The term Ecosystem refers to a biological community of living organisms interacting with each other and their physical environment. It includes both biotic (living) and abiotic (non-living) components that are interlinked through nutrient cycles and energy flows.
This chapter is an important part of Bihar Board Class 12 Biology Ecosystem ,helping students understand the relationships between organisms and their environment. Below are 50 important objective questions with one-word answers to help students prepare effectively for their exams.
Bihar Board Class 12 Biology Ecosystem Objective Questions and Answers (50 MCQs with One Word Answer)
Objective Questions and Answers –Class 12 Biology Ecosystem
Q1. What is the study of ecosystems called?
Answer: Ecology
Q2. Who introduced the term “Ecosystem”?
Answer: A.G. Tansley
Q3. Which of the following is an abiotic component of the ecosystem?
(a) Plants (b) Animals (c) Bacteria (d) Water
Answer: Water
Q4. Energy flow in an ecosystem is always —
(a) Cyclic (b) Unidirectional (c) Multidirectional (d) None
Answer: Unidirectional
Q5. The major source of energy for an ecosystem is —
Answer: Sun
Q6. Green plants are also known as —
Answer: Producers
Q7. Consumers depend on —
Answer: Producers
Q8. The first trophic level in an ecosystem is —
Answer: Producers
Q9. Herbivores are —
Answer: Primary consumers
Q10. Carnivores are —
Answer: Secondary consumers
Q11. The last trophic level in a food chain is —
Answer: Decomposers
Q12. Decomposers are mostly —
Answer: Bacteria and fungi
Q13. A group of similar ecosystems is called —
Answer: Biome
Q14. The flow of energy in an ecosystem follows —
Answer: 10% law
Q15. The concept of ecological pyramid was given by —
Answer: Charles Elton
Q16. The base of an ecological pyramid represents —
Answer: Producers
Q17. Which ecosystem has the highest productivity?
Answer: Tropical rainforest
Q18. The total amount of energy trapped by producers is called —
Answer: Gross Primary Productivity (GPP)
Q19. Net Primary Productivity (NPP) = GPP – ?
Answer: Respiration
Q20. Which ecosystem has the least productivity?
Answer: Desert
Q21. Nutrient cycles are of two types —
Answer: Gaseous and sedimentary
Q22. The carbon cycle involves the exchange of —
Answer: CO₂
Q23. The nitrogen cycle involves —
Answer: Nitrogen fixation
Q24. The organisms that convert ammonia into nitrates are called —
Answer: Nitrifying bacteria
Q25. The organisms that convert nitrates into nitrogen gas are called —
Answer: Denitrifying bacteria
Q26. The term “food chain” was introduced by —
Answer: Charles Elton
Q27. The network of interconnected food chains is called —
Answer: Food web
Q28. The term “biome” refers to —
Answer: Major ecosystem type
Q29. The main decomposers in an ecosystem are —
Answer: Fungi and bacteria
Q30. The pyramid of energy is always —
Answer: Upright
Q31. In a pond ecosystem, the producers are —
Answer: Phytoplankton
Q32. In a forest ecosystem, the consumers are —
Answer: Herbivores and carnivores
Q33. The term “biological magnification” is related to —
Answer: Biomagnification
Q34. The total dry weight of organisms in an ecosystem is called —
Answer: Biomass
Q35. The pyramid of number in a forest ecosystem is usually —
Answer: Inverted
Q36. The pyramid of biomass in the ocean is —
Answer: Inverted
Q37. Detritus food chain starts from —
Answer: Dead organic matter
Q38. Which ecosystem is man-made?
Answer: Crop field
Q39. The flow of nutrients in an ecosystem is —
Answer: Cyclic
Q40. Which process returns carbon dioxide to the atmosphere?
Answer: Respiration
Q41. The organisms that feed on dead animals are called —
Answer: Scavengers
Q42. Which gas is released during decomposition?
Answer: Carbon dioxide
Q43. The process of decomposition is faster in —
Answer: Warm and moist conditions
Q44. A self-sustaining functional unit of nature is —
Answer: Ecosystem
Q45. The grazing food chain starts from —
Answer: Green plants
Q46. Which ecosystem covers the largest area on Earth?
Answer: Marine ecosystem
Q47. Which bacteria fix atmospheric nitrogen?
Answer: Rhizobium
Q48. The rate of energy transfer from one trophic level to another is about —
Answer: 10%
Q49. The study of energy flow and cycling of materials in the ecosystem is called —
Answer: Ecosystem ecology
Q50. The biotic component that breaks down complex organic matter is —
Answer: Decomposer
FAQs- Class 12 Biology Ecosystem
Q1. What is an ecosystem?
Answer: An ecosystem is a community of living organisms interacting with their physical environment.
Q2. What are the main components of an ecosystem?
Answer: Biotic and abiotic components.
Q3. What is the main source of energy in an ecosystem?
Answer: The Sun.
Q4. Who introduced the term “Ecosystem”?
Answer: A.G. Tansley.
Q5. What are producers?
Answer: Green plants that prepare their own food.
Q6. What are consumers?
Answer: Organisms that depend on producers for food.
Q7. What is the 10% law?
Answer: Only 10% of energy is transferred from one trophic level to the next.
Q8. What is a food web?
Answer: A network of interconnected food chains.
Q9. What is decomposition?
Answer: The breakdown of complex organic matter into simpler forms.
Q10. Which ecosystem has the highest productivity?
Answer: Tropical rainforest.
Conclusion- Class 12 Biology Ecosystem
The Ecosystem chapter helps students understand the balance and interdependence among living and non-living components in nature. It emphasizes the energy flow, food chains, food webs, and nutrient cycles that keep the biosphere functioning. Mastering these objective questions and answers ensures a better grasp of fundamental ecological concepts, especially for Bihar Board Class 12th Biology exams.