The polar bear, $\textit{Ursus maritimus}$, is found in the Arctic regions of the USA, Canada, Norway and Russia. Polar bears travel over the Arctic ice sheet to catch prey such as seals. Fig. 1.1 shows a polar bear. The area covered by the Arctic ice sheet changes during the year. Fig. 1.2 presents how the extent of the Arctic ice sheet varies from July to November in 1979 and 2009.
(a)[2]
Calculate the percentage decrease in the area covered by the ice sheet from 1979 to 2009 for September. Give your answer to the nearest whole number. Show your working.
(b)[3]
In 2008 the government of the USA listed $\textit{U. maritimus}$ as an endangered species because it is threatened with extinction. Suggest why $\textit{U. maritimus}$ has become endangered.
(c)[3]
$\textit{U. maritimus}$ is a eukaryotic organism. Helpful bacteria, which are prokaryotic cells, live in the gut of $\textit{U. maritimus}$. State three differences between the cells of $\textit{U. maritimus}$ and its gut bacteria.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “36 ” …