PW Class 7 Science Chapter 9 Notes: Life Processes in Animals

Animals perform several life processes every day, but understanding how these processes work together can be difficult. Food must be digested and absorbed, oxygen must reach body cells, wastes need to be removed, and the body must carry out reproduction. Learning the roles of different organs and understanding how these processes are connected requires careful revision.

PW Class 7 Science Chapter 9 Notes make these concepts easier to revise with clear explanations, examples, comparisons, and important points. You can use the notes to understand nutrition, digestion, respiration, circulation, excretion, and reproduction in humans and other animals before solving textbook questions and preparing for school assessments.

How Does Nutrition Take Place in Animals?

Animals need food to obtain nutrients and energy required for growth, movement, repair, and other life processes. Food contains complex substances such as carbohydrates, proteins, and fats that must be broken down into simpler substances before they can be used by the body.

What Is Digestion?

Digestion is the process of breaking down complex food into simpler substances that can be absorbed and used by the body.

In humans, digestion takes place mainly in the alimentary canal, a long tube that extends from the mouth to the anus.

How Does Digestion Occur in Human Beings?

The human digestive system consists of different organs that work together to digest food, absorb nutrients, and remove undigested waste.

What Happens in the Mouth?

Digestion begins in the mouth cavity.

• Teeth break food into smaller pieces by crushing and chewing. This is called mechanical digestion.

• Saliva moistens the food and makes it easier to swallow.

• Saliva contains the enzyme amylase, which begins the digestion of starch into simpler sugars.

• This is why foods such as rice and chapati may taste slightly sweet when chewed for some time.

What Happens in the Stomach?

The swallowed food moves from the mouth through the food pipe into the stomach.

• The stomach produces gastric juice.

• Hydrochloric acid (HCl) provides an acidic environment and helps kill many harmful microorganisms.

• The enzyme pepsin helps digest proteins.

• The stomach mixes food with digestive juices to form a semi-liquid mixture.

What Happens in the Small Intestine?

Most digestion and absorption of nutrients take place in the small intestine.

• Bile helps in the digestion of fats.

• Pancreatic juice contains enzymes that help digest carbohydrates, proteins, and fats.

• Digestion is completed in the small intestine.

• Digested nutrients are absorbed into the blood through the walls of the small intestine.

What Happens in the Large Intestine?

The remaining material passes into the large intestine.

• Water is absorbed from the undigested food.

• Helpful bacteria in the large intestine act on some undigested fibre.

• The remaining waste is formed into faeces.

What Is Egestion?

The removal of undigested food from the body through the anus is called egestion.

Why Is Oral Hygiene Important?

A healthy mouth is important for proper digestion and overall health.

• Brush your teeth twice a day.

• Clean your tongue regularly.

• Rinse your mouth after meals.

• Avoid excessive sugary foods.

• Good oral hygiene helps prevent tooth decay and bad breath.

What Is Celiac Disease?

Celiac disease is a condition in which the body reacts to gluten, a protein found in foods containing wheat, barley, and rye.

• Gluten can damage the inner lining of the small intestine in people with celiac disease.

• This damage can interfere with the absorption of nutrients.

• Avoiding gluten-containing foods is an important part of managing the condition.

• Naturally gluten-free grains such as jowar, bajra, and ragi can be suitable alternatives.

How Do Other Animals Digest Food?

Animals have different digestive systems depending on their food habits and body structures.

Digestion in Ruminants

Animals such as cows eat grass and other plant material containing cellulose.

• Grass is swallowed with little chewing.

• It enters a specialised stomach compartment called the rumen.

• Microorganisms in the rumen help break down cellulose.

• Partly digested food returns to the mouth as cud.

• The animal chews the cud again, a process called rumination.

• The food then passes through the remaining digestive compartments for further digestion and absorption.

Digestion in Birds

Birds do not have teeth, so they use specialised organs for processing food.

• The crop temporarily stores food.

• The gizzard helps grind food.

• Small stones swallowed by birds can assist grinding in the gizzard.

• Digestion continues in the intestine, where nutrients are absorbed.

How Are Digestion and Food Habits Connected?

Different animals have digestive systems suited to the food they consume.

• Plant-eating animals need adaptations for digesting cellulose.

• Birds use a gizzard because they do not have teeth.

• Humans have different organs that work together to digest a variety of foods.

These differences show how digestive systems are adapted to the feeding habits of animals.

What Is the Difference Between Breathing and Respiration?

Breathing and respiration are related but different processes.

Breathing supplies oxygen to the body, while cellular respiration uses oxygen or other pathways to release energy from food.

What Happens During Inhalation and Exhalation?

Breathing involves two main movements: inhalation and exhalation.

What Are Aerobic and Anaerobic Respiration?

Cells release energy from food through respiration. Depending on the availability of oxygen, respiration can occur through different pathways.

Aerobic Respiration

Aerobic respiration takes place in the presence of oxygen.

