Natural selection and speciationEdexcel A-Level Biology B: Mind map

Exam questions on Natural selection and speciation

1. Rock pocket mice live in the Arizona desert. On pale sandy ground most of the mice have pale fur, but on areas of dark volcanic rock most have dark fur. Owls hunt the mice by sight at night. Fur colour is controlled by a single gene with a dark allele and a pale allele, and mice of both fur colours are born in both types of area.
   Explain how natural selection has led to a higher proportion of dark-furred mice on the dark rock.2 marks
2. The kangaroo rat lives in North American deserts. It has long, powerful hind legs and a long tail, spends the hot day in a cool burrow, forages for seeds at night, and produces very small volumes of highly concentrated urine.
   Explain how the kangaroo rat's behaviour of spending the day in a burrow increases its chance of survival in the desert.2 marks
3. About 10 000 years ago a river changed course and became a wide, fast-flowing barrier that ground squirrels cannot cross, splitting one population into two. The environment differs on the two sides: one side is dry scrubland and the other is woodland. The two populations now differ in body size and breeding season, and in captivity their members do not produce fertile offspring.
   Explain how the change in the course of the river could have led to the formation of two species of ground squirrel.3 marks