NEET Biology Ecosystem MCQs Set 27

Answer: (d) Characterized by a major vegetation type

Explanation:
1. An ecosystem is a self-sufficient functional unit with a cyclic exchange of materials between organisms and environment.
2. Its only external input is energy (sunlight).
3. It may be characterised by minor as well as major vegetation types, so the last statement is not true.

Teacher's Note:
1. An ecosystem can be as small as a pond.
2. Sunlight is the only input needed.

Answer: (c) Green plants, animals, decomposers and abiotic environment

Explanation:
1. An ecosystem has producers, consumers and decomposers (biotic part) together with the abiotic environment.
2. Omitting any of these makes the list incomplete.

Teacher's Note:
1. Ecosystem equals biotic plus abiotic components.
2. Energy flows through it and nutrients cycle.

Answer: (d) All of these

Explanation:
1. Large dams, reservoirs, lakes, canals, fishery tanks and aquaria are all man-made aquatic ecosystems.

Teacher's Note:
1. Artificial ecosystems are created and managed by humans.
2. Cropland is the largest anthropogenic terrestrial ecosystem.

Answer: (a) Productivity

Explanation:
1. Species composition, diversity, stratification and the abiotic components describe the structure of an ecosystem.
2. Productivity, decomposition, energy flow and nutrient cycling are functional aspects.

Teacher's Note:
1. Structure means the parts, function means the processes.
2. Productivity is a functional aspect.

Answer: (c) Homeostasis

Explanation:
1. Productivity, decomposition, energy flow, nutrient cycling and homeostasis are functional aspects.
2. Species composition, inorganic nutrients and topography describe structure.

Teacher's Note:
1. Homeostasis is the self-regulation of an ecosystem.
2. It works by feedback.

Answer: (b) Biotic potential

Explanation:
1. Carrying capacity, self-regulation and feedback help an ecosystem to stay stable.
2. Biotic potential is only the inherent growth capacity of a population.

Teacher's Note:
1. Homeostasis needs regulating mechanisms.
2. Biotic potential does not regulate the ecosystem.

Answer: (c) Herbivores

Explanation:
1. Herbivores are called key industry animals because they link producers to higher consumers.

Teacher's Note:
1. Producers feed herbivores, and herbivores feed carnivores.
2. They pass on plant energy to the next level.

Answer: (b) Detritus food chain

Explanation:
1. In a tropical rain forest most plant matter falls and is eaten by decomposers.
2. So most energy flows through the detritus food chain.

Teacher's Note:
1. In land ecosystems the detritus chain is usually more important.
2. In oceans the grazing chain dominates.

Answer: (b) Binds the inorganic nutrients into organic matter

Explanation:
1. The grazing food chain starts with green plants that bind inorganic nutrients into organic matter by photosynthesis.
2. It is based on solar energy and supplies energy to the system.

Teacher's Note:
1. Grazing chain starts with producers.
2. Detritus chain starts with dead matter.

Answer: (a) Upright

Explanation:
1. In a cropland, many plants support fewer herbivores, which support fewer carnivores.
2. So the pyramid of numbers is upright.

Teacher's Note:
1. Pyramid of numbers is upright in grassland, pond and crop fields.
2. It is inverted in a single big tree with many insects.

Answer: (b) Increases

Explanation:
1. Higher trophic level organisms are larger and more active.
2. They need more energy for maintenance of the body, so less energy is left for growth.

Teacher's Note:
1. That is why the number of trophic levels is limited.
2. Energy needs rise at higher levels.

Answer: (d) Omnivores – Cockroaches, Crows

Explanation:
1. Cockroaches and crows eat both plants and animals, so they are omnivores.
2. Zooplankton are primary consumers, viruses are not primary colonisers, and a nano-ecosystem is much smaller than a valley or forest.

Teacher's Note:
1. Omnivores feed on more than one trophic level.
2. Match carefully before choosing.

Answer: (a) Forest ecosystem

Explanation:
1. Forests have the highest biomass of the options.
2. Tropical rain forests, coral reefs, estuaries and sugarcane fields are highly productive.

Teacher's Note:
1. Biomass is the dry weight of living matter.
2. Forest has the largest standing crop.

Answer: (b) Lichens

Explanation:
1. Pioneer species on bare rock are lichens.
2. They secrete acids that dissolve rock, which helps weathering and soil formation.

Teacher's Note:
1. Lichens start the xerarch succession.
2. Mosses come after lichens.

Answer: (a) Standing crop

Explanation:
1. The mass of living material present at a trophic level at a particular time is the standing crop.
2. It is measured as fresh or dry weight per unit area.

Teacher's Note:
1. Standing crop is biomass at an instant.
2. Productivity is a rate.

Answer: (d) a(ii), b(i), c(iv), d(iii)

Explanation:
1. An earthworm is a detritivore.
2. Succession begins with pioneer species.
3. Pollination is an ecosystem service.
4. Natality is the birth rate that drives population growth.

Teacher's Note:
1. Match each term to its ecological meaning.
2. Ecosystem services include pollination, clean air and water.

Answer: (b) Rock

Explanation:
1. Phosphorus does not have a gaseous phase.
2. Its natural reservoir is the rock, from which weathering releases it.

Teacher's Note:
1. Phosphorus cycle is a sedimentary cycle.
2. Carbon and nitrogen cycles have a gaseous reservoir.

Answer: (d) Forest

Explanation:
1. In forests a few large trees support many herbivores such as insects, so the pyramid of numbers is not upright there.
2. Lake, pond and grassland have upright pyramids.

Teacher's Note:
1. Pyramid of numbers can be inverted.
2. Biomass and energy pyramids work differently.

Answer: (d) Less than 50%

Explanation:
1. Photosynthetically active radiation (PAR) is only about 50 percent or less of the incident solar radiation.
2. It is the visible range of 400-700 nm.

Teacher's Note:
1. Plants use only PAR for photosynthesis.
2. Less than 50 percent is the NCERT value.

Answer: (b) Net primary productivity

Explanation:
1. Net primary productivity (GPP minus respiration) is the biomass available to herbivores and decomposers.

Teacher's Note:
1. NPP equals GPP minus R.
2. It is the food available to the next trophic level.

Answer: (b) Tropical rain forest

Explanation:
1. Tropical rain forests have the highest net primary productivity among the land ecosystems listed.
2. Warmth, rain and sunlight are plentiful all year.

Teacher's Note:
1. Rain forests produce the most biomass per unit area on land.
2. Temperate forests have a shorter growing season.