NEET Biology Ecosystem MCQs Set 24

Answer: (b) Ocean

Explanation:
1. The ocean is the largest and the most stable ecosystem, as its conditions change very little.
2. Deserts and mountains vary greatly.

Teacher's Note:
1. Large size gives more buffering.

Answer: (b) Landscape

Explanation:
1. An ecosystem is a structural and functional unit of a landscape, with its biotic and abiotic parts.
2. It regulates itself and sustains itself.

Teacher's Note:
1. A community is only the biotic part.

Answer: (d) a, b, c and d

Explanation:
1. The habitat of an organism includes its physico-chemical environment and all the biotic factors, such as other species, predators, parasites and competitors.

Teacher's Note:
1. All four statements are correct.

Answer: (a) Optimum conditions

Explanation:
1. Biotic potential is the maximum reproductive capacity of a population under optimum conditions.

Teacher's Note:
1. It is not reached in nature, as the environment resists growth.

Answer: (d) Micro-organisms

Explanation:
1. Water, minerals and litter are non-living (abiotic) components.
2. Micro-organisms are living, so they are biotic components.

Teacher's Note:
1. Decomposers are biotic.

Answer: (b) Temperature

Explanation:
1. Temperature affects enzyme activity, metabolism and the distribution of organisms.
2. It is therefore considered the most ecologically relevant abiotic factor.

Teacher's Note:
1. Water, light and soil follow.

Answer: (c) Reflected by a surface

Explanation:
1. Albedo is the fraction of incident light reflected by a surface.
2. Snow has a high albedo and dark soil has a low one.

Teacher's Note:
1. It affects the energy balance of an area.

Answer: (b) The functions of an ecosystem

Explanation:
1. These four processes are the functional aspects of an ecosystem.
2. The structure includes species composition and stratification.

Teacher's Note:
1. Both biotic and abiotic components take part in the functions.

Answer: (a) c and d

Explanation:
1. An ecotone is a transition zone between two different communities, such as a forest and a grassland.
2. It often shows greater species diversity due to the edge effect.

Teacher's Note:
1. It is not between species or populations.

Answer: (d) Man

Explanation:
1. An omnivore eats both plant and animal food, as man does.

Teacher's Note:
1. The frog and the lion are carnivores and the deer is a herbivore.

Answer: (d) All of the above

Explanation:
1. Edge species live in the ecotone and are more diverse and denser there.
2. This is known as the edge effect.

Teacher's Note:
1. All the options describe them.

Answer: (b) Stratification

Explanation:
1. Stratification is the vertical distribution of species and is a structural feature.

Teacher's Note:
1. Productivity, energy flow and decomposition are functional units.

Answer: (b) Rain forest

Explanation:
1. Tropical rain forests have the highest gross primary productivity among land ecosystems because of year-round warmth and rain.

Teacher's Note:
1. Grasslands are less productive.

Answer: (b) A-iv, B-v, C-i, D-ii, E-iii

Explanation:
1. GPP is the total photosynthetic production, and NPP is the part available to primary consumers.
2. A lake is self-sustaining and an aquarium is human-regulated.

Teacher's Note:
1. Decomposition is an oxygen-requiring process.

Answer: (b) Standing crop

Explanation:
1. Standing crop is the living biomass at a trophic level at a given time.
2. It is expressed as mass per unit area.

Teacher's Note:
1. Standing state is the amount of nutrients in the soil.

Answer: (c) Producers and decomposers

Explanation:
1. Producers supply the energy and decomposers recycle the nutrients.
2. Without them the ecosystem cannot sustain itself.

Teacher's Note:
1. Consumers are not strictly essential.

Answer: (a) Energy

Explanation:
1. Energy flows in one direction from the sun to producers and then to consumers, and is lost as heat.

Teacher's Note:
1. Nutrients such as carbon, nitrogen and potassium are cycled.

Answer: (d) Charles Elton

Explanation:
1. Charles Elton introduced ecological pyramids, so they are called Eltonian pyramids.

Teacher's Note:
1. Tansley proposed the term ecosystem and Odum is known for ecosystem ecology.

Answer: (b) O2 / A0

Explanation:
1. The O horizon has two layers: O1 with undecomposed litter and O2 with partly decomposed organic matter (duff).

Teacher's Note:
1. The B horizons are mineral layers below.

Answer: (d) Oceans

Explanation:
1. About 71% of the carbon is found dissolved in the oceans.
2. The atmosphere holds only about 1% of the carbon.

Teacher's Note:
1. Oceans are the largest carbon reservoir.

Answer: (a) Nutrient immobilisation

Explanation:
1. Immobilisation is the temporary locking of nutrients in microbial biomass.

Teacher's Note:
1. Mineralisation is the release of inorganic nutrients and leaching is washing them down in water.

Answer: (b) 6% each

Explanation:
1. According to the study of Costanza et al., soil formation is about 50% of the total cost, while climate regulation and wildlife habitat are about 6% each.

Teacher's Note:
1. Recreation is about 3%.

Answer: (b) Fragmentation - carried out by organisms such as earthworms

Explanation:
1. Detritivores such as earthworms break detritus into smaller pieces by fragmentation.

Teacher's Note:
1. Leaching moves nutrients down, humus decomposes very slowly, and catabolism is the enzymatic breakdown by microbes.