🧬 Chapter Introduction
Animals perform several essential activities to remain alive, grow and function properly. These activities are known as life processes.
In this chapter, we explore important life processes in animals, especially nutrition and respiration. We learn how animals obtain food, how food is digested and absorbed, and how animals breathe and obtain energy from food.
🌱 1. What Are Life Processes?
Life processes are the basic activities carried out by living organisms that help them survive and maintain their bodies.
Nutrition
Obtaining food and using its nutrients for energy, growth and maintenance.
Respiration
A process through which energy is released from food.
Transportation
Movement of useful substances and wastes within the body.
Excretion
Removal of waste substances produced by the body.
🍽️ 2. What Do Animals Eat?
Animals have different food habits. Their diets depend on their body structures, habitats and adaptations.
Herbivores
Animals that mainly eat plants are called herbivores.
Examples: Cow, deer and goat.
Carnivores
Animals that mainly eat other animals are called carnivores.
Examples: Lion, tiger and eagle.
Omnivores
Animals that eat both plant and animal foods are called omnivores.
Examples: Humans, bears and crows.
🥗 3. Nutrition in Animals
Animals cannot generally prepare their own food like green plants. They obtain food from plants or other organisms.
The food we eat contains substances such as carbohydrates, proteins, fats, vitamins, minerals and water. The body uses these nutrients for different purposes.
Why do animals need food?
- To obtain energy.
- For growth and development.
- To repair and maintain body tissues.
- To perform different body activities.
🍞 4. Digestion
Many foods contain complex substances that cannot be directly absorbed by the body. During digestion, these complex food substances are broken down into simpler substances.
Major steps involved in nutrition
1. Ingestion
Taking food into the body is called ingestion.
2. Digestion
Digestion changes complex food substances into simpler forms.
3. Absorption
Digested nutrients pass into the blood or other body fluids and become available to body cells.
4. Assimilation
The absorbed nutrients are used by the cells of the body for energy, growth, repair and other activities.
5. Egestion
The removal of undigested food from the body is called egestion.
🧑🔬 5. Human Digestive System
In humans, food passes through a long tube called the alimentary canal. Different organs help in the digestion and absorption of food.
👄 Mouth
Digestion begins in the mouth. Teeth break food into smaller pieces and saliva mixes with the food.
➡️ Food Pipe
The food pipe, or oesophagus, carries swallowed food towards the stomach.
🥣 Stomach
The stomach churns food and mixes it with digestive juices. Digestion continues here.
🧬 Small Intestine
Much of the digestion and absorption of nutrients takes place in the small intestine.
💧 Large Intestine
The large intestine absorbs much of the remaining water from the undigested material and helps form faeces.
🚪 Rectum and Anus
Faeces are stored temporarily in the rectum and are finally removed from the body through the anus.
🔬 6. Important Digestive Organs
| Organ | Main Role |
|---|---|
| Mouth | Chews food and mixes it with saliva. |
| Food Pipe | Moves swallowed food towards the stomach. |
| Stomach | Stores, churns and partially digests food. |
| Small Intestine | Completes much of digestion and absorbs nutrients. |
| Large Intestine | Absorbs remaining water and forms faeces. |
| Liver | Produces bile, which helps in digestion of fats. |
| Pancreas | Produces digestive juices that help break down food. |
🐄 7. Nutrition in Grass-Eating Animals
Animals such as cows, buffaloes and other ruminants have special adaptations for digesting plant material.
Grass and other plant foods contain a large amount of cellulose. Ruminants have a specialised digestive system that helps them process plant food with the help of microorganisms.
This repeated chewing is called rumination. It helps break plant food into smaller pieces and aids digestion.
🐦 8. Nutrition in Birds
Birds have special structures adapted to their feeding habits. They do not have teeth, so food is not chewed in the mouth as it is in humans.
Many birds swallow their food, and different parts of their digestive system help in storing and processing the food.
🫁 9. Respiration in Animals
Animals need energy for movement, growth, repair and other activities. Energy is released from food through respiration.
Breathing and Respiration are not the same
Breathing is the physical process of taking air into the body and releasing air from the body.
Respiration is the process in cells in which food is broken down to release usable energy.
🌬️ 10. Breathing
During breathing, animals take in air containing oxygen and release air containing more carbon dioxide.
