TRB PG Assistant - Ecosystem ecology – structure, function, energy flow, mineral cycling Online Test (MCQ Quiz)

1. What is the primary definition of an ecosystem in ecological terms?

A) A community of living organisms interacting with each other. B) A geographical area with specific climatic conditions. C) A community of living organisms and their physical environment interacting as a system. D) The total biodiversity of a region.

2. Which of the following represents the biotic component of an ecosystem?

A) Sunlight B) Soil C) Water D) Producers, consumers, and decomposers

3. Abiotic components of an ecosystem include:

A) Plants and animals B) Fungi and bacteria C) Temperature, rainfall, and soil pH D) Algae and plankton

4. What is the term for organisms that produce their own food, usually through photosynthesis?

A) Consumers B) Decomposers C) Producers D) Omnivores

5. Which trophic level consists of organisms that feed on producers?

A) Primary consumers B) Secondary consumers C) Tertiary consumers D) Decomposers

6. Herbivores are classified as which type of consumer?

A) Primary consumers B) Secondary consumers C) Tertiary consumers D) Apex predators

7. Carnivores that feed on herbivores are known as:

A) Primary consumers B) Secondary consumers C) Decomposers D) Autotrophs

8. Organisms that break down dead organic matter are called:

A) Producers B) Consumers C) Decomposers D) Detritivores

9. Which group of organisms is crucial for nutrient recycling in an ecosystem?

A) Large herbivores B) Top predators C) Decomposers and detritivores D) Photosynthetic bacteria

10. The flow of energy in an ecosystem is:

A) Cyclical B) Unidirectional C) Bidirectional D) Intermittent

11. What is the primary source of energy for most ecosystems on Earth?

A) Geothermal energy B) Chemical energy from rocks C) Solar energy D) Electrical energy from lightning

12. The rate at which producers convert light energy into chemical energy is known as:

A) Respiration rate B) Net primary productivity C) Gross primary productivity D) Decomposition rate

13. Net Primary Productivity (NPP) represents:

A) The total energy captured by producers. B) The energy available to consumers after producers respire. C) The energy lost through decomposition. D) The energy flow to the decomposer trophic level.

14. What is the approximate percentage of energy transferred from one trophic level to the next in most ecosystems?

A) 50-60% B) 30-40% C) 10-20% D) 70-80%

15. The '10% law' in ecology refers to:

A) The percentage of producers that are consumed. B) The energy transfer efficiency between trophic levels. C) The percentage of decomposers in an ecosystem. D) The proportion of water recycled in an ecosystem.

16. A pyramid of energy represents:

A) The biomass at each trophic level. B) The number of individuals at each trophic level. C) The amount of energy available at each trophic level. D) The rate of nutrient cycling at each trophic level.

17. Which of the following is NOT a type of mineral cycling (biogeochemical cycle)?

A) Carbon cycle B) Nitrogen cycle C) Energy cycle D) Phosphorus cycle

18. The process by which carbon dioxide is removed from the atmosphere and converted into organic compounds is called:

A) Respiration B) Combustion C) Photosynthesis D) Decomposition

19. What is the role of decomposers in the carbon cycle?

A) They absorb CO2 from the atmosphere. B) They release CO2 into the atmosphere through respiration. C) They convert organic carbon into inorganic carbon. D) They fix atmospheric nitrogen into organic compounds.

20. Nitrogen fixation is the process of converting atmospheric nitrogen (N2) into:

A) Ammonia (NH3) B) Nitrates (NO3-) C) Organic nitrogen compounds D) All of the above

21. Which bacteria are primarily responsible for nitrification?

A) Nitrobacter and Nitrosomonas B) Rhizobium C) Azotobacter D) Clostridium

22. Denitrification is the process by which:

A) Nitrates are converted back to atmospheric nitrogen. B) Ammonia is converted to nitrites. C) Organic nitrogen is converted to ammonia. D) Atmospheric nitrogen is converted to ammonia.

23. The primary reservoir for phosphorus in most ecosystems is:

A) The atmosphere B) Oceans and sedimentary rocks C) Living organisms D) Surface water

24. Which process is largely absent in the phosphorus cycle compared to the carbon or nitrogen cycle?

A) Uptake by producers B) Release by decomposers C) Atmospheric phase D) Weathering of rocks

25. Eutrophication in aquatic ecosystems is often caused by excessive input of which nutrient?

A) Carbon B) Nitrogen and Phosphorus C) Oxygen D) Potassium

26. What is the main function of detritivores in an ecosystem?

A) To photosynthesize and produce organic matter. B) To break down large organic particles into smaller pieces. C) To convert inorganic nutrients into organic forms. D) To release energy through aerobic respiration.

