Interpret phenotype distributions to distinguish stabilising, disruptive and directional selection, explaining which variants are favoured and how the population pattern changes in Cambridge A Level Biology questions.
Red deer feed on a wide range of plants.
Fig. 7.1
The number of red deer in the UK increased from 135000 in 1960 to 360000 in 2010.
Environmental factors affect the population size of red deer so that numbers do not continue to increase.
Suggest environmental factors that may prevent further increases in the size of red deer populations.
The body mass of red deer shows wide variation within a population. This is shown in Fig. 7.2.
Fig. 7.2
A selection pressure acted consistently over many years against red deer of low body mass in a population.
Sketch a curve on Fig. 7.3 to show the pattern of variation of body mass in this red deer population after this time.
Fig. 7.3
Name the type of force of natural selection that is acting on this population.
A selection pressure acted consistently over many years against red deer of medium body mass in a population.
Sketch a curve on Fig. 7.4 to show the pattern of variation of body mass in this red deer population after this time.
Fig. 7.4
Name the type of force of natural selection that is acting on this population.