Ecosystems, Food Chains and Biodiversity — O/L Science

How do I practise Ecosystems, Food Chains and Biodiversity?

1 question with a worked solution · 6 marks

1. 2020 · Paper II · 6 marks
   Question 11 supplies a table of three organism populations in a freshwater pond across three years. It asks you to suggest one reason for the fall in the producer population, to explain the relationship the data shows between the two consumer populations, and to define biodiversity with one reason it matters.
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   (i) Reduced light penetration (eutrophication / pollution reducing photosynthesis); or increased grazing by small fish (accept any valid environmental cause). (ii) As large fish decrease (fewer predators), small fish numbers could initially increase — but the data shows both decline together, suggesting a common stressor (e.g. habitat loss / pollution) or time lag in predator-prey dynamics. (iii) Biodiversity = the variety of living organisms in an ecosystem. It is important because it maintains ecosystem stability and provides food, medicines, and ecosystem services.
   Source: Department of Examinations, Sri Lanka — G.C.E. O/L Science 2020, Paper II, Question 11 · https://doenets.lk/pastpapers

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