NEET Biology Organisms and Populations MCQs Set 04

Answer: (c) Set of conditions and resources it uses

Explanation:
1. Habitat is the place where a population lives, but the niche is the functional role of the species.
2. The niche is the set of physical conditions and resources that the species uses, so only option (c) is right.

Teacher's Note:
1. Do not confuse habitat with niche.
2. Habitat is the address of a species, while niche is its profession.

Answer: (d) A-III, B-II, C-IV, D-I

Explanation:
1. A population is a group of similar individuals of one species (III).
2. A community is an assemblage of different species in an area (II) and an ecosystem is the interaction of organisms with their physical environment (IV).
3. The ecosphere (biosphere) is the part of the earth with all ecosystems (I). So A-III, B-II, C-IV, D-I.

Teacher's Note:
1. Move up the levels of organisation: individual, population, community, ecosystem, biome, biosphere.
2. Each level adds a new kind of interaction.

Answer: (a) Physiologically dry soil

Explanation:
1. A water logged soil is full of water, yet roots cannot absorb it easily because of lack of oxygen and the poor availability of water to the plant.
2. Hence it is called physiologically dry soil.

Teacher's Note:
1. Physiologically dry soil has water but the plant cannot use it.
2. Saline soil and water logged soil are common examples.

Answer: (a) Ecotone

Explanation:
1. A transition zone between two adjacent ecosystems is an ecotone.
2. The increase in species number at the junction is the edge effect, but the area itself is the ecotone.

Teacher's Note:
1. The ecotone is the area and the edge effect is the property of that area.
2. Ecotypes are genetically distinct local populations of one species.

Answer: (c) Prairie - epiphytes

Explanation:
1. Tundra has permafrost, savanna has scattered acacia trees and coniferous forests have evergreen conifers.
2. Prairie is temperate grassland with no trees, so epiphytes are not characteristic of it.

Teacher's Note:
1. Epiphytes belong to wet tropical rain forests.
2. Prairies are dominated by grasses.

Answer: (b) Diapause

Explanation:
1. Many zooplankton species in lakes and ponds enter a stage of suspended development when conditions become unfavourable.
2. This stage is called diapause.

Teacher's Note:
1. Hibernation is winter sleep and aestivation is summer sleep in animals.
2. Diapause is the suspended development stage in zooplankton and insects.

Answer: (d) None of these

Explanation:
1. A stable population has a bell shaped pyramid in which the pre-reproductive and reproductive groups are nearly equal.
2. Diagram C is a triangle with a broad base (expanding population), diagram B is inverted with a very narrow base, and diagram A is spindle shaped with a small pre-reproductive base (declining).
3. None of them shows a bell shaped stable pyramid.

Teacher's Note:
1. Expanding means a triangular pyramid, stable means a bell shape and declining means an urn shape.
2. Look at the width of the base compared with the middle bars.

Answer: (a) Commensalism

Explanation:
1. The egret feeds on insects disturbed by grazing cattle and gets benefit.
2. The cattle are neither harmed nor benefited, so the interaction is commensalism (+, 0).

Teacher's Note:
1. Commensalism benefits one species and leaves the other unaffected.
2. Orchids on a mango tree are another example.

Answer: (d) c and d only

Explanation:
1. In mutualism both species benefit, and in commensalism only one benefits, so statements (a) and (b) are false.
2. In predation one organism kills and feeds on another, and in symbiosis (living together) both partners benefit, so (c) and (d) are true.

Teacher's Note:
1. Mutualism is (+, +) and commensalism is (+, 0).
2. Predation is (+, -).

Answer: (d) more than one option is correct

Explanation:
1. Predators transfer energy from one trophic level to the next.
2. They also keep prey populations under control and, by reducing the competition among prey, help maintain species diversity.
3. So options (a), (b) and (c) are all correct.

Teacher's Note:
1. Predators act as natural pest controllers.
2. Removal of a key predator can let one prey species eliminate others.

Answer: (c) +, +, Commensalism

Explanation:
1. Mutualism is (+, +), parasitism and predation are (+, -).
2. Commensalism is (+, 0), not (+, +), so option (c) is the incorrect match.

Teacher's Note:
1. Learn the signs for every interaction: mutualism (+,+), competition (-,-), commensalism (+,0), amensalism (-,0).
2. Predation and parasitism are both (+,-).