Class 7 Chapter 10 Notes

 Life Processes in Plants

Class 7 Science — Chapter 10 | Complete Chapter Notes

1. Introduction

All living beings grow and need food for their growth. While animals eat food to grow, what about plants? Have you ever seen plants eating like animals? As animals grow, their size and weight increase, and their bodies change. What changes do you notice in plants as they grow? Food provides nutrients like carbohydrates, fats, proteins, vitamins, and minerals, along with water, all essential for growth.

Let's explore how plants obtain these nutrients for their growth.

2. How Do Plants Grow?

Plant growth involves visible changes such as the emergence of new leaves and branches, increased height, and a thicker stem. These changes occur as plants obtain essential resources like water, sunlight, and nutrients from their environment.

Role of Sunlight and Water

• Sunlight provides energy for food production, while water is crucial for nutrient transport and maintaining plant structure.

• Plants grown with both sunlight and water show better growth, with more leaves, greater height, and vibrant green leaves, compared to those lacking either resource.

• For instance, a plant without water may wilt or die, and one without sunlight may have pale or yellow leaves due to reduced food production.

📌 Fascinating Fact: Vrikshayurveda The ancient Indian text Vrikshayurveda states, "Trees do not produce fruits and flowers merely because they are planted." This text contains valuable observations about plant growth, soil, and farming methods to improve crop health and yield. Based on practical experience and long-term patterns, it systematically guides agricultural practices. For example, it describes ways to prepare organic manure using water, barley, and seeds like green gram, black gram, and horse gram.

📌 Multiple Choice Question What do roots absorb from the soil for plant growth? A. Carbon dioxide and chlorophyll B. Fruits and flowers C. Sunlight and air D. Water and minerals Correct Answer: D Roots absorb water and minerals from the soil, which are vital for growth and development. This absorption is essential for processes like cell division and tissue formation. Without these nutrients, plants cannot grow properly.

3. How Do Plants Get Food for Their Growth?

Unlike animals, plants produce their own food through a process called photosynthesis, primarily in their leaves. This food, stored as starch (a carbohydrate), provides energy and building blocks for growth.

Leaves: The 'Food Factories' of Plants

Leaves are the primary sites for food production due to their broad, flat structure and the presence of chlorophyll, a green pigment that captures sunlight. Chlorophyll enables leaves to convert sunlight, water, and carbon dioxide into food.

Starch Production

• Leaves store food as starch, a carbohydrate.

• The presence of starch can be confirmed by an iodine test, where a leaf turns blue-black if starch is present.

• This indicates that the leaf has produced food.

📌 Dive Deeper: Iodine Test Decolourisation of a leaf at the beginning of testing enables us to easily observe color change and, thus, the presence of starch.

📌 Fascinating Facts: Non-Green Leaves & Photosynthesis Some plant leaves look red, violet, or brown because they have more colored pigments than green chlorophyll, which hides the green color. Some of these pigments also assist in photosynthesis. You can perform an iodine test on such leaves to detect starch, which shows that photosynthesis has occurred.

Chlorophyll & Food Production

• Leaves have green and non-green patches due to the presence or absence of chlorophyll.

• Starch is produced only in the green parts of the leaf where chlorophyll is present.

• Non-green patches usually lack sufficient chlorophyll and do not produce detectable starch.

• The presence of starch can be confirmed by performing an iodine test, where starch turns blue-black.

• Leaves exposed to sunlight produce starch, while leaves kept in darkness do not, even if they have green patches.

• This shows that chlorophyll, in the presence of sunlight, is essential for the preparation of starch in plants.

• Because leaves produce food through this process, they are often called the 'food factories' of plants.

📌 Multiple Choice Question What is the primary function of chlorophyll in plants? A. Captures sunlight for photosynthesis B. Stores food as starch C. Produces oxygen during respiration D. Absorbs water from the soil Correct Answer: A The primary function of chlorophyll in plants is to capture sunlight for photosynthesis. Chlorophyll is a green pigment found in leaves and is essential for the process of photosynthesis, which allows plants to convert sunlight, water, and carbon dioxide into food.

