A-LevelBiologyBiodiversity and conservation9700/43 · May/June 2025 · Q108 Marks

The golden poison dart frog, Phyllobates terribilis, lives in the Colombian rainforest ecosystem. Fig. 10.1 shows golden poison dart frogs. [Figure 10.1]

(a)Define the term ecosystem.[3]
(b)(i)One way of estimating the size of a population of golden poison dart frogs is to use the mark-release-recapture method. Suggest the assumptions that must be made for the mark-release-recapture method to be valid.[3]
(b)(ii)A first sample of 27 golden poison dart frogs was captured, marked and released. When a second sample of 33 frogs was captured, 13 had marks on them. Use the Lincoln index to estimate the population size of the frogs. estimate of population size = (n₁ x n₂) / m₂ n₁ = number of individuals captured in first sample n₂ = number of individuals (both marked and unmarked) captured in second sample m₂ = number of marked individuals recaptured in second sample answer [2]

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Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

[3] 10(a) any three from: 1 self-contained unit ; 2 community of organisms ; A idea of several species 3 biotic and abiotic factors / named; 4 ref. to interaction; 5 AVP; e.g. flow of energy and cycling of minerals / nutrients
[3] 10(b)(i) any three from: 1 (frogs are) mobile; 2 marking, not harmful / cannot be removed ; 3 (sufficient time for) marked individuals to mix with rest of population; 4 no, births / deaths or no, immigration / emigration / migration or constant population size;
[2] 10(b)(ii) 69 ;; must be a whole number, one mark only if not whole number 27 x 33 13 credit working if wrong answer

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