NEET Biology Ecosystem MCQs Set 22

Answer: (a) mutualism/symbiosis

Explanation:
1. Mutualism (symbiosis) is a relationship in which both partners benefit and depend on each other for survival, as in lichens.

Teacher's Note:
1. Commensalism helps one partner and leaves the other unaffected.
2. Both partners benefit in mutualism.

Answer: (a) symbiosis

Explanation:
1. A lichen is a mutualistic association: the alga makes food by photosynthesis and the fungus supplies water, minerals and protection.

Teacher's Note:
1. Lichens are also pollution indicators.
2. Alga and fungus live as symbionts.

Answer: (b) always upright

Explanation:
1. In a grassland many producers (grasses) support fewer herbivores and still fewer carnivores, so the pyramid of numbers is upright.

Teacher's Note:
1. Tree ecosystems can show a spindle shape.
2. Grassland numbers pyramid is upright.

Answer: (c) Phytoplankton  Zooplankton  Fish

Explanation:
1. Phytoplankton are eaten by zooplankton and zooplankton by fish, so this is the only chain in correct order of feeding.

Teacher's Note:
1. Every chain must start with a producer.
2. Producer to herbivore to carnivore.

Answer: (b) detritus food chain

Explanation:
1. In a detritus food chain, decomposers and detritivores act on dead organic matter produced by producers.

Teacher's Note:
1. It is the major energy pathway in terrestrial ecosystems.
2. Dead matter starts the detritus chain.

Answer: (d) species

Explanation:
1. All individuals of the same kind that can interbreed make up a species.

Teacher's Note:
1. A genus is a group of related species.
2. Same kind means one species.

Answer: (c) individuals in a trophic level

Explanation:
1. A pyramid of numbers shows the number of individuals present at each trophic level.

Teacher's Note:
1. Pyramid of biomass shows dry weight instead.
2. It counts individuals per trophic level.

Answer: (a) Ecology

Explanation:
1. Ecology is the study of interactions between organisms and their environment.

Teacher's Note:
1. Ethology is the study of animal behaviour.
2. Ecology studies organism and environment.

Answer: (c) upright

Explanation:
1. In a pond, producers (phytoplankton) are very numerous and are eaten by fewer zooplankton and fish, so the pyramid of numbers is upright.

Teacher's Note:
1. Pyramid of biomass in a pond is inverted.
2. Pond numbers pyramid is upright.

Answer: (c) green food

Explanation:
1. Green plants are the producers that provide food and so are the basic need of every animal in a community.

Teacher's Note:
1. Without producers, no energy enters the community.
2. Producers feed the community.

Answer: (c) energy

Explanation:
1. Energy decreases at every trophic level as heat is lost, so the pyramid of energy is always upright.

Teacher's Note:
1. Number and biomass pyramids may be inverted.
2. Energy pyramid is always upright.

Answer: (a) producers

Explanation:
1. Producers form the base of the food chain and are the most numerous organisms in a chain.

Teacher's Note:
1. Numbers decrease at higher levels.
2. Producers are most numerous.

Answer: (a) zooplankton

Explanation:
1. Phytoplankton are first, being producers, and zooplankton feeding on them are the second most important trophic level of a lake.

Teacher's Note:
1. Benthos live on the bottom, neuston at the surface.
2. Zooplankton are primary consumers.

Answer: (d) Ocean

Explanation:
1. The ocean is the largest and most stable ecosystem because its conditions change little and it is very large.

Teacher's Note:
1. Deserts are fragile.
2. Oceans are most stable.

Answer: (d) newly-exposed habitat with no record of earlier vegetation

Explanation:
1. Primary succession starts on a place that never had vegetation, such as bare rock or a newly exposed habitat.

Teacher's Note:
1. Secondary succession starts where soil is already present.
2. Primary succession begins on bare area.

Answer: (b) fungi

Explanation:
1. Mycorrhiza is a mutualistic association between fungal hyphae and plant roots; the fungus helps absorb water and phosphorus.

Teacher's Note:
1. The plant gives sugars to the fungus.
2. Mycorrhiza is root and fungus.

Answer: (d) Anabaena

Explanation:
1. Anabaena is a cyanobacterium with heterocysts that fixes atmospheric nitrogen. The other three are fungi.

Teacher's Note:
1. Nostoc is another nitrogen-fixing cyanobacterium.
2. Anabaena fixes nitrogen.

Answer: (d) herbivores

Explanation:
1. Primary consumers feed directly on producers, so they are herbivores.

Teacher's Note:
1. Secondary consumers are carnivores.
2. Primary consumers are herbivores.

Answer: (b) Phosphorus and sulphur

Explanation:
1. Phosphorus and sulphur have their reservoir in the earth's crust (rocks), so they follow the sedimentary cycle.

Teacher's Note:
1. Carbon and nitrogen are gaseous cycles.
2. Phosphorus and sulphur are sedimentary.

Answer: (b) 10%

Explanation:
1. By the 10 percent law only about 10 percent of energy passes from one trophic level to the next.

Teacher's Note:
1. The rest is lost mainly as respiratory heat.
2. About 10 percent is transferred.

Answer: (a) climate

Explanation:
1. The climax community remains in equilibrium with the climate of the region, so climate decides its nature.

Teacher's Note:
1. Climate controls the final stage of succession.
2. Climate decides the climax.

Answer: (a) function at its place of occurrence

Explanation:
1. Niche is the functional role of a species in its habitat, including what it eats and its interactions.

Teacher's Note:
1. Habitat is only the place.
2. Niche means function.

Answer: (d) contribute to ecosystem properties

Explanation:
1. Keystone species affect community structure and ecosystem properties far more than their numbers suggest.

Teacher's Note:
1. Removing them can collapse the community.
2. Keystone species have a large effect.

Answer: (b) Azotobacter

Explanation:
1. Azotobacter is a free-living, aerobic, non-photosynthetic nitrogen fixer. Rhizobium is symbiotic and Nostoc is photosynthetic.

Teacher's Note:
1. Azospirillum is also free living but associative.
2. Azotobacter is the aerobic free-living fixer.

Answer: (b) endemic

Explanation:
1. Species confined to one region are endemic.

Teacher's Note:
1. Sympatric species share the same area.
2. Endemic means restricted to an area.