Role of Air in Food Preparation

Air, specifically carbon dioxide, is a key component in photosynthesis. Plants take in carbon dioxide from the air to produce food.

• Carbon Dioxide Requirement: Carbon dioxide from the air is essential for plants to prepare food (starch). When a leaf is kept in an environment without carbon dioxide, starch is not produced in that part. This shows that carbon dioxide is a key ingredient required for photosynthesis.

• Oxygen Release During Photosynthesis: During photosynthesis, plants release oxygen gas. Oxygen production is evident when plants are exposed to sunlight, and bubbles of oxygen can be observed. The release of oxygen confirms that photosynthesis happens only in the presence of sunlight.

Photosynthesis: In a Nutshell

Photosynthesis is the process by which plants use sunlight, chlorophyll, carbon dioxide, and water to produce glucose (a simple carbohydrate) and oxygen.

• Glucose serves as an immediate energy source and can be converted into starch for storage.

• Oxygen is released as a by-product, which is vital for the survival of other living beings.

• Photosynthesis occurs mainly in leaves but also in other green parts of the plant containing chlorophyll.

📌 Word Equation for Photosynthesis Carbon dioxide + Water  ──(Sunlight / Chlorophyll)──►  Glucose + Oxygen

📌 Know A Scientist: Rustom Hormusji Dastur (1896–1961) Many scientists worldwide have contributed to understanding photosynthesis. In India, Rustom Hormusji Dastur (1896–1961) was a notable plant scientist who studied this process. He served as the head of the Botany Department at the Royal Institute of Science, Bombay (now the Institute of Science, Mumbai) from 1921 to 1935. Dastur researched how factors like water availability, temperature, and light color affect photosynthesis, highlighting their importance in the process.

4. How Do Leaves Exchange Gases During Photosynthesis?

Leaves have tiny pores called stomata on their surface, which facilitate the exchange of gases during photosynthesis and respiration.

• These pores allow carbon dioxide to enter the leaf for photosynthesis and oxygen to exit as a by-product.

• Stomata also play a role in respiration by allowing oxygen intake and carbon dioxide release.

Transport in Plants

Plants have a transport system to move water, minerals, and food to different parts, ensuring growth and survival. Roots absorb water and minerals from the soil, which are transported to other parts of the plant through specialized tissues called xylem and phloem.

• All living beings need water to grow, and plants use water for photosynthesis.

• Water and minerals from the soil are absorbed by the roots of plants.

• Minerals are essential nutrients for plant growth.

• Water and minerals travel from the roots to other parts of the plant through a tissue called xylem.

• The xylem consists of thin tube-like structures in stems, branches, and leaves that carry water and dissolved minerals upward.

• The movement of water and minerals can be demonstrated by placing plant twigs in colored water, where the color travels up the stem and into leaves and flowers.

• Water transported through the xylem supports various functions in the plant.

Transport of Food (Phloem)

Food produced in the leaves is distributed to non-green parts of the plant, such as roots, stems, and fruits, for growth and storage, through specialized tissue called phloem.

• Leaves are the primary site of photosynthesis, where food is prepared.

• The phloem is vascular tissue that transports food from the leaves to other parts of the plant.

• This ensures that areas not involved in photosynthesis, like roots and developing fruits, receive the energy and nutrients they need.

• Some of this transported food is stored in other parts of the plant, such as seeds and roots.

📌 Multiple Choice Question What is the function of stomata in leaves? A. Produce glucose B. Exchange gases C. Transport water D. Store starch Correct Answer: B The function of stomata in leaves is to exchange gases. Here's how stomata work: • They allow carbon dioxide to enter the leaf for photosynthesis. • They enable oxygen to exit as a by-product. • They also help with respiration by letting oxygen in and carbon dioxide out. This gas exchange is crucial for the process of photosynthesis and the overall survival of plants.

Do Plants Respire?

