Support Ecosystem Cycling With Evidence - Biology

1. Which evidence best supports increased carbon sequestration in a reforested area?

   Rising tree biomass and increasing soil organic carbon. More carbon stored in both above and below-ground pools.

2. What is the overall chemical equation for photosynthesis?

   $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$. Six $CO_2$ and water molecules produce glucose and oxygen.

3. Which evidence best supports transpiration increasing on a hot, dry day?

   Higher water loss rate from leaves or increased local humidity. Heat increases evaporation rate from plant surfaces.

4. Which evidence best supports phosphate limitation in a lake ecosystem?

   Algal growth increases after phosphate is added. Phosphate addition stimulates growth when it's the limiting nutrient.

5. What is a trophic level in the context of matter cycling?

   A feeding position where matter is transferred by consumption. Each feeding level in a food chain or web.

6. Which statement is supported if decomposers are removed and detritus accumulates?

   Nutrient recycling slows due to reduced decomposition. Without decomposers, organic matter accumulates instead of recycling.

7. Which evidence best supports assimilation of nitrate by plants?

   Plant tissue nitrate decreases as organic nitrogen increases. Inorganic nitrogen is converted to organic plant compounds.

8. Which term describes the movement of nutrients from one trophic level to the next?

   Consumption (trophic transfer of matter). Nutrients pass from prey to predator through feeding.

9. What is the term for nutrients entering an ecosystem from outside sources?

   Nutrient input. External sources add nutrients to the ecosystem.

10. Which evidence best supports increased runoff after deforestation?

    Greater stream discharge and reduced infiltration after tree removal. Trees normally absorb water; removal increases surface flow.

11. Which water-cycle process moves water from leaves to the atmosphere?

    Transpiration. Plants release water vapor through leaf pores (stomata).

12. What is the largest active reservoir of carbon on Earth?

    Oceans (dissolved inorganic carbon). Ocean water holds more dissolved carbon than the atmosphere.

13. Which evidence best supports that soil microbes drive nutrient cycling?

    Sterilized soil shows reduced nitrate formation and plant growth. Killing microbes disrupts the biological processes they perform.

14. Which option best supports that phosphorus can limit productivity in freshwater ecosystems?

    Adding phosphate increases primary production more than controls. Experimental evidence shows phosphorus controls growth rate.

15. What nitrogen-cycle process converts nitrate to $N_2$ gas under low-oxygen conditions?

    Denitrification. Bacteria reduce nitrate to nitrogen gas without oxygen.

16. Which phosphorus-cycle feature is correct: does it have a major atmospheric gas phase?

    No, phosphorus lacks a major atmospheric gas phase. Phosphorus cycles mainly through rocks, soil, and water.

17. What is the overall chemical equation for cellular respiration?

    $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$. Glucose and oxygen are broken down to release $CO_2$ and water.

18. What is the key difference between energy flow and matter cycling in ecosystems?

    Energy flows one-way; matter is recycled. Energy is lost as heat; matter atoms are conserved and reused.

19. Which evidence best supports mineralization in forest litter over time?

    Organic nitrogen decreases while inorganic ammonium/nitrate increases. Decomposition converts organic nitrogen to inorganic forms.

20. What nitrogen-cycle process converts ammonium to nitrite and then nitrate?

    Nitrification. Bacteria oxidize ammonia compounds to more oxidized forms.

21. Which evidence best supports ammonification in a decomposing compost pile?

    Rising ammonium concentration during decay. Decomposition releases ammonia as organic matter breaks down.

22. Which evidence best supports nutrient transfer up a food chain?

    Higher tissue nitrogen or carbon in consumers after feeding. Consumption transfers nutrients from food into consumer tissues.

23. Which term describes carbon stored long-term in wood, soils, or sediments?

    Carbon sequestration. Carbon is removed from atmosphere and stored long-term.

24. Which evidence best supports nitrogen fixation in legume root nodules?

    Higher plant nitrogen content when nodules are present. Bacteria in nodules provide nitrogen, increasing plant growth.

