Biodiversity
Near a village pond you see frogs, fish, dragonflies, lotus plants, crows and snails. So many kinds live in one small place.
Biodiversity (जैवविविधता) is the variety of all the living things of a particular area.
Rule 1: Observing biodiversity — Note the shape, colour, sound or shelter of living things you cannot name, or draw them. Partly eaten fruits, fallen feathers, tracks, dung, nests, eggs and honeycombs show that living things are present.
In the figure : In the figure the different living things around a village pond together show its biodiversity.
- Easy : Easy: A pond has many living things.
- Medium : Medium: Feathers on the ground show that birds visit.
- Exam-type : Exam: Observe by day and night and in different seasons.
Rule 2: How scientists observe — Scientists observe by day and night and in different seasons, use special devices for great heights, depths and tiny micro-organisms, and combine many observations over a long time.
- Easy : Easy: Scientists observe over many months.
- Medium : Medium: A microscope-type device sees micro-organisms.
- Exam-type : Exam: Many observations are combined for a true picture.
Biodiversity = variety of living things of a place. Observe and note signs.
Thinking only animals make biodiversity. Plants and micro-organisms count too.
Memory clue: "सर्व सजीव = जैवविविधता".
Spot the difference
| Sign | Shows |
|---|---|
| Feather | Birds |
| Tracks | Animals |
| Honeycomb | Bees |
Practice questions
- 1What is biodiversity?
- 2Name two signs of living things.
- 3What should you do for an unknown living thing?
- 4When do scientists observe?
- 5What does a honeycomb show?
- 6Why observe in different seasons?
- 7In a pond you list 5 fish kinds, 3 bird kinds and 4 plant kinds. How many kinds in all?
- 8Why is a pond richer in biodiversity than a bare rock?
Show answers (try them yourself first)
- 1Variety of all living things of an area.
- 2Nests and feathers.
- 3Note its shape, colour, sound or draw it.
- 4Day, night and in different seasons.
- 5Bees live there.
- 6Different living things appear in different seasons.
- 75 + 3 + 4 = 12.
- 8It gives water, food and shelter to many living things.
The environment
A fish out of water struggles, and a plant kept in a dark cupboard turns pale. Every living thing needs the right surroundings.
The environment (पर्यावरण) is the surroundings and the conditions in them that affect the life of living things.
Rule 1: Parts of the environment — The environment has non-living parts (sunlight, air, water, soil) and living parts (plants and animals). They depend on each other.
In the figure : In the figure the environment is made of non-living and living things that depend on each other.
- Easy : Easy: Air and water are non-living parts.
- Medium : Medium: Plants and animals are living parts.
- Exam-type : Exam: Name four non-living parts.
Rule 2: Interaction — Living and non-living things give and take from each other; this is interaction (आंतरक्रिया). Environmental Science (पर्यावरणशास्त्र) studies these interactions.
- Easy : Easy: A plant takes water from soil.
- Medium : Medium: Animals breathe air and give out carbon dioxide.
- Exam-type : Exam: Environmental Science studies interactions.
Environment = non-living + living, interacting.
Thinking environment means only trees and plants. It includes air, water, soil and sunlight.
Memory clue: "निर्जीव + सजीव = पर्यावरण".
Spot the difference
| Part | Examples |
|---|---|
| Non-living | Sunlight, air, water, soil |
| Living | Plants, animals |
Practice questions
- 1What is the environment?
- 2Name two non-living parts.
- 3Name two living parts.
- 4What is interaction?
- 5What does Environmental Science study?
- 6Give one example of interaction.
- 7Is a cow part of the environment of a field?
- 8A pond dries up. Which non-living part changed and which living things suffer?
Show answers (try them yourself first)
- 1The surroundings and conditions that affect living things.
- 2Air and soil.
- 3Plants and animals.
- 4Give and take between living and non-living things.
- 5These interactions.
- 6A plant takes water from soil.
- 7Yes, as a living part.
- 8Water changed; fish, frogs and plants suffer.
The food chain
At lunch, a banana feeds you and a goat eats leaves. In the field, a grasshopper eats grass and a bird eats the grasshopper. Food passes from one to another like a chain.
A food chain (अन्नसाखळी) shows who eats whom. Each part is a link (दुवा).
Rule 1: Links of a chain — Grasshoppers eat grass and leaves; birds eat grasshoppers. Each is food for the next. If one link is lost, the chain breaks. Example: grass → worm → frog → snake → kite.
In the figure : In the figure each link is food for the next one; the arrow points to the one that eats.
- Easy : Easy: A frog eats a worm.
- Medium : Medium: In grass → worm → frog, the frog is the third link.
- Exam-type : Exam: If frogs vanish, worms increase and snakes lose food.
Rule 2: Reading arrows — In a chain the arrow goes from the food to the eater: grass → worm means the worm eats the grass. Count the links to know the length. The chain grass → worm → frog → snake → kite has 5 links.
- Easy : Easy: Arrow goes to the eater.
- Medium : Medium: Chain with 5 links has 4 arrows.
- Exam-type : Exam: Write a food chain of 4 links.
Food chain: who eats whom. Arrow points to the eater. Lose a link, the chain breaks.
Drawing the arrow towards the food. It points to the eater.
Memory clue: "बाण = खाणारा".
