What is Nutrition in Animals Class 7: Complete NCERT Guide

Definition and Importance of Nutrition in Animals

Nutrition in animals is the process by which living organisms take in food and convert it into energy and nutrients needed for growth, repair, and maintenance of body functions. It is essential because:

• Provides energy for daily activities
• Supplies raw materials for growth and repair
• Helps maintain body temperature and metabolism

In Class 7 NCERT Science, understanding nutrition helps students learn how animals survive and adapt to their environment.

Types of Nutrition in Animals Explained

Animals exhibit different types of nutrition based on their food sources and methods of obtaining food. The main types are:

1. Holozoic Nutrition: Animals consume solid or liquid food, digest it, and absorb nutrients. Example: Humans, dogs. 2. Saprophytic Nutrition: Animals feed on dead and decaying organic matter. Example: Earthworms. 3. Parasitic Nutrition: Animals live on or inside other animals (hosts) and depend on them for food. Example: Tapeworms, lice. 4. Symbiotic Nutrition: Two animals live together and benefit from each other. Example: Termites and protozoa.

Each type shows unique adaptations in animals for survival.

Holozoic Nutrition: The Most Common Type

Holozoic nutrition involves several steps:

• Ingestion: Taking food into the body.
• Digestion: Breaking down complex food into simpler forms.
• Absorption: Nutrients pass into the bloodstream.
• Assimilation: Nutrients are used by body cells.
• Egestion: Removal of undigested waste.

Example: In humans, food is ingested through the mouth, digested in the stomach and intestines, absorbed in the small intestine, and waste is egested as faeces.

This process provides energy and materials for growth and repair.

Comparison of Nutrition Types in Animals

Here is a comparison table summarizing the key features of different nutrition types:

This table helps Class 7 students quickly identify nutrition types and examples.

Special Adaptations in Animal Nutrition

Animals have developed special adaptations to suit their nutrition types:

• Carnivores have sharp teeth and claws for hunting.
• Herbivores have flat teeth for grinding plants.
• Parasites have hooks or suckers to attach to hosts.
• Filter feeders like whales strain food from water.

Example: A cow's stomach has four chambers to digest tough plant material efficiently.

These adaptations help animals obtain and process their food effectively.

Worked Example: Understanding Digestion in Humans

Let's see how digestion works in humans, a holozoic animal:

• Food enters the mouth where teeth break it down.
• Saliva contains enzymes that start digestion.
• Food passes to the stomach where acids and enzymes further digest it.
• Nutrients are absorbed in the small intestine.
• Waste moves to the large intestine and is egested.

This stepwise process ensures maximum nutrient extraction for energy and growth.