Nutrition in Animals – Class 7 Science (NCERT Syllabus Explained)

Introduction

Nutrition in Animals: Nutrition is the process by which living organisms take in food and utilise it for energy, growth, repair, and maintenance of their bodies. In the animal kingdom, nutrition plays a vital role because animals cannot prepare their own food like plants. They depend on other organisms for nourishment. In this chapter, we will study how different animals take food, how food is digested, absorbed, and finally utilised by the body. Understanding animal nutrition is not only essential for exams but also helps students connect with their daily eating habits and health.

Why Study Nutrition in Animals?

Class 7 students must understand nutrition because it forms the foundation for biology and health science. It explains how the body gets energy, how the digestive system works, and why balanced food is necessary. Moreover, many questions in science exams are asked from this chapter, making it an important topic to master.

Modes of Nutrition in Animals

Unlike plants, animals are heterotrophic, meaning they depend on other organisms for food. The major modes of nutrition include:

1. Herbivores – Animals like cows, goats, and rabbits that feed on plants.
2. Carnivores – Animals like lions, tigers, and wolves that eat other animals.
3. Omnivores – Animals like humans, bears, and dogs that eat both plants and animals.
4. Parasites – Organisms like tapeworms and leeches that feed on the blood or body fluids of other living beings.

The Process of Nutrition

Nutrition in animals generally involves five major steps:

1. Ingestion – The process of taking in food.
2. Digestion – Breaking down complex food into simpler, absorbable forms.
3. Absorption – Nutrients are absorbed into the blood.
4. Assimilation – Nutrients are used by cells for energy, growth, and repair.
5. Egestion – Removal of undigested food from the body.

Digestion in Humans

The human digestive system is a complex system of organs that help in breaking down and absorbing food. The digestive process involves several important organs:

1. The Mouth and Buccal Cavity

• Food intake begins in the mouth.
• Teeth help in chewing and grinding food (mechanical digestion).
• Saliva from salivary glands mixes with food and contains the enzyme salivary amylase, which begins the digestion of starch.
• The tongue helps in mixing food and pushing it into the esophagus.

2. The Esophagus (Food Pipe)

• Food passes down through rhythmic contractions called peristalsis.
• No digestion takes place here, only movement of food.

3. The Stomach

• A muscular bag-like organ where food is churned and mixed with gastric juice.
• Gastric juice contains hydrochloric acid (HCl), pepsin enzyme, and mucus.
• HCl kills harmful bacteria and creates an acidic medium.
• Pepsin helps in breaking down proteins into simpler forms.

4. The Small Intestine

• The most important site of digestion and absorption.
• It receives secretions from the liver and pancreas.
  • The liver produces bile, which breaks down fats into small droplets (emulsification).
  • The pancreas secretes enzymes like trypsin, lipase, and amylase that digest proteins, fats, and carbohydrates.
• The inner wall of the small intestine has finger-like projections called villi, which increase the surface area for absorption of nutrients into the blood.

5. The Large Intestine

• Absorbs water and minerals from undigested food.
• Remaining waste is pushed toward the rectum.

6. The Rectum and Anus

• Waste is stored in the rectum and removed through the anus as feces (egestion).

Digestion in Ruminants (Herbivorous Animals)

• Animals like cows and buffaloes chew grass and swallow it quickly.
• The swallowed food goes into a special stomach chamber called the rumen.
• Microorganisms in the rumen help in partial digestion of food, producing cud.
• The animal later brings the cud back into its mouth and chews it again. This process is called rumination.

Digestion in Simple Organisms

• Amoeba: Amoeba captures food with the help of finger-like projections called pseudopodia. Food is digested inside food vacuoles.
• Hydra: Uses tentacles to capture food and digestion occurs in its gastrovascular cavity.

Importance of a Balanced Diet

Nutrition is incomplete without a balanced diet. A balanced diet contains carbohydrates, proteins, fats, vitamins, minerals, and water in proper proportions.

• Carbohydrates provide energy.
• Proteins help in growth and repair.
• Fats provide long-term energy.
• Vitamins and minerals protect us from diseases.

Nutrition in Animals – Summary

• Nutrition in animals involves ingestion, digestion, absorption, assimilation, and egestion.
• The human digestive system includes the mouth, stomach, intestines, and associated glands like the liver and pancreas.
• Ruminants like cows undergo rumination.
• Simple organisms like amoeba and hydra also have unique methods of nutrition.
• A balanced diet is essential for proper nutrition and health.

Exam-Oriented Notes (Marks Weightage)

FAQs on Nutrition in Animals (Class 7)

Q1. What are the five steps of nutrition in animals?
Ingestion, digestion, absorption, assimilation, and egestion.

Q2. Which enzyme in saliva helps in digestion?
Salivary amylase, which breaks down starch into sugar.

Q3. What is rumination?
The process by which ruminants like cows bring back cud into the mouth and chew it again.

Q4. What is the role of bile juice in digestion?
Bile helps in emulsification of fats.

Q5. How does amoeba take food?
Amoeba uses pseudopodia to engulf food, which is digested inside food vacuoles.

Nutrition in Animals: Conclusion

Nutrition in animals (NCERT Syllabus Explained) is a fascinating topic that explains how living organisms depend on food for survival and energy. From simple organisms like amoeba to complex beings like humans, each follows a unique process to obtain and utilize nutrients. For students of Class 7, mastering this chapter not only helps in scoring well in exams but also creates awareness about healthy eating habits in daily life.