The natural ecosystem on Hawadax Island in Alaska was disrupted in the 1780s when brown rats, Rattus norvegicus, swam to the island from a sinking ship and then rapidly increased their population size. The rats occupied a new niche on the island as predators. The rats ate the eggs and chicks of birds such as the black oystercatcher, Haematopus bachmani, and the glaucous-winged gull, Larus glaucescens. These birds make nests, lay eggs and rear their chicks on the beaches of the island.

1. (a)(i)Define the terms ecosystem and niche. ecosystem[2]
2. (a)(ii)Define the terms ecosystem and niche. niche[1]
3. (b)(i)Conservation ecologists carried out a project to try to restore the natural ecosystem of Hawadax Island. In 2008, they removed all rats from the island. Before removing the rats, the ecologists measured the abundance of birds, invertebrates and seaweeds on eight of the island's beaches. Seaweeds are large algae that grow attached to rocks on the beach. The ecologists repeated these measurements in 2013 and in 2019, so that they could calculate the percentage change in abundance from 2008. To measure the abundance of invertebrates and seaweeds, the ecologists used this method: • They laid 30 m tapes from high-tide mark to low-tide mark on the beach. • They placed quadrats at 5 metre intervals next to the tapes. • They took a photograph of each quadrat. • They analysed the photographs to calculate the percentage cover of seaweeds and the percentage cover of invertebrates such as mussels and sea snails. State the name of the sampling technique used.[1]
4. (b)(ii)Biodiversity can be assessed at a number of different levels. Identify the levels of biodiversity: • that were assessed by this sampling technique • that were not assessed by this sampling technique.[3]
5. (c)(i)Table 2.1 shows 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 that has increased in abundance.[1]
6. (c)(ii)Seaweeds were once thought to be plants but are now classified in the kingdom Protoctista. Outline the features of the kingdom Protoctista that are shown by seaweeds.[2]
7. (d)To evaluate the success of the Hawadax Island restoration project, the ecologists obtained data from other islands near to Hadawax Island. • Some islands had never been occupied by rats (rat-free islands) and had a healthy ecosystem. • Some islands were still occupied by 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. With reference to Table 2.1 and Table 2.2, suggest and explain how removing rats has restored the ecosystem on Hawadax Island.[4]