Spot the difference
| Link | Role |
|---|---|
| Grass | First link, food maker |
| Worm, grasshopper | Eats plants |
| Frog, bird | Eats small animals |
| Snake, kite | Top eaters |
Practice questions
- 1What is a food chain?
- 2What is a link?
- 3Who eats grass in the chain?
- 4Who eats the grasshopper?
- 5Complete: grass → worm → frog → ?
- 6Which way does the arrow point?
- 7How many links in grass → worm → frog → snake → kite?
- 8If all snakes disappear, what happens to frogs?
Show answers (try them yourself first)
- 1A chain showing who eats whom.
- 2Each part of the chain.
- 3The worm (or grasshopper).
- 4A bird.
- 5Snake.
- 6Towards the eater.
- 75.
- 8Frogs will first increase and then run short of worms.
The food web and plants
A mother cooks with rice, vegetables and spices from the field. The sun, soil and water made every one of them. At the base of all food, there is a plant.
Plants make their own food using sunlight, water and carbon dioxide, and give out oxygen. So plants are the main support of every food chain.
Rule 1: Food web — One living thing can be part of several chains. A frog may eat worms and flies, and a snake and a bird may both eat frogs. Interlinked chains form a food web (अन्नजाळे).
In the figure : In the figure several food chains join to make a food web; plants are at the base of every chain.
The food web and plants
In the app you can move this figure with your finger.
Open in the appThe food web and plants
In the app you can move this figure with your finger.
Open in the app- Easy : Easy: Plants are at the base.
- Medium : Medium: A frog can be in two chains.
- Exam-type : Exam: Plants make food, so every chain starts with them.
Rule 2: Why a web is safer — In a web, an animal has several kinds of food. If one food runs short, it can eat another. So a food web is steadier than a single chain.
- Easy : Easy: A web has many chains.
- Medium : Medium: A kite eats snakes or mice.
- Exam-type : Exam: A web is steadier than a single chain.
Plants are the base. Chains join → food web.
Thinking animals make their own food. Only plants do.
Memory clue: "वनस्पती = अन्न कारखाना".
Spot the difference
| Item | Meaning |
|---|---|
| Food chain | One line of eating |
| Food web | Many chains joined |
| Plants | Base of every chain |
Practice questions
- 1Why are plants the base of food chains?
- 2What do plants need to make food?
- 3What gas do plants give out?
- 4What is a food web?
- 5Can one animal be in two chains?
- 6Why is a food web steadier?
- 7Frog eats worms and flies. How many foods does the frog have?
- 8Draw a 3-link chain starting with a plant.
Show answers (try them yourself first)
- 1They make their own food.
- 2Sunlight, water and carbon dioxide.
- 3Oxygen.
- 4Interlinked food chains.
- 5Yes.
- 6An animal has other food if one runs short.
- 7Two.
- 8Grass → grasshopper → bird.
Environmental balance
Leaves fall from a tree, rot in the soil and feed the same tree again. Nothing is wasted. Nature runs in circles.
Environmental balance (पर्यावरणीय समतोल) is kept when natural cycles go on without a break.
Rule 1: Cycles in nature — Micro-organisms decompose plant residue, dead animals and excreta, adding useful substances to the soil that plants use again. The water cycle gives water to all living things.
In the figure : In the figure the water cycle gives water to every living thing and keeps going round and round.
Environmental balance
In the app you can move this figure with your finger.
Open in the app- Easy : Easy: Dead leaves become soil food.
- Medium : Medium: Micro-organisms rot dead matter.
- Exam-type : Exam: The cycle returns useful substances to the soil.
Rule 2: Oxygen and carbon dioxide — Living things use oxygen and give out carbon dioxide. Plants use carbon dioxide and give out oxygen. This is another cycle. When all cycles run without interruption, the balance is kept, and it has been kept for thousands of years.
In the figure : In the figure plants give oxygen to animals and people, and animals and people give carbon dioxide to plants.
- Easy : Easy: Plants give oxygen.
- Medium : Medium: Animals give carbon dioxide to plants.
- Exam-type : Exam: Uninterrupted cycles keep the balance.
Cycles in nature keep the balance: water, soil substances, oxygen and carbon dioxide.
Thinking waste just disappears. Micro-organisms turn it into soil food.
Memory clue: "चक्र तुटले = समतोल बिघडला".
Spot the difference
| Cycle | What goes round |
|---|---|
| Water cycle | Water |
| Soil cycle | Useful substances |
| Gas cycle | Oxygen and carbon dioxide |
Practice questions
- 1What is environmental balance?
- 2What do micro-organisms do to dead plants?
- 3What does the water cycle give?
- 4What do plants give out?
- 5What do animals give out?
- 6How long has the balance been kept?
- 7Cutting too many trees breaks which cycle?
- 8How can you help keep the balance in your school?
Show answers (try them yourself first)
- 1Natural cycles going on without a break.
- 2Decompose them into soil substances.
- 3Water to all living things.
- 4Oxygen.
- 5Carbon dioxide.
- 6For thousands of years.
- 7The oxygen and carbon dioxide cycle.
- 8Plant trees, make compost, save water.
Quick revision
- Biodiversity = variety of living things in a place.
- Environment = living + non-living surroundings.
- Plants are the base of every food chain; food chains join to form a food web.
- Cycles in nature keep the environment in balance.