27. The structure of an ecosystem refers to:

A) The rate of energy flow. B) The biodiversity and trophic composition. C) The rate of mineral cycling. D) The climatic conditions.

28. The function of an ecosystem is primarily related to:

A) The number of species present. B) The physical size of the ecosystem. C) Energy flow and nutrient cycling. D) The geographic location.

29. In a forest ecosystem, what would be an example of a producer?

A) Deer B) Wolf C) Oak tree D) Earthworm

30. In a grassland ecosystem, what would be an example of a primary consumer?

A) Lion B) Grasshopper C) Hawk D) Fungus

31. Which of the following is a decomposer found in most terrestrial ecosystems?

A) A rabbit B) A mushroom C) A snake D) A sunflower

32. The term 'trophic level' refers to:

A) The physical habitat of an organism. B) The position an organism occupies in a food chain. C) The rate of reproduction of a species. D) The environmental tolerance of an organism.

33. What is the main consequence of the unidirectional energy flow in an ecosystem?

A) Energy is lost as heat at each trophic level. B) Energy is recycled back to producers. C) Energy accumulates at higher trophic levels. D) Energy input from decomposers is highest.

34. Biogeochemical cycles are essential for:

A) Increasing the temperature of the ecosystem. B) Recycling essential elements and nutrients. C) Increasing the biomass of producers. D) Maintaining atmospheric pressure.

35. Which element's cycle involves significant atmospheric gas exchange?

A) Phosphorus B) Sulfur C) Carbon and Nitrogen D) Potassium

36. The process of ammonification in the nitrogen cycle involves:

A) Conversion of atmospheric N2 to ammonia. B) Conversion of organic nitrogen to ammonia. C) Conversion of ammonia to nitrites. D) Conversion of nitrates to atmospheric N2.

37. In aquatic ecosystems, the primary producers are often:

A) Large trees B) Phytoplankton and algae C) Decomposers D) Zooplankton

38. What is the role of mycorrhizal fungi in nutrient cycling?

A) They fix atmospheric nitrogen. B) They break down dead organic matter. C) They enhance phosphorus uptake by plants. D) They convert nitrates to nitrogen gas.

39. Which type of ecosystem typically has the highest net primary productivity per unit area?

A) Desert B) Temperate grassland C) Tropical rainforest D) Arctic tundra

40. The process of photosynthesis is represented by the equation:

A) C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy B) 6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2 C) N2 + 3H2 → 2NH3 D) NH3 + O2 → NO2- + H2O

41. Respiration in living organisms primarily releases:

A) Energy B) Carbon dioxide C) Water D) All of the above

42. A food web is a more realistic representation of energy flow than a food chain because:

A) It shows only producers. B) It depicts multiple feeding relationships. C) It illustrates nutrient cycling. D) It emphasizes the 10% law.

43. Which component of an ecosystem is responsible for converting dead organic matter back into inorganic nutrients?

A) Producers B) Primary consumers C) Secondary consumers D) Decomposers

44. The term 'standing crop' in ecosystem ecology refers to:

A) The total energy available at a trophic level. B) The biomass of organisms present at a particular time. C) The rate of nutrient uptake by plants. D) The rate of decomposition in the soil.

45. What role do sulfur bacteria play in the sulfur cycle?

A) They convert sulfates to hydrogen sulfide. B) They convert hydrogen sulfide to sulfates. C) They fix atmospheric nitrogen. D) They photosynthesize using sulfur compounds.

46. Which of the following is a key process in the water cycle that returns water vapor to the atmosphere from plants?

A) Evaporation B) Condensation C) Transpiration D) Precipitation

47. If a lake ecosystem is polluted with excess phosphates, what is a likely consequence?

A) Increased dissolved oxygen levels. B) Decreased algal growth. C) Algal blooms and potential oxygen depletion. D) Increased biodiversity of fish species.

48. The overall efficiency of energy transfer between the producer level and the primary consumer level is approximately:

A) 0.1% B) 1% C) 10% D) 50%

49. Which of the following best describes the function of an ecosystem?

A) The collection of all species in a habitat. B) The physical structure of the environment. C) The dynamic processes of energy and matter transfer. D) The geographical boundaries of a biological community.

Ecosystem ecology – structure, function, energy flow, mineral cycling - Online Test

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