Evolution, speciation and conservation conflictsEdexcel International A Level Biology: Mind map

Exam questions on Evolution, speciation and conservation conflicts

1. A population of beetles lives on a recently formed island of dark volcanic rock. Beetle colour is controlled by one gene with a dominant allele B for dark colour and a recessive allele b for pale colour. Birds feed on the beetles and find pale beetles easier to see against the rock. The frequency of allele B was 0.30 in the first generation studied and 0.55 five generations later.
   Explain why the frequency of allele B increased over the five generations.2 marks
2. A river changed course and split a large population of ground squirrels into two populations living on opposite banks. The squirrels cannot swim the river, and the habitat on one bank is dry grassland while on the other bank it is wet woodland. After several thousand years, scientists have found that the two populations differ in body size, in alleles at several genes and in the calls used in courtship.
   Explain how the geographical separation of the squirrel populations led to the formation of new species.2 marks
3. Apple maggot flies lay their eggs on fruit, and the larvae feed in the fruit. Originally the flies fed only on hawthorn fruit. After apple trees were introduced to the same area, some flies began to lay eggs on apples, which ripen earlier than hawthorn fruit. The flies mate on the fruit on which they developed. Both groups of flies live in the same orchards. A scientist genotyped 100 flies from each group for one gene. Of the 200 alleles in the hawthorn flies, 124 were allele A, and of the 200 alleles in the apple flies, 70 were allele A.
   Explain how the two groups of flies living in the same orchards could become separate species by sympatric speciation.3 marks