Analyze Ecosystem Change and Recovery - Biology

1. What is resistance in an ecosystem?

   Ability to remain relatively unchanged when disturbed. Stable systems show high resistance to environmental changes.

2. Which evidence best indicates negative effects of habitat fragmentation?

   Reduced gene flow and increased local extinctions in isolated patches. Small patches cannot support viable populations long-term.

3. Which study design best supports a causal claim about ecosystem recovery actions?

   Controlled comparison with treatment and control sites over time. Controls eliminate alternative explanations for observed changes.

4. Which population pattern best indicates overshoot of carrying capacity ($K$)?

   Rapid increase followed by sharp decline (crash). Population exceeded $K$ then crashed due to resource depletion.

5. Which observation indicates improving stream water quality after cleanup?

   Increase in pollution-sensitive macroinvertebrates (for example, mayflies). Sensitive species return when water quality improves sufficiently.

6. What is hypoxia in aquatic ecosystems?

   Low dissolved oxygen levels that stress or kill aquatic organisms. Results from algal decomposition consuming dissolved oxygen rapidly.

7. What is bioremediation?

   Use of organisms (often microbes) to remove or detoxify pollutants. Bacteria can break down oil spills and other contaminants.

8. Which evidence most directly indicates eutrophication in a lake?

   High nitrate/phosphate with low dissolved oxygen and algal blooms. Nutrients fuel algae; decomposition depletes oxygen levels.

9. Which evidence best indicates successful reforestation after clear-cutting?

   Increasing canopy cover with native tree recruitment and soil stabilization. Shows forest structure and function are being restored successfully.

10. Which observation is strongest evidence of climate-driven range shifts?

    Species distributions moving poleward or to higher elevations over decades. Species track suitable temperature zones as climate warms.

11. Which evidence most strongly supports that a new species is invasive?

    Rapid spread with decline of native species and altered community structure. Shows ecosystem disruption and competitive displacement patterns.

12. What is a disturbance in ecosystem ecology?

    An event that disrupts community structure and resource availability. Can be natural (fire, flood) or human-caused (logging, pollution).

13. What is resilience in an ecosystem?

    Ability to recover structure and function after disturbance. Measured by speed and completeness of recovery processes.

14. What is a bioindicator used to assess water quality in streams?

    Macroinvertebrate community composition (sensitive vs tolerant taxa). Different species have varying tolerance to pollution levels.

15. What is bioaccumulation?

    Toxin buildup within an organism over time. Occurs within individual organisms, unlike biomagnification across levels.

16. What evidence most strongly indicates secondary succession after a fire?

    Rapid regrowth from surviving roots and existing soil nutrients. Shows secondary succession utilizing pre-existing soil resources.

17. Which observation is best evidence of biomagnification?

    Top predators show highest concentrations of persistent pollutants. Demonstrates toxin concentration increasing up food chains.

18. Identify the independent variable in a study testing fertilizer runoff effects on algae.

    Fertilizer (nutrient) input level. The manipulated variable that researchers control in the experiment.

19. Identify the dependent variable in a study testing fertilizer runoff effects on algae.

    Algal growth (for example, chlorophyll concentration). The measured response variable that depends on fertilizer input.

20. What is the relationship between GPP, respiration, and NPP?

    $NPP = GPP - R$. NPP is energy remaining after plants use some for respiration.

21. What is eutrophication?

    Nutrient enrichment causing algal blooms and oxygen depletion. Excessive nutrients stimulate rapid algae growth and decay.

22. What is ecological succession?

    Directional community change over time after disturbance or new habitat. Involves predictable stages from pioneer to climax species.

23. What is a keystone species?

    Species with disproportionately large ecosystem effects relative to abundance. Removal causes cascading effects throughout the entire ecosystem.

24. If $GPP = 1200$ and $R = 800$, what is $NPP$?

    $400$. Subtract respiration from gross primary productivity: $1200 - 800$.

25. What is restoration ecology?

    Science of assisting recovery of degraded, damaged, or destroyed ecosystems. Focuses on returning ecosystems to functional, self-sustaining states.

26. What is correlation in ecological data analysis?

    Statistical association between variables without proving causation. Shows relationship but does not establish cause-and-effect mechanisms.

27. What is a baseline in environmental monitoring?

    Reference condition used to compare changes over time. Establishes starting point for measuring ecosystem changes accurately.

28. What evidence suggests an ecosystem is recovering after a disturbance?

    Increasing native species richness and stable nutrient cycling. Indicates restoration of ecological structure and function.

29. What is biodiversity (species richness) in a community?

    Number of different species present in a defined area. Higher richness generally indicates healthier, more stable ecosystems.

30. What is phytoremediation?

    Use of plants to absorb, immobilize, or degrade contaminants. Plants can extract heavy metals and other toxins from soil.

31. What is carrying capacity ($K$)?

    Maximum population size an environment can sustainably support. Determined by resource availability and environmental constraints.

32. If $NPP = 500$ and $R = 300$, what is $GPP$?

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

33. If a forest changes from absorbing $2$ to emitting $1$ unit of carbon, what change occurred?

    It shifted from carbon sink to carbon source. Net carbon flux reversed from negative to positive values.

34. What is a trophic cascade?

    Indirect effects across trophic levels triggered by predator changes. Classic example: wolves controlling deer populations affects vegetation.

35. Which evidence best indicates ocean acidification is increasing at a reef site?

    Decreasing pH with reduced calcification rates in corals or shellfish. Ocean absorbs atmospheric CO₂, forming carbonic acid that lowers pH.

36. What is a limiting factor?

    Resource or condition that restricts population growth or distribution. Could be food, water, space, or any essential resource.

37. What is a pioneer species?

    Early colonizer that tolerates harsh conditions and initiates soil formation. Examples include lichens on rock and grasses after disturbance.

38. Which statement correctly distinguishes correlation from causation in ecosystem change?

    Correlation shows association; causation requires evidence of mechanism and control. Experimental design and controls help establish causal relationships.

39. What is an invasive species?

    Non-native species that spreads and causes ecological or economic harm. Lacks natural predators or competitors in new environment.

40. What is species evenness?

    How evenly individuals are distributed among species. High evenness means no single species dominates the community.

41. What is habitat fragmentation?

    Breaking continuous habitat into smaller, isolated patches. Creates edge effects and isolates populations from each other.

42. What is the greenhouse effect in the context of ecosystem change?

    Atmospheric gases trap heat, increasing Earth surface temperature. CO₂ and other greenhouse gases absorb and re-emit infrared radiation.

43. What evidence most strongly indicates primary succession on new rock?

    Lichens and mosses colonizing bare rock with minimal soil. These organisms break down rock to create the first soil.

44. What is secondary succession?

    Succession after disturbance where soil and seed bank remain. Faster than primary succession due to existing soil infrastructure.

45. Which measurement is a direct indicator of primary productivity in an ecosystem?

    Net primary productivity (NPP) rate. Measures energy available to support higher trophic levels.

46. What is biomagnification?

    Increase in toxin concentration at higher trophic levels. Fat-soluble toxins accumulate through predator-prey relationships.

47. What is primary succession?

    Succession beginning on bare substrate with no soil present. Requires soil formation before plant establishment can occur.

48. What is a carbon sink?

    Reservoir that absorbs more carbon than it releases (for example, forests). Photosynthesis removes CO₂ from atmosphere and stores it long-term.

49. What is an indicator species?

    Species whose presence or absence reflects specific environmental conditions. Used for monitoring ecosystem health and environmental quality.

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