CBSE Class 11 – Page 25

NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption

January 5, 2022June 18, 2021 by Raju

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:

Kill bacteria and germs
Loosens fibrous material of food.
Activates proenzyme pepsinogen to its active form pepsin.
Gives an acidic medium for action by pepsin.
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.

(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.

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:

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:

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 English Hornbill Chapter 7 The Adventure

January 5, 2022June 18, 2021 by Prasanna

Here we are providing NCERT Solutions for Class 11 English Hornbill Chapter 7 The Adventure. Students can get Class 11 English The Adventure NCERT Solutions, Questions and Answers designed by subject expert teachers.

The Adventure NCERT Solutions for Class 11 English Hornbill Chapter 7

The Adventure NCERT Text Book Questions and Answers

The Adventure Understanding the text

I. Tick the statements that are true.
Answer:
The true statements are:

The story’ hinges on a particular historical event.
The story’ tries to relate history to science.

II. Briefly explain the following statements from the text.

Question 1.
“You neither travelled to the past nor the future. You were in the present experiencing a different world. ”
Answer:
This statement is made by Rajendra Deshpande to Professor Gangadharpant Gaitonde. Here he tries to give a possible explanation to Prof Gaitonde’s unique experience in the two days following his collision with a truck. According to the speaker, Professor Gaitonde did not travel in time. In fact, he was in the present but was experiencing a different world. This statement emphasises on the idea that reality is not unique. There are many worlds and many realities. A person’s reality is based on his/her experience at a particular time at a particular place.

Question 2.
“You have passed through a fantastic experience: or more correctly, a catastrophic experience. ”
Answer:
In this statement Rajendra Deshpande tries to rationalise Professor Gaitonde’s experience of making a transition to another world. According to him, Professor Gaitonde has had a fantastic experience. Here, the word fantastic means both extraordinary and fanciful. However, he immediately finds a better word for the experience and calls it catastrophic. Now, this word is a reference to Catastrophe Theory which is a branch of mathematics and is concerned with abrupt changes. Professor Gaitonde’s experience of travelling to a parallel world without moving back or forth in time seems to be an apt example of a catastrophic experience to Rajendra Deshpande.

Question 3.
Gangadharpant could not help comparing the country he knew with what he was witnessing around him.
Answer:
This statement is made by the third person narrator of the story. Professor Gaitonde, who travels to another world in the present, witnesses a different India which is completely different from the India he has known from this childhood. The country he witnesses in the alternative world refused to surrender to the colonising powers and stood up against them.

The people of this country are more honest, more efficient, well organised and quite modem. Everything that he sees in this country poses a stark contrast to the country he lives in. This compels him to compare the country he knows so well with the country he witnesses around him.

Question 4.
“The lack of determinism in quantum theory! ”
Answer:
This statement is made by Prof Gaitonde in response to Rajendra Deshpane’s explanation of how indeterminable the behaviour of electrons is. Here he maintains that even a person like him, who is not an expert of science, knows about the lack of determinism in quantum theory. Quantum theory believes in the randomness or uncertainty of the universe. This is quite succinctly explained by Rajendra Deshpande with the example of electrons orbitting the nucleus of an atom. The electrons could move in any of the large number of specified states and could even jump from one state to another. There is no certainty of an electron’s presence in a particular state.

Question 5.
“You need some interaction to cause a transition. ”
Answer:
This statement is made by Rajendra Deshpande in response to Professor Gaintonde’s question of why he made the transition to the other world. Rajendra Deshpande says that in order to make a transition like this, one must have an interaction. By interaction, he means something that gives the transition a particular direction. In this case, the focused thought of Professor Gaitonde about the probable course of history in case the third battle of Panipat had had a different result functioned as the interaction and determined the transition for him.

The Adventure Talking about the text

Question 1.
Discuss the following statements in groups of two pairs, each pair in a group taking opposite points of view.

