Chapter Exam

Chapter 11: Organisms and Populations — Online MCQ Test

Q: The study of interactions among organisms and between organisms and their physical environment is called:

Answer: A. Ecology — Ecology deals with the relationships of organisms with one another and with their abiotic environment.

Q: Which of the following is an abiotic factor affecting organisms?

Answer: C. Temperature — Temperature is a physical or abiotic component of the environment, unlike biotic interactions such as predation and parasitism.

Q: The specific place where an organism lives is called its:

Answer: B. Habitat — Habitat refers to the place or area where an organism lives. Niche refers to its functional role in the ecosystem.

Q: In a population, natality refers to:

Answer: B. Number of births per unit time — Natality is the birth rate in a population, whereas mortality is the death rate.

Q: According to Allen's rule, mammals from colder climates generally have:

Answer: B. Shorter ears and limbs to reduce heat loss — Allen's rule states that animals in colder climates tend to have shorter extremities to reduce surface area and heat loss.

Q: A population has 1000 individuals. During a year, 80 births, 20 deaths, 10 immigrants, and 20 emigrants are recorded. What is the population size at the end of the year?

Answer: B. 1050 — Population change = (births + immigration) - (deaths + emigration) = (80 + 10) - (20 + 20) = 50. Final population = 1050.

Q: For a population following logistic growth, the population growth rate dN/dt is maximum when:

Answer: B. N = K/2 — In logistic growth, dN/dt = rN((K-N)/K) is maximum at half the carrying capacity, N = K/2.

Q: In a population, birth rate is 0.12 per individual per year and death rate is 0.08 per individual per year. If immigration and emigration are absent, the intrinsic rate of natural increase is:

Answer: A. 0.04 per individual per year — The intrinsic rate of natural increase r is approximately birth rate minus death rate, so r = 0.12 - 0.08 = 0.04.

BIOLOGY · Grade 12 · CBSE(NCERT)

Practice Chapter 11: Organisms and Populations with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 12 BIOLOGY. This chapter covers: Organisms Population Ecology Abiotic Factors Adaptation Population Growth Exponential Growth Logistic Growth Predation Competition Mutualism Commensalism Parasitism. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 11: Organisms and Populations — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 12 BIOLOGY — Chapter 11: Organisms and Populations, with answers and explanations. These are sample questions; the exam has its own separate question set.

The study of interactions among organisms and between organisms and their physical environment is called:

A. Ecology ✓
B. Ethology
C. Genetics
D. Evolution

Answer: A. Ecology
Ecology deals with the relationships of organisms with one another and with their abiotic environment.

Which of the following is an abiotic factor affecting organisms?

A. Predation
B. Competition
C. Temperature ✓
D. Parasitism

Answer: C. Temperature
Temperature is a physical or abiotic component of the environment, unlike biotic interactions such as predation and parasitism.

The specific place where an organism lives is called its:

A. Niche
B. Habitat ✓
C. Biome
D. Population

Answer: B. Habitat
Habitat refers to the place or area where an organism lives. Niche refers to its functional role in the ecosystem.

In a population, natality refers to:

A. Number of deaths per unit time
B. Number of births per unit time ✓
C. Number of individuals leaving a population
D. Number of predators in a population

Answer: B. Number of births per unit time
Natality is the birth rate in a population, whereas mortality is the death rate.

A desert kangaroo rat can live without drinking water. Which adaptation mainly helps it survive?

A. It stores large amounts of water in its stomach
B. It produces very concentrated urine and uses metabolic water ✓
C. It absorbs water directly through its skin
D. It remains active during the hottest part of the day

Answer: B. It produces very concentrated urine and uses metabolic water
Kangaroo rats conserve water by producing concentrated urine and obtaining water from metabolic oxidation of fats.

According to Allen's rule, mammals from colder climates generally have:

A. Longer ears and limbs to lose more heat
B. Shorter ears and limbs to reduce heat loss ✓
C. No body hair to prevent overheating
D. Flattened bodies to absorb more sunlight

Answer: B. Shorter ears and limbs to reduce heat loss
Allen's rule states that animals in colder climates tend to have shorter extremities to reduce surface area and heat loss.

A population has 1000 individuals. During a year, 80 births, 20 deaths, 10 immigrants, and 20 emigrants are recorded. What is the population size at the end of the year?

A. 1030
B. 1050 ✓
C. 1070
D. 1090

Answer: B. 1050
Population change = (births + immigration) - (deaths + emigration) = (80 + 10) - (20 + 20) = 50. Final population = 1050.

In the logistic growth equation dN/dt = rN((K-N)/K), the term ((K-N)/K) represents:

A. Age structure of the population
B. Environmental resistance due to limited resources ✓
C. Birth rate alone
D. Migration rate alone

Answer: B. Environmental resistance due to limited resources
The term ((K-N)/K) reduces growth as population size approaches carrying capacity, representing the effect of resource limitation.

For a population following logistic growth, the population growth rate dN/dt is maximum when:

A. N = 0
B. N = K/2 ✓
C. N = K
D. N is much greater than K

Answer: B. N = K/2
In logistic growth, dN/dt = rN((K-N)/K) is maximum at half the carrying capacity, N = K/2.

In a population, birth rate is 0.12 per individual per year and death rate is 0.08 per individual per year. If immigration and emigration are absent, the intrinsic rate of natural increase is:

A. 0.04 per individual per year ✓
B. 0.08 per individual per year
C. 0.12 per individual per year
D. 0.20 per individual per year

Answer: A. 0.04 per individual per year
The intrinsic rate of natural increase r is approximately birth rate minus death rate, so r = 0.12 - 0.08 = 0.04.

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