NUTRITION IN ANIMALS

1. What are the different parts of human digestive system?

Ans The Alimentary canal along with digestive glands is called digestive system. The human digestive system consists of the following organs-

ALIMENTARY CANAL

1. Buccal cavity/mouth

2. Oesophagus/food pipe

3. Stomach

4. Small intestine

5. Large intestine

6. Rectum

7. Anus

DIGESTIVE GLANDS

1. Salivary glands

2. Liver

3. Pancreas

2. Explain the different steps of nutrition in animals 

Ans 1. Ingestion

Process by which food is taken into the body of an organism

2. Digestion

The process of converting solid and complex food into simple and soluble form.

3. Absorption 

The process by which digested nutrients are absorbed by the blood vessels in the walls of the small intestine.

4. Assimilation

The process of utilizing absorbed nutrients by each and every cell of the body for energy, growth and development.

5. Egestion 

The process of removing undigested food material from the body in the form of faeces.

3. Write the functions of the following-

a) Tongue: It help us to taste food and in speaking. It mixes saliva with the food and helps in swallowing the food.

b) Saliva: Saliva makes the food soft and breaks down starch into sugars.

4. Draw a neat labeled  diagram of human digestive system and explain.

Ans 1. Mouth- The mouth contains tongue, teeth and salivary glands.

2. Oesophagus- Oesophagus is a muscular tube between the mouth and the stomach. The food is pushed down towards the stomach by the peristaltic movement (Contraction, relaxation) of the muscles of the food pipe.

3. Stomach- The stomach is a thick-walled bag. 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 mucus, hydrochloric acid and digestive juices. The mucus protects the inner lining of the stomach. The acid kills many bacteria that enters along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. The digestive juices breaks down the proteins into simpler substances. 

4. Small intestine- The small intestine is highly coiled and is about 7.5 m long. It receives secretions form the liver and the pancreas and its walls also secretes juices.

5. Liver- The Liver is a reddish brown gland situated in the upper part of the abdomen on the right side. It is the largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder. The bile plays an important role in digestion of fats.

6. Pancreas- Pancreas is a large cream coloured gland located just below the stomach.The pancreatic juice acts on carbohydrates, fats and proteins and changes them into simpler forms.
The digestion of food is completed in the small intestine. The carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol and proteins into amino acids. 

Absorption in small intestine
The digested food can now pass into the blood vessels in the walls of the small intestine which is called absorption. The inner wall of the small intestine have thousands of finger-like outgrowths called villi. The villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its urface. The surface of the villi absorbs the digested food material.

Assimilation

The absorbed substance are transported via the blood vessels to different organs of the body where they are used to build complex substance such as the proteins required by the body is called assimilation. In the cells, glucose breaks down with the help of oxygen into carbon dioxide and water and energy is released.

Large Intestine

The food that remains undigested and unabsorbed materials enter into the large intestine. It is 1.5 m in length. It absorb water and some salts from the undigested food materials. Remaining waste goes to the Rectum and time to time is egested out through the Anus.

5. How does digestion of food take place in ruminants. Explain.

Ans. 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 cud returns to the mouth in small lumps and the animal chews it. This is called rumination and these animals are callled ruminants.

Ruminants have a large sac-like structure called Caecum between the small intestine and large intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

6. Explain the process of nutrition in amoeba.

Ans. Amoeba has a cell membrane, a rounded dense nucleus and many small bubble-like vacuoles in its cytoplasm. Amoeba constantly changes its shape and position. It pushes out one, ore more finger-like projections, called pseudopodia or false feet for movement and capture of food.

Amoeba feeds on small microscopic organisms. When it sensed 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 which act on the food and breaks it into simpler substances. Gradually the digested food is absorbed. The absorbed substances are used for growth, maintenance and multiplication. the undigested residue of the food is expelled outside by the vacuole.