Ecosystem Dynamics — MCQs Biology

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1. Ecosystem dynamics refers to:
(A) Only soil composition
(B) Changes in structure, function, and species composition over time
(C) DNA replication in microbes
(D) Only energy flow in cells

2. Energy in an ecosystem flows:
(A) Randomly among species
(B) From producers to consumers to decomposers
(C) From consumers to producers only
(D) In a cyclic manner like matter

3. Matter in ecosystems cycles:
(A) Through biogeochemical cycles
(B) Only from producers to consumers
(C) Only as energy
(D) Only through food chains

4. Primary productivity refers to:
(A) Rate of decomposition only
(B) Rate at which consumers feed
(C) Rate at which producers synthesize organic compounds
(D) Rate of nutrient loss only

5. Gross primary productivity (GPP) is:
(A) Energy in decomposers only
(B) Energy lost to consumers
(C) Total energy fixed by producers
(D) Energy in soil only

6. Net primary productivity (NPP) is:
(A) Energy remaining after plant respiration
(B) Total energy consumed by herbivores
(C) Energy in detritus only
(D) Energy lost as heat only

7. Secondary productivity refers to:
(A) Photosynthesis only
(B) Energy fixed by producers
(C) Soil nutrients only
(D) Energy stored in herbivores and carnivores

8. Ecological efficiency is:
(A) Percentage of energy transferred between trophic levels
(B) Total biomass only
(C) Soil nutrient content only
(D) Only predator-prey interactions

9. Food chains are:
(A) Linear sequence of energy flow through trophic levels
(B) Circular energy flow
(C) Only microbial interactions
(D) Random interactions in soil

10. Food webs are:
(A) Interconnected food chains in an ecosystem
(B) Single chain of herbivores only
(C) Detritus decomposition only
(D) Nutrient cycles only

11. Trophic levels represent:
(A) Hierarchical levels in a food chain
(B) Soil layers only
(C) Atmospheric layers only
(D) Water zones only

12. Producers occupy which trophic level?
(A) Fourth
(B) Second
(C) Third
(D) First

13. Primary consumers occupy which trophic level?
(A) Fourth
(B) First
(C) Third
(D) Second

14. Secondary consumers occupy which trophic level?
(A) Second
(B) First
(C) Third
(D) Fourth

15. Tertiary consumers occupy which trophic level?
(A) First
(B) Fourth
(C) Second
(D) Third

16. Detritivores are:
(A) Organisms that feed on dead organic matter
(B) Primary producers
(C) Herbivores only
(D) Top predators only

17. Decomposers play a role in:
(A) Eating predators only
(B) Consuming producers only
(C) Recycling nutrients back to the soil
(D) Photosynthesis only

18. Ecological pyramids can represent:
(A) Only water content
(B) Only population size
(C) Only soil nutrients
(D) Number, biomass, or energy

19. Pyramid of numbers shows:
(A) Energy only
(B) Number of organisms at each trophic level
(C) Biomass only
(D) Nutrient content only

20. Pyramid of biomass shows:
(A) Energy only
(B) Number only
(C) Total mass of organisms at each trophic level
(D) Water content only

21. Pyramid of energy shows:
(A) Biomass only
(B) Number only
(C) Energy flow through trophic levels
(D) Soil nutrients only

22. Biogeochemical cycles include:
(A) Only carbon cycle
(B) Carbon, nitrogen, phosphorus, and water cycles
(C) Only oxygen cycle
(D) Only soil mineral cycles

23. Carbon cycle involves:
(A) Water cycle only
(B) Nitrogen fixation only
(C) Sulfur cycle only
(D) Photosynthesis, respiration, and decomposition

24. Nitrogen cycle involves:
(A) Sulfur cycle only
(B) Photosynthesis only
(C) Nitrogen fixation, nitrification, denitrification
(D) Carbon cycle only

25. Phosphorus cycle lacks:
(A) Atmospheric phase
(B) Soil and rock phases
(C) Water transport
(D) Decomposition involvement

