Habitat, biotic and abiotic components
Near Sunita's house there is a pond with fish, frogs and lotus plants, and a patch of forest behind it. Her teacher asks her to list everything she sees in each place, living or not.
A habitat is the place where an organism lives and finds what it needs. The living parts of a habitat are its biotic components; the non-living parts (air, water, sunlight, temperature, soil) are its abiotic components.
Key idea 1: Every habitat has both kinds — In a pond, fish, frogs and algae are biotic, while water, soil and sunlight are abiotic. A forest has different organisms and different conditions, so each habitat suits different living things. A habitat can be big, like a forest, or tiny, like the bark of a tree.
- Easy: Fish, frog and lotus are biotic; water and soil are abiotic.
- Medium: A pond and a forest both have living and non-living parts, but the organisms are different.
- Exam-type: In the list fish, water, algae, snail, air, mud there are 3 biotic items (fish, algae, snail) and 3 abiotic items.
In the figure: A pond habitat has living (biotic) and non-living (abiotic) parts side by side.
Key idea 2: What organisms need from a habitat — A fish gets food, a biotic need, from small plants and animals, and oxygen, an abiotic need, from the water. A pond gives food, oxygen, shelter and space. Different organisms can share one habitat and still use it differently: a snake may hunt at night while a rodent is active by day.
- Easy: A fish gets its oxygen from the water.
- Medium: A pond that dries up cannot support fish, because the water is gone.
- Exam-type: A night-active snake and a day-active rodent share one forest because they face different conditions at different times.
In the figure: A pond meets a fish's biotic and abiotic needs together.
A habitat is an organism's home; biotic means living and abiotic means non-living.
Calling soil, water or air biotic because living things use them. They are non-living.
Ask whether it is alive. Memory clue: BIOtic = life; A-biotic = "not alive" (A means not).
Spot the difference
| Term | Meaning | Examples |
|---|---|---|
| Biotic | living | fish, frog, algae |
| Abiotic | non-living | water, soil, sunlight |
| Habitat | place to live | pond, forest, tree bark |
Practice questions
- 1What is a habitat?
- 2Name two biotic and two abiotic components of a pond.
- 3What does abiotic mean?
- 4From where does a fish get its oxygen?
- 5Why are the organisms in a pond and in a forest different?
- 6Is a mushroom biotic or abiotic?
- 7A student lists frog, soil, algae, air, snail and sunlight. How many are biotic?
- 8What happens to the fish when a pond dries up in summer, and why?
Show answers (try them yourself first)
- 1The place where an organism lives and finds what it needs.
- 2Biotic: fish and frog; abiotic: water and soil.
- 3Non-living.
- 4From the water.
- 5Each habitat offers different living conditions.
- 6Biotic, because it is a living thing.
- 7Three: frog, algae and snail.
- 8They die or must leave, because the water that gives oxygen, shelter and space is gone.
Population, community and ecosystem
A school garden has 30 marigold plants, some bees, a few earthworms, soil, water and sunlight. The marigolds, the bees and the garden as a whole each form a different level of living together.
A population is a group of the same kind of organism in a habitat at a given time. A community is all the populations living together in a habitat. An ecosystem is a community together with the abiotic parts, all interacting.
Key idea 1: From small to large — A population is part of a community, and a community is part of an ecosystem. In a 1 m by 1 m patch with 20 grass plants and 5 clover plants there are two populations. The fish, frogs, plants and microbes of a pond together form its community.
- Easy: 25 frogs of one kind in a pond are a population.
- Medium: All the fish, frogs, plants and microbes of a pond are a community.
- Exam-type: The statement "an ecosystem is part of a community" is wrong; the community is part of the ecosystem.
In the figure: A population sits inside a community, and a community sits inside an ecosystem.
Key idea 2: Kinds of ecosystem and their interactions — Aquatic ecosystems are ponds, rivers and lakes; terrestrial ecosystems are forests, grasslands and farms. Farmland is human-made, and ecosystems can overlap. Interactions happen between biotic and abiotic parts (earthworm in moist soil), between two abiotic parts (sunlight evaporating water) and between two biotic parts (a frog eating insects). Living things also change the non-living: roots hold soil in place.
- Easy: A river is aquatic; a forest is terrestrial.
- Medium: Roots holding soil and stopping erosion is a biotic part affecting an abiotic part.
- Exam-type: A river flowing past a forest and a farm shows overlapping aquatic and terrestrial ecosystems.
In the figure: Ecosystems may be aquatic, terrestrial or made by people.
Population, community, ecosystem: this is the order from small to large.
Thinking an ecosystem has only living things. It also includes the abiotic parts.
One kind means population; many kinds means community; living plus non-living means ecosystem. Memory clue: P-C-E = "Please Come Early".
Spot the difference
| Term | Meaning | Example |
|---|---|---|
| Population | one kind, one place | 25 frogs in a pond |
| Community | all populations together | fish, frogs, plants, microbes |
| Ecosystem | community plus abiotic parts | the whole pond with water and sunlight |
Practice questions
- 1Define a population.
