CBSE Class 12 Biology Very Short Answer Questions – Organisms and Populations (NCERT Based)

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

CBSE Class 12 Biology Chapter 13 Very Short Answer 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: Strictly as per NCERT
• Usefulness: CBSE Board Exams, School Tests, Quick Revision

Very Short Answer Type Questions (20–30 Words Each)

(Prepared exactly as per NCERT concepts and CBSE answer-writing standards)

Section A: Organism and Environment (Q1–Q8)

Q1. What is ecology?
Ans: Ecology is the branch of biology that studies interactions among organisms and between organisms and their physical environment.

Q2. Define habitat.
Ans: Habitat is the specific place or environment where an organism normally lives, grows, and reproduces.

Q3. What is the biosphere?
Ans: The biosphere is the global sum of all ecosystems, representing the zone of life on Earth.

Q4. Why are organisms considered open systems?
Ans: Organisms continuously exchange energy and matter with their environment, making them open systems.

Q5. What determines the distribution of organisms?
Ans: Abiotic factors, biotic interactions, and historical factors determine the distribution of organisms.

Q6. What is environmental stress?
Ans: Environmental stress refers to adverse conditions that reduce growth, survival, or reproduction of organisms.

Q7. Name the major levels of ecological organization.
Ans: Organism, population, community, ecosystem, biome, and biosphere are major ecological levels.

Q8. Why is environment important for survival?
Ans: The environment provides essential resources like food, water, shelter, and suitable conditions for survival.

Section B: Major Abiotic Factors (Q9–Q16)

Q9. Name the four major abiotic factors.
Ans: Temperature, water, light, and soil are the four major abiotic factors affecting organisms.

Q10. Why is temperature called the most important abiotic factor?
Ans: Temperature affects enzyme activity, metabolism, growth, reproduction, and distribution of organisms.

Q11. What are eurythermal organisms?
Ans: Eurythermal organisms can tolerate a wide range of temperatures.

Q12. What are stenothermal organisms?
Ans: Stenothermal organisms can survive only within a narrow range of temperature.

Q13. How does water affect plant distribution?
Ans: Availability of water determines the type and distribution of vegetation in an area.

Q14. What are xerophytes?
Ans: Xerophytes are plants adapted to survive in dry or desert conditions.

Q15. Why is light important for plants?
Ans: Light is essential for photosynthesis, flowering, and overall plant growth.

Q16. How does soil influence vegetation?
Ans: Soil affects vegetation through its texture, pH, mineral content, and water-holding capacity.

Section C: Responses to Abiotic Factors (Q17–Q24)

Q17. What is regulation in organisms?
Ans: Regulation is the ability of organisms to maintain constant internal conditions despite environmental changes.

Q18. Name one regulating organism.
Ans: Birds and mammals are regulating organisms.

Q19. What is conformation?
Ans: Conformation is a response where internal conditions of organisms change according to the external environment.

Q20. Give an example of conformer.
Ans: Fishes and reptiles are examples of conformers.

Q21. What is migration?
Ans: Migration is the seasonal movement of organisms to more favorable environments.

Q22. Why do organisms migrate?
Ans: Organisms migrate to avoid unfavorable conditions and to access food and breeding sites.

Q23. What is suspension?
Ans: Suspension is a survival strategy where organisms reduce metabolic activity during unfavorable conditions.

Q24. Name two types of suspension.
Ans: Hibernation and aestivation are common types of suspension.

Section D: Adaptations (Q25–Q32)

Q25. Define adaptation.
Ans: Adaptation is a structural, physiological, or behavioral trait that enhances survival in a specific environment.

Q26. Mention one adaptation of desert plants.
Ans: Desert plants have thick cuticles and reduced leaves to minimize water loss.

Q27. What is CAM pathway?
Ans: CAM pathway is a photosynthetic adaptation in desert plants to reduce water loss.

Q28. Name one adaptation of aquatic animals.
Ans: Streamlined body shape helps aquatic animals move easily in water.

Q29. How are fishes adapted for respiration?
Ans: Fishes possess gills that extract dissolved oxygen from water.

Q30. What is an adaptation at high altitude?
Ans: Increased red blood cell count helps organisms cope with low oxygen levels.

Q31. Why do mountain animals have thick fur?
Ans: Thick fur provides insulation against extremely low temperatures.

Q32. Are adaptations inherited?
Ans: Yes, adaptations are genetically inherited and passed to future generations.

Section E: Population Attributes (Q33–Q40)

Q33. Define population.
Ans: A population is a group of individuals of the same species living in a defined area at a given time.

Q34. What is population density?
Ans: Population density is the number of individuals of a species per unit area or volume.

Q35. Name any two population attributes.
Ans: Birth rate and death rate are population attributes.

Q36. What is natality?
Ans: Natality is the number of individuals added to a population by birth per unit time.

Q37. Define mortality.
Ans: Mortality is the number of individuals lost from a population due to death per unit time.

Q38. What is age distribution?
Ans: Age distribution refers to the proportion of individuals in different age groups within a population.

Q39. Name the three age groups in a population.
Ans: Pre-reproductive, reproductive, and post-reproductive age groups.

Q40. What does an expanding age pyramid indicate?
Ans: An expanding age pyramid indicates a growing population.

Section F: Population Growth and Interactions (Q41–Q50)

Q41. What is population growth?
Ans: Population growth is the change in population size over time due to births, deaths, immigration, and emigration.

Q42. What is exponential growth?
Ans: Exponential growth occurs when population increases rapidly under unlimited resource conditions.

Q43. Name the curve of exponential growth.
Ans: Exponential growth produces a J-shaped growth curve.

Q44. What is logistic growth?
Ans: Logistic growth occurs when population growth slows due to limited resources.

Q45. What is carrying capacity?
Ans: Carrying capacity is the maximum population size that an environment can sustain.

Q46. Name the curve of logistic growth.
Ans: Logistic growth produces an S-shaped or sigmoid curve.

Q47. What is mutualism?
Ans: Mutualism is an interaction where both species benefit.

Q48. Define competition.
Ans: Competition occurs when organisms compete for limited resources, harming both species.

Q49. What is predation?
Ans: Predation is an interaction where one organism kills and feeds on another organism.

Q50. What is parasitism?
Ans: Parasitism is an interaction where one organism benefits while the host is harmed.

Exam Tip

These very short answer questions are ideal for 1-mark questions, quick revision, and last-minute CBSE board preparation, strictly following NCERT wording.