IB Biology HL A4.2.2 Current Vs Past Biodiversity Questions

Practise explaining why current species diversity may exceed past estimates while fossil gaps and incomplete records make comparisons uncertain.

Exam points

State the estimate of about 9 million species and note that many remain undescribed.
Use fossils and radiometric dating as incomplete evidence of past biodiversity.
Compare current and past species diversity cautiously because fossil gaps make the result uncertain.

[Maximum number: 2]

Knowledge of deep-water fish is important for fisheries and marine reserve management. Scientists analysed data from scientific trawls made from 1977 to 1989 (early period) and from 1997 to 2002 (late period). These were at depths from 800 m to 4800 m in the Porcupine Seabight and Porcupine Abyssal Plain area southwest of Ireland. The graphs represent the abundance of fish and the number of species for each of these trawls.

Figure for Question IB Biology HL A4.2.2 Current Vs Past Biodiversity Questions question 1 — IB Biology HL

Discuss the evidence in these data for a decline in the biodiversity of fish between the early period and the late period.

no evidence that there are fewer species;
difficult to compare as more trawls in the early period / early period of longer duration than late period;
diversity may have increased from (around) $2000\mathrm{m}$ to $4000\mathrm{m}$ / outliers for greater species diversity are all late period;
not enough details about time of year/duration of trawls.

Accept any other valid argument.
Do not accept answers stating only "not enough data".

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IB Biology HL A4.2.2 Current Vs Past Biodiversity Questions question 1