AQA GCSE Combined Science: Biology: Inheritance, Variation, Evolution and Ecology
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.
On a remote island, a population of beetles varies in colour from pale grey to dark brown. Birds hunt the beetles by sight on the dark bark of the island's trees. Over many generations, the population becomes almost entirely dark brown.
Explain, using the theory of evolution by natural selection, how the beetle population changed from being varied in colour to being almost entirely dark brown. (6 marks)
In a species of plant, flower colour is controlled by a single gene. The allele for red flowers (R) is dominant to the allele for white flowers (r).
Two plants that are both heterozygous (Rr) are crossed.
(a) Complete a Punnett square for this cross to show the genotypes of the offspring. (2 marks)
(b) State the ratio of red-flowered to white-flowered offspring expected from this cross. (1 mark)
(c) State what is meant by the term heterozygous. (1 mark)
Some organisms reproduce sexually and some reproduce asexually. Strawberry plants can do both: they make seeds (sexual) and also grow "runners" that produce new plants (asexual).
(a) Give one advantage to the strawberry plant of reproducing asexually by runners. (1 mark)
(b) Explain why offspring produced by sexual reproduction show variation, whereas those produced asexually do not. (2 marks)
The diagram below describes a simple food chain in a meadow ecosystem (each arrow shows the direction of energy/biomass transfer):
grass → field mouse → owl
(a) Name the producer in this food chain. (1 mark)
(b) Foxes also hunt the field mice in this meadow. Predict and explain what would happen to the number of field mice if a disease killed most of the foxes. (2 marks)
Carbon is constantly recycled through ecosystems in the carbon cycle. Carbon dioxide is removed from the atmosphere by one main process and returned to it by others.
State the process that removes carbon dioxide from the atmosphere, and one process that returns carbon dioxide to the atmosphere. (2 marks)
The genome of an organism is important in genetics.
Define what is meant by the term genome. (1 mark)