Chapter 2 - Nutrition in Animals Class - 7 | Long answer type questions

 

Science - Chapter 2 - Nutrition in Animals

Class - 7

NCERT -  Important Questions 

Long Answer Type Questions

Questions 1. Why we cannot digest cellulose like the cattle do?

Answer:

* Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine.

* The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

 

Question 2. Can we survive only on raw, leafy vegetables/grass? Discuss.

Answer: No, human cannot survive only on raw, leafy vegetables, or grass because they are rich in cellulose, which is a type of carbohydrate that humans are not able to digest due to the absence of cellulose-digesting enzymes.

 

Question 3. Explain the process of digestion in grass eating animals.

Answer:

* Grass eating animals quickly swallow the grass and store it in a part of the stomach called rumen. Here the food gets partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it.

 

Question 4. Write a short note on digestion in starfish.

Answer:

Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested.

 

Question 5. Write a short note on large intestine.

Answer:

* The large intestine is wider and shorter than small intestine. It is about 1.5 metre in length.

* Its function is to absorb water and some salts from the undigested food material. The remaining waste passes into the rectum and remains there as semi-solid faeces.

 

Question 6. How can we prevent tooth decay?

Answer: We can prevent tooth decay in the following manner: 

* By cleaning the teeth with a brush  and dental floss at least twice a day and rinse the mouth after every meal.

* By not putting dirty fingers or any unwashed object in the mouth.

 

Question 7. What are villi? What is their location and function?

Answer:

* The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus). These are found in small intestine.

* Villi increase the surface area for absorption of the digested food. i.e The surface of the villi absorbs the digested food materials.

 

Question 8. What are the functions of the tongue in human body?

Answer:

* Functions of the tongue in human body helps in talking.

* It mixes saliva with the food during chewing and helps in swallowing food.

*  It has taste buds that detect different tastes of food.

 

Question 9. Draw a labelled diagram of amoeba.

 

Question 10. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.

Answer:

* Cellulose is a type of carbohydrate that can be digested by ruminants but not by humans.

* Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine.

* The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

 

Question 11. What is tooth decay?

Answer:

* Bacteria are present in our mouth but they are not harmful to us. However, if we do not clean our teeth and mouth after eating, many harmful bacteria also begin to live and grow in it.

* These bacteria break down the sugars present from the leftover food and release acids.

* The acids gradually damage the teeth. This is called tooth decay.

 

Question 12. Explain the process of nutrition in Amoeba.

 Answer:

* Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole.

* Digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed.

 

Question 13. What substances are secreted in the stomach?

Answer:

* The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices.

* The mucous protects the lining of the stomach.

* The acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act.

* The digestive juices break down the proteins into simpler substances.

 

Question 14. Write one similarity and one difference between the nutrition in amoeba and human beings.

Answer:

Similarity

* In amoeba, digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed.

* In human, digestive juices are secreted in buckle cavity, liver and small intestine.

 Difference

* Amoeba captures its food with help of pseudopodia. In human being, food is taken into the body through the mouth.

 

Question 15. How does the stomach work?

Answer:

* The stomach is a thick-walled bag. Its shape is like a flattened U and it is the widest part of the alimentary canal.

* It receives food from the food pipe at one end and opens into the small intestine at the other.

* The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices.

* The mucous protects the lining of the stomach. The acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. The digestive juices break down the proteins into simpler substances.

 

Question- Can we survive only on raw, leafy vegetables / grass? Discuss.

Answer: We know that animals like most of the bacteria, non-green plants and human being do not possess the ability to synthesize their own food. Therefore, they depend upon autotrophs for their food supply either directly or indirectly.

The green plants (leafy vegetables / grass) trap solar energy and manufacture their food in the form of glucose. So, leafy vegetables and grass can provide sufficient energy required for the survival of human being.

 

Question-  Write one similarity and one difference between nutrition in amoeba and human beings.

Answer:

Similarity: During the digestion of food, in amoeba digestive juices are secreted into the food vacuole. They act on the food and break it into simpler substances. In human being, the inner walls of stomach and the small intestine also secrete the digestive juices. The digestive juices convert complex substances of food to simpler ones.

Difference: Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particles. The food is trapped in a food vacuole. Human beings take food through the mouth, digest and utilize it. The food is gradually digested as food travels through the various compartments.