• Glucose is completely broken down.

• Carbon dioxide and water are formed.

• A larger amount of energy is released.

Glucose + Oxygen → Carbon dioxide + Water + Energy

Anaerobic Respiration

Anaerobic respiration takes place without the use of oxygen.

• Glucose is incompletely broken down.

• Less energy is released.

• Different organisms may produce different end products.

In yeast, anaerobic respiration produces alcohol and carbon dioxide.

Glucose → Ethyl alcohol + Carbon dioxide + Energy

This process is also called fermentation and is used in making products such as bread and certain beverages.

How Does Respiration Occur in Humans?

In humans, the respiratory system brings oxygen into the body and removes carbon dioxide.

Respiratory Pathway

Nostrils → Nasal Cavity → Pharynx → Trachea → Bronchi → Lungs

• Air enters through the nostrils.

• The nasal cavity filters, warms, and moistens the air.

• The trachea carries air towards the lungs.

• The bronchi carry air into the lungs.

• In the lungs, oxygen passes into the blood, and carbon dioxide moves from the blood into the air spaces to be exhaled.

Composition of Inhaled and Exhaled Air

The difference shows that the body takes in oxygen and releases more carbon dioxide during respiration.

How Do Other Animals Respire?

Animals use different respiratory organs depending on their body structure and habitat.

Animals Using Lungs

Animals such as birds, lions, and lizards breathe using lungs. The structure of their lungs may differ according to their needs and lifestyles.

Animals Using Gills

Aquatic animals such as fish use gills.

• Gills take dissolved oxygen from water.

• Carbon dioxide is released into the surrounding water.

Respiration in Frogs

Frogs use different respiratory surfaces during different stages of their life.

• Tadpoles mainly use gills.

• Adult frogs use lungs on land.

• They can also exchange gases through their moist skin, especially when in water.

Respiration Through Skin

Earthworms breathe through their moist skin.

The moisture allows oxygen and carbon dioxide to pass through the skin during gas exchange.

What Are the Harmful Effects of Smoking?

Smoking introduces harmful chemicals into the respiratory system and can seriously damage health.

• It damages lung tissues.

• It increases the risk of lung cancer and other respiratory diseases.

• It can cause persistent coughing and breathing problems.

• It can increase susceptibility to respiratory infections.

• Smoke can also harm people nearby through passive smoking.

Avoiding smoking helps protect the lungs and reduces exposure to harmful substances.

How Does the Circulatory System Help Animals?

The circulatory system transports important substances throughout the body.

It consists mainly of:

• Heart

• Blood

• Blood vessels

What Does the Heart Do?

The heart is a muscular organ that pumps blood throughout the body.

It helps ensure that oxygen and nutrients reach cells while waste products are carried away.

What Does Blood Do?

Blood transports:

• Oxygen

• Digested nutrients

• Carbon dioxide

• Waste products

• Hormones and other substances

What Are Blood Vessels?

Blood vessels form a network through which blood travels.

• Arteries: Carry blood away from the heart.

• Veins: Carry blood towards the heart.

• Capillaries: Tiny blood vessels where substances are exchanged between blood and body cells.

What Are the Main Components of Blood?

How Does Blood Circulate Through the Human Heart?

The human heart has four chambers:

• Right atrium: Receives oxygen-poor blood from the body.

• Right ventricle: Pumps oxygen-poor blood to the lungs.

• Left atrium: Receives oxygen-rich blood from the lungs.

• Left ventricle: Pumps oxygen-rich blood to the rest of the body.

The right and left sides of the heart are separated, helping prevent the mixing of oxygen-rich and oxygen-poor blood.

What Is Double Circulation?

Humans have double circulation because blood passes through the heart twice during one complete journey through the body.

1. Pulmonary circulation: Blood moves between the heart and lungs for gas exchange.

2. Systemic circulation: Oxygen-rich blood moves from the heart to the body and returns after delivering oxygen and collecting carbon dioxide.

What Is Pulse Rate?

Each contraction and relaxation of the heart forms a heartbeat. The expansion of arteries caused by the pumping of blood can be felt as a pulse.

• Pulse can be felt at places such as the wrist and neck.

• Pulse rate is the number of pulses counted in one minute.

• Physical activity generally increases heart rate because working muscles require more oxygen and energy.

How Does Excretion Occur in Animals?

Excretion is the process of removing metabolic waste products from the body. Removing these wastes is necessary to prevent their accumulation and maintain normal body functions.

What Are the Main Excretory Organs in Humans?

The human excretory system includes:

• Kidneys: Filter the blood and remove wastes, excess salts, and excess water.

• Ureters: Carry urine from the kidneys to the urinary bladder.

• Urinary bladder: Stores urine temporarily.

• Urethra: Carries urine outside the body.

How Is Urine Formed?