Plants, like animals, respire to produce energy for growth and other functions. Respiration occurs in all parts of the plant, whether green or non-green. During respiration, plants break down glucose using oxygen, releasing carbon dioxide, water, and energy.

📌 Word Equation for Respiration Glucose + Oxygen  ──►  Carbon dioxide + Water + Energy

• The energy released supports processes like growth, cell repair, and nutrient transport.

• An experiment with soaked moong bean seeds shows that carbon dioxide is released during respiration, which turns lime water milky. This carbon dioxide comes from the seeds respiring inside the flask.

• The energy produced in respiration is used by plants for growth and development.

• All parts of the plant, whether green or non-green, carry out respiration.

• Plants have distinct processes for synthesizing food (photosynthesis), transporting food, and using it to produce energy (respiration).

5. Terms to Remember

Term	Definition
Photosynthesis	The process by which plants use sunlight, chlorophyll, carbon dioxide, and water to produce glucose and oxygen.
Chlorophyll	A green pigment in leaves that captures sunlight for photosynthesis.
Stomata	Tiny pores on leaf surfaces that allow gas exchange (carbon dioxide in, oxygen out) during photosynthesis and respiration.
Xylem	Vascular tissue that transports water and minerals from roots to other parts of the plant.
Phloem	Vascular tissue that transports food from leaves to other parts of the plant.
Respiration	The process by which plants break down glucose using oxygen to release energy, carbon dioxide, and water.
Glucose	A simple carbohydrate produced during photosynthesis, used as an energy source or stored as starch.
Starch	A carbohydrate stored in plants, produced from glucose during photosynthesis.

Class 7 Chapter 9 Notes

 Life Processes in Animals

Class 7 Science — Chapter 9 Notes

1. Introduction

Animals eat different types of food depending on their habitat and habits. For example:

• Bees and sunbirds suck nectar from flowers.

• Human infants and the infants of many other animals feed on their mother’s milk.

• Snakes, such as pythons, swallow the animals they catch.

• Some aquatic animals filter tiny food particles from water.

All animals, including humans, obtain energy from food. This energy is essential for carrying out life processes. Food contains complex components such as carbohydrates, proteins, and fats. These components must be broken down into simpler forms before the body can use them.

This breakdown of food takes place in a long tube called the alimentary canal, which starts at the mouth and ends at the anus. As food passes through this canal, digestive juices secreted by different organs help convert it into simpler substances. These nutrients are then absorbed and transported to various parts of the body for energy production, growth, repair, and other life processes.

2. Nutrition in Animals

Animals obtain energy from food, but the way food is broken down and used varies among different species. To understand this process, let us study digestion in humans.

3. Digestion in Human Beings

Digestion is the process of breaking down complex food into simpler substances. It occurs in the alimentary canal, a long tube that extends from the mouth to the anus.

The following stages describe how digestion takes place in human beings from beginning to end.

1. Beginning with the Mouth Cavity

• Digestion begins in the mouth, where food enters and is broken down into smaller pieces by the teeth through crushing and chewing. This is called mechanical digestion.

• When you think of your favourite food, your mouth produces more saliva. Saliva moistens the food and makes it easier to swallow.

• Saliva contains the enzyme salivary amylase, which begins breaking down starch, a carbohydrate, into simpler sugars. This is why starchy foods such as chapati or rice may taste sweet when chewed for some time.

Science and Society — Oral Hygiene A healthy mouth requires good oral hygiene. We should brush our teeth and clean our tongue twice a day. We should also rinse our mouth with water after each meal to help prevent tooth decay and bad breath. Find out the ways in which our elders maintained oral hygiene.

Activity: Investigate Saliva’s Role Aim: To observe the effect of saliva on the breakdown of starch in boiled rice. Materials Needed: Two test tubes, a teaspoon, boiled rice, water, and iodine solution. Procedure: Label test tubes 'A' and 'B'. Place 1 teaspoon of boiled rice in test tube A and 1 teaspoon of chewed boiled rice in test tube B. Add 3–4 mL of water to both test tubes. Note the initial colour. Add 3–4 drops of iodine solution to each test tube and mix the contents. Observe the colour changes. Observations: In test tube A, the boiled rice turns blue-black, indicating the presence of starch. In test tube B, the chewed rice does not change colour or shows a very light blue-black colour, indicating that starch was broken down into simpler sugars by saliva.

