Food, growth and development
A puppy drinks milk, breathes and plays all day, and in a few months it becomes a big dog. A stone kept next to it stays the same for years. The puppy is alive because it uses air, food and water to grow.
Every living thing needs air, food and water. Food gives energy for growth. Growth (वाढ) is increase in size and mass; development (विकास) is progress in the body, skills and work capacity.
In the figure : Air, food and water are needed by all living things; food gives energy for growth.
Rule 1: Basic needs — All living things need air, food and water.
- Easy : A fish uses the air dissolved in water to live.
- Medium : A plant makes its own food by photosynthesis (प्रकाशसंश्लेषण). An animal gets food from plants or other animals.
- Exam-type : A cactus lives in a desert with very little water because it stores water in its stem.
Rule 2: Growth and development — Growth is increase in size; development is better skills and abilities. Animals grow only for a fixed period; plants grow as long as they live.
- Easy : A calf becoming heavier is growth.
- Medium : A child learning to ride a cycle shows development.
- Exam-type : A banyan tree keeps growing for hundreds of years; a dog stops growing after some time.
Food gives energy for growth. Without air, food and water, a living thing cannot survive for long.
Thinking growth and development are the same. Growth is in size; development is in ability.
Memory clue: AFW – Air, Food, Water.
Spot the difference
| Point | Growth | Development |
|---|---|---|
| Meaning | Increase in size and mass | Progress in skills and ability |
| Example | Calf becomes heavier | Child learns to cycle |
| Seen in | Height, weight, size | Skills, intelligence, work capacity |
Practice questions
- 1Name the three basic needs of all living things.
- 2What does food give to a living thing?
- 3Which process do plants use to make food?
- 4How do animals get their food?
- 5Is a child learning to read an example of growth or development?
- 6Who grows for a fixed period only – plants or animals?
- 7A balloon becomes bigger when air is blown into it. Is this growth? Why?
- 8Why can a cactus survive in a desert?
Show answers (try them yourself first)
- 1Air, food and water.
- 2Energy for growth.
- 3Photosynthesis
- 4From plants or from other animals.
- 5Development
- 6Animals
- 7No. Growth happens by food and cells inside a living thing; a balloon is non-living.
- 8It stores water in its stem.
Response to stimuli
If you touch a hot pan by mistake, you pull your hand back at once. Your skin sensed the heat and your hand acted on it. Plants also react: the leaves of a touch-me-not fold when touched.
What a living being senses in its surroundings is a stimulus (उद्दीपक). What it does about it is a response (प्रतिसाद). Sensing and responding is a sign of life.
In the figure : A stimulus is what a living being senses; its action is the response.
Rule 1: Stimulus and response — Every response follows a stimulus.
- Easy : Smell of food (stimulus) → mouth waters (response).
- Medium : Bright light (stimulus) → pupil of the eye becomes smaller (response).
- Exam-type : Earthworm keeps away from sunlight; roots grow towards water.
Rule 2: Plants also respond — Plants respond slowly, animals more quickly.
- Easy : A sunflower turns towards the Sun.
- Medium : Branches grow towards sunlight; roots grow downwards.
- Exam-type : Sir J. C. Bose showed with his instrument that plants sense heat, cold and pain.
Stimulus first, response next. Both animals and plants respond.
Thinking only animals respond. Plants respond too, but more slowly.
Memory clue: S → R – Sense first, React next.
Spot the difference
| Stimulus | Response |
|---|---|
| Touch of a hot pan | Hand pulled back |
| Touch to touch-me-not | Leaves fold |
| Sunlight | Sunflower turns |
Practice questions
- 1Define stimulus.
- 2Define response.
- 3What happens to the leaves of a touch-me-not when touched?
- 4What is the stimulus when your mouth waters?
- 5Which way do roots grow – towards or away from water?
- 6What did J. C. Bose prove about plants?
- 7Name the stimulus and the response: a dog runs after hearing its name.
- 8Why do we say a plant is alive, although it does not run?
Show answers (try them yourself first)
- 1What a living being senses in its surroundings.
- 2The action of a living being on a stimulus.
- 3They fold.
- 4Smell or sight of food.
- 5Towards water.
- 6They sense heat, cold and pain.
- 7Stimulus: its name called. Response: running.
- 8It senses and responds, for example roots grow to water and branches to light.
Excretion and reproduction
After eating, you pass urine and sweat; a tree sheds dry leaves in summer. These are ways of removing waste. A hen lays eggs and a mango seed grows into a tree; living things make new living things like themselves.
Excretion (उत्सर्जन) is the removal of waste from the body. Reproduction (प्रजनन) is the production of new organisms like oneself. A seed growing into a plant is germination (अंकुरण).
In the figure : Germination needs moisture, fresh air and sunlight.
Rule 1: Excretion — Animals give out carbon dioxide, water vapour, sweat and urine. Plants shed leaves and bark and release gum.
- Easy : We breathe out carbon dioxide.
- Medium : A tree sheds old leaves and bark along with waste.
- Exam-type : Gum from the babul tree is a plant waste.
Rule 2: Reproduction and germination — Some animals lay eggs, some give birth to young ones; most plants make seeds. A seed needs moisture, fresh air and sunlight (warmth) to germinate.
- Easy : A hen lays eggs; a cow gives birth to a calf.
- Medium : A bean seed in wet cotton wool grows a root and a shoot in a few days.
- Exam-type : A dry seed kept in a closed box does not germinate.
Reproduction keeps the species alive. Excretion keeps the body clean.
Thinking sweating is only for cooling. Sweat also removes waste.
Memory clue: Excrete = Exit of waste; Reproduce = Repeat the species.
