Biodiversity and populations — Question 10

10a)

37 000

• identifies number of seal pups in 1800 [1 mark]

10b)

$\mathrm{P}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\,\mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h}=15\,000-2000\,$

$=13\,000$

• determines population growth [1 mark]

$\mathrm{P}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\,\mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h}=(\mathrm{b}\mathrm{i}\mathrm{r}\mathrm{t}\mathrm{h}\mathrm{s}+\mathrm{i}\mathrm{m}\mathrm{m}\mathrm{i}\mathrm{g}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n})-(\mathrm{d}\mathrm{e}\mathrm{a}\mathrm{t}\mathrm{h}\mathrm{s}+\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{g}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n})$

$13\,000=(\mathrm{B}+\mathrm{I})-(\mathrm{D}+\mathrm{E})$

$13\,000=(\mathrm{B}+1500)-(1\,217\,900+600)\,$

$13\,000=\mathrm{B}-1\,217\,000$

$13\,000+1\,217\,000=1\,230\,000$

• determines the number of births [1 mark]

10c)

The fur seal population hasn’t reached carrying capacity. The number of seal pups has been increasing since ~1890 (except 1960–1970) and shows no signs of plateauing. This suggests the ecosystem has sufficient resources to support a growing population.

• infers the fur seal population has not reached carrying capacity [1 mark]

• justifies response using appropriate evidence from the graph [1 mark]

10d)

As krill are a main food source for fur seals, a 40% decrease in the krill population would mean insufficient food to support the current population, reducing carrying capacity.

• predicts the carrying capacity of fur seals would decrease [1 mark]

• explains reasoning [1 mark]

10e)

$\mathrm{N}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\,\mathrm{o}\mathrm{f}\,\mathrm{s}\mathrm{e}\mathrm{a}\mathrm{l}\,\mathrm{p}\mathrm{u}\mathrm{p}\mathrm{s}\,\mathrm{i}\mathrm{n}\,2025=\frac{(230\times 250)}{2}$

$=28\,750$

• calculates number of seal pups in 2025 [1 mark]

$\mathrm{G}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h}\,\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{e}=\frac{(28\,750-15\,000)}{15\,000}$

$=92\%$

• determines growth rate [1 mark]

$\mathrm{A}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{g}\mathrm{e}\,\mathrm{a}\mathrm{n}\mathrm{n}\mathrm{u}\mathrm{a}\mathrm{l}\,\mathrm{p}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\,\mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h}\,\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{e}=\frac{92\%}{25\,\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}\mathrm{s}}$

$=3.7\%\,/\,\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}$

• determines average annual population growth rate [1 mark]