CBSE Class 12 Biology Case-Based Questions – Organisms and Populations (NCERT Based)

Unit V: Ecology and Environment | Chapter 13: Organisms and Populations

CBSE Class 12 Biology Chapter 13 Case-Based Questions – Organisms and Populations (NCERT)

Course & Examination Details

• Course: CBSE Class 12 Biology
• Unit: Unit V – Ecology and Environment
• Chapter: Chapter 13 – Organisms and Populations
• Board: Central Board of Secondary Education (CBSE)
• Syllabus Base: Strictly as per NCERT Textbook
• Exam Relevance: CBSE Class 12 Board Examinations (Case-Based / Competency-Based Questions)

Case-Based Questions with Answers

(Prepared strictly according to NCERT concepts and CBSE competency-based question pattern)

Section A: Organism and Environment (Case 1–5)

Case 1

A group of organisms lives in a forest ecosystem where temperature, rainfall, and light vary seasonally. Their survival depends on adjusting to these changes.

Q1. Which branch of biology studies such interactions?
Ans: Ecology studies interactions among organisms and between organisms and their environment.

Q2. Name two environmental factors affecting these organisms.
Ans: Temperature and water availability affect survival and distribution.

Case 2

Certain organisms are found only in specific geographical regions despite similar food availability elsewhere.

Q1. What determines such restricted distribution?
Ans: Abiotic factors and tolerance limits determine species distribution.

Q2. What happens if tolerance limits are exceeded?
Ans: Organisms experience stress, migrate, or may die.

Case 3

An organism constantly exchanges gases, nutrients, and waste products with its surroundings.

Q1. What type of system is the organism?
Ans: It is an open system.

Q2. Why is this exchange essential?
Ans: Exchange maintains metabolism, growth, and survival.

Case 4

Plants growing in a region show stunted growth due to unfavorable conditions.

Q1. What is this condition called?
Ans: Environmental stress.

Q2. Mention one possible cause.
Ans: Water scarcity or extreme temperature.

Case 5

A biologist studies organisms at different levels from individuals to the biosphere.

Q1. Name the level above population.
Ans: Community.

Q2. Name the highest level of ecological organization.
Ans: Biosphere.

Section B: Major Abiotic Factors (Case 6–10)

Case 6

Reptiles are inactive during cold mornings but active in sunlight.

Q1. Which abiotic factor affects them most?
Ans: Temperature.

Q2. What type of organisms are reptiles based on temperature response?
Ans: Conformers.

Case 7

Some plants survive in deserts with minimal rainfall.

Q1. What are such plants called?
Ans: Xerophytes.

Q2. Name one adaptation helping their survival.
Ans: Thick cuticle or reduced leaves.

Case 8

Aquatic plants are found only near the surface of deep lakes.

Q1. Which abiotic factor limits their distribution?
Ans: Light.

Q2. Why does light decrease with depth?
Ans: Due to absorption and scattering in water.

Case 9

Certain organisms cannot survive in saline water.

Q1. Which abiotic factor is responsible?
Ans: Salinity.

Q2. Why does salinity affect organisms?
Ans: It disturbs osmotic balance.

Case 10

Different vegetation types are observed in different soil regions.

Q1. Which soil property influences vegetation?
Ans: Soil pH, texture, and mineral content.

Q2. How does soil indirectly affect animals?
Ans: By determining vegetation patterns.

Section C: Responses to Abiotic Factors (Case 11–15)

Case 11

Birds maintain a constant body temperature in all seasons.

Q1. Which response is shown here?
Ans: Regulation.

Q2. Why is regulation energy-intensive?
Ans: It requires continuous metabolic activity.

Case 12

Fishes show changes in body temperature with water temperature.

Q1. What type of response is this?
Ans: Conformation.

Q2. Name one advantage of conformation.
Ans: Reduced energy expenditure.

Case 13

Many birds move to warmer regions during winter.

Q1. What is this phenomenon called?
Ans: Migration.

Q2. Why is migration important?
Ans: It helps avoid unfavorable conditions.

Case 14

Certain animals sleep through winter with reduced metabolism.

Q1. Name this survival strategy.
Ans: Hibernation.

Q2. Under which broader response does it fall?
Ans: Suspension.

Case 15

Insects stop development during extreme conditions.

Q1. What is this condition called?
Ans: Diapause.

Q2. Why is it beneficial?
Ans: It ensures survival during stress.

Section D: Adaptations (Case 16–20)

Case 16

A plant has spines instead of leaves and a thick cuticle.

Q1. Identify the habitat.
Ans: Desert habitat.

Q2. What type of adaptation is this?
Ans: Morphological adaptation.

Case 17

Fish have streamlined bodies and fins.

Q1. What is the advantage of a streamlined body?
Ans: Reduced resistance during swimming.

Q2. Which environment requires such adaptation?
Ans: Aquatic environment.

Case 18

People living in mountains have higher red blood cell counts.

Q1. Why is this adaptation needed?
Ans: To cope with low oxygen availability.

Q2. Name the type of adaptation.
Ans: Physiological adaptation.

Case 19

Polar animals have thick fur and fat layers.

Q1. What is the function of thick fur?
Ans: Insulation against cold.

Q2. Which abiotic factor is involved?
Ans: Low temperature.

Case 20

Certain plants open stomata at night instead of daytime.

Q1. Name this pathway.
Ans: CAM pathway.

Q2. Why is it advantageous?
Ans: It reduces water loss.

Section E: Population Attributes, Growth & Interactions (Case 21–25)

Case 21

A group of deer lives in a forest area.

Q1. What ecological term describes this group?
Ans: Population.

Q2. Name one population attribute.
Ans: Population density.

Case 22

A population has more young individuals than old ones.

Q1. What does this indicate?
Ans: Expanding population.

Q2. Which diagram represents this?
Ans: Expanding age pyramid.

Case 23

A population grows rapidly under unlimited resources.

Q1. What type of growth is this?
Ans: Exponential growth.

Q2. Name the curve formed.
Ans: J-shaped curve.

Case 24

Population growth slows as resources become limited.

Q1. Identify the growth pattern.
Ans: Logistic growth.

Q2. What limits population size here?
Ans: Carrying capacity.

Case 25

Bees obtain nectar while flowers get pollinated.

Q1. What type of interaction is this?
Ans: Mutualism.

Q2. How does it benefit ecosystems?
Ans: It enhances reproduction and stability.

CBSE Exam Note

These case-based questions strengthen analytical thinking, application of NCERT concepts, and are fully aligned with the CBSE competency-based assessment pattern.