- 2Name one aquatic and one terrestrial ecosystem.
- 3Is a farm a natural or a human-made ecosystem?
- 4A patch has 15 neem seedlings and 6 tulsi plants. How many populations are there?
- 5Which is larger, a community or a population?
- 6Give one interaction between two abiotic components.
- 7Why can a habitat not have only one kind of organism?
- 8Say whether each is biotic-abiotic, abiotic-abiotic or biotic-biotic: (a) a frog eats insects, (b) roots hold soil, (c) wind makes waves on a pond.
Show answers (try them yourself first)
- 1A group of the same kind of organism in a habitat at a given time.
- 2Aquatic: a pond or a river; terrestrial: a forest or a grassland.
- 3Human-made.
- 4Two populations.
- 5A community.
- 6Sunlight makes pond water evaporate.
- 7All would need the same food, water and space, so there would be scarcity.
- 8(a) biotic-biotic, (b) biotic-abiotic, (c) abiotic-abiotic.
Producers, consumers and decomposers
In the monsoon Raju sees a mushroom sprouting on a rotting log, ants carrying a dead beetle and a deer munching grass nearby. Everyone is feeding, but in very different ways.
Producers (autotrophs) make their own food by photosynthesis; green plants are producers. Consumers (heterotrophs) depend on other organisms for food. Decomposers (saprotrophs), such as fungi and bacteria, break dead matter into simple substances and return nutrients to the soil.
Key idea 1: Kinds of consumers — Herbivores eat only plants (deer, hare). Carnivores eat only animals (tiger, shikra). Omnivores eat both plants and animals (crow, mouse, fox).
- Easy: A hare eats only plants, so it is a herbivore.
- Medium: A bird that eats seeds and insects is an omnivore.
- Exam-type: Among a tree, a deer, a tiger and a mushroom, the tree is a producer, the deer and tiger are consumers, and the mushroom is a decomposer.
In the figure: Consumers are grouped by what they eat: plants, animals or both.
Key idea 2: Decomposition and recycling — Fungi and bacteria break down dead plants and animals, and small beetles and flies help break down dung. The nutrients go back to the soil, where plants take them up again. In nature nothing is wasted; everything is reused. Without decomposers, dead matter would pile up.
- Easy: A mushroom growing on dead matter is a decomposer.
- Medium: Beetles and flies on elephant dung help break it down and recycle its nutrients.
- Exam-type: If all decomposers vanished, dead matter would pile up and the soil would lose its nutrients, so plants would suffer.
In the figure: Producers make food, consumers eat it and decomposers recycle what is left.
Producers make food, consumers eat, decomposers recycle.
Thinking a mushroom is a producer because it looks like a plant. It cannot make food with sunlight.
Ask whether it makes, eats or recycles. Memory clue: P-C-D = Plants Prepare, Consumers Chew, Decomposers Dissolve.
Spot the difference
| Group | How it gets food | Example |
|---|---|---|
| Producer | makes its own food | grass, tree |
| Consumer | eats other organisms | deer, tiger, crow |
| Decomposer | breaks down dead matter | mushroom, bacteria |
Practice questions
- 1What do producers do?
- 2Name one herbivore and one carnivore.
- 3Give one example of a decomposer.
- 4What is an omnivore? Give an example.
- 5Why is a mushroom not a producer?
- 6What does decomposition give back to the soil?
- 7What would happen in a forest if all decomposers disappeared?
- 8A farmer sees fallen leaves vanish and the soil turn richer. Explain why.
Show answers (try them yourself first)
- 1They make their own food by photosynthesis.
- 2Herbivore: deer; carnivore: tiger.
- 3A mushroom, a fungus or bacteria.
- 4An animal that eats both plants and animals, such as a crow.
- 5It cannot make food using sunlight; it feeds on dead matter.
- 6Nutrients.
- 7Dead matter would pile up and nutrients would not return to the soil, so plants would suffer.
- 8Decomposers such as fungi and bacteria broke the leaves into nutrients that made the soil richer.
Food chains, food webs and trophic levels
A hungry eagle circles over a millet field. The eagle eats mice and the mice eat millet grains. If any one of them is removed, the others feel the effect.
A food chain is a simple sequence showing who eats whom. An arrow points from the food to the eater. The position of an organism in the chain is its trophic level.
Key idea 1: Chains and levels — A chain starts with a producer at the first level. Herbivores come at the second level, small carnivores at the third and large carnivores at the next. In grass, grasshopper, frog, snake, eagle, the frog is at the third level.
- Easy: Grass, hare, leopard is a food chain.
- Medium: In grass, grasshopper, frog, snake, eagle the snake is at the fourth level.
- Exam-type: In a chain with the Sun, grass, grasshopper, frog and snake, the Sun is not counted as a level, so the snake is at the fourth level.
In the figure: Each arrow carries food from one organism to the one that eats it.
Food chains, food webs and trophic levels
In the app you can move this figure with your finger.
