Module 7 · Answers
Answers & explanations
Section A — Easy
01
Any three: food, water, mates, shelter, territory.
02
(a) Discontinuous (b) Continuous (c) Continuous (d) Discontinuous
03
In the nucleus.
04
A feature of an organism that helps it survive in its environment.
05
Any two: climate change, habitat destruction, new predators / competitors, disease, asteroid impact.
Section B — Medium
06
Thick fur and fat layer — insulate against the cold. White fur — camouflage in snow for hunting. Big paws — spread weight on snow / used as paddles when swimming.
07
(a) Environmental (b) Genetic (c) Both (genetic predisposition + diet/exercise)
08
1) Variation between individuals. 2) Competition for limited resources. 3) Best-adapted survive and reproduce. 4) Their helpful features pass to the next generation.
09
Soot darkened the trees. Dark moths were now better camouflaged, so birds caught fewer of them. Dark moths survived to breed in greater numbers, passing the dark colour on.
10
Through natural selection, bacteria that happen to resist the antibiotic survive and reproduce, while non-resistant ones die. Over time, the resistant strain dominates and the antibiotic stops working.
Section C — Hard
11
Slower rabbits are more likely to be caught and eaten — fewer breed. Faster rabbits survive and pass on the "fast" genes. Over generations the average running speed of the population increases.
12
Identical twins share genetic information, but environmental factors differ — diet, illness, exercise, accidents, friends, language exposure — all influence variation.
13
For: each species has intrinsic value, plays a role in its ecosystem and may have undiscovered uses. Against: protecting every species is costly and sometimes impossible (e.g. against climate change); resources may save more biodiversity if focused elsewhere.
14
If the environment changes, a species needs at least some individuals with helpful variations to survive. Low variation means few individuals are different, so the chance of any being suited to the new conditions is small. The whole population may die out.