Textbook Solutions: Nutrition in Animals | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

A. Choose the correct option. 

1.
Ans: (b)
Canines are known as tearing teeth. They have a pointed edge which helps in tearing food.

2.
Ans: (d)
Amoeba has Pseudopodia and Food vacuole. Pseudopodia helps in movement and capturing food, while food vacuole helps in digestion.

3.
Ans: (a)
Saliva digests Carbohydrates. It contains an enzyme called amylase that breaks down complex carbohydrates into simpler sugars.

4.
Ans: (c)
Bile helps in the digestion of Fats. It emulsifies fats, breaking them down into smaller droplets for easier digestion.

5.
Ans: (c)
Villi increase the surface area of absorption in the small intestine. They are small finger-like projections that absorb nutrients from the digested food.

B. Fill in the blanks with the correct words.

1. 
Ans: The process of taking in food into the body is called Ingestion.

2.
Ans: Hydra has tentacles to draw food particles into the body.

3. 
Ans: Frogs have a sticky tongue to catch their prey.

4.
Ans: Finger-like outgrowths formed by Amoeba are called Pseudopodia.

5. 
Ans: Canines are present on either side of incisors.

6. 
Ans: Digestion of carbohydrates begins in the Mouth.

7. 
Ans: Hydrochloric acid is secreted in the Stomach.

8. 
Ans: Digestive juice called bile is secreted by Liver.

9.
Ans: Sheep is an example of a ruminant.

10. 
Ans: Digested food from the Abomasum passes into the small intestine.

C. Name the following. 

1.
Ans: Canines

2.
Ans: Salivary Glands

3.
Ans: Liver

4.
Ans: Large Intestine

5.
Ans: Tongue

6.
Ans: Rumen

D. Answer the following questions.

1.
Ans: Nutrition is the process by which organisms take in and utilize substances necessary for growth, maintenance, and reproduction. It involves five stages: ingestion (intake of food), digestion (breakdown of food into simpler substances), absorption (uptake of soluble substances), assimilation (use of simple substances to build complex substances), and egestion (elimination of undigested food from the body).

2.
Ans: Different animals have different ways of taking in food. Amoeba uses pseudopodia to take in food particles, Hydra uses tentacles to draw food particles into the body while Paramoecium uses cilia all over its body. Insects and worms have special mouth parts for taking in food. Birds have beaks, which are modified mouth parts, to catch and eat food. Frogs have a sticky tongue to catch their prey. Snakes do not have specific mouth parts; they swallow their food whole. Bigger animals, such as fishes, reptiles, and mammals, have teeth to chew their food.

3.
Ans: Amoeba is a single-celled organism. When an Amoeba comes near food, it grows finger-like outgrowths called pseudopodia from its body. The pseudopodia capture the food into a hollow space called a food vacuole. The Amoeba then secretes digestive juices into the food vacuole, which digests the food particle. The digested food is then absorbed and utilized by Amoeba, and the undigested waste is thrown out of the body.

4.
Ans: Four major types of teeth are present in the human jaw for chewing food, each with a different function. Incisors are the front teeth used for cutting and biting food. Canines are present on either side of the incisors and have sharp edges for tearing food. Premolars are broader than canines or incisors and are used for chewing and grinding food. Molars are present at the back of each jaw and are also used for grinding food.

5.
Ans: Digestive glands are glands that secrete juices which help in the digestion of food. There are three main digestive glands in the human digestive system - salivary glands, liver, and pancreas. Salivary glands secrete saliva which helps in the initial digestion of food. The liver secretes bile which is responsible for the digestion of fats. The pancreas secretes pancreatic juice that digests carbohydrates, proteins, and fats.

6.
Ans: Human digestion begins with ingestion, where food enters the body through the mouth. The teeth break down the food, and saliva starts the digestion of starch. The food then travels through the esophagus to the stomach, where gastric juices break down proteins. It then moves to the small intestine, where further digestion occurs with the help of bile from the liver and enzymes from the pancreas. The digested nutrients are absorbed in the small intestine and transported to the body's tissues for assimilation. Indigestible food is passed to the large intestine, where water is absorbed, and the remaining waste is egested through the rectum and anus.

7.
Ans: Most of the absorption of nutrients from the digested food occurs in the small intestine. The lining of the small intestine bears several finger-like projections called villi that increase the surface area for absorption.

8.
Ans: The liver secretes bile, which helps in the digestion of fats. It breaks down large fat globules into smaller ones, increasing their surface area for the action of lipase, a fat-digesting enzyme.

9.
Ans: The nutrients that are digested and absorbed are used by the body cells to produce energy. For instance, the final product of carbohydrate digestion is glucose. It is further broken down in the cells in presence of oxygen to produce energy. The final product of protein digestion is amino acids. They are used to repair worn out cells and tissues. The final products of fat digestion is fatty acids and glycerol. These are stored as energy reserves inside the body.

10.
Ans: Rumination is the process of bringing back swallowed food into the mouth to chew it again. Ruminants are animals that undergo rumination, and examples of ruminants include cows, goats, and deer.

11.
Ans: A ruminant's stomach has four chambers: rumen, reticulum, omasum, and abomasum. The rumen is the largest chamber and it stores large quantities of partially chewed food. The reticulum helps in moving the swallowed food back into the mouth for further chewing. The omasum absorbs excess water from food and also helps to digest the food. The abomasum secretes juices that digest the food. The digested food from the abomasum passes into the small intestine, where it mixes with juices secreted by the liver and pancreas. Most of the digestion of carbohydrates, proteins, and fats takes place in the small intestine.