Urine formation in the kidneys involves important processes:

1. Filtration: Blood is filtered in the kidneys.

2. Reabsorption: Useful substances and some water are returned to the blood.

3. Urine formation: Remaining wastes and excess water form urine.

Urine then travels through the ureters to the urinary bladder and leaves the body through the urethra.

What Role Do Other Organs Play in Excretion?

Waste removal is not limited to the kidneys.

• Lungs: Remove carbon dioxide and water vapour during exhalation.

• Skin: Removes water and salts through sweat.

• Liver: Helps process harmful substances and converts some nitrogenous waste into urea, which is later removed by the kidneys.

How Do Other Animals Remove Wastes?

Different animals have specialised excretory organs.

• Earthworms: Use structures called nephridia.

• Insects: Use Malpighian tubules.

• Fish: Remove nitrogenous wastes mainly through their gills and kidneys.

• Amphibians: Use kidneys along with other body surfaces for waste removal.

What Is Reproduction in Animals?

Reproduction is the life process through which organisms produce new individuals of their own kind. It helps maintain the continuity of a species.

Animals reproduce mainly through:

• Asexual reproduction: Usually involves one parent and does not involve the fusion of male and female gametes.

• Sexual reproduction: Usually involves two parents and the fusion of male and female gametes.

How Does Sexual Reproduction Occur in Humans?

Human sexual reproduction involves male and female reproductive systems that produce specialised reproductive cells called gametes.

• Male gamete: Sperm

• Female gamete: Ovum or egg

What Are the Main Male Reproductive Organs?

• Testes: Produce sperm and the hormone testosterone.

• Sperm ducts: Transport sperm.

• Penis: Helps transfer sperm into the female reproductive tract.

What Are the Main Female Reproductive Organs?

• Ovaries: Produce ova and hormones such as oestrogen.

• Fallopian tubes: Carry ova from the ovaries towards the uterus.

• Uterus: Provides a place for the developing embryo.

• Vagina: Connects the uterus to the outside of the body.

What Is Fertilisation?

Fertilisation is the fusion of a male gamete and a female gamete to form a zygote.

• In humans, fertilisation usually takes place in the fallopian tube.

• The zygote divides repeatedly.

• It develops into an embryo.

• The embryo attaches to the lining of the uterus.

• Further development takes place in the uterus.

What Is the Difference Between Internal and External Fertilisation?

Fertilisation can occur inside or outside the body.

Animals with external fertilisation often release many eggs and sperm because not all of them successfully meet and develop.

How Are Different Life Processes Connected?

Life processes in animals do not work independently. Nutrition, respiration, circulation, excretion, and reproduction are connected and support the functioning of the body.

• Nutrition provides nutrients needed by the body.

• Digestion breaks complex food into simpler substances.

• Respiration releases energy from nutrients.

• Circulation transports oxygen, nutrients, and other substances.

• Excretion removes metabolic wastes.

• Reproduction ensures the continuation of a species.

Together, these processes help animals obtain energy, grow, maintain their bodies, respond to their surroundings, and continue their species.

Class 7 Science Chapter 9 Notes PDF

Use the CBSE Class 7 Science Chapter 9 Notes PDF to revise nutrition, digestion, respiration, circulation, excretion, reproduction, and other important life processes in animals.

What Can You Learn from Physics Wallah Class 7 Science Chapter 9 Notes?

Physics Wallah Class 7 Science Chapter 9 Notes cover Life Processes in Animals through descriptive explanations, examples, comparisons, and important concepts. They help you understand how animals obtain nutrients, release energy, transport substances, remove wastes, and reproduce.

• Understand Animal Nutrition: Revise how animals obtain food and why digestion is necessary.

• Learn Human Digestion: Recall the functions of the mouth, stomach, small intestine, large intestine, and other parts of the alimentary canal.

• Compare Breathing and Respiration: Understand the difference between these processes and their roles in the body.

• Revise Types of Respiration: Differentiate between aerobic and anaerobic respiration with suitable examples.

• Explore Respiration in Animals: Learn how lungs, gills, and moist skin help different animals exchange gases.

• Understand Circulation: Revise the functions of the heart, blood, and blood vessels in transporting substances.

• Learn About Excretion: Understand how kidneys and other organs remove waste products from the body.

• Study Reproduction: Revise sexual and asexual reproduction, human reproductive organs, and fertilisation.

• Prepare for School Assessments: Recall important definitions, processes, comparisons, examples, and key concepts before examinations.

Understanding how animals obtain nutrients, release energy, transport substances, remove wastes, and reproduce shows how different life processes work together. These notes cover digestion, respiration, circulation, excretion, and reproduction with important examples and explanations. Revising these concepts can help strengthen your understanding and support effective preparation for school assessments.

Related Resources

• CBSE Class 7 Science Syllabus

• CBSE Class 7 Science Notes

• CBSE Class 7 Science NCERT Solutions

• CBSE Class 7 Science Important Questions

• CBSE Class 7 Science Sample Papers