CBSE Class 7 Science Revision Notes Chapter 2

 Class 7 Science Chapter 2 Notes

CBSE Class 7 Science Revision Notes Chapter 2 – Nutrition in Animals

The Class 7 Science Chapter 2 Notes provided by Extramarks make learning easier with in-depth knowledge about distinct concepts in this chapter. Class 7 Science Chapter 2 Notes are created in line with the CBSE guidelines. These notes are easily accessible at the convenience of students. They are concise and easy to understand for quick revisions before exams.

Extramarks offers CBSE Class 7 Science Notes Chapter 2 Nutrition in Animals. The basics of nutrition in animals are briefly explained in these notes. Topics such as animal nutrition, classification of animals based on feeding habits, mode of taking food, nutrition, digestion in animals, etc., are covered in this chapter. These revision notes can be accessed by the students from the website, and they can go through these notes for their exams.

Revision Notes for CBSE Class 7 Science Chapter 2

Access Class 7 Science Chapter 2 – Nutrition in Animals Notes

Animal Nutrition:

The combination of the nutrient requirements of the animal, the manner of food intake, and the use of the food in their bodies is called animal nutrition. Animals consume plants or other animals for nutrients.

Classification of Animals Based on Feeding Habits:

All organisms have different methods of food intake as it is significant for their growth and the regular operation of their bodies. Their feeding habits decide their classification as

  • Herbivorous: The term is derived from the words “herbi”, which means “plant”, and “vore,” which means “eaters.” The group of animals that consume only plants or plant-based products is called herbivorous. For example, cows, deer, sheep, kangaroos, rabbits, etc.
  • Carnivorous: The term is derived from the words “carni”, which means “meat”, and “vore”, which means “eaters”. The group of living beings that consume the meat of other animals is called carnivores. For example, tigers, lions, snakes, etc.
  • Omnivorous: The term is derived from the words “Omni,” which means “all,” and “vore,” which means “eaters.” The group of animals that eat plants as well as the meat of other animals is called omnivorous. For example, dogs, human beings, etc.
  • Scavengers: The group of animals consumes the flesh of dead and decaying meat after the predator has left the animal’s remains. For example – Vulture, jackal, etc.

Mode of Taking Food:

All organisms require food. However, they all digest food in slightly different ways. They are all used to it in a way that makes it easier for them. The modes of taking food could be as follows:Chewing: This mode of consuming food includes biting and chewing the food with the teeth in the mouth. Examples – Humans, dogs, etc.

  1. Scraping: In this method of eating, the jaw or another organ scrapes the food off the surface. Examples – Snails, ants, etc.
  2. Syphoning: In this mode of ingesting food, the food is soaked up into the mouth. Example –  Butterflies, etc.
  3. Capturing and swallowing: In this mode of consuming food, the living being generally captures the food and later on swallows it. Example: Lizard, etc.
  4. Sucking: This method of food intake involves piercing the food and then sucking the liquid out of it.Example: Mosquitoes, etc.
  5. Sponging: In this mode of food consumption, the saliva is combined with the food to dissolve it in the mouth. Example: Houseflies, etc.


Nutrition is the process of ingesting food and converting it into the necessary energy and nutrients for the development and growth of a certain organism. There are several steps involved in the complex process of nutrition, which is as follows:

  • Ingestion: It is the process of taking food into the body
  • Digestion: It is the process by which complex food molecules are broken down into more easily absorbed molecular forms.
  • Absorption: The digested food in the small intestines passes into the blood vessels on the wall of the intestines. This is absorption.
  • Assimilation: The absorbed food substances are transported to the different organs via blood vessels to create essential substances like proteins, etc. needed by the body.
  • Egestion: The process through which waste or faecal matter is expelled from the body.

Digestion in Humans:

  • Food is consumed by the mouth in humans, and it travels through an extended canal that begins at the buccal cavity and ends at the anus.
  • All the elements of this canal together are called the alimentary canal or digestive tract.
  • The digestive tract linked to the connected digestive glands is called the digestive system.
  • The various elements of the digestive tract and their functions in the entire process of digestion are stated below:
  1. Buccal cavity:
  • The buccal cavity is present in the mouth, which consists of the teeth, tongue, and palate. This is the starting point of the alimentary canal and where digestion starts. The food is taken in by the mouth and is broken down by the distinct sets of teeth.
  • The saliva is secreted by the salivary glands, which appear as a clear liquid that aids in lubricating the food.
  • The saliva is combined with the food by the tongue.
  • A ball of chewed food is formed, which is called a bolus, that passes through the alimentary canal for further digestion.
  1. Oesophagus or the food pipe:
  • The partly digested food travels through the oesophagus.
  • The wall of the oesophagus pushes the food forward and downwards, leading it to the stomach.
  • The food that is not taken up by our body is pushed out through the mouth and is called vomiting.


  • The food from the oesophagus is transported to the stomach, which looks like a J-shaped, thick-walled bag. It is the widest part of the alimentary canal.
  • The stomach’s inner wall discharges mucus, which saves the stomach lining, and hydrochloric acid, which annihilates the maximum bacteria in the food, and aids the digestive juices to work on the food.
  • The digestive juices are secreted by the stomach and break down the proteins into amino acids.

      3.Small intestine:

  • The partially digested food penetrates into the small intestine, which is a coiled structure that scales up to around 7.5 metres in length.
  • Bile is the secretion from the liver, which works on the fats and discharges from the pancreas, and pancreatic juice, which works on carbohydrates and proteins.
  • The intestinal juice is present at the end of the small intestine and finishes the entire process of digestion of the food, and glucose is derived from carbohydrates, fatty acids from fats, and amino acids from proteins.
  • The intestinal walls later absorb the digested food through the finger-like structure called villi, which resides in them. The absorbed substances are afterward transferred to the different organs of the body with the help of blood vessels.
  • The glucose is transformed into carbon dioxide and water with the release of energy once they exist in the cell.

