Biology 9700 · AS & A Level · Biodiversity

Biodiversity — practice question

During the 1780s, the normal ecosystem on Hawadax Island in Alaska was thrown off balance when brown rats, Rattus norvegicus, swam ashore from a sinking ship and then their population expanded rapidly. On the island, the rats occupied a new niche as predators. They consumed the eggs and chicks of birds including the black oystercatcher, Haematopus bachmani, and the glaucous-winged gull, Larus glaucescens. These birds nest, lay eggs and raise their chicks on the island beaches.
(a(i))[2]

Define what is meant by an ecosystem.

(a(ii))[1]

Define what is meant by a niche.

(b(i))[1]

State the name of the sampling method used.

(b(ii))[3]

Biodiversity may be measured at several different levels. Identify the levels of biodiversity that this sampling technique measured and the levels that it did not measure.

(c(i))[1]

Table 2.1 gives the percentage change in abundance of some of the seaweeds, invertebrates and birds found on the beaches of Hawadax Island. Use Table 2.1 to state the genus name of one organism whose abundance has increased.

(c(ii))[2]

Seaweeds were formerly regarded as plants but are now placed in the kingdom Protoctista. Outline the characteristics of the kingdom Protoctista that are shown by seaweeds.

(d)[4]

To evaluate how successful the Hawadax Island restoration project was, the ecologists collected data from other islands close to Hawadax Island. Some islands had never had rats (rat-free islands) and had a healthy ecosystem. Other islands still contained rats (rat-occupied islands) and had a disrupted ecosystem. Table 2.2 shows the percentage differences in the abundance of organisms in rat-free islands compared with rat-occupied islands. Using Table 2.1 and Table 2.2, suggest and explain how the removal of rats has restored the ecosystem on Hawadax Island.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: a community made up of different organisms/populations/species together with their interactions

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