🌸Chapter 12
Ecosystem
(3Marks)
Basics of Ecosystem
1.
Q: Define ecosystem and explain its
components.
A: An ecosystem is a functional unit of nature where living organisms
interact with each other and with non-living components. Components:
- Biotic: Producers, consumers,
decomposers.
- Abiotic: Sunlight, water, temperature,
soil, air.
2.
Q: Give two examples each of natural
and artificial ecosystems.
A:
- Natural: Forest, pond.
- Artificial: Garden, aquarium.
3.
Q: Distinguish between biotic and
abiotic components with examples.
A:
- Biotic: Living organisms like
plants, animals, microbes.
- Abiotic: Non-living factors
like soil, water, temperature, light.
4.
Q: What are producers? Give two
examples.
A: Organisms that synthesize their own food via photosynthesis.
Examples: Grass, Phytoplankton.
5.
Q: What are consumers? Classify them
with examples.
A: Consumers are organisms that depend on other organisms for food.
- Primary consumers: Herbivores (grasshopper, deer)
- Secondary consumers: Carnivores (frog, snake)
- Tertiary consumers: Top carnivores (hawk, tiger)
6.
Q: What are decomposers? Name two
examples.
A: Decomposers break down dead organic matter and recycle nutrients.
Examples: Fungi, Bacteria.
7.
Q: Differentiate between herbivores,
carnivores, and omnivores.
A:
- Herbivores: Eat plants (cow,
deer)
- Carnivores: Eat animals (lion,
snake)
- Omnivores: Eat both plants and
animals (humans, bears)
8.
Q: Explain the role of decomposers in
the ecosystem.
A: They recycle nutrients, break down dead matter, maintain soil
fertility, and help sustain energy flow.
9.
Q: Define abiotic factors. How do they
influence ecosystems?
A: Non-living physical and chemical factors like temperature, water,
light, and soil. They determine species composition, productivity, and energy
flow in an ecosystem.
10.
Q: Give an example of a biotic
interaction in an ecosystem.
A: Predator-prey relationship: Lion (predator) and deer (prey).
Food Chain, Food Web, and Trophic
Levels
11.
Q: What is a food chain? Give an
example.
A: A linear sequence of organisms where energy is transferred from one
organism to another.
Example: Grass → Grasshopper → Frog → Snake → Hawk.
12.
Q: Define food web. Give an example.
A: A network of interconnected food chains showing complex feeding
relationships.
Example: Grass → Grasshopper → Frog → Snake / Hawk; Grass → Rabbit → Fox →
Hawk.
13.
Q: What is a trophic level? Name the
different levels.
A: A trophic level is the position an organism occupies in a food chain.
Levels:
- Producer (1st)
- Primary consumer (2nd)
- Secondary consumer (3rd)
- Tertiary consumer (4th)
- Decomposers
14.
Q: Explain the 10% law of energy
transfer in ecosystems.
A: Only 10% of energy is transferred from one trophic level to the next;
90% is lost as heat during metabolic activities.
15.
Q: Differentiate between a food chain
and a food web.
A:
- Food chain: Linear transfer of energy.
- Food web: Network of interconnected food
chains showing multiple feeding relationships.
16.
Q: Give an example of an inverted
pyramid of numbers and explain why it occurs.
A: Tree ecosystem: Few large trees (producers) support many insects
(primary consumers), making the pyramid inverted.
17.
Q: Explain why the pyramid of energy
is always upright.
A: Energy decreases at each trophic level due to metabolic loss; hence
the pyramid is always upright.
18.
Q: Name the primary and secondary
consumers in the following chain: Grass → Grasshopper → Frog → Snake → Hawk.
A:
- Primary consumer: Grasshopper
- Secondary consumer: Frog
19.
Q: What are primary consumers? Give
two examples.
A: Herbivores that feed on producers. Examples: Grasshopper, Cow.
20.
Q: What is the role of omnivores in an
ecosystem?
A: Omnivores maintain energy flow by feeding on both plants and animals,
controlling populations at multiple trophic levels.
Productivity and Energy Flow
21.
Q: Define Gross Primary Productivity
(GPP) and Net Primary Productivity (NPP).
A:
- GPP: Total energy captured by
producers through photosynthesis.
