NEET 2025 MCQ with Answer Explanation : Organisms and Populations.

1. What is the carrying capacity of an environment?
   A) The maximum population size of a species that an environment can sustain.
   B) The minimum population size of a species that an environment can sustain.
   C) The rate at which the population grows.
   D) The number of species in a community.

Answer: A) The maximum population size of a species that an environment can sustain.

Explanation:
Carrying capacity refers to the maximum number of individuals of a species that an environment can support over time without causing environmental degradation.

2. Which of the following factors does not directly affect population growth?
   A) Birth rate
   B) Death rate
   C) Immigration rate
   D) Soil type

Answer: D) Soil type

Explanation:
Soil type affects habitat quality, but does not directly influence population growth. Birth rate, death rate, and immigration rate are all crucial factors in determining the growth of a population.

3. A population that grows exponentially is represented by which of the following curves?
   A) J-shaped curve
   B) S-shaped curve
   C) Linear curve
   D) Parabolic curve

Answer: A) J-shaped curve

Explanation:
Exponential growth occurs under ideal conditions where resources are unlimited. As a result, the population size increases rapidly, represented by a J-shaped curve.

4. Which type of population growth is typically observed in a population with unlimited resources?
   A) Logistic growth
   B) Exponential growth
   C) Cyclic growth
   D) Oscillatory growth

Answer: B) Exponential growth

Explanation:
Exponential growth occurs when a population has unlimited resources and grows at a constant rate, resulting in rapid population expansion.

5. The age structure of a population is important for understanding:
   A) The species diversity in an ecosystem.
   B) The migration patterns of a population.
   C) The future growth potential of a population.
   D) The environmental carrying capacity.

Answer: C) The future growth potential of a population.

Explanation:
The age structure reveals the proportion of individuals in different age groups, helping predict future growth, reproduction rates, and the overall sustainability of the population.

6. Which of the following is a density-dependent factor that limits population growth?
   A) Earthquake
   B) Flood
   C) Predation
   D) Climate change

Answer: C) Predation

Explanation:
Density-dependent factors, such as predation, disease, and competition, intensify as the population density increases, thereby limiting growth.

7. Which of the following statements is true regarding r-strategists?
   A) They produce few offspring but invest significant care.
   B) They are typically large animals.
   C) They exhibit rapid population growth and have many offspring.
   D) They live in stable environments.

Answer: C) They exhibit rapid population growth and have many offspring.

Explanation:
R-strategists tend to reproduce rapidly, producing many offspring with little parental care. They thrive in unstable environments where rapid reproduction is advantageous. Examples include insects and rodents.

8. What does the term “niche” refer to in an ecological context?
   A) The habitat where an organism lives.
   B) The role or function of an organism in an ecosystem.
   C) The genetic makeup of an organism.
   D) The diversity of species in an area.

Answer: B) The role or function of an organism in an ecosystem.

Explanation:
A niche encompasses the unique role an organism plays in its ecosystem, including its interactions with other species, its habitat, and its use of resources.

9. Which of the following terms refers to the study of the interactions between organisms and their environment?
   A) Ecology
   B) Evolution
   C) Genetics
   D) Physiology

Answer: A) Ecology

Explanation:
Ecology is the branch of biology that deals with the relationships between organisms and their physical surroundings, including how they interact with each other and their environment.

10. The competitive exclusion principle states that:
    A) Two species can coexist if they occupy different niches.
    B) Two species cannot occupy the same niche at the same time.
    C) A species will always adapt to its environment.
    D) A species will evolve to fit multiple niches.

Answer: B) Two species cannot occupy the same niche at the same time.

Explanation:
This principle suggests that if two species attempt to occupy the same ecological niche, one will be outcompeted and eventually excluded, as they would have identical needs for resources.