Class 7 Science

Chapter 2: Nutrition in Animals

STAGE 0: Foundation / Basics

Animals need food to get energy, grow, repair their body, and stay healthy.

Unlike plants, animals cannot make their own food. They depend on plants or other animals for food.

The process of taking food and using it in the body is called Nutrition.

STAGE 1: Different Steps of Nutrition

Nutrition in animals takes place in five steps:

1. Ingestion – Taking food into the body
2. Digestion – Breaking food into simple substances
3. Absorption – Digested food enters the blood
4. Assimilation – Food is used by body cells
5. Egestion – Removal of undigested food

Digestive System in Humans

The digestive system helps in digestion and absorption of food.

Main parts of the digestive system:

• Mouth
• Oesophagus (Food pipe)
• Stomach
• Small intestine
• Large intestine
• Anus

Digestion in the Mouth

Food is chewed by teeth and mixed with saliva.

Saliva contains an enzyme called amylase which helps in digesting starch.

Digestion in the Stomach

The stomach releases digestive juices.

• Hydrochloric acid – kills germs
• Pepsin – digests proteins

Digestion in the Small Intestine

Most digestion and absorption of food happens in the small intestine.

Digested food is absorbed into the blood through tiny finger-like structures called villi.

Nutrition in Other Animals

Ruminants (Cow, Buffalo):

They chew cud and have a four-chambered stomach.

Amoeba:

Digestion takes place inside food vacuoles.

STAGE 2: NCERT Textbook Questions & Answers

Q1. Name the five steps of nutrition.

Ingestion, Digestion, Absorption, Assimilation, Egestion

Q2. Where does digestion of starch begin?

Digestion of starch begins in the mouth.

Q3. What is the function of saliva?

Saliva helps in digestion of starch.

STAGE 3: Exam-Oriented Questions

Fill in the blanks:

• Digestion of proteins takes place in the stomach.
• Villi are present in the small intestine.

Very Short Answer:

Which organ absorbs digested food?
Answer: Small intestine

Quick Revision Points

• Animals cannot prepare their own food
• Nutrition has five steps
• Digestion starts in the mouth
• Absorption happens in the small intestine