- NPP: Energy available to
consumers after respiration; NPP = GPP – Respiration.
22.
Q: Which ecosystem has maximum
productivity? Which has minimum?
A: Maximum: Tropical rainforest
Minimum: Desert
23.
Q: What is secondary productivity?
Give an example.
A: Rate of biomass production by consumers. Example: Biomass gained by a
deer feeding on grass.
24.
Q: Name two factors affecting primary
productivity.
A: Light intensity and availability of nutrients (nitrogen, phosphorus).
25.
Q: Why is energy flow in an ecosystem
unidirectional?
A: Energy flows from sun → producers → consumers → decomposers and is
lost as heat; it is not recycled.
26.
Q: Explain why NPP is important for
ecosystems.
A: NPP represents energy available for consumers and maintains food
chain stability.
27.
Q: Differentiate between GPP and NPP
with an example.
A: GPP = Total photosynthetic output; NPP = Energy left after
respiration.
Example: GPP = 1400 kcal/m²/year, Respiration = 400 kcal/m²/year, NPP = 1000
kcal/m²/year.
28.
Q: Give an example of an inverted
pyramid of biomass.
A: Pond ecosystem: Phytoplankton (producers) have low biomass, but
support large zooplankton populations (primary consumers).
29.
Q: What is the fate of 90% energy lost
at each trophic level?
A: Lost as heat due to metabolism, movement, and respiration.
30.
Q: Why do deserts have very low
productivity?
A: Low rainfall, low vegetation, and extreme temperatures limit
photosynthesis.
Ecological Succession
31.
Q: Define ecological succession. Name
its types.
A: Gradual, predictable change in species composition of a community
over time.
Types: Primary (bare rock → climax), Secondary (disturbed soil → climax).
32.
Q: Give an example of primary and
secondary succession.
A: Primary: Lichen colonizing bare rock
Secondary: Abandoned farmland → grass → shrubs → trees
33.
Q: Name pioneer species in primary
succession.
A: Lichens and mosses.
34.
Q: What is a climax community?
A: A stable, mature community at the final stage of succession.
35.
Q: Define sere and seral community.
A:
- Sere: Stage in succession
- Seral community: Transitional community between
pioneer and climax stages
36.
Q: Give the correct sequence in
primary succession.
A: Lichen → Moss → Grass → Shrubs → Trees
37.
Q: What factor controls the direction
of succession?
A: Abiotic factors like climate, soil, water, and light.
38.
Q: What is the difference between
primary and secondary succession?
A: Primary: No soil initially, colonization of bare rock
Secondary: Soil present, regrowth after disturbance
39.
Q: Give an example of secondary
succession in a grassland.
A: Abandoned farmland → grass → shrubs → trees.
40.
Q: What is the role of pioneer species
in succession?
A: They colonize harsh environments, help in soil formation, and
facilitate establishment of other species.
Biogeochemical Cycles
41.
Q: Name the key processes in the
nitrogen cycle.
A: Nitrogen fixation, ammonification, nitrification, denitrification.
42.
Q: Which bacteria fix nitrogen in
legumes?
A: Rhizobium.
43.
Q: Why is the phosphorus cycle unique?
A: It does not involve the atmosphere; phosphorus moves through rocks,
soil, plants, and animals.
44.
Q: What is ammonification?
A: Conversion of organic nitrogen from dead organisms into ammonia by
decomposers.
45.
Q: What is denitrification?
A: Conversion of nitrates (NO₃⁻) into nitrogen gas (N₂) by denitrifying
bacteria.
46.
Q: What is the largest carbon
reservoir?
A: Oceans.
47.
Q: Give an example of human activity
affecting the carbon cycle.
A: Deforestation and burning fossil fuels increase atmospheric CO₂.
48.
Q: Define hydrological cycle.
A: Continuous circulation of water via evaporation, condensation,
precipitation, and runoff.
49.
Q: What is the role of decomposers in
nutrient cycles?
A: Recycling nutrients like nitrogen, carbon, and phosphorus back into
the ecosystem.
50.
Q: Explain why nutrient cycles are
important.
A: They maintain ecosystem stability and support the growth of
producers, ensuring energy flow and ecological balance.