2. Food Pipe (Oesophagus): A Passage from the Mouth to the Stomach

• After chewing, saliva moistens the food, making it soft and easy to swallow.

• The tongue mixes the chewed food with saliva and pushes it into the food pipe or oesophagus.

• The oesophagus is a long, flexible tube that connects the mouth to the stomach.

• Food moves down the oesophagus by a wave-like movement called peristalsis. During peristalsis, the walls of the food pipe contract and relax gently.

• This movement continues throughout the alimentary canal and pushes food forward for digestion.

3. Stomach

• The walls of the food pipe contract and relax in a wave-like motion to push food down into the stomach.

• The walls of the stomach contract and relax to churn the food and mix it thoroughly.

• The stomach lining secretes digestive juice, acid, and mucus.

• Digestive juice helps break down proteins into simpler substances.

• The acid provides the acidic medium needed for protein digestion and helps kill harmful bacteria.

• Mucus protects the stomach lining from being damaged by the acid.

• Food is partially digested in the stomach and changed into a semi-liquid mass that is ready for the next stage of digestion.

Fascinating Facts — Discovery of Stomach Functions In 1822, Alexis St. Martin was accidentally shot in the stomach. After treatment, a small permanent opening remained. Dr William Beaumont used this opening to directly observe digestion, study how different foods are broken down, and explore how emotions affect digestion. This accidental discovery significantly advanced our understanding of the stomach.

4. Small Intestine

After leaving the stomach, partially digested food enters the small intestine. It is about 6 metres long, making it the longest part of the alimentary canal.

• The small intestine receives digestive secretions from:

• Its own inner lining.

• The liver, which produces bile.

• The pancreas, which produces pancreatic juice.

• Bile is mildly basic. It helps neutralise stomach acid and breaks fats into tiny droplets, making them easier to digest.

• Pancreatic juice is also basic. It helps neutralise acid and contains substances that help break down carbohydrates, proteins, and fats.

• Digestive juices from the small intestine further break down fats, proteins, and carbohydrates into simpler substances.

• Nutrients are absorbed into the blood through the inner lining of the small intestine.

• The lining has thousands of finger-like projections called villi. These projections increase the surface area for efficient absorption.

• Absorbed nutrients provide energy, help in growth and repair, and support the proper functioning of the body.

Science and Society — Celiac Disease & Dietary Alternatives Celiac disease is a condition in which the body reacts to gluten, a protein found in wheat, barley, and rye. This reaction damages the inner lining of the small intestine and affects nutrient absorption. The main way to manage celiac disease is to avoid gluten-containing foods. Millets such as jowar, bajra, and ragi are good alternatives because they are naturally gluten-free.

5. Large Intestine

• After nutrient absorption in the small intestine, undigested food moves into the large intestine.

• The large intestine is about 1.5 metres long. It is shorter but wider than the small intestine.

• Its main function is to absorb water and some salts from undigested food.

• This process changes the waste into a semi-solid form called stool.

• Stool is stored in the rectum until the body is ready to eliminate it.

• The waste is expelled through the anus in a process called egestion.

• Eating fibre-rich foods, such as fruits, vegetables, and whole grains, helps keep the large intestine healthy and makes stool easier to pass.

Fascinating Facts & Science and Society Gut Microflora: The large intestine contains helpful bacteria that break down undigested fibre and produce substances important for health. Fermented foods like curd and pickles support healthy digestion. Ayurveda & Digestive Health: The ancient Ayurvedic text Charaka Samhita stresses easily digestible foods and traditional spices like ginger, black pepper, and cumin. Modern nutrition similarly emphasizes timely, mindful eating.

