
  • Adipose tissue is another type of loose connective tissue located mainly beneath the skin. The cells of this tissue are specialised to store fats.

(ii) Dense connective tissue :

  • Fibres and fibroblasts are compactly packed in the dense connective tissues.
  • Orientation of fibres show a regular or irregular pattern and are called dense regular and dense irregular tissues.
  • In the dense regular connective tissues, the collagen fibres are present in rows between many parallel bundles of fibres.
  • Tendons, which attach skeletal muscles to bones and ligaments which attach one bone to another are examples of this tissue.
  • Dense irregular connective tissue has fibroblasts and many fibres (mostly collagen) that are oriented differently. This tissue is present in the skin.

(iii) Specialised connective tissue :

  • Cartilage, bones and blood are various types of specialised connective tissues.
  • The intercellular material of cartilage is solid and pliable and resists compression.
  • Cells of this tissue (chondrocytes) are enclosed in small cavities within the matrix secreted by them.
  • Cartilage is present in the tip of nose, outer ear joints, between adjacent bones of the vertebral column, limbs and hands in adults.

Bones : It has a hard and non-pliable ground substance rich in calcium salts and collagen fibres which give bone its strength. It is the main tissue that provides structural frame to the body.
Blood : It is a fluid connective tissue containing plasma, red blood cells (RBC), white bloo4 cells (WBC) and platelets. It is the main circulating fluid that helps in the transport of various substances.

Question 3.
Describe the alimentary canal of earthworm.
Solution:
The alimentary canal is a straight tube and mns between first to last segment of the boay. It has following parts.
Mouth : A terminal mouth opens into the buccal cavity (1-3 segments) which leads into muscular pharynx.
oesophagus: A small narrow tube, oesophagus (5-7 segments), continues into a muscular gizzard (8-9 segments). It helps in grinding the soil particles and decaying leaves, etc.
Stomach : The stomach extends from 9-14 segments. The food of the earthworm is decaying leaves and organic matter mixed with soil. Calciferous glands, present in the stomach, neutralise the humic acid present in humus.
• Intestine starts from the 15th segment onwards and continues till the last segment. A pair of short and conical intestinal caecae project from the intestine on the 26th segment.
Typhosole : The characteristic feature of the intestine between 26-35 segments is the presence of internal median fold of dorsal wall called typhlosole. This increases the effective area of absorption in the intestine.
Anus : The alimentary canal opens to the exterior by a small rounded aperture called anus. The ingested organic rich soil passes through the digestive tract where digestive enzymes breakdown complex food into smaller absorbable units. These simpler molecules are absorbed through intestinal membranes and are utilised.

Question 4.
Draw a labelled diagram of external features of cockroach.
Solution:
NCERT Solutions for Class 11 Biology Chapter 7 Structural Organization in Animals 14

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