1. 1
   A population of ground beetles living on a moorland shows variation in wing length: some beetles have long wings and can fly, others have short, stubby wings and cannot fly. A prolonged drought reduces the amount of food available and increases the risk of the beetles being blown out to sea by strong winds. Over several generations, short-winged beetles become far more common in the population.

   (a)

   What is the most likely cause of the original variation in wing length before the drought began?

   [1 mark]

   • AMutations occurring during reproduction
   • BThe beetles deliberately changing their wing length to survive
   • CThe drought directly shortening the wings of some beetles
   • DBeetles inheriting acquired characteristics from their parents' lifetime activity

   (b)

   Which statement best explains why short-winged beetles became more common after the drought?

   [1 mark]

   • ALong-winged beetles chose to fly away rather than compete for food
   • BShort-winged beetles were less likely to be blown out to sea and more likely to survive to breed, passing the short-wing characteristic to their offspring
   • CAll beetles gradually developed shorter wings during their own lifetimes in response to the wind
   • DShort wings appeared suddenly in every beetle at the same time because of the drought

   (c)

   Explain, using Darwin's theory of evolution by natural selection, why the proportion of short-winged beetles increased over several generations rather than changing within a single beetle's lifetime.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In a hospital ward, a patient is treated with a course of antibiotics for a bacterial infection. A few days into treatment, doctors find that some of the bacteria in the patient's infection are no longer killed by the antibiotic.

   (a)

   What is the origin of the antibiotic-resistant bacteria?

   [1 mark]

   • AThe antibiotic itself caused the bacteria to change and become resistant
   • BAll bacteria in the infection became resistant at exactly the same time
   • CResistant bacteria were transferred from the antibiotic tablets
   • DRandom mutations already present in a small number of bacteria before treatment began gave them resistance

   (b)

   The patient stops taking the antibiotic course early because they feel better. Which outcome is most likely as a result?

   [1 mark]

   • AAll remaining bacteria, including resistant ones, will be killed naturally over time
   • BThe bacteria will lose their resistance because the antibiotic is no longer present
   • CThe surviving resistant bacteria will reproduce, increasing the proportion of resistant bacteria in the population
   • DStopping early has no effect on the bacterial population

   (c)

   Suggest two ways in which the development of antibiotic-resistant bacteria could be slowed down.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Before the Industrial Revolution, most peppered moths in a woodland were pale in colour, which camouflaged them against pale lichen-covered tree bark, while a small number of darker moths existed due to a mutation. As industrial pollution blackened the tree trunks with soot over several decades, the proportion of dark-coloured moths increased sharply, while pale moths became rare.

   (a)

   Explain how natural selection caused this change in the moth population.

   [3 marks]

   (b)

   Scientists studying the peppered moth also use the fossil record to look for evidence of past insect populations, but very few insect fossils from this period have been found. Explain why the fossil record is often incomplete, and suggest what other type of evidence (besides fossils) supports the idea that species can change through natural selection over time.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In 1858, Alfred Russel Wallace independently developed a theory of evolution by natural selection very similar to Charles Darwin's, prompting Darwin to publish 'On the Origin of Species' in 1859. Despite the strength of the evidence Darwin had gathered, his theory was only gradually accepted by other scientists and by society.

   (a)

   Explain Darwin's theory of evolution by natural selection, and discuss the reasons why it took many years to become widely accepted.

   [6 marks]

   (b)

   A single species of small bird colonises two separate islands that are far apart and have very different food sources. Over many thousands of years, the birds on the two islands evolve noticeably different beak shapes, and when a small number of birds from one island are later transported to the other, they are unable to breed successfully with the local population. Explain, using the idea of natural selection, how the two populations came to have different characteristics, and explain what has happened to the two populations in terms of speciation.

   [6 marks]

   Total for question 4: 12 marks

End of questions