(i) A single event may change the course of the history of a nation.
For:

Events like the defeat of important leaders like Napoleon, Hitler and so on have helped construct today’s version of historic events for different nations.
Had one of these events not happened, chances are that history may have been entirely different.
Similarly, this text tries to present what would have happened if the Marathas had not been defeated by the British in India.
The India that is constructed in the text, is heavily influenced by the Marathi kingdom, unlike the British India that we’ve known through historic events. Therefore, altering historic events can change the history of a nation.

Against:

It is impossible to predict if altering a single event can in reality change the course of history.
While this text attempts to show that, had the Marathas won the war, the British could have still taken over and created the British India that we know of.
All that is portrayed here is speculation, as it is impossible to go back and change historic events.

(ii) Reality is what is directly experienced through the senses.
For:

Gaitonde’s construction of the alternate version of history is so real that he believes he actually witnessed a different version of reality than the one we are familiar with.
Similarly, he is able to convince Rajendra of this reality because he has a piece of paper which contains notes of all these alternate events.
Both these characters believe that what they experience through the senses is real.
They show us that the senses construct reality for us.
The school of thought that believes reality is constructed through our experiences is called empiricism.

Against:

The lack of clarity or established proof that any of the events Gaitonde believed actually happened indicates that all of this could have just been his imagination.
Similarly, the piece of paper he presents as proof may have just been a work of fiction constructed by him.
This may also be the impact of the accident where Gaitonde’s memory may have been affected or damaged, leading him to believe in alternate realities.
All of the events in this story can be explained through rational thought as well.

(iii) The methods of inquiry of history, science and philosophy are similar.
For:

In the story we see Gaitonde, a history academic experiencing an alternate version of historical events closely connected to time, which Rajendra compares to the quantum theory in physics.
The method that Rajendra uses to explain the science behind this to Gaitonde is very close to how philosophers explained things, attempting to simplify complicated concepts using examples.
Thus we see all three disciplines closely connected in the text through their understanding of time and reality.

Against:

If all three disciplines were so closely connected in their methods and fields of inquiry, they wouldn’t be studied separately.
But because the concepts they deal with are radically different, they are studied separately.
Further, while the inquiry may be similar in the text, this does not imply that-all methods of inquiry used by these disciplines are similar, as the text only picks up one particular incident.
And this may broadly differ in these fields on other instances.

Question 2.
(i) The story is called‘The Adventure’. Compare it with the adventure described in ‘We’re Not Afraid to Die…’
Answer:
“We’re Not Afraid to Die…” narrates a family’s adventures on a boat at sea facing a terrible storm. It describes various efforts made by the parents to guide their boat to safety and presents the courage of their children while the parents panicked. “The Adventure” constructs an alternate version of reality, which is what would have happened had the Marathas defeated the British. How the Indian nation would have appeared under the influence of Indian rulers instead of the British. While the events of “We’re Not Afraid to Die.. .’’are realistic and depict encounters that may have happened around the world, the events in “The Adventure” are fictional and speculative.

(ii) Why do you think Professor Gaitonde decided never to preside over meetings again?
Answer:
In the alternate reality of India, Professor Gaitonde attempted to take the empty chair on stage that he was so accustomed to take, only to be met with hostility from the crowd, who threw eggs and tomatoes at him and ran him off stage. The impact of this incident on him is so traumatic, at what he considers his thousandth address as chair, that when he returns to his actual reality he refuses to preside over any more meetings again.

The Adventure Thinking about language

Question 1.
In which language do you think Gangadharpant and Khan Sahib talked to each other? Which language did Gangadharpant use to talk to the English receptionist?
Answer:
Since Khan Sahib is from Peshawar, he may have spoken to Gangadharpant in Hindi or Urdu. However, since Gangadharpant was speaking to the English receptionist in territory controlled by the British, one can assume he spoke to her in the English language.

Question 2.
In which language do you think Bhausahebanchi Bakhar was written?
Answer:
Since the Bhausahebanchi Bakhar describes the victory of the Marathas over the British, and appears to be a seminal book in a library in Maharashtra, the language used may have been Marathi.

