B4.1 Adaptation to environment. Practice questions with markscheme.

• A: habitat = the place, with its characteristic abiotic conditions, where an organism, population or community normally lives; the role it plays there is its niche;

• D: letting body temperature rise by about 6 °C through the day stores heat that would otherwise have to be removed by evaporating sweat, so water is saved; the stored heat is lost without using water to the cooler night air, and a body temperature closer to the air temperature also cuts heat gain from the air; sweating costs water (A), the camel still regulates its temperature but starts each day cooler (C), and a 6 °C range takes enzymes away from any single optimum (D);

• A: for a given temperature and rainfall pattern the graph predicts the one natural ecosystem type likely to develop, here temperate forest, which covered most of Ireland before farming; clearance, grazing and cultivation keep the land as grassland, and abandoned land would return towards forest; the mild climate (A), the temperature (B) and the present climate (C) all suit temperate forest, as the graph shows;

• C: zonation on shores reflects tolerance limits interacting with competition/predation (as Connell demonstrated);

• B: added carbon dioxide forms carbonic acid whose hydrogen ions remove carbonate ions from solution, reducing the material available for coral skeletons; chlorophyll is not denatured (it is a pigment, not a protein) and the algae are not killed directly by a small pH change (B), pH does not change water clarity (C), and salinity is set by dissolved salts, which are not removed by acidification (D);

• a semi-natural habitat has been influenced by humans (e.g. by past management / felling) but is dominated by wild species, whereas a park is dominated by planted / cultivated species, OWTTE;
• in the park, where plants grow is decided by people (planting, mowing, weeding, watering), so distribution would not reflect the plant's tolerance of abiotic conditions;
• in the woodland the moss has established itself where conditions allow, so any correlation between its distribution and light intensity is more likely to reflect a real (causal) relationship, OWTTE;
• management of the park (e.g. mowing, fertilizer, irrigation) would change other variables at the same time as light, confounding the investigation;

Accept any three. Do not accept "the woodland has more moss" without a reason.

• aerial/pneumatophore roots obtain oxygen (mud is anoxic/waterlogged);
• salt is excluded at the roots / excreted by (leaf) salt glands / tolerated in tissues;
• stilt/prop roots anchor the tree in soft, shifting mud;
• (some have) buoyant, viviparous seedlings (propagules) that disperse in water, OWTTE;

• (a) [2]
  • lowest altitude (2400 m): 18.0 − (1800 ÷ 100 × 0.6) = 7.2 °C;
  • highest altitude (3500 m): 18.0 − (2900 ÷ 100 × 0.6) = 0.6 °C;

  Units not required. Award [1] if both temperature drops (10.8 °C and 17.4 °C) are correct but not subtracted from 18.0 °C.

• (b) [2]
  • lower limit: 1000 + (16.2 − 7.2) ÷ 0.6 × 100 = 2500 m;
  • upper limit: the summit, 2900 m, because the summit (16.2 − 11.4 = 4.8 °C) is still warmer than the coldest temperature the plant tolerates / 0.6 °C would only be reached at 3600 m, above the summit, OWTTE;

  ECF from (a). Accept 2500 m to 2900 m. Award [1] for 2500 m to 3600 m (upper limit not checked against the summit).

• (c) [2]
  • the lower limit rises by 1.5 ÷ 0.6 × 100 = 250 m, to 2750 m;
  • (2900 − 2750) ÷ (2900 − 2500) × 100 = 150 ÷ 400 × 100 = 37.5 % / 38 %;

  ECF from (b). Accept 37 % to 38 %.

• (d) [2 max]
  • on mountain A both limits move up by 250 m, to 2650 m and 3750 m, which is still below the summit (4000 m), so the plant keeps a band 1100 m deep, OWTTE;
  • on mountain B the upper limit is already the summit, so only the lower limit can move up and the band shrinks from 400 m to 150 m, OWTTE;
  • on mountain B the plant has no higher ground to move to, so the population may become very small / die out there, OWTTE;

  Answers must use the calculated altitudes for full marks.

• (e) [2 max]
  • another abiotic variable may lie outside its range of tolerance on mountain B, e.g. soil pH / soil depth / water supply / length of time under snow / light, OWTTE;
  • the temperature at a given altitude may differ from the prediction, e.g. because of the direction a slope faces / shade / a different fall in temperature with altitude, OWTTE;
  • the summit area may be bare rock / cliffs / permanent ice with no soil in which to grow, OWTTE;
  • seeds of the plant may never have reached mountain B, OWTTE;

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

  • B4.2 taller plants (grasses, shrubs) in the lower part of the band may outcompete it;

  Content pivot. Mark the first two answers only.