Why does breathing rate increase after exercise?
During physical activity, muscles require more energy. The body therefore needs increased gas exchange to support greater energy demands. As a result, breathing generally becomes faster after exercise.
🐟 11. Breathing in Different Animals
Different animals have different organs or body surfaces adapted for exchanging gases with their surroundings.
Humans
Humans breathe mainly through the lungs.
Fish
Fish use gills to obtain dissolved oxygen from water.
Earthworms
Earthworms exchange gases through their moist skin.
Frogs
Frogs can exchange gases through their skin and also use lungs when on land.
⚡ 12. Aerobic Respiration
In aerobic respiration, oxygen is involved in the process of releasing energy from food.
The released energy is used by cells for various activities required to keep the body functioning.
💪 13. Anaerobic Respiration
In some situations, cells can release energy from food without using oxygen in the same way as aerobic respiration. This is called anaerobic respiration.
In humans, during intense physical activity when oxygen supply cannot meet the muscles' immediate demand, muscles may temporarily rely partly on anaerobic pathways.
🔍 14. Breathing vs Respiration
| Breathing | Respiration |
|---|---|
| Physical process of taking in and giving out air. | Process of releasing energy from food in cells. |
| Involves movement of air. | Involves chemical reactions in cells. |
| Can be observed as inhalation and exhalation. | Provides energy required by cells. |
🔗 15. How Life Processes Work Together
Life processes do not work independently. They are connected.
Nutrition
Provides nutrients and food molecules.
Respiration
Releases energy that cells can use.
Transport
Helps move substances around the body.
Excretion
Removes waste substances from the body.
⚡ Chapter 9 Quick Revision
- Life processes are essential activities that help living organisms survive.
- Animals obtain food from their surroundings.
- Digestion breaks complex food substances into simpler forms.
- The human alimentary canal includes the mouth, food pipe, stomach, small intestine, large intestine, rectum and anus.
- Most absorption of digested nutrients takes place in the small intestine.
- Ruminants have adaptations that help them digest plant food.
- Birds have specialised structures adapted to their feeding habits.
- Breathing is different from cellular respiration.
- Humans mainly use lungs for breathing.
- Fish use gills to obtain oxygen from water.
- Respiration releases energy from food for use by cells.
- Life processes are interconnected and work together to maintain the body.
📖 Important Terms
✏️ Important Practice Questions
1. What are life processes?
Life processes are essential activities carried out by living organisms to survive and maintain their bodies.
2. What is nutrition?
Nutrition is the process through which organisms obtain and use food and its nutrients.
3. What is digestion?
Digestion is the breakdown of complex food substances into simpler substances that can be absorbed by the body.
4. What is absorption?
Absorption is the process by which digested nutrients pass into the blood or other body fluids.
5. What is rumination?
Rumination is the process in which certain grass-eating animals bring partially digested food back to the mouth and chew it again.
6. What is respiration?
Respiration is the process through which energy is released from food inside cells.
7. What is the difference between breathing and respiration?
Breathing is the physical movement of air into and out of the body, whereas respiration is the cellular process through which energy is released from food.
8. Why does our breathing rate increase after exercise?
Exercise increases the energy demand of muscles. The body therefore increases breathing and gas exchange to support the increased demand.
9. How do fish breathe?
Fish use gills to obtain dissolved oxygen from water.
10. Why are life processes interconnected?
Different life processes depend on one another. For example, nutrition provides food molecules, respiration releases energy, transport moves useful substances, and excretion removes wastes.
🤔 Think & Explore
❓ Frequently Asked Questions
What is Chapter 9 of Class 7 Science?
Chapter 9 of the NCERT Class 7 Science textbook Curiosity is titled Life Processes in Animals.
What are the main topics in this chapter?
The chapter focuses on important life processes in animals, especially nutrition, digestion, breathing and respiration.
What is the difference between digestion and absorption?
Digestion breaks complex food into simpler substances, while absorption is the movement of digested nutrients into the body fluids for use by cells.
What is the difference between breathing and respiration?
Breathing is the physical exchange of air, while respiration is the cellular process through which energy is released from food.
Which organ is mainly responsible for absorption of nutrients?
The small intestine is the major site where digested nutrients are absorbed.
How do fish obtain oxygen?
Fish use gills to obtain dissolved oxygen from water.