Organisms and Population Chapter-Wise Test 12

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following statements about the nitrogen cycle is correct?

Nitrogen fixation converts atmospheric nitrogen into a usable form.
Denitrification increases the availability of nitrogen to plants.
Nitrification directly converts nitrogen gas into ammonia.
Plants absorb nitrogen directly from the atmosphere.
1

Nitrogen fixation by bacteria converts atmospheric nitrogen (N₂) into ammonia (NH₃), making it available for plants.

Which factor contributes to a decrease in population size?

High natality
High immigration
Increased emigration
Stable birth rate
3

Emigration, or individuals leaving a population, leads to a decrease in population size.

Which term describes an organism’s functional role in an ecosystem?

Habitat
Niche
Community
Biome
2

A niche refers to an organism’s functional role, including its interactions with biotic and abiotic factors.

Which of the following is a characteristic of an expanding population?

Broad reproductive age group
Narrow base in age pyramid
More post-reproductive individuals
Declining birth rate
1

An expanding population has a broad reproductive age group, leading to increased birth rates.

Which of the following is an incorrect statement about carrying capacity?

Carrying capacity is the maximum population an environment can support.
It remains constant regardless of environmental conditions.
It is influenced by resource availability and competition.
Populations may temporarily exceed carrying capacity before declining.
2

Carrying capacity is not fixed; it fluctuates based on environmental factors such as food supply and habitat conditions.

Which type of age pyramid indicates a declining population?

Triangular age pyramid
Bell-shaped age pyramid
Inverted age pyramid
Pyramid with a broad base
3

An inverted age pyramid indicates a declining population, with a higher number of post-reproductive individuals and fewer young individuals.

Which of the following statements about the carbon cycle is incorrect?

Photosynthesis removes carbon dioxide from the atmosphere.
Respiration releases carbon dioxide back into the atmosphere.
The burning of fossil fuels has no effect on atmospheric carbon dioxide levels.
Oceans act as carbon sinks by absorbing atmospheric CO₂.
3

Burning fossil fuels increases atmospheric CO₂ levels, contributing to global climate change.

Which of the following is a correct statement about secondary succession?

It begins in areas where no life previously existed.
It is slower than primary succession.
It occurs in areas where an ecosystem was disturbed but soil remains.
It does not involve pioneer species.
3

Secondary succession occurs after disturbances like wildfires, where the soil remains intact, allowing for faster recovery.

What does a higher intrinsic rate of natural increase (r) indicate?

Slower population growth
Lower birth rate
Higher potential for population growth
Longer lifespan
3

A higher intrinsic rate of natural increase (r) indicates a greater capacity for population growth.

Which of the following is NOT a characteristic of an r-selected species?

High reproductive rate
Short lifespan
Large body size
Minimal parental care
3

r-selected species typically have small body sizes, high reproductive rates, and little parental care.

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