Question 3.
There is mention of three communities in the story: the Marathas, the Mughals, the Anglo-Indians. Which language do you think they used within their communities and while speaking to the other groups?
Answer:
Within the community, the Marathas would have used Marathi, the Mughals Urdu, and the Anglo-Indians would’ve used English. While speaking to other groups, considering that the British had little influence over India in the alternate version of history, Marathi may have been the common language because of the influence that Marathi rulers had on the outcome of India. Urdu could also have been the common language since the Mughal rule continued in Delhi or Hindi because of the historical association of the nation with the language.
(Answers will vary)

Question 4.
Do you think that the ruled always adopt the language of the ruler?
Answer:
While the ruled may be inclined to learn the language of the ruler, history has shown us through the diversity of languages that exists across the nation that not all people solely adopt a single language being promoted. While people across the nation use a common language to speak to one another, which is the ruler or administration’s language, they also retain association with local languages used in smaller spaces like the household.
(Answers will vary)

The Adventure Working with words

I. Tick the item that is closest in meaning to the following phrases.

to take issue with—iii) to disagree .
to give vent to—(i) to express
to stand on one’s feet—(ii) to be independent
to be wound up—(ii) to stop operating
to meet one’s match—(iii) to meet someone who is equally able as oneself

II. Distinguish between the following pairs of sentences.

Question 1.
(i) He was visibly moved.
Answer:
The features on his face showed how he was emotionally affected,

(ii) He was visually impaired.
Answer:
He had trouble seeing things because of loss of vision.

Question 2.
(i) Green and black stripes were used alternately.
Answer:
Green stripes and black stripes were both used, one after the other.

(ii) Green stripes could be used or alternatively black ones.
Answer:
Either green stripes could be used everywhere or black ones in its place.

Question 3.
(i) The team played the two matches successfully.
Answer:
The team performed well in two specific matches they played

(ii) The team played two matches successively.
Answer:
The team played two consecutive matches, one followed by the other.

Question 4.
(i) The librarian spoke respectfully to the learned scholar.
Answer:
The librarian showed a sense of respect for the scholar while speaking to him.

(ii) You will find the historian and the scientist in the archaeology and natural science sections of the museum respectively.
Answer:
You will find the historian in the archaeology section and the scientist in the science section of the museum.

The Adventure Things to do

II. Look up the Internet or an encyclopedia for information on the following theories.

(i) Quantum theory
Quantum theory in physics is the study of the smallest particles in the universe found in atomic and subatomic particles. It observes the energy produced by particles like protons, neutrons and electrons where one unit is referred to as quanta, which led to the name Quantum theory. This theory was put together by the physicist Max Planck in 1900, who was later awarded the Nobel Prize.

(ii) Theory of relativity
This was established by the famous scientist Albert Einstein first in 1905. Einstein drew connections between space and time, arguing that these concepts were not fixed as previously understood by physics but fluid with possibilities of change. In the absence of a gravitational field, it was possible to convert matter into huge quantities of energy, and different bodies could experience time differently.

(iii) Big Bang theory
The Big Bang theory is a scientific explanation to the beginning of the world. According to this, the universe that we know began with a small singularity, a small and dense source of energy, which gradually expanded over time. This expanded into the stars and planets that we know of in the universe today.

(iv) Theory of evolution
The theory of evolution was given by Charles Darwin in his book On the Origin of Species in 1859. Darwin believed that all life on earth was connected to each other, and that humans evolved through a process of natural selection. Natural selection states that through a process of evolution from previous animal forms in different centuries, the human form has evolved by learning to adapt to natural habitat on the planet.

NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom

January 5, 2022June 18, 2021 by Raju

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.

Chlorophyceae: The members of Chlorophyceae are commonly called green algae.
Phaeophyceae: The members of Phaeophyceae or brown algae, are found primarily in marine habitats.
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

Bryophytes
Pteridophytes and
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.

