← Back to Chapter 15
❓ Important Questions
These questions cover ecosystem, food chains,
energy flow, decomposition, biomagnification,
ozone layer and environmental protection.
Section A – Very Short Answer
Q1
What is an ecosystem?
An ecosystem is a functional unit consisting of living organisms
and the non-living environment interacting with one another.
Q2
What are biotic components?
They are the living components of an ecosystem.
Q3
What are abiotic components?
They are non-living physical and chemical components such as
air, water, soil, light and temperature.
Q4
What is a trophic level?
A trophic level is a position occupied by an organism in
a food chain.
Q5
What is biomagnification?
It is the increasing concentration of certain persistent
pollutants at higher trophic levels.
Q6
What is the function of the ozone layer?
It absorbs a large fraction of the Sun's harmful ultraviolet radiation.
Section B – Short Answer
Q7
Why are decomposers important in an ecosystem?
They break down dead organic matter and help recycle nutrients
back into the ecosystem.
Q8
Why is energy flow in an ecosystem considered unidirectional?
Energy enters mainly through producers and passes through
successive trophic levels, with much of it eventually
dissipated as heat.
Q9
Why are there usually only a few trophic levels in a food chain?
Only a small fraction of energy is transferred to the next
trophic level, limiting the amount of energy available higher up.
Q10
Why can non-biodegradable waste create long-term environmental problems?
Such materials may persist for long periods and accumulate
or spread through ecosystems.
Q11
Why are food webs generally more stable representations
than simple food chains?
Food webs show multiple feeding pathways, so organisms may
have alternative food sources.
Q12
Why can persistent pesticides undergo biomagnification?
They are not easily degraded and can accumulate in organisms,
with concentrations increasing at higher trophic levels.
Section C – Reasoning Questions
Q13
Why are producers essential for most ecosystems?
They introduce energy into the food system by converting
solar energy into chemical energy stored in food.
Q14
Why does energy decrease at successive trophic levels?
Organisms use energy for metabolism and other life processes,
and much of it is dissipated as heat rather than transferred onward.
Q15
Why are decomposers called nature's recyclers?
They convert complex dead organic matter into simpler substances,
helping return nutrients to the environment.
Q16
Why is excessive non-biodegradable waste difficult to manage?
It persists for long periods and does not readily return to
the natural nutrient cycle through biological decomposition.
Section D – Long Answer
Q17
Explain the components of an ecosystem.
Explain producers, consumers, decomposers and abiotic factors
with suitable examples and their interactions.
Q18
Explain energy flow through a food chain.
Explain producer level, successive consumers, energy loss,
10% transfer approximation and why higher trophic levels
receive less energy.
Q19
Explain biological magnification with an example.
Describe entry of a persistent pollutant into a food chain,
its accumulation in organisms and higher concentration
at successive trophic levels.
Q20
Explain the importance of the ozone layer and ozone depletion.
Explain ultraviolet radiation, protective role of stratospheric
ozone and effects associated with increased UV exposure.
Section E – Application / Competency
Q21
A lake receives agricultural runoff containing a persistent
chemical. Explain how the chemical may reach organisms
higher in the food chain.
The chemical can enter lower trophic-level organisms and,
if persistent, become increasingly concentrated in organisms
at higher trophic levels through biomagnification.
Q22
In a food chain grass → insect → frog → snake, why does the
snake receive much less energy than the grass contains?
Energy is used and dissipated at every trophic transfer,
so only a small fraction, approximately 10% as a teaching
approximation, reaches the next level.
Q23
A community replaces disposable plastic items with reusable
and recyclable alternatives. How can this help the environment?
It can reduce waste generation, decrease persistent waste
entering ecosystems and conserve resources when materials
are reused or recycled effectively.
Q24
Why can removing decomposers from an ecosystem seriously
disturb nutrient cycling?
Dead organic matter would accumulate and nutrients would
not be efficiently returned to forms accessible to producers.
Section F – Diagram-Based Questions
Q25
Draw a food chain with four trophic levels.
Example:
Grass → Grasshopper → Frog → Snake
Q26
Draw an energy pyramid for a four-level food chain.
Show the producer level at the base and progressively
smaller energy availability toward higher trophic levels.
Q27
Draw a food web involving plants, herbivores and carnivores.
Show multiple interconnected feeding relationships rather
than a single straight chain.
Q28
Draw and label the role of decomposers in an ecosystem.
Show dead organic matter being broken down and nutrients
returning to the environment.
⚡ Final Exam Focus
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Ecosystem components
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Food chain and food web
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Trophic levels
-
Energy flow and 10% law
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Decomposers and decomposition
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Biodegradable and non-biodegradable substances
-
Biomagnification
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Ozone layer and ozone depletion