What Is Nutrition in Animals Class 7: Complete NCERT Guide

Definition of Nutrition in Animals for Class 7

Nutrition in animals is the biological process where animals consume food to obtain energy and nutrients necessary for their growth, repair, and maintenance. According to the NCERT Class 7 Science syllabus, nutrition involves four main steps:

• Ingestion: Taking in food through the mouth.
• Digestion: Breaking down complex food into simpler forms.
• Absorption: Nutrients pass into the bloodstream.
• Egestion: Removal of undigested waste as faeces.

This process ensures animals get carbohydrates, proteins, fats, vitamins, and minerals essential for life.

Types of Nutrition in Animals Explained

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

• Heterotrophic Nutrition: Animals depend on other organisms for food.
• Autotrophic Nutrition: Rare in animals, mostly plants; animals do not perform this.

Within heterotrophic nutrition, animals can be:

• Herbivores: Eat only plants (e.g., cow, deer).
• Carnivores: Eat only other animals (e.g., lion, tiger).
• Omnivores: Eat both plants and animals (e.g., humans, bears).
• Parasites: Live on or inside other animals and feed on them (e.g., leeches, lice).

Understanding these types helps classify animals and study their adaptations.

How Animals Digest Food: Different Digestive Systems

The digestive system varies among animals depending on their diet:

• Simple Digestive System: Found in animals like earthworms; food passes through a straight tube.
• Complex Digestive System: Involves specialized organs like stomach, intestines (e.g., humans, cows).

For example, ruminants like cows have a four-chambered stomach to digest tough plant material efficiently.

This diversity helps animals extract maximum nutrients from their specific diets.

Nutrition in Herbivores, Carnivores, and Omnivores

Herbivores, carnivores, and omnivores have distinct feeding habits and digestive adaptations:

• Herbivores: Have flat teeth for grinding plants; longer intestines to digest cellulose.
• Carnivores: Sharp teeth and claws to catch prey; shorter intestines for meat digestion.
• Omnivores: Combination of flat and sharp teeth; moderate intestine length.

Example:

• Cow (herbivore) uses cud chewing to break down grass.
• Lion (carnivore) uses strong jaws and sharp teeth to tear meat.
• Human (omnivore) can digest both plant and animal foods.

These adaptations ensure efficient nutrition based on diet.

Parasitic Nutrition: How Some Animals Depend on Hosts

Parasitic animals obtain nutrition by living on or inside other animals (hosts), often harming them. Examples include:

• Leeches: Attach to skin and suck blood.
• Tapeworms: Live inside intestines and absorb digested food.
• Lice: Live on hair and feed on blood.

Parasitic nutrition differs because parasites do not digest food themselves but absorb nutrients directly from the host. This can cause diseases or weakness in the host animal.

Understanding parasitic nutrition highlights the diversity of feeding strategies in the animal kingdom.

Worked Example: Comparing Digestive Systems of Cow and Lion

Let's compare the digestive systems of a cow (herbivore) and a lion (carnivore):

This comparison shows how diet influences digestive anatomy and function in animals.