 

Question- Can we survive only on raw, leafy vegetables/grass? Discuss.

Answer: We know that including all animals, fungi, many bacteria, non-green plants, and human beings do not possess the ability to synthesize their own food. Therefore depend on autotrophs for their food supply either directly or indirectly.

The green plants (leafy vegetables/grass) trap solar energy and manufacture their food in the form of glucose. So, leafy vegetables and grass can provide sufficient energy required for the survival of human beings.

 

Question- What are the functions of the tongue in human body?

Answer: The functions of the tongue are as follows:

1. it is used for talking, it is not possible to talk without this.

2. It mixes saliva with the food during chewing and helps in swallowing of food.

3. Due to the presence of taste buds on it, It is used to identify the taste of food like sweet or Salty etc.

 

Question- Explain tooth decay?

Answer:

* Our mouth contains some useful bacteria but if we do not clean our teeth and mouth after eating, many harmful bacteria also begin to live and grow in it .

* These bacteria break down the sugars present from the leftover food and release acids. These acids gradually damage the teeth and causes tooth decay.

 

Question- What are secreted inside the stomach?

Answer:

* Gastric juice is secreted by the walls of stomach which contains HCl and Pepsin.

* HCI helps to kill the germs present in food. After mixing with the food it provides an acidic medium to the food which is essential for the activation of pepsin enzyme.

* Pepsin digests protein into peptides.

 

Question-  Explain digestive enzymes?

Answer:

* There are different types of enzymes which are used for the digestion of different food materials like carbohydrates, fats, protein etc.

* The process of digestion involves the association of several catalytic organic compounds such as amylase, pepsin, lipase, trypsin etc. These organic compounds are known as digestive enzymes.

 

Question- Name and explain the type of carbohydrates that can be digested by ruminants but not by humans.

Answer:

* Cellulose is the carbohydrate that can be digested by ruminants. Ruminants have large sac like structure between the small intestine and large intestine which is Responsible for digestion of cellulose in  them. The cellulose of the food is digested by the action of certain bacteria which are not present in human beings.

 

Question-  Describe nutrition in amoeba.

Answer:

* Amoeba is a single-celled organism found in pond water. It has a cell membrane, a dense, rounded nucleus and many bubble-like vacuoles.

* Amoeba constantly changes its shape and position. It pushes out one or more finger like projections, called pseudopodia or false feet for movement and capturing of food.

* Amoeba feeds on microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped ina food vacuole and digested by the digestive juices.

 

Question- Differentiate between assimilation and egestion.

Answer:

* Absorbed digested food materials are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This process is called assimilation.

* The process of removal of waste faecal matter through the anus from time-to-time is called egestion.

 

Question- How does digestion occur in ruminants grass-eating animals?

Answer:

* Ruminants quickly swallow the grass and store it in a separate part of the stomach called rumen. Here the food gets partially digested and is called cud.

* Later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination.

* The cellulose present in grass is digested here by the action of certain bacteria which are not present in humans.

 

Question- What happens to the food in mouth and oesophagus of the digestive tract?

Answer:

* When food is ingested the salivary glands which secrete saliva acts on it in the mouth. The saliva breaks down the starch into sugars.

* Oesophagus is a long, narrow, muscular tube which directly leads to the stomach. It is about 25 cm long and passes downwards through the neck, the thorax and the abdominal cavity.

* Oesophagus gently pushes masticated food down to the stomach in a wave - like action, called peristalsis

 

Question- What happens to the food in stomach of the digestive tract?

Answer:

* The inner lining of the stomach secretes mucous, hydrochloric acid and Digestive juices. The mucous protects the lining of the stomach.

* The hydrochloric acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic. The digestive juices break down the proteins into simpler substances.

 

Question- What happens to the food in small intestine of the digestive tract?

Answer:

* The small intestine is highly coiled and is about 7.5 metres long. Liver is the  largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder.  It digests fats.

* The pancreas is cream colour red gland secretes pancreatic juice that acts on carbohydrates and proteins and changes them into simpler forms. The carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol, and proteins into amino acid.

Digested food can now pass into the blood vessels in the wall of the intestine having thousands of finger-like villi. The surface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body.