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 on sporophyll which are arranged spirally along an axis to form strobili or cones.
The strobili bearing microsporophylls and microsporongia are called microsporangiate or male strobili.
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.
The development of pollen grain takes place within microsporangia.
The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili.
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.
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 females cones are borne on the main plant body of the sporophyte. The megaspore mother cell divides meiotically to form four megaspore.
One of the megaspore enclosed within the megasporangium develops into a multicellular female gametophyte that bears 2 or more archegonia or female sex organs.
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:

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.
Nos toe, Anabaena, etc., are useful in increasing fertility of soil. Antibiotic chlorellin is extracted from Chlorella.
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.
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 :

Gymnosperms helps in checking soil erosion.
Seeds of Pinns gerardiana, Gnetnm gnemon and Ginkgo biloba are eaten.
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.
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:

Genera like Selaginella and Salvinia which produce two kinds of spores macro and microspores are known as heterosporous.
The megaspore and microspores germinate and give rise to female and male gametophytes, respectively.
The female gametophytes in these plants are retained on the parent sporophyte for variable periods.
The development of the zygotes into young embryo takes place within the female gametophytes.
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

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:

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 English Snapshots Chapter 5 Mother’s Day

January 5, 2022June 18, 2021 by Prasanna

Here we are providing NCERT Solutions for Class 11 English Snapshots Chapter 5 Mother’s Day. Students can get Class 11 English Mother’s Day NCERT Solutions, Questions and Answers designed by subject expert teachers.

Mother’s Day NCERT Solutions for Class 11 English Snapshots Chapter 5

Mother’s Day NCERT Text Book Questions and Answers

Question 1.
This play, written in the 1950s, is a humorous and satirical depiction of the status of the mother in the family.
(i) What are the issues it raises?
(ii) Do you think it caricatures these issues or do you think that the problems it raises are genuine? How does the play resolve the issues? Do you agree with the resolution?
Answer:
The play, written in the 1950s, is a humorous and satirical depiction of the status of the mother in the family.
It raises very poignant social issues of women, as housewives, being taken for granted by the family. The husband, son and daughter—all take the mother for granted. She gets no respite and no gratitude for all that she does. The day, she refuses to attend to them, they are outraged.

These issues are genuine, especially in a country like India where there is still a gender bias. The housewife is supposed to perform all the chores of the house as her duty. The scenario is now, however, showing some signs of change although we still have a long way to go before we achieve equality.

Question 2.
If you were to write about these issues today what are some of the incidents, examples and problems that you would think of as relevant?
Answer:
Hints-problems related to this issue:

mother working at a job and struggling with the housework alone
generation gap
sibling rivalry
marital discord in parents
single parent family

Question 3.
Is drama a good medium for conveying a social message? Discuss.
Answer:
The modem artist is, in the words of August Strindberg, “a lay preacher popularising the pressing questions of his time.” Millet, Meunier, Turgenev, Dostoyevsky, Emerson, Walt Whitman, Tolstoy, Ibsen, Strindberg, Hauptmann and a host of others mirror in their work as much of the spiritual and social revolt as is expressed by the most fiery speeches of the propagandist. And more important still, they compel far greater attention. Their creative genius, instilled with the spirit of sincerity and truth, strikes root where the ordinary word often falls on barren soil.

The medium mirrors every phase of life and embraces every strata of society, showing each and all, caught in the throes of the tremendous changes going on, and forced either to become part of the process or be left behind. Ibsen, Strindberg, Hauptmann, Tolstoy, Shaw, Galsworthy and the other dramatists represent the social iconoclasts of our time. They know that society has gone beyond the stage of patching up, and that man must throw off the dead weight of the past, if he is , to go free to meet the future.Drama is the dynamite which undermines superstition, shakes the social pillars, and prepares men and women for the reconstruction.

Question 4.
Read the play out in parts. Enact the play on a suitable occasion.
Answer:
The play’s title Mother’s Day indicates that a suitable occasion for it to be performed may be the 2nd Sunday in May, when Mother’s Day is most commonly celebrated. This day has been set aside every year to honour mothers and motherhood all over the world. The foundations for this day being celebrated as Mother’s Day were laid by Anna Marie Jarvis in the United States. She chose this day to honour her mother and all mothers at a church memorial ceremony in West Virginia in 1908.

