Interpret Matter and Energy Cycles - Biology

1. What is ammonification (mineralization) in the nitrogen cycle?

   Decomposers convert organic nitrogen to $NH_4^+$. Bacterial decomposition releases ammonia from dead organic nitrogen compounds.

2. State the equation that relates GPP, respiration, and NPP.

   $NPP = GPP - R$. Net productivity equals gross productivity minus respiratory energy losses.

3. What is the main pathway by which carbon enters food webs?

   Producers fixing $CO_2$ during photosynthesis. Primary producers capture atmospheric $CO_2$ and make it available to consumers.

4. Identify the missing coefficient: $\_\ CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$.

   $6$. Balance carbon atoms: six $CO_2$ molecules needed for one glucose molecule.

5. What is the balanced overall equation for aerobic cellular respiration?

   $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$. Glucose is oxidized using oxygen to release energy, water, and $CO_2$.

6. Calculate $NPP$ if $GPP = 2000$ and $R = 800$ (same units).

   $1200$. Subtract respiration from gross productivity: $2000 - 800 = 1200$.

7. What is precipitation in the water cycle?

   Water falling from clouds as rain, snow, sleet, or hail. Gravity pulls condensed water droplets from clouds to Earth's surface.

8. Which organisms perform most biological nitrogen fixation?

   Nitrogen-fixing bacteria (free-living or symbiotic). Only certain prokaryotes possess the enzyme nitrogenase for this conversion.

9. If producers store $10{,}000\ \text{kJ}$, what energy is expected in primary consumers at $10\%$ transfer?

   $1000\ \text{kJ}$. Apply 10% efficiency rule: $10{,}000 \times 0.10 = 1000$ kJ transferred.

10. What is nitrification in the nitrogen cycle?

    Conversion of $NH_4^+$ to $NO_2^-$ and then to $NO_3^-$. Two-step bacterial oxidation process that produces plant-usable nitrate ions.

11. What does arrow thickness commonly indicate in cycle diagrams?

    Relative magnitude of the flux or transfer rate. Thicker arrows represent faster or larger magnitude transfers between pools.

12. What do arrows usually represent in matter-cycle diagrams (for example, carbon cycle)?

    Direction of matter transfer between reservoirs. Shows movement of matter from one storage pool to another in the cycle.

13. What do arrows usually represent in energy-flow diagrams (for example, food webs)?

    Direction of energy transfer between trophic levels. Indicates energy transfer from one feeding level to the next higher level.

14. What is the key reason phosphorus cycles lack a major atmospheric component?

    Phosphorus does not have a common gaseous form. Phosphorus compounds are not volatile, limiting atmospheric transport mechanisms.

15. What term describes organisms that break down dead matter and recycle nutrients?

    Decomposers (for example, fungi and bacteria). Essential organisms that return nutrients from dead matter to the ecosystem.

16. What is carbon fixation in the carbon cycle context?

    Conversion of inorganic $CO_2$ into organic molecules. Process that incorporates atmospheric $CO_2$ into organic biomolecules.

17. Choose the word that correctly completes: Matter is _____ in ecosystems; energy is _____.

    recycled; flows one-way and dissipates as heat. Matter cycles through ecosystems while energy flows through and exits as heat.

18. Which carbon reservoir is typically the largest on Earth?

    Sedimentary rocks and marine sediments. Geological formations store carbon for millions of years as calcium carbonate.

19. What form does most untransferred energy take as it leaves a trophic level?

    Heat released during metabolism and respiration. Energy is lost as thermal energy during metabolic processes at each level.

20. If secondary consumers contain $50\ \text{kJ}$ and transfer is $10\%$, what was primary consumer energy?

    $500\ \text{kJ}$. Divide by efficiency to find source: $50 \div 0.10 = 500$ kJ required.

21. What does a box or pool in a cycle diagram usually represent?

    A reservoir where matter is stored. Represents locations where matter accumulates and is temporarily stored.

22. What process releases phosphate from rocks into soil and water?

    Weathering and erosion. Physical and chemical breakdown of rocks releases phosphate into the environment.

23. What is the largest nitrogen reservoir on Earth in nitrogen-cycle diagrams?

    The atmosphere as $N_2$. Vast atmospheric pool contains about 78% nitrogen as unreactive dinitrogen gas.

24. What term describes organisms that obtain energy by consuming other organisms?

    Consumers (heterotrophs). Other-feeding organisms that acquire energy by eating producers or other consumers.

25. What is nitrogen fixation in the nitrogen cycle?

    Conversion of $N_2$ gas into ammonia or ammonium. Specialized bacteria convert unusable $N_2$ gas into biologically available forms.

