Nutrition in Animals | Class 7 | Chapter 2

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Nutrition in Animals|Class 7|Chapter 2

Nutrition in Animals

Different Ways of Taking Food:

  • Each species has its own way of taking in food.
  • Bees and hummingbirds suck plant nectars.
  • Infants of humans and some animals feed on mother’s milk.
  • Snakes like pythons consume animals they prey upon.
  • Aquatic animals filter small food particles from the water.

Digestion in Humans:

Digestion in Humans

  • The digestive system consists of the digestive tract and associated glands.
  • The digestive tract includes the esophagus, stomach, small intestine, and large intestine.
  • Major digestive glands are salivary glands, liver, and pancreas.

Buccal Cavity:

  • The buccal cavity, or mouth, is the beginning of the digestive system.
  • It consists of the tongue and teeth.
  • Teeth help in chewing and breaking down food.
  • The tongue helps in mixing saliva with food while chewing. 

Oesophagus or Food Pipe:

  • It is a muscular tube that transports food from the mouth to the stomach.
  • Food is propelled down by the movement of the food pipe’s walls.


  • The tongue is a fleshy and muscular organ in our mouth.
  • It is attached at the back of the base of the mouth.
  • The tongue helps us mix saliva with food while chewing and helps us swallow the food.
  • It also has taste buds that allow us to recognize different tastes.

Tooth decay:

  • Tooth decay happens when bacteria in our mouth break down the sugars from leftover food.
  • This produces acid that slowly damages our teeth and causes tooth decay.
  • It’s important to take care of our teeth to prevent tooth decay.


  • It is a thick-walled bag-like structure that receives food from the food pipe.
  • The inner lining of the stomach produces mucus, hydrochloric acid, and digestive juices.
  • In the stomach, food is mixed and churned, forming a partially solid mass.
  • Enzymes in gastric juice help in the disintegration of food. 

Small Intestine:

  • It is a highly coiled organ of 7.5 meters in length.
  • The small intestine gets secretions from the liver and pancreas.
  • Complete digestion and absorption of food occur in it.
  • The inner walls of the intestine have finger-like outgrowths called villi.
  • Villi increase the surface area for the absorption of food.

Large Intestine:

  • It is wider and shorter than the small intestine.
  • Absorption of water and salt from undigested food occurs in the large intestine.
  • Waste matter is passed out through the rectum.
  • Faecal matter is removed through the anus in the process of egestion. 

Saliva and Salivary Glands:

  • Saliva, secreted by salivary glands, helps in the breakdown of food.
  • Saliva contains mucous and salivary amylase.
  • Mucous aids in the easy passage of food through the food pipe.
  • Salivary amylase breaks down starch into simpler sugars. 

Gall Bladder:

  • It is a small pear-shaped organ located under the liver.
  • The gallbladder stores bile juice secreted by the liver.
  • Bile plays an important role in the digestion of fats. 

Ingestion and Digestion:

  • Ingestion is the process of taking food into the body.
  • Digestion is the breakdown of complex food components into simpler substances.
  • Partial digestion occurs in the stomach, while complete digestion occurs in the intestine. 

Absorption and Assimilation in Small Intestine:

  • Absorption is the uptake of digested food by the blood vessels lining the small intestine.
  • Assimilation refers to the utilization of absorbed food by various organs to build complex substances like proteins.
  • Villi in the small intestine increase the surface area for absorption.

Digestion in Grass-Eating Animals:

  • Grass-eating animals have a different digestive system than humans.
  • They chew continuously and have a special chamber called the rumen to partially digest food.
  • The partially digested food, called cud, is regurgitated and chewed again through rumination.

Feeding and Digestion in Amoeba:

amoeba feeding

  • Amoeba is a single-celled organism found in pond water.
  • It captures food particles using pseudopodia in a process called phagocytosis.
  • Digestive juices break down food inside a food vacuole, and the digested food is absorbed. 

Visit for more: Nutrition in Plants | Modes of Nutrition

(a) Digestion of starch starts in the mouth. (F)

(b) The tongue helps in mixing food with saliva. (T)

(c) The gall bladder temporarily stores bile. (T)

(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T)

Villi are finger-like projections present on the inner wall of the small intestine. Their location is in the small intestine, specifically in the mucosa lining. The function of villi is to increase the surface area available for the absorption of nutrients from the digested food into the bloodstream.

Bile is produced in the liver and stored in the gallbladder. It is released into the small intestine to aid in the digestion and absorption of fats.

The type of carbohydrate that can be digested by ruminants but not by humans is cellulose. Ruminants, such as cows, have a specialized digestive system that contains microorganisms capable of breaking down cellulose into simpler molecules. Humans lack the necessary enzymes to digest cellulose efficiently.

We get instant energy from glucose because it is readily absorbed into the bloodstream and can be used by our cells for immediate energy production through cellular respiration.

The parts of the digestive canal involved in the following functions are:

(i) Absorption of food: Small intestine

(ii) Chewing of food: Mouth or oral cavity

(iii) Killing of bacteria: Stomach (due to the presence of hydrochloric acid)

(iv) Complete digestion of food: Small intestine

(v) Formation of feces: Large intestine or colon

One similarity between nutrition in amoeba and human beings is that both involve the process of digestion to break down complex molecules into simpler ones for absorption. However, a significant difference is that amoeba performs extracellular digestion in the food vacuoles, whereas humans perform both extracellular and intracellular digestion in specialized organs and tissues.

Match the items of Column I with suitable items in Column II: Column I Column II

(a) Salivary gland (iii) Saliva secretion

(b) Stomach (iv) Acid release

(c) Liver (i) Bile juice secretion

(d) Rectum (vii) Release of faeces

(e) Small intestine (v) Digestion is completed

(f) Large intestine (vi) Absorption of water

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