However, as the play portrays how mothers are taken for granted in the family, any occasion may be suitable for a performance of this play. This is a common social issue across the Indian subcontinent and the world, mothers everywhere are taken for granted by their families’ all the time. Like the family depicted, people are often so self- involved that they forget about the amount of responsibilities shouldered by mothers. The lesson this play seeks to convey is that other members of the family must learn to share responsibilities, and not leave everything for the mother to do.

Question 5.
Discuss in groups plays or films with a strong message of social reform that you have watched.
(Answers may vary.)Sample answer:
Answer:
Some plays with a strong message of social reform include:
The Good Person of Szechwan –
This is a play written by the German playwright Bertolt Brecht. This play is about a young poor condemned Chinese woman who offers shelter to Gods who visit one evening and they bless her with money to open a business. Other people in her village who earlier shunned her then take advantage of her and oppress her, forcing her to invent an alter ego to fight against their cruelty. The play portrays the changing attitudes of people towards members of different classes, and the necessity to be strong to fight oppression in society.

The Death of a Salesman –
This play, written by the Irish playwright Arthur Miller, describes the trajectory of a salesman who focuses most of his time and energy on his career and neglects his family in the process. His son blames him for not having a role model to follow and destroying his possibilities for a stable future. After the salesman loses his job, he feels he has lost everything. This play highlights how difficult career struggles can be, and how they can destroy our lives and that we should not neglect family in the process. Both as parents and as children it is important to recognise and appreciate people close to us.

A Raisin in the Sun –
This play, written by African-American playwright Lorraine Vivian Hansberry, describes the financial struggles of an African-American family living in a poor neighbourhood in Chicago. After the family receives an inheritance each of them wishes to use this sum in different ways to better their lives. It touches upon how important staying together as a family can be during difficult circumstances. The play also portrays racial discrimination against African-Americans in America, when the family tries to move into a neighbourhood of white people they are threatened by a racist white association. The message the play leaves us with is a need for change in the way we treat each other.

Some films with a strong message of social reform include:

English Vinglish –
This Indian film is about a housewife who is taken for granted by her daughter and husband, who ridicule her for her poor English speaking skills, making her suffer from confidence issues. She starts taking classes to improve her English keeping this secret from her immediate family. Gradually this helps her become more confident and feel better about herself, changing the way her family view her. This film leaves us with the message that we should learn to appreciate everyone’s strengths and not mock people who have not received the same education we have.

The Boy in the Striped Pajamas –
This British-American film is set in World War II and describes the experiences of the Jewish people who were forced into concentration camps by Nazi soldiers. This depiction is portrayed through a friendship that develops between two 8-year-old boys who live on opposite sides of the camp – a Jewish prisoner and the son of a Nazi commander. The film ends with both of them being executed inside the gas chambers, while the commander and his Nazi soldiers desperately search for his son. This film depicts the violence of war and the cruel methods in which prisoners were made to live and disposed of.

12 Years a Slave –
This American film is based in 1841, when slavery was still legal in certain parts of the world. It describes the experiences of a free American man who is drugged and sold into slavery. The film highlights how slaves were brutally whipped and beaten by white overseers of estates and their masters. It also highlights the experiences of female slaves who were abused and exploited by these white men. This film seeks to remind us through its heart¬breaking account, how historically cruel people with power working at such plantations were towards their poor and oppressed slaves.

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

January 5, 2022June 18, 2021 by Raju

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.

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.

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.
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.
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.

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.
Respiration, nutrition, release of energy for the body are carried out within the cells only.
Even the animals and plants reproduce because the cells reproduce individually.
Growth occurs because cell grow and multiply.
In Amoeba all the life processes are performed within the boundaries of the single cell.
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.
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.
Each tissue is specialized to perform specific functions. Different tissues then get organised into organs which perform certain specific functions.
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.
These tissues, organs and organ system of the organisms work because the cells work.
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:

(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:

Under the electron microscope, each centriole is seen to be formed of nine sets of tubular structures arranged in a circular fashion.
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.
Sometimes delicate strands appear to connect sets of the triplet to each other.
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.
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.

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.

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