26. What is evaporation in the water cycle?

    Liquid water changing to water vapor. Heat energy causes water molecules to transition from liquid to gas phase.

27. Which nitrogen form is most directly used by many plants in diagrams?

    $NO_3^-$ (nitrate). Most plants preferentially absorb this highly oxidized, soluble nitrogen form.

28. What is the primary biological process that releases $CO_2$ to the atmosphere?

    Cellular respiration. Organisms break down glucose using oxygen, releasing carbon dioxide as waste.

29. What is condensation in the water cycle?

    Water vapor changing to liquid droplets (cloud formation). Cooling water vapor forms tiny droplets that create visible clouds.

30. In phosphorus-cycle diagrams, what is sedimentation?

    Phosphate settling and forming sediments/rock over time. Phosphate removal from water through particle settling forms future rock deposits.

31. What is the difference between a reservoir and a flux in a matter-cycle diagram?

    Reservoir stores matter; flux is the transfer between stores. Static storage versus dynamic movement distinguishes these diagram components.

32. What is the reservoir for groundwater in water-cycle diagrams?

    Aquifers (water stored in permeable rock and soil). Underground water storage in porous rock and soil formations.

33. What is the law of conservation of matter as used in biogeochemical cycles?

    Atoms are rearranged; total matter is conserved. Fundamental principle that atoms cannot be created or destroyed in chemical reactions.

34. What is the primary biological process that removes $CO_2$ from the atmosphere?

    Photosynthesis. Plants use light energy to convert atmospheric carbon dioxide into glucose.

35. What is the balanced overall equation for photosynthesis?

    $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$. Light energy converts six molecules each of $CO_2$ and water into glucose.

36. What is transpiration in the water cycle?

    Water vapor loss from plant leaves. Plants release water vapor through leaf pores during gas exchange.

37. What is denitrification in the nitrogen cycle?

    Conversion of $NO_3^-$ to $N_2$ gas by bacteria. Anaerobic bacteria reduce nitrate back to gaseous nitrogen, completing the cycle.

38. What term describes organisms that convert light energy to chemical energy?

    Producers (autotrophs). Self-feeding organisms that capture energy and convert it to biomass.

39. Which process moves carbon from dead organisms into long-term soil carbon pools?

    Decomposition by decomposers. Microorganisms break down dead tissue, converting it to stable soil carbon.

40. What is the law of conservation of energy as used in ecosystem energy diagrams?

    Energy is transformed, not created or destroyed. First law of thermodynamics applied to ecosystem energy flow and transformations.

41. Identify the missing coefficient: $C_6H_{12}O_6 + \_\ O_2 \rightarrow 6CO_2 + 6H_2O$.

    $6$. Balance oxygen atoms: six $O_2$ molecules required to oxidize one glucose.

42. What is runoff in the water cycle?

    Surface water flowing to streams, rivers, lakes, or oceans. Gravity moves surface water downhill toward larger water bodies.

43. What does net primary productivity (NPP) represent in ecosystem energy equations?

    Energy stored as biomass after producer respiration. Energy remaining in plant biomass after subtracting metabolic energy costs.

44. What is the primary energy source for most ecosystems in energy-flow diagrams?

    Sunlight. Solar radiation provides virtually all energy input for Earth's ecosystems.

45. What is the typical ecological efficiency between trophic levels in energy pyramids?

    About $10\%$ transfer to the next trophic level. Rule of thumb for energy transfer efficiency in food chains.

46. What does the $R$ term represent in $NPP = GPP - R$?

    Producer respiration energy use. Represents energy consumed by producer cellular respiration and metabolism.

47. What is infiltration in the water cycle?

    Water soaking into soil and entering groundwater. Water penetrates soil pores and moves downward through permeable layers.

48. Identify the correct direction of energy flow in a food chain diagram.

    From resource (prey/producer) to consumer (predator). Energy flows upward from energy source to energy consumer in the chain.

49. What is combustion in the carbon cycle?

    Burning biomass or fossil fuels releasing $CO_2$. Chemical reaction that rapidly oxidizes carbon compounds, releasing stored carbon.

50. Calculate $GPP$ if $NPP = 500$ and $R = 300$ (same units).

    $800$. Add respiration to net productivity: $500 + 300 = 800$.

51. What is assimilation in the nitrogen cycle?

    Plant uptake of $NO_3^-$ or $NH_4^+$ into organic molecules. Plants absorb inorganic nitrogen and incorporate it into proteins and nucleic acids.

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