🌸Chapter 12
Ecosystem
( 5 Marks)
Basics of Ecosystem
1.
Q: Define ecosystem. Describe its
components with examples.
A: An ecosystem is a functional unit of nature where living organisms
interact with each other and with non-living components to maintain energy flow
and nutrient cycling.
- Biotic components: Producers (plants,
phytoplankton), consumers (herbivores, carnivores, omnivores), decomposers
(bacteria, fungi)
- Abiotic components: Sunlight, water, air, soil,
temperature.
Example: Forest ecosystem, pond ecosystem.
2.
Q: Differentiate between natural and
artificial ecosystems with examples.
A:
- Natural ecosystems: Occur naturally; balanced;
e.g., forests, oceans
- Artificial ecosystems: Human-made; may need
management; e.g., gardens, aquariums
3.
Q: Explain the importance of producers
in ecosystems.
A: Producers synthesize their own food using sunlight (photosynthesis) and
form the base of food chains. They provide energy for herbivores and indirectly
for higher trophic levels. They also contribute oxygen and organic matter to
the ecosystem.
4.
Q: Explain the role of consumers in
ecosystems.
A: Consumers transfer energy from one trophic level to another:
- Primary consumers: Feed on producers (herbivores)
- Secondary consumers: Feed on herbivores
(carnivores)
- Tertiary consumers: Feed on secondary consumers
(top carnivores)
They maintain population balance and food web dynamics.
5.
Q: Explain the role of decomposers in
nutrient cycling and energy flow.
A: Decomposers break down dead organisms into inorganic compounds,
releasing nutrients (N, P, C) back to the soil or water, making them available
for producers. They prevent accumulation of waste and complete nutrient
cycling.
6.
Q: Explain the interrelationship
between biotic and abiotic components with an example.
A: Abiotic factors provide energy and habitat (sunlight, water, soil).
Producers use these abiotic resources to produce food, herbivores feed on
producers, carnivores feed on herbivores, and decomposers recycle nutrients
back to soil.
Example: Pond ecosystem – water, sunlight (abiotic) → phytoplankton
(producers) → fish (consumers) → bacteria (decomposers).
7.
Q: Explain the difference between
habitat and niche with examples.
A:
- Habitat: Place where an organism lives
(pond, forest)
- Niche: Role of the organism in
ecosystem (feeding, interactions)
Example: Frog lives in pond (habitat), eats insects (niche).
8.
Q: Explain ecological balance. Give
examples.
A: Ecological balance is the stable state of an ecosystem where species
population, resources, and energy flow are in equilibrium.
Example: Predator-prey balance in a forest (lions and deer),
decomposition of dead matter.
9.
Q: Explain the concept of energy flow
in ecosystems.
A: Energy enters ecosystems from sunlight, captured by producers,
transferred to consumers, and finally decomposers. Energy is lost as heat at
each trophic level. It is unidirectional.
10.
Q: Explain the different types of
ecological pyramids with examples.
A:
- Pyramid of numbers: Shows number of organisms;
e.g., tree ecosystem (inverted)
- Pyramid of biomass: Shows total biomass; e.g.,
pond ecosystem (inverted)
- Pyramid of energy: Shows energy at each trophic
level; always upright
Food Chain, Food Web, and Trophic
Levels
11.
Q: Explain a food chain with an
example.
A: Linear sequence of organisms showing energy transfer.
Example: Grass → Grasshopper → Frog → Snake → Hawk.
12.
Q: Explain a food web with an example.
A: Interconnected food chains showing feeding relationships.
Example: Grass → Grasshopper → Frog → Snake → Hawk; Grass → Rabbit → Fox →
Hawk.
13.
Q: Explain the 10% law of energy
transfer with an example.
A: Only 10% of energy passes to the next trophic level; 90% is lost as
heat.
Example: Grass (1000 kcal) → Grasshopper (100 kcal) → Frog (10 kcal) → Snake (1
kcal).
14.
Q: Explain inverted pyramid of numbers
and biomass with examples.
A:
- Inverted pyramid of numbers: Few large producers support
many herbivores (Tree → insects)
- Inverted pyramid of biomass: In aquatic ecosystems, low
biomass of phytoplankton supports higher biomass of zooplankton
15.
Q: Explain why the pyramid of energy
is always upright.
A: Because energy decreases at each trophic level due to metabolic loss
and heat dissipation; it cannot increase upward.
16.
Q: Explain trophic levels with
examples.
A: Levels in food chain showing feeding position:
- Producer: Grass
- Primary consumer: Grasshopper
- Secondary consumer: Frog
- Tertiary consumer: Hawk
- Decomposers: Fungi
17.
Q: Explain the significance of
decomposers in energy flow.
A: Decomposers recycle nutrients back into the ecosystem, help in energy
transfer, and prevent accumulation of dead organic matter.
18.
Q: Explain energy flow in grazing and
detritus food chains.
A:
- Grazing chain: Producers → herbivores →
carnivores → decomposers
- Detritus chain: Dead organic matter →
decomposers → carnivores
Both maintain ecosystem stability.
19.
Q: Explain why energy flow in
ecosystems is unidirectional.
A: Energy comes from sunlight, moves through trophic levels, and
dissipates as heat; it is not recycled.
20.
Q: Explain primary, secondary, and
tertiary consumers with examples.
A:
- Primary: Herbivores (grasshopper,
rabbit)
- Secondary: Carnivores feeding on
herbivores (frog, snake)
- Tertiary: Top carnivores (hawk, tiger)
Ecological Succession
21.
Q: Define ecological succession.
Explain primary and secondary succession with examples.
A: Succession is the gradual, predictable change in species composition
over time.