25. Which process is best supported by evidence of rising atmospheric $CO_2$ from burning fuels?

    Combustion transferring carbon to the atmosphere. Burning fossil fuels adds stored carbon to the atmosphere.

26. Which nitrogen-cycle process converts $N_2$ gas into ammonia or ammonium?

    Nitrogen fixation. Converts atmospheric $N_2$ into forms plants can use.

27. What is the term for nutrients leaving an ecosystem via water or harvesting?

    Nutrient output (loss). Nutrients exit the ecosystem through various pathways.

28. Which water-cycle process is indicated by water vapor turning into liquid droplets?

    Condensation. Water vapor loses energy and forms liquid droplets.

29. Which direct measurement best supports that respiration returns carbon to the atmosphere?

    Increased $CO_2$ output from organisms or soil. Metabolic activity releases carbon back to the atmosphere.

30. Which term describes organisms that convert inorganic carbon to organic molecules?

    Producers (autotrophs). They make organic molecules from $CO_2$ through photosynthesis.

31. What is eutrophication in terms of nutrient cycling evidence?

    Nutrient enrichment causing algal blooms and oxygen decline. Excess nutrients cause algal overgrowth and oxygen depletion.

32. Which option is the most direct evidence that carbon cycles between plants and animals?

    Plants fix $CO_2$; animals release $CO_2$ during respiration. Shows carbon moving between autotrophs and heterotrophs.

33. Which term describes the conversion of organic matter into inorganic nutrients by microbes?

    Mineralization. Microbes break down complex organic compounds to simple ions.

34. Which evidence best supports nutrient loss from soil after heavy rainfall?

    Decreased soil nitrate with increased nitrate in runoff water. Water carries dissolved nutrients away from soil.

35. Which measurement is direct evidence that carbon is stored in biomass?

    Increased dry mass or increased percent carbon in tissues. Direct measurement shows carbon accumulated in living tissues.

36. What is the definition of a biogeochemical cycle?

    Movement of matter through biotic and abiotic parts of ecosystems. Matter cycles through living organisms and non-living components.

37. Which evidence pattern best supports eutrophication in a pond?

    High nitrate/phosphate, algal bloom, then low dissolved $O_2$. Classic sequence shows nutrient input leading to oxygen loss.

38. Which term describes organisms that break down dead matter and recycle nutrients?

    Decomposers. They return nutrients from organic matter back to the environment.

39. Which evidence best supports nitrification occurring in soil?

    Ammonium decreases while nitrate increases over time. Conversion from reduced to oxidized nitrogen forms over time.

40. Which evidence best supports denitrification in waterlogged soils?

    Nitrate decreases and $N_2$ (or $N_2O$) emissions increase. Conversion of nitrate to gaseous forms in anaerobic conditions.

41. Which term describes the total mass of living organic matter in an ecosystem?

    Biomass. Total weight of all living organisms in an area.

42. What nitrogen-cycle process converts organic nitrogen in dead matter into ammonium?

    Ammonification (decomposition). Organic nitrogen is broken down back to inorganic forms.

43. What is the term for water soaking into the ground from the surface?

    Infiltration. Water penetrates soil surface and moves underground.

44. Which organisms perform most biological nitrogen fixation in ecosystems?

    Nitrogen-fixing bacteria (often in root nodules). Specialized bacteria convert $N_2$ gas into ammonia compounds.

45. What carbon-cycle process is indicated by increased soil nutrients after leaf litter decays?

    Decomposition and mineralization. Dead organic matter breaks down, releasing carbon and nutrients.

46. Which process releases phosphate from rocks into soil and water?

    Weathering and erosion. Physical breakdown of rocks releases phosphate into ecosystems.

47. Which process moves carbon from organisms to the atmosphere without combustion?

    Cellular respiration. All living organisms release $CO_2$ during metabolism.

48. What nitrogen-cycle process moves nitrate from soil into plant tissues?

    Assimilation. Plants absorb and incorporate nitrogen into their tissues.

49. What is the primary evidence that photosynthesis removes $CO_2$ from the atmosphere?

    Atmospheric $CO_2$ decreases during daylight in vegetated areas. Plants consume $CO_2$ faster during active photosynthesis.

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