1. 1
   A team of ecologists is studying a population of bark-dwelling beetles over several decades, recording how the proportion of pale grey and dark brown beetles changes as the colour of the tree bark in the area changes.

   (a)

   A population of beetles living on tree bark shows variation in colour, from pale grey to dark brown. Over many generations, the population becomes mostly dark brown after the trees in the area become darker due to pollution. Which process best explains this change?

   [1 mark]

   • ANatural selection
   • BAsexual reproduction
   • CGenetic engineering
   • DMeiosis alone, without selection

   (b)

   The ecologists find that pale grey beetles are far more visible to birds when resting on darkened, pollution-stained bark than dark brown beetles are. What is the most likely explanation for how this visibility difference affects the beetle population over time?

   [1 mark]

   • ADark brown beetles will become pale grey through use of camouflage
   • BPale grey beetles will change colour during their lifetime to match the bark
   • CVisibility to birds has no effect on which alleles are passed to the next generation
   • DPale grey beetles are more likely to be eaten by birds, so fewer survive to reproduce and pass on their alleles

   (c)

   Explain why genetic variation within the beetle population was necessary before natural selection could cause the shift from mostly pale grey beetles to mostly dark brown beetles.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A researcher is investigating how a river that formed thousands of years ago split a single insect population into two isolated groups living on opposite riverbanks, which have since become genetically distinct.

   (a)

   A population of insects living on a mainland is separated into two groups when a new river forms, splitting their habitat in two. After many generations living apart, the two groups can no longer interbreed to produce fertile offspring. What term describes the formation of these two separate species?

   [1 mark]

   • AMitosis
   • BSpeciation
   • CFertilisation
   • DDecay

   (b)

   The researcher explains that after the two insect populations were separated by the river, each population experienced natural selection independently, based on the slightly different conditions on each riverbank. What role does isolation, such as the formation of the river, play in the process leading to the formation of new species?

   [1 mark]

   • AIsolation prevents genetic variation from arising in either population
   • BIsolation causes both populations to become identical to each other
   • CIsolation stops the two populations interbreeding, allowing each population's alleles and selection pressures to change independently over time
   • DIsolation has no effect unless the two populations are also exposed to genetic engineering

   (c)

   Describe the sequence of steps, after the two insect populations became separated by the river, that could lead to the formation of two distinct species.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A science historian is writing an article comparing Lamarck's theory of inheritance with Darwin's theory of evolution by natural selection, using a population of long-necked, leaf-eating animals as the example.

   (a)

   A science historian is comparing Lamarck's theory of inheritance with Darwin's theory of evolution by natural selection, using the example of a population of long-necked animals feeding on leaves high in trees. Lamarck proposed that individual animals developed longer necks during their lifetime by stretching to reach leaves, and that this acquired longer neck was then inherited by their offspring. Explain why this explanation is not accepted by modern science.

   [3 marks]

   (b)

   Explain how Darwin's theory of evolution by natural selection accounts for the long necks seen in the population of leaf-eating animals, without requiring any individual animal to change during its own lifetime.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A conservation organisation is investigating why a population of crop-damaging insects, once well controlled by a widely used pesticide, has become largely resistant to that pesticide after years of repeated spraying on farmland.

   (a)

   A conservation organisation is studying a population of insects that has evolved resistance to a pesticide that used to control it effectively on farmland. Explain, using the theory of evolution by natural selection, how repeated use of the pesticide could have led to a population of insects that is now largely resistant to it.

   [6 marks]

   (b)

   The conservation organisation now wants to develop an evidence-based recommendation for farmers to slow down the development of further pesticide resistance in insect populations. Using your understanding of natural selection, describe and evaluate two strategies farmers could use, explaining why each strategy would reduce the rate at which resistance develops.

   [6 marks]

   Total for question 4: 12 marks

End of questions