Ecosystems: Structure and Functions (Food Chain, Food Web, Energy Flow) Questions

Question 1

Differentiate between producers, consumers and decomposers (any three points).

Accepted Answer

Producers make food; consumers depend on others for food; decomposers break down dead matter and recycle nutrients. Producers are autotrophs; consumers and decomposers are heterotrophs.

Question 2

Define ecosystem.

Accepted Answer

Ecosystem is a system formed by interaction of living organisms with their physical environment.

Question 3

Who are producers?

Accepted Answer

Producers are green plants/algae that manufacture food by photosynthesis.

Question 4

Who are decomposers?

Accepted Answer

Decomposers are bacteria and fungi that break down dead organic matter.

Question 5

What is a food chain?

Accepted Answer

Food chain is a linear sequence showing transfer of energy from one organism to another.

Question 6

What is a food web?

Accepted Answer

Food web is a network of interconnected food chains in an ecosystem.

Question 7

State the 10% law.

Accepted Answer

10% law states only about 10% of energy is transferred to the next trophic level.

Question 8

Write any three abiotic components of an ecosystem.

Accepted Answer

Air, water, soil, sunlight, temperature and nutrients are abiotic components (any three).

Question 9

Explain grazing food chain with an example.

Accepted Answer

Grazing food chain starts with producers (green plants). Example: grass → deer → tiger.

Question 10

Explain detritus food chain with an example.

Accepted Answer

Detritus food chain starts with dead organic matter. Example: leaf litter → earthworm → bird.

Question 11

Why is food web more stable than a food chain? (any three points)

Accepted Answer

Food web provides alternative food sources, reduces dependence on one organism, and maintains balance if one species declines. Hence it is more stable than a single food chain.

Question 12

Write any three ecosystem services.

Accepted Answer

Oxygen production, soil fertility, water purification, pollination and climate regulation are ecosystem services (any three).

Question 13

Explain ecosystem: structure and functions.

Accepted Answer

An ecosystem is a functional unit of nature where living organisms (biotic components) interact with the physical environment (abiotic components).

Structure of ecosystem:
1) Abiotic components: sunlight, air, water, soil, temperature, nutrients.
2) Biotic components:
   - Producers (autotrophs): plants/algae that make food.
   - Consumers (heterotrophs): herbivores, carnivores and omnivores.
   - Decomposers: bacteria and fungi that break down dead matter.

Functions:
- productivity (primary production by producers)
- decomposition (breakdown of dead organic matter)
- nutrient cycling (recycling of carbon, nitrogen, etc.)
- energy flow through food chains and webs

Thus ecosystem maintains balance and supports life through energy flow and nutrient cycling.

Question 14

Explain food chain and food web with differences and examples.

Accepted Answer

Food chain is a linear sequence of organisms through which energy is transferred.
Example: grass → deer → tiger.

Food web is a network of interconnected food chains.
Example: in a grassland, grass is eaten by insects, rabbits and deer; insects are eaten by birds; rabbits may be eaten by fox; so many chains connect to form a web.

Differences:
- Food chain is single path; food web has many paths.
- Food web is more stable because organisms have alternative food sources.
- Food chain shows simple energy transfer; food web shows realistic ecosystem relationships.

Both represent how energy moves across trophic levels.

Question 15

Explain energy flow and 10% law with trophic levels.

Accepted Answer

Energy flow in an ecosystem is one-way: Sun → producers → consumers → decomposers.

Trophic levels:
- Producers are first trophic level.
- Primary consumers (herbivores) are second.
- Secondary/tertiary consumers are higher levels.

10% law (Lindeman): Only about 10% of energy at one trophic level is transferred to the next level; the rest is lost as heat during respiration and activity.

Therefore:
- higher trophic levels have less available energy
- energy pyramid is always upright
- population size generally decreases at higher trophic levels

This explains why food chains usually have limited trophic levels.

Ecosystems: Structure and Functions (Food Chain, Food Web, Energy Flow)

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