Open in the appKey idea 2: Pyramids and food webs — Higher levels have fewer organisms, so the numbers form a pyramid with producers at the base. One organism is often eaten by several kinds, so food chains join into a food web. A change in one population then spreads along the web.
- Easy: The base of the pyramid is made of producers, which are the most numerous.
- Medium: Food chains link up because one organism can be eaten by two or more kinds of organisms.
- Exam-type: With 60 millet plants, 12 mice and 2 eagles, millet is at the base, mice in the middle and eagles at the top.
In the figure: Each higher level has fewer organisms than the one below it.
The arrow points from the food to the eater, and producers are at the first level.
Drawing the arrow from the eater to the food.
Follow the arrow to find who eats. Memory clue: the arrow Arrives at the Eater.
Spot the difference
| Term | Meaning | Example |
|---|---|---|
| Food chain | one line of who eats whom | grass, hare, leopard |
| Food web | many chains joined together | grass, hare, mouse, fox, eagle |
| Trophic level | position in a chain | hare is at the second level |
Practice questions
- 1What does a food chain show?
- 2In which direction does the arrow point?
- 3Which organisms are at the first trophic level?
- 4In grass, grasshopper, frog, snake, at which trophic level is the snake?
- 5Why do food chains link into webs?
- 6A field has 40 millet plants, 9 mice and 1 eagle. Which is at the base of the pyramid?
- 7In grass, grasshopper, frog, snake, what happens to grasshoppers and snakes if frogs vanish?
- 8Why did India ban the export of frog legs?
Show answers (try them yourself first)
- 1Who eats whom in an ecosystem.
- 2From the food (the organism eaten) to the eater.
- 3Producers, that is, green plants.
- 4The fourth trophic level.
- 5Because one organism can be eaten by two or more kinds of organisms.
- 6Millet, because it is the most numerous.
- 7Grasshoppers increase and snakes decrease.
- 8Fewer frogs let insect pests increase, so farmers used more harmful pesticides.
Food chains, food webs and trophic levels
In the app you can move this figure with your finger.
Open in the appRelationships, balance and caring for ecosystems
A honeybee sips nectar from a mango flower, an orchid sits on a branch and a tick clings to a stray dog. These are three pairs with three different kinds of relationship.
In mutualism both organisms benefit; in commensalism one benefits and the other is not affected; in parasitism one benefits and the other is harmed. Organisms also compete for food, water, space and sunlight.
Key idea 1: Relationships and competition — A bee and a flower show mutualism, an orchid on a tree shows commensalism, and a tick on a dog shows parasitism. Competition keeps populations under control, so no single species takes over. The balance of an ecosystem is dynamic, not fixed.
- Easy: A bee and a flower both gain, so it is mutualism.
- Medium: A tick benefits and the dog is harmed, so it is parasitism.
- Exam-type: Competition stops one species from multiplying too much and keeps the ecosystem balanced.
In the figure: Count who gains and who loses to name the relationship.
Key idea 2: Caring for ecosystems — Forests give fresh air, food, timber and medicines, and mangroves of the Sundarbans slow strong winds and waves in storms. Deforestation, pollution, overuse of resources and invasive species threaten ecosystems, so national parks and sanctuaries protect them. Farming too must be sustainable: overusing chemicals and growing one crop again and again harm soil and pollinators, while compost and growing different crops in turn help.
- Easy: Forests give fresh air, food, timber and medicines.
- Medium: Mangroves slow down strong winds and waves, so a village behind them is less hurt in a storm.
- Exam-type: Overusing chemicals lowers soil microbes and harms soil health; compost and rotating crops protect it.
In the figure: A single change in an ecosystem can set off a chain of other changes.
An ecosystem's balance can be broken by natural or human-made changes.
Thinking that commensalism harms the second organism. It is neither helped nor harmed.
Count who gains and who loses. Memory clue: Mutualism = Me and You win; Commensalism = Me wins, You are unaffected; Parasitism = Me wins, You lose.
Spot the difference
| Relationship | First organism | Second organism |
|---|---|---|
| Mutualism | gains | gains |
| Commensalism | gains | not affected |
| Parasitism | gains | harmed |
Practice questions
- 1Name the relationship in which both organisms benefit.
- 2Give an example of parasitism.
- 3Name two benefits that forests give us.
- 4What is commensalism? Give an example.
- 5How does competition help an ecosystem?
- 6How do mangroves help people living on the coast?
- 7Why is growing the same crop again and again on one land harmful?
- 8Students see fewer butterflies in the school garden. Suggest two steps to bring them back.
Show answers (try them yourself first)
- 1Mutualism.
- 2A tick on a dog.
- 3Any two of fresh air, food, timber and medicines.
- 4One organism benefits and the other is not affected, such as an orchid growing on a tree.
- 5It keeps population sizes under control, so no species takes over.
- 6They slow down strong winds and waves during storms.
- 7It reduces biodiversity, harms pollinators and degrades the soil.
- 8Plant flowering plants and avoid using pesticides.