4. Digestion in Other Animals

Not all animals digest food in the same way as humans. Their digestive systems are adapted to their diets and habitats.

1. Ruminants

• Ruminants are grass-eating animals. They partially chew grass and swallow it into their stomachs, where it undergoes partial digestion.

• The food is then brought back to the mouth for thorough chewing. This process is called rumination.

• Ruminants may spend about 8 hours a day chewing their food.

• After thorough chewing, the food moves down the alimentary canal for further digestion.

2. Birds

• Birds lack teeth but have a special muscular stomach chamber called the gizzard.

• The gizzard breaks down food by contracting and relaxing. Small stones, called grit, swallowed by birds may help grind the food.

• Animals show variations in their digestive systems according to the types of food they eat.

• Nutrients from digested food help build and repair the body or are broken down to release energy.

• The process of using nutrients to release energy is called respiration.

5. Respiration in Animals

• Respiration is the process by which animals use oxygen to break down nutrients such as glucose and release energy. Carbon dioxide and water are formed as products of this process.

• Breathing is a physical process that brings oxygen into the body and removes carbon dioxide. Respiration is a chemical process that takes place in cells.

Respiration in Humans

• Breathing is the process of inhaling, or breathing in, oxygen-rich air and exhaling, or breathing out, air containing more carbon dioxide.

• Breathing is essential for survival. Without breathing, humans cannot live for more than a few minutes.

• All living organisms exchange gases with their surroundings. Plants and animals also carry out respiration.

• The respiratory system is the body system responsible for breathing and gas exchange.

Key Components of the Human Respiratory System:

• Nostrils: Openings in the nose through which air is inhaled and exhaled.

• Nasal passages: Passages after the nostrils lined with tiny hairs and mucus that trap dust and dirt. Breathing through the nose is better than through the mouth due to this filtration.

• Windpipe (Trachea): A tube that carries air from the nasal passages to the lungs and divides into two branches.

• Lungs and Alveoli: The windpipe branches inside the lungs into finer tubes ending in tiny balloon-like sacs called alveoli, where gas exchange occurs.

• Protection: The lungs are protected by the rib cage, a bony structure surrounding them.

Science and Society — Respiratory Health Although the respiratory system filters out much of the dust in inhaled air, small infectious particles can still enter the lungs. For example, during the COVID-19 pandemic, the SARS-CoV-2 virus affected the respiratory system, causing breathing difficulties and serious lung problems in many people.

Activity: Simple Breathing Mechanism Model Materials Needed: Wide transparent plastic bottle with lid and bottom removed, Y-shaped hollow tube, two deflated balloons, rubber bands, sealing clay, thin rubber sheet, large rubber band. Procedure: Make a hole in the bottle lid. Fix deflated balloons to the Y-tube branches with rubber bands. Insert straight end through the lid and seal with clay. Attach thin rubber sheet tightly to open base with large rubber band. Pull sheet downwards and observe balloons, then release upwards. Observations: When pulled downwards, balloons inflate (inhalation). When released upwards, balloons deflate (exhalation). Balloons represent lungs; rubber sheet represents diaphragm.

6. How Breathing Happens
(i) Inhalation

• When you breathe in, or inhale, your chest expands as your ribs move up and outwards.

• The diaphragm is a dome-shaped muscle located below the lungs. It moves downwards during inhalation.

• This movement increases the space inside the chest and allows air to enter the lungs.

(ii) Exhalation

• When you breathe out, or exhale, your ribs move down and inwards, while the diaphragm moves upwards.

• This reduces the space inside the chest and helps to push air out of the lungs.

• In the activity described above, the balloons represent the lungs and the rubber sheet represents the diaphragm.

Science and Society — Traditional Breathing Practices Breathing exercises such as Pranayama (India, controlled breathing for concentration) and Tummo (Ladakh/cold regions, for body warmth) have been practised for centuries to support calmness, well-being, and mental clarity.

