Biology MCQ, Class-12, Chapter-11, Organisms and Populations

NCERT based Biology MCQ of Class 12th, Chapter-11, Organisms and Populations with brief explanation for competitive exams like TGT HTET, KVS PGT, SSC and all other state competition exams. 

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NCERT Based MCQ with Explanation:

1. What is ecology primarily concerned with?

(a) Study of individual organisms

(b) Interactions among organisms and their environment

(c) Genetic makeup of species

(d) Evolution of single cells

Explanation: Ecology studies the relationships of living organisms with abiotic and biotic components of their environment, as stated in the chapter.

2. Who is known as the Father of Ecology in India?

(a) Charles Darwin

(b) Ramdeo Misra

(c) W. H. Pearsall

(d) Sanjay Gandhi

Explanation: Ramdeo Misra is revered as the Father of Ecology in India for his foundational work in ecology, as mentioned in the document.

3. At which level does natural selection primarily operate?

(a) Individual

(b) Population

(c) Community

(d) Biome

Explanation: The chapter explains that natural selection operates at the population level to evolve desired traits, not at the individual level.

4. Which of the following is NOT a level of biological organization studied in ecology?

(a) Organisms

(b) Populations

(c) Molecules

(d) Biomes

Explanation: Ecology focuses on organisms, populations, communities, and biomes, not molecules, which are more relevant to molecular biology.

5. What does the term "population" imply in ecological studies?

(a) Isolated individuals

(b) A group of individuals of the same species in a defined area

(c) Different species living together

(d) Plants only

Explanation: A population is defined as a group of individuals of the same species sharing or competing for resources in a specific area.

6. Which of these is an attribute exclusive to populations, not individuals?

(a) Birth rate

(b) Height

(c) Weight

(d) Lifespan

Explanation: Birth rate is a population attribute, whereas height, weight, and lifespan pertain to individual organisms.

7. If 10 new lotus plants are added to a population of 50, what is the birth rate per lotus per year?

(a) 0.1

(b) 0.2

(c) 0.3

(d) 0.4

Explanation: Birth rate = new individuals / initial population = 10 / 50 = 0.2 offspring per lotus per year.

8. What does an age pyramid represent?

(a) Population density

(b) Age distribution of a population

(c) Sex ratio

(d) Birth rate

Explanation: The age pyramid shows the percentage of individuals in different age groups, reflecting population growth status.

9. A triangular age pyramid indicates what type of population?

(a) Stable

(b) Declining

(c) Growing

(d) Extinct

Explanation: A broad base in an age pyramid signifies a high birth rate, indicating a growing population.

10. What is population density technically designated as?

(a) K

(b) N

(c) r

(d) B

Explanation: Population density is represented as "N" in ecological equations, as per the chapter.

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11. Which measure is more meaningful for population density of a banyan tree compared to carrot grass?

(a) Number of individuals

(b) Percent cover

(c) Total births

(d) Death rate

Explanation: For large organisms like a banyan tree, percent cover or biomass is more meaningful than just numbers.

12. What is often used to estimate tiger population density indirectly?

(a) Direct counting

(b) Pug marks and fecal pellets

(c) Biomass

(d) Percent cover

Explanation: The chapter mentions that tiger census relies on indirect methods like pug marks and fecal pellets.

13. Which process contributes to a decrease in population density?

(a) Natality

(b) Immigration

(c) Emigration

(d) Reproduction

Explanation: Emigration (individuals leaving the habitat) decreases population density, unlike natality and immigration.

14. In the equation N_t+1 = N_t + [(B + I) - (D + E)], what does "I" represent?

(a) Immigration

(b) Emigration

(c) Mortality

(d) Natality

Explanation: "I" stands for immigration, the number of individuals entering the habitat.

15. What happens to population density if (B + I) > (D + E)?

(a) It decreases

(b) It remains stable

(c) It increases

(d) It becomes zero

Explanation: If births plus immigration exceed deaths plus emigration, population density increases.

16. Which factor is most significant in population growth during initial colonization?

(a) Birth rate

(b) Immigration

(c) Death rate

(d) Emigration

Explanation: Immigration contributes more significantly to growth when a new habitat is being colonized.

17. What type of growth occurs when resources are unlimited?

(a) Logistic

(b) Exponential

(c) Linear

(d) Static

Explanation: Exponential growth occurs under unlimited resource conditions, resulting in a J-shaped curve.

18. In the equation dN/dt = rN, what does "r" represent?

(a) Carrying capacity

(b) Intrinsic rate of natural increase

(c) Population density

(d) Death rate

Explanation: "r" is the intrinsic rate of natural increase, a key parameter in population growth.

19. What is the integral form of the exponential growth equation?

(a) N_t = N_0 e^rt

(b) N_t = N_0 + rt

(c) N_t = rN

(d) N_t = K - N

Explanation: This is the integral form of exponential growth, where "e" is the base of natural logarithms.

20. What shape does an exponential growth curve resemble?

(a) S-shaped

(b) J-shaped

(c) Straight line

(d) Bell-shaped

Explanation: Exponential growth plots as a J-shaped curve due to rapid increase over time.

21. What limits exponential growth in nature?

(a) Unlimited resources

(b) Carrying capacity

(c) High birth rates

(d) Lack of predators

22. Which growth model is considered more realistic in nature?

(a) Exponential

(b) Logistic

(c) Linear

(d) Geometric

23. In the logistic growth equation dN/dt = rN((K-N)/K), what does "K" represent?

(a) Intrinsic rate

(b) Population density

(c) Carrying capacity

(d) Birth rate

24. What phase follows the lag phase in logistic growth?

(a) Decline

(b) Acceleration

(c) Asymptote

(d) Extinction

25. What does the asymptote in a logistic growth curve indicate?

(a) Population crash

(b) Carrying capacity reached

(c) Exponential growth

(d) Zero growth

26. Which organism breeds only once in its lifetime?

(a) Bamboo

(b) Sparrow

(c) Elephant

(d) Human

27. Which type of offspring production maximizes reproductive fitness in oysters?

(a) Few large-sized offspring

(b) Many small-sized offspring

(c) No offspring

(d) One large offspring

28. What drives the evolution of life history traits?

(a) Random mutations

(b) Abiotic and biotic constraints

(c) Population size

(d) Immigration rates

29. Which interaction benefits both species involved?

(a) Predation

(b) Mutualism

(c) Parasitism

(d) Competition

30. In which interaction do both species suffer?

(a) Mutualism

(b) Competition

(c) Commensalism

(d) Amensalism

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