- Primary: Bare rock → lichens → moss →
grass → shrubs → trees; e.g., Himalayas
- Secondary: Soil present → grass → shrubs
→ trees; e.g., abandoned farmland
22.
Q: Explain the stages of primary
succession in detail.
A: Pioneer stage (lichens) → mosses → grasses → shrubs → trees → climax
community. Soil formation and nutrient accumulation occur progressively.
23.
Q: Explain secondary succession in
abandoned farmland.
A: Grass colonizes first → shrubs → small trees → large trees → climax
forest. Faster than primary succession as soil is already present.
24.
Q: Define climax community and explain
its ecological significance.
A: Stable, mature community at the end of succession. Maintains
biodiversity, nutrient cycling, and ecosystem stability.
25.
Q: Explain the role of pioneer species
in succession.
A: Pioneer species colonize harsh environments, fix nutrients, form
soil, and facilitate establishment of subsequent species.
26.
Q: Define sere and seral community
with examples.
A:
- Sere: Stage in succession; e.g.,
grass stage, shrub stage
- Seral community: Transitional community between
pioneer and climax; e.g., shrub community
27.
Q: Explain the factors controlling
succession.
A:
- Abiotic: Climate, soil, temperature,
water, light
- Biotic: Competition, predation,
mutualism
- Human impact: Deforestation, agriculture
28.
Q: Explain the importance of
succession in ecosystem stability.
A: Restores degraded land, increases productivity, biodiversity, and
nutrient cycling.
29.
Q: Explain the difference between
primary and secondary succession.
A:
- Primary: No soil initially, pioneer
species create soil
- Secondary: Soil already present, regrowth
after disturbance
30.
Q: Explain how succession affects
species diversity.
A: Diversity increases with succession as more species colonize the
habitat until climax is reached, after which it stabilizes.
Biogeochemical Cycles
31.
Q: Explain the nitrogen cycle in
detail.
A: Key processes:
- Nitrogen fixation: N₂ → NH₃ (Rhizobium)
- Nitrification: NH₃ → NO₂⁻ → NO₃⁻
- Assimilation: Plants absorb nitrates
- Ammonification: Organic N → NH₃
- Denitrification: NO₃⁻ → N₂
Maintains nitrogen availability in soil.
32.
Q: Explain the phosphorus cycle.
A: Phosphorus moves from rocks → soil → plants → animals → decomposers →
soil. No gaseous phase. Essential for ATP, DNA, RNA.
33.
Q: Explain the carbon cycle.
A: Carbon moves from CO₂ in atmosphere → plants → animals → decomposers
→ atmosphere (respiration, combustion). Maintains carbon balance.
34.
Q: Explain the hydrological cycle with
diagram.
A: Water moves via evaporation → condensation → precipitation → runoff →
groundwater → rivers → oceans. Maintains water availability.
35.
Q: Explain the role of decomposers in
nutrient cycling.
A: Decomposers break organic matter into inorganic nutrients, ensuring
continuous nutrient supply for producers.
36.
Q: Explain human impact on carbon and
nitrogen cycles.
A: Fossil fuel burning → ↑CO₂ → global warming; excess fertilizers →
nitrogen leaching → water pollution, eutrophication.
37.
Q: Explain eutrophication and its
ecological effects.
A: Excess nutrients in water → algal bloom → oxygen depletion → death of
aquatic animals.
38.
Q: Explain biological magnification.
A: Persistent toxins (DDT, Hg) accumulate at higher trophic levels,
harming top predators.
39.
Q: Explain acid rain and its effects
on ecosystems.
A: SO₂ and NO₂ react with rain → H₂SO₄, HNO₃ → damages plants, soil,
aquatic life, and biodiversity.
40.
Q: Explain global warming and its
ecological consequences.
A: Greenhouse gases trap heat → rising temperatures → glacier melting,
sea level rise, altered ecosystems, biodiversity loss.
Ecosystem Types and Conservation
41.
Q: Describe forest ecosystems.
A: Multi-layered vegetation, high biodiversity, high productivity,
complex food webs, and nutrient-rich soil.
42.
Q: Describe grassland ecosystems.
A: Dominated by grasses, moderate rainfall, supports herbivores (bison,
deer) and carnivores (lion, cheetah).
43.
Q: Describe desert ecosystems.
A: Arid, low vegetation, xerophytes, extreme temperature fluctuations,
low productivity.
44.
Q: Describe aquatic ecosystems.
A: Freshwater (ponds, lakes) and marine (oceans, estuaries). Producers
are phytoplankton; energy flows through grazing and detritus chains.
45.
Q: Explain biodiversity hotspots with
examples.
A: Regions with high species richness and endemism; important for
conservation. Examples: Himalayas, Western Ghats, Indo-Burma.
46.
Q: Explain the role of national parks,
sanctuaries, and biosphere reserves.
A: Protect species, maintain ecological balance, allow sustainable human
use in buffer zones, and conserve biodiversity.
47.
Q: Explain EDGE species.
A: Evolutionarily Distinct and Globally Endangered species important for
ecosystem diversity; e.g., Pangolin, Asiatic lion.
48.
Q: Explain bioremediation with
examples.
A: Use of microorganisms to clean pollutants. Examples: Oil spills →
bacteria degrade oil; pesticides → fungi degrade chemicals.
49.
Q: Explain CITES and its role in
conservation.
A: Convention on International Trade in Endangered Species regulates
trade of threatened species to prevent extinction.
50.
Q: Explain REDD program.
A: Reducing Emissions from Deforestation and Forest Degradation promotes
forest conservation, reduces CO₂ emissions, and encourages sustainable forest
management.