Spot the difference
| Process | Meaning | Example |
|---|---|---|
| Excretion | Removing waste | Sweat, urine |
| Reproduction | Making new organisms | Hen lays eggs |
| Germination | Seed grows into a plant | Bean seed |
Practice questions
- 1Define excretion.
- 2Define reproduction.
- 3What is germination?
- 4Name two wastes given out by animals.
- 5How do plants remove waste?
- 6Name one animal that lays eggs and one that gives birth.
- 7A seed is kept dry in a closed box. Will it germinate? Why?
- 8Meena says sweat is only for cooling. Is it true?
Show answers (try them yourself first)
- 1Removal of waste from the body.
- 2Producing a new organism like oneself.
- 3A seed growing into a plant.
- 4Sweat and urine (or carbon dioxide).
- 5By shedding leaves and bark and by releasing gum.
- 6Hen lays eggs; cow gives birth.
- 7No. It has no moisture, fresh air or sunlight.
- 8No. Sweat also carries waste out of the body.
Respiration and movement
When you run, you breathe faster. Your cells need more energy from food, and for that they need more oxygen. Respiration gives the energy for running, jumping, even thinking.
Respiration (श्वसन) is the reaction of oxygen with food in the cells that gives energy. Breathing (श्वासोच्छ्वास) is taking air in (inhalation) and out (exhalation). Plants also respire.
In the figure : Breathing brings air in and out, while respiration in the cells releases energy from food.
Rule 1: Breathing and respiration — Breathing takes air in and out; respiration releases energy in the cells.
- Easy : We breathe with our lungs; fish breathe with gills.
- Medium : Running makes breathing faster because cells need more energy.
- Exam-type : Respiration goes on in every cell, day and night, even in plants.
Rule 2: Movement — Animals move to find food, to escape danger and to get shelter. Plants do not change place but show movements.
- Easy : A deer runs to escape a tiger.
- Medium : Roots and branches grow in a direction; buds open into flowers.
- Exam-type : Leaves of some plants fold at night.
Breathing is only taking air in and out. Respiration is the energy-making reaction in the cells.
Using "breathing" and "respiration" as the same word.
Memory clue: Breathe in the lungs, respire in the cells.
Spot the difference
| Point | Breathing | Respiration |
|---|---|---|
| Where | Lungs, gills | Cells |
| What happens | Air goes in and out | Food gives energy |
| Result | Oxygen enters | Energy is released |
Practice questions
- 1Define respiration.
- 2What are inhalation and exhalation?
- 3Which organs do fish use to breathe?
- 4Do plants respire?
- 5Why do animals move?
- 6Give one movement shown by plants.
- 7Why does your breathing become faster when you run?
- 8Raju says breathing and respiration are the same. Correct him.
Show answers (try them yourself first)
- 1The reaction of oxygen with food in the cells that gives energy.
- 2Taking air in and giving air out.
- 3Gills
- 4Yes, in their cells.
- 5To find food, to get protection and shelter.
- 6Roots grow downwards, leaves fold, buds bloom.
- 7Cells need more energy, so more oxygen is needed.
- 8Breathing takes air in and out; respiration happens in cells and gives energy.
Cells, life cycle and living vs non-living
A butterfly was once a tiny egg, then a caterpillar. A frog was first a tadpole with a tail. Every living thing, small or big, is made of cells and passes through stages of life.
The body of every organism is made of cells (पेशी). New cells heal wounds and make new shoots. Growth and reproduction are the main signs of life. A frog changes its body in stages: egg, tadpole, adult – this is metamorphosis (रूपांतरण).
In the figure : A frog changes its body shape in stages: egg, tadpole and adult.
Rule 1: Cells — Cells are the building blocks of every living thing. New cells heal wounds.
- Easy : A cut on the finger heals as new cells grow.
- Medium : A plant's new shoot is made by new cells.
- Exam-type : A stone and a bicycle have no cells – they are non-living.
Rule 2: Life cycle — Frog: egg → tadpole with gills and tail → tadpole with hind legs → adult frog.
- Easy : A tadpole breathes through gills; an adult frog breathes with lungs.
- Medium : Butterfly: egg → caterpillar → pupa → butterfly.
- Exam-type : A seed is alive even if it looks still; it grows when it gets water and warmth.
In the figure : Only living things grow and reproduce.
Living: butterfly, fish, tree. Non-living: stone, bicycle, book, air, kite, bus.
Calling a moving bus or a flying kite living. Moving alone does not make a thing living.
Memory clue: GR – Growth and Reproduction prove life.
Spot the difference
| Living | Non-living |
|---|---|
| Butterfly, fish, tree | Stone, book, air |
| Have cells | No cells |
| Grow and reproduce | Do not grow or reproduce |
Practice questions
- 1What is the body of every organism made of?
- 2Name the main signs of life.
- 3What is metamorphosis?
- 4Name the stages in the life cycle of a frog.
- 5Which is living: stone or fish?
- 6Name the stages in the life cycle of a butterfly.
- 7A bus moves and uses fuel. Is it living? Why?
- 8Is a dry seed living or non-living? Give a reason.
Show answers (try them yourself first)
- 1Cells
- 2Growth and reproduction.
- 3Change of body shape in stages, like egg → tadpole → frog.
- 4Egg, tadpole, adult frog.
- 5Fish
- 6Egg, caterpillar, pupa, butterfly.
- 7No. It does not grow or reproduce and is not made of cells.
- 8Living. It grows into a plant when it gets water and warmth.
Quick revision
- Characteristics: nutrition, growth, response to stimuli, excretion, respiration, movement, reproduction, cells.
- Main signs of life: growth and reproduction.
- Germination = seed to plant. Metamorphosis = life cycle of a frog.
Quick revision
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