Describe how evolution occurs through natural selection.
The total number of eggs a bird lays in one nest is known as the clutch size. Variation in clutch size was studied in the zebra finch across several years. The results are displayed in Fig. 2.1.
Describe the pattern displayed by the data in Fig. 2.1.
The data from this investigation were gathered more than 60 years ago. If the same investigation were repeated today, it would show the same pattern of results. Explain how the selection factors acting on zebra finches would keep the same pattern of results.
The Hardy-Weinberg principle is applied to work out allele, genotype and phenotype frequencies in populations. A bird breeder keeps 86 budgerigars in one enclosed area. Two phenotypes are observed, blue feathers and green feathers. Feather colour is