6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
A species of beetle lives on the bark of trees. Most of the beetles are pale grey, but a few are dark. When soot from factories darkened the tree bark, the dark beetles became far more common over several generations.
Explain, using the theory of evolution by natural selection, how the dark beetles came to be the more common form. (6 marks)
In mice, fur colour is controlled by a single gene. The allele for brown fur (B) is dominant to the allele for white fur (b). Two mice, both heterozygous (Bb), are crossed.
(a) Complete a Punnett square for this cross to show the genotypes of the offspring. (2 marks)
(b) State the expected ratio of brown to white offspring. (1 mark)
(c) State the probability that any one offspring will have white fur. Give your answer as a fraction or a percentage. (1 mark)
A mutation is a change in the DNA of an organism. Mutations are a source of variation.
(a) State what is meant by the term variation. (1 mark)
(b) Explain why most mutations have no effect on an organism, while a few can be harmful. (2 marks)
Genetic engineering can be used to transfer a gene from one organism into another. For example, the human gene for insulin has been transferred into bacteria so that the bacteria produce human insulin.
(a) State what is meant by genetic engineering. (1 mark)
(b) Give one potential benefit and one potential concern of genetically engineering crops. (2 marks)
A farmer wants to produce dairy cows that give a higher milk yield. Over many generations they use selective breeding.
Describe how the farmer could use selective breeding to increase the milk yield of their herd. (2 marks)
Meiosis is the type of cell division that produces gametes (sex cells).
State the number of sets of chromosomes in a cell produced by meiosis, compared with the parent cell. (1 mark)