26. Water cycle involves:
(A) Only soil absorption
(B) Only groundwater flow
(C) Only evaporation
(D) Evaporation, condensation, precipitation, and runoff

27. Ecological succession refers to:
(A) Soil formation only
(B) Instant species replacement
(C) Gradual change in species composition over time
(D) Water movement only

28. Primary succession occurs on:
(A) Forest floor only
(B) Abandoned farmland
(C) Bare land with no previous life
(D) Wetlands only

29. Secondary succession occurs on:
(A) Oceans only
(B) Newly formed rocks only
(C) Previously inhabited land after disturbance
(D) Deserts only

30. Climax community is:
(A) Stable, mature community at the end of succession
(B) Initial stage of succession
(C) Temporary community
(D) Microbial colony only

31. Disturbances in ecosystems can lead to:
(A) Only photosynthesis reduction
(B) Only soil erosion
(C) Only water loss
(D) Changes in species composition

32. Resilience in ecosystems refers to:
(A) Only species diversity
(B) Energy loss only
(C) Only nutrient cycling
(D) Ability to recover after disturbance

33. Resistance in ecosystems refers to:
(A) Only nutrient retention
(B) Only biomass accumulation
(C) Ability to remain unchanged despite disturbance
(D) Only energy efficiency

34. Trophic cascades occur when:
(A) Changes in top predators affect multiple lower trophic levels
(B) Only herbivores increase
(C) Producers decline only
(D) Soil nutrients increase

35. Bottom-up control in ecosystems is driven by:
(A) Decomposers only
(B) Predator abundance only
(C) Human activity only
(D) Availability of nutrients and primary productivity

36. Top-down control in ecosystems is driven by:
(A) Nutrients only
(B) Predators regulating lower trophic levels
(C) Soil microbes only
(D) Water flow only

37. Successional dynamics can be influenced by:
(A) Temperature only
(B) Soil minerals only
(C) Only water availability
(D) Climate, soil, species interactions, and disturbances

38. Ecosystem engineers are:
(A) Only predators
(B) Species that modify habitats, affecting other species
(C) Only plants
(D) Microbes only

39. Examples of ecosystem engineers include:
(A) Only trees
(B) Beavers and corals
(C) Only microbes
(D) Only predators

40. Biodiversity affects ecosystem dynamics by:
(A) Only reducing energy flow
(B) Reducing stability
(C) Enhancing resilience and ecosystem functions
(D) Only reducing nutrient cycles

41. Human activities affecting ecosystem dynamics include:
(A) Only predation
(B) Photosynthesis only
(C) Deforestation, pollution, and climate change
(D) Natural decomposition only

42. Primary succession typically leads to:
(A) Loss of species only
(B) Desertification only
(C) Soil formation and colonization by pioneer species
(D) Soil erosion only

43. Secondary succession is faster than primary because:
(A) Energy is absent
(B) No soil is present
(C) Only microbes colonize
(D) Soil and seed bank already exist

44. Disturbance regimes include:
(A) Only herbivore grazing
(B) Only droughts
(C) Only deforestation
(D) Fire, storms, floods, and human activities

45. Ecosystem stability depends on:
(A) Only soil nutrients
(B) Only energy flow
(C) Only water availability
(D) Biodiversity, trophic interactions, and nutrient cycling

46. Autotrophs drive ecosystem dynamics by:
(A) Decomposing only
(B) Consuming other species
(C) Producing energy and organic matter
(D) Reducing biodiversity only

47. Decomposers influence ecosystem dynamics by:
(A) Predation only
(B) Consuming producers only
(C) Recycling nutrients and maintaining soil fertility
(D) Photosynthesis only

48. Ecosystem productivity is influenced by:
(A) Only water availability
(B) Only soil pH
(C) Only sunlight
(D) Climate, nutrients, and species interactions

49. Succession and disturbance together determine:
(A) Only energy flow
(B) Only soil nutrients
(C) Community structure and species composition
(D) Only water cycles

50. Understanding ecosystem dynamics is essential for:
(A) Conservation, resource management, and predicting environmental change
(B) Soil testing only
(C) Only agricultural practices
(D) Only laboratory research