A4.2 Conservation of biodiversity. Practice questions with markscheme.

• C: non-native species make up 0 % of the species in the forest, about 6 % on farmland (2 of 32), about 17 % in the suburbs (5 of 29) and about 33 % in the city centre (4 of 12); A fails because the suburbs have more non-native species (5) than the city centre (4); B fails because the total number of species falls from 42 to 12; C fails because 18 native species are lost but only 5 non-native species are gained;

• A: 'splitters' recognize more species than 'lumpers' from the same observations, because deciding how much variation separates species involves judgement (NOS); A fails because there is no single correct number independent of the criteria used; B fails because preserved specimens do not evolve; C fails because both examined the same collection;

• A: deciding which species matters more involves ethical, cultural and economic priorities, so it has to be debated; A, B and D are claims that can be tested with evidence (dating of divergence, population surveys, assessment against published criteria);

• B: seeds are stored dried and cold so they remain viable for decades; this ex situ germplasm storage insures against loss of species and crop varieties (genetic diversity), allowing future reintroduction/breeding;

• D: peer review and publication of the methods and data allow other scientists to check how the evidence was collected and analysed, and to repeat the surveys; A fails because repetition in the media does not check the evidence; B fails because the reputation of the author is not a check on the method; D fails because data that cannot be seen cannot be checked, however large the data set;

• (a) [3 max]
  • in both cases humans hunted the birds directly and destroyed their habitat;
  • both species were easy to kill: the dodo was flightless and unafraid of people, whereas passenger pigeons nested and roosted in huge, predictable colonies where many could be killed at once, OWTTE;
  • the dodo was also affected by introduced species (pigs, rats, monkeys) eating eggs and young, whereas the passenger pigeon was not;
  • the passenger pigeon was killed on an industrial scale for city markets, with flocks located by telegraph and the birds shipped by rail, whereas the dodo was taken by small numbers of sailors and settlers;

  Award marks only for explicitly comparative statements.

• (b) [2 max]
  • the species bred only in enormous colonies, so once numbers fell below a threshold breeding failed (small flocks could not raise young);
  • harvesting removed adults faster than the low reproductive rate (one egg per pair) could replace them;
  • loss of the mature forest that supplied its food acted at the same time as hunting, so numbers collapsed rapidly, OWTTE;

• some individuals are likely to carry alleles that let them survive a new disease / changed conditions, so the species can persist/adapt;
• low diversity increases inbreeding / vulnerability (a single threat can affect all individuals), OWTTE;

Beyond this subtopic. Award if given; the marks above can be earned without it.

• D4.1 genetic diversity provides the variation on which natural selection acts;

• (a) [1]
  • 51 % / 51.0 %;

  Working: 24.5 / 48.0 × 100. Accept 51–51.1 %.

• (b) [2 max]
  • as the area of oil palm increased, the area of forest decreased / negative correlation;
  • the increase in oil palm (15.3 thousand km²) is smaller than the loss of forest (23.5 thousand km²), so not all the lost forest became oil palm, OWTTE;
  • the rate of forest loss was greatest between 1990 and 2005 (9.5 thousand km² lost), when oil palm also expanded rapidly (by 6.3 thousand km²), OWTTE;
• (c) [1 max]
  • logging for timber / fires / clearance for other crops or settlements / road and mine building;
  • drought-related fires made worse by logging, OWTTE;

  Mark the first cause only.

• (d) [2 max]
  • the population and the forest loss are correlated, but correlation does not show causation;
  • population growth is an overarching / indirect cause acting through demand for land, food and income, OWTTE;
  • much of the oil palm is grown for export, so demand from outside the region (not the local population) may be the main driver;
• (e) [2 max]
  • species diversity: many species of the forest are lost because the plantation is a monoculture / supports few species;
  • genetic diversity: surviving populations are smaller (and fragmented), so alleles are lost;
  • ecosystem diversity: the forest ecosystem (type) is lost from the region and replaced by a uniform plantation, OWTTE;

  Content pivot. Award a mark only when the level is named and linked to the forest loss.