       4.Large intestine:

  • The large intestine, which can extend as long as 1.5 metres and is smaller and wider than the small intestine, receives the undigested food.
  • Here, salt, and water are absorbed, and the leftover solid waste is pushed downward into the rectum as faeces for anus excretion.

Digestion in Grass-Eating Animals:

  • Several animals that feed on plant-based beings like cows, buffaloes, etc., take in the grass quickly and store it in the largest part of their stomach, which is known as the rumen.
  • The food in the rumen is partially digested and is known as the “cud”. Later on, this cud returns back into the mouth, and the animal chews it gently. This whole procedure is known as rumination, and the animals that exhibit these characteristics are called ruminants.
  • These animals are considered grass-eating animals, like cattle. The bacteria present in the rumen aid the digestion of the cellulose of the grass.
  • A few animals have a large sac-like form called the caecum between the oesophagus and the small intestine for the purpose of digesting cellulose. For example, horses.

Feeding and Digestion in Amoeba:

  • An Amoeba is a single-celled microscopic organism that shifts its shape regularly with the use of its finger-like projections called pseudopodia.
  • Amoeba captures the food with finger-like projections, consumes it, and the food gets entangled in a food vacuole.
  • The food is broken down into simple substances for absorption to help it grow through the digestive juices that are secreted.

Class 7 Science Chapter 2 Revision Notes

Class 7 Science Chapter 2 Notes are easily accessible from the Extramarks website at students’ convenience. These notes provide an in-depth knowledge of these concepts and encourage students to remember them while answering the chapter’s questions. By referring to these notes, students will gain a foundational understanding of all the topics covered in this chapter Nutrition in Animals, and save time while preparing for the exams. 

Class 7 Science Chapter 2 Revision Notes

All plants prepare their food by the process of photosynthesis. However, different animal species have a different way of taking in the food. Since animals cannot prepare their own food, they are dependent on other life forms for their food. They consume plants directly or indirectly by eating other animals that consume plants. While some animals feed on both plants and animals.

2.1 Animals Are Classification Based on Eating Habits

  • Herbivorous: It includes animals that consume plants or plant products. Examples: Cows, deer, elephants, goats, sheep, etc.
  • Carnivorous:  It includes animals that depend on the flesh of other animals for survival. They do not consume plants. Examples: Tiger, lion, cheetah, etc.
  • Omnivorous: It includes animals that eat both plants and other animals for food.. Examples: Bears,  human beings, etc.
  • Parasites: These include organisms that obtain their food by either living inside or outside the body of other animals. Examples: Tapeworm, roundworms, etc.
  • Scavengers: These include animals that eat the remains of dead animals hunted down by predators. Examples: Vultures, etc.

2.2. Digestion in Animals

Animal nutrition involves the manner of food intake and its uses as well as the nutrient needs in the body. The alimentary canal and secretory glands constitute the human digestive system. It involves:

  • Buccal cavity,
  • Oesophagus,
  • Stomach,
  • Small intestine,
  • Large intestine
  • Anus

The essential digestive glands that produce digestive juices are:

  • Salivary glands
  • Liver
  • Pancreas.

The walls of the small intestine and the stomach wall produce digestive juices.

The methods of feeding differ in several organisms.

Nutrition is a Complex Process Involving:

  • Ingestion
  • Digestion
  • Absorption
  • Assimilation
  • Egestion

Several digestive juices are produced by the stomach and small intestine walls. Diverse organisms have developed different feeding habits. Ingestion, digestion, absorption, assimilation, and egestion are all steps in the complex process of nutrition.

The consumption of food begins in the mouth, which is called ingestion. Teeth aid in munching the food and breaking it down into smaller pieces. The saliva is combined with the food by the tongue during chewing and assists in swallowing the food. The food is pushed down with the help of a food pipe.

The stomach obtains the food at one end from the food pipe and, at the other end, it opens up into the small intestine. The digestion of protein commences in the stomach, whereas the digestion of carbohydrates like starch begins in the buccal cavity. The bile is discharged from the liver, and the pancreatic juice is secreted from the pancreas. However, the digestive juice from the intestinal wall finishes the digestion processes of all components of food present in the small intestine. In the blood vessels, the digested food is absorbed.

The food-absorbed substances are transferred to various parts of the body. The water and some salts are consumed from undigested food in the large intestine. Anus aids in the elimination of undigested and unabsorbed residues. Animals that feed on plants are called ruminants. For example, buffaloes, cows, and deer. These animals consume and then swallow their leafy food immediately, and keep it in the large first compartment of their stomach. The food returns to the mouth for further breaking down of the food. The animal again chews it continuously.

Amoeba contains a finger-like structure known as pseudopodia that helps consume its food. Later,  digestion takes place in the food vacuole.

FAQs (Frequently Asked Questions)

1. How is tooth decay caused?

Our mouth already contains several Bacteria. However, they are harmless. However, if the teeth and mouth are not cleaned regularly after eating, many dangerous bacteria may begin to grow and live. The sugars present in the leftover food are broken down by the bacteria and released by acids. The teeth are constantly damaged by these acids. This is known as tooth decay.

2. What is an oral rehydration solution?

Diarrhoea is a condition where one passes watery stools regularly. It is most prevalent in India, especially among children, and can be deadly in severe situations. A substantial loss of water and salts from the body in the case of an infection, food poisoning, or indigestion leads to this condition. Diarrhoea must not be ignored. Prior to consulting a doctor, plenty of boiled and cooled water with a pinch of salt and sugar mixture should be offered to the patient. This is known as Oral Rehydration Solution (ORS).