7. What Do We Breathe Out?

When we exhale, the air we breathe out contains more carbon dioxide than the air we inhale. This can be demonstrated through an experiment with lime water:

• Lime water is a clear solution that turns milky when it reacts with carbon dioxide.

• Two test tubes containing equal amounts of fresh lime water are taken (Test Tube A and Test Tube B).

• Air similar to inhaled air is passed through test tube A using a syringe.

• Exhaled air is blown through a straw into test tube B.

• Test tube B turns milky because of its reaction with carbon dioxide, while Test tube A remains clear.

• This indicates that exhaled air contains a higher concentration of carbon dioxide than inhaled air.

(iii) Gas Exchange

• Fresh air enters the lungs during breathing and fills tiny sacs called alveoli.

• Alveoli have thin walls and are surrounded by blood vessels.

• Carbon dioxide from the blood passes into the alveoli and is removed from the body during exhalation.

• Oxygen from the alveoli passes into the blood and is carried to the entire body.

• Oxygen is used to break down glucose from food and release energy in a process called respiration.

Glucose  +  Oxygen   ➔   Carbon dioxide  +  Water  +  Energy

• Inhaled air contains about 21% oxygen and 0.04% carbon dioxide.

• Exhaled air contains about 16–17% oxygen and 4–5% carbon dioxide.

• Breathing is a physical process involving the intake and release of air.

• Respiration is a chemical process inside cells that produces energy.

• Both breathing and respiration are vital for survival.

Difference Between Breathing and Respiration

• Breathing and respiration are related but occur at different levels in the body.

• Breathing is the simple act of moving air in and out of the lungs, whereas respiration is the chemical process inside cells that releases energy from food.

Feature	Breathing	Respiration
Type of Process	Physical process involving intake and release of air	Chemical process inside cells that produces energy
Location & Level	Occurs at organ system level (lungs, respiratory tract)	Occurs at cellular level (inside cells)

8. Role of the Circulatory System

• The circulatory system transports nutrients, oxygen, and waste products throughout the body.

• It consists of the heart, blood, and blood vessels.

• The heart pumps blood through blood vessels to deliver oxygen and nutrients and remove waste products.

Science and Society — Effects of Smoking Smoking damages the lungs and increases the risk of lung cancer and other respiratory diseases. It causes persistent coughing, makes the body prone to infections, and releases toxic chemicals that harm others through passive smoking. Avoiding smoking protects both personal and public health.

Respiration in Other Animals

Different animals live in different habitats and have different breathing mechanisms suited to their surroundings:

• Lungs: Animals such as birds, elephants, lions, cows, lizards, and snakes breathe through lungs, though lung structures vary.

• Gills: Aquatic animals such as fish use gills to extract dissolved oxygen from water and release carbon dioxide.

• Skin and Gills: Amphibians such as frogs use gills as tadpoles, lungs as adults on land, and moist skin for gas exchange in water.

• Moist Skin: Earthworms breathe through their moist skin, which allows direct exchange of oxygen and carbon dioxide.

9. Terms to Remember

Term	Definition
Alimentary canal	The long tube in the digestive system that extends from the mouth to the anus and in which food is digested and absorbed.
Mechanical digestion	The physical breakdown of food into smaller pieces, such as by chewing.
Peristalsis	Wave-like muscle contractions that move food through the digestive system.
Villi	Finger-like projections in the small intestine that increase the surface area for nutrient absorption.
Egestion	The process of expelling undigested waste, or stool, through the anus.
Ruminants	Animals such as cows that partially digest food, bring it back to the mouth, and chew it again.
Gizzard	A muscular chamber in birds that grinds food, often with the help of swallowed stones.
Alveoli	Tiny air sacs in the lungs where oxygen and carbon dioxide are exchanged.
Diaphragm	A dome-shaped muscle below the lungs that helps in breathing by moving up and down.
Respiration	The chemical process in cells in which oxygen helps break down glucose to release energy.
Circulatory system	The system made up of the heart, blood, and blood vessels that transports nutrients, oxygen, and waste products.