Noesis
Level 2 — RecallConservation & Human Impact

Conservation & Human Impact

⏱ 30 minutes40 marksprintable — key stays hidden on paper

Level 2 (Recall & Standard Problems)

Time limit: 30 minutes Total marks: 40

Instructions: Answer all questions. Marks are shown in brackets. Write clearly and use biological terms accurately.

Q1. Define biodiversity and state two major human-caused reasons for its loss. (4 marks)

Q2. Habitat fragmentation breaks a large habitat into smaller patches. (a) State what is meant by the "edge effect." (2 marks) (b) Explain two ways fragmentation reduces the survival of animal populations. (4 marks)

Q3. Distinguish between bioaccumulation and biomagnification. (4 marks)

Q4. A pesticide (DDT) is present in water at 0.0010.001 ppm. Along a food chain the concentration factor is ×25\times 25 at each trophic level. (a) Calculate the DDT concentration in a fish that is three trophic levels above the water. (3 marks) (b) State one reason top predators are most affected by biomagnification. (1 mark)

Q5. Describe the greenhouse effect and name two greenhouse gases. (4 marks)

Q6. Explain the process of eutrophication in a lake, in correct sequence. (5 marks)

Q7. (a) Which gas is mainly responsible for ozone depletion in the stratosphere? (1 mark) (b) State two harmful effects of increased UV radiation reaching Earth's surface. (2 marks)

Q8. Explain two ways an invasive species can harm a native ecosystem. (4 marks)

Q9. (a) Distinguish between in-situ and ex-situ conservation, giving one example of each. (4 marks) (b) Define sustainable resource management. (2 marks)

Q10. State one conservation strategy that could reduce each of the following, and briefly justify: (3 marks) (i) greenhouse gas emissions (ii) overfishing (iii) habitat loss

End of paper

Answer keyMark scheme & solutions

Q1. (4 marks)

  • Biodiversity = the variety of living organisms (species, genetic and ecosystem diversity) in a given area/on Earth. (2)
  • Any two causes (1 each): deforestation/habitat destruction; pollution; overexploitation/overhunting; climate change; invasive species; agriculture/land-use change. (2) Why: Definition tests recall of the concept's three levels; causes are standard anthropogenic drivers.

Q2. (6 marks) (a) Edge effect = altered conditions (light, temperature, wind, humidity) at the boundary of a fragment, differing from the interior, favouring edge species and stressing interior species. (2) (b) Any two (2 each): smaller populations → reduced genetic diversity/inbreeding; barriers prevent migration and gene flow; reduced food/territory area; isolation prevents recolonisation after local extinction; increased predation/human access at edges. (4)

Q3. (4 marks)

  • Bioaccumulation = build-up of a toxin in a single organism over time, as intake exceeds excretion. (2)
  • Biomagnification = increase in toxin concentration at each successive trophic level up a food chain. (2)

Q4. (4 marks) (a) Concentration =0.001×253= 0.001 \times 25^3 =0.001×15625=15.625= 0.001 \times 15625 = 15.625 ppm. (3) (method 2, answer 1) (b) Top predators eat many contaminated prey / accumulate toxins from all lower levels, so concentration is highest. (1)

Q5. (4 marks)

  • Greenhouse effect: greenhouse gases in the atmosphere absorb and re-radiate outgoing infrared (long-wave) radiation from Earth's surface, trapping heat and warming the planet. (2)
  • Two gases (1 each): carbon dioxide, methane, water vapour, nitrous oxide, CFCs. (2)

Q6. (5 marks) (1 mark per correct sequence step)

  1. Nutrient runoff (nitrates/phosphates from fertilisers/sewage) enters the lake.
  2. Nutrients cause rapid algal growth / algal bloom.
  3. Bloom blocks light; plants/algae below die.
  4. Decomposers (bacteria) break down dead matter and multiply.
  5. Decomposition depletes dissolved oxygen → fish and aquatic organisms die (hypoxia).

Q7. (3 marks) (a) Chlorofluorocarbons (CFCs) / chlorine. (1) (b) Any two (1 each): skin cancer; cataracts/eye damage; sunburn; weakened immune system; damage to plants/phytoplankton. (2)

Q8. (4 marks) Any two (2 each): outcompete native species for food/space/resources; prey on natives lacking defences; introduce new diseases/parasites; no natural predators so population explodes; hybridise with/reduce native genetic diversity.

Q9. (6 marks) (a) In-situ = conservation within the natural habitat (e.g., national park/nature reserve). (2) Ex-situ = conservation outside the natural habitat (e.g., zoo, botanical garden, seed bank). (2) (b) Sustainable resource management = using resources at a rate that meets present needs without depleting them, so they remain available for future generations. (2)

Q10. (3 marks) (1 each: strategy + justification) (i) Switch to renewable energy / reforestation → reduces/absorbs CO2CO_2. (ii) Fishing quotas / no-take zones → allow stocks to reproduce and recover. (iii) Protected areas / wildlife corridors → preserve and reconnect habitat.

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  {"claim":"Q4a: DDT concentration = 0.001 * 25**3 = 15.625 ppm","code":"conc = 0.001 * 25**3\nresult = (conc == 15.625)"},
  {"claim":"Q4a: 25**3 equals 15625","code":"result = (25**3 == 15625)"},
  {"claim":"Q1: total marks add to 40","code":"marks = [4,6,4,4,4,5,3,4,6,3]\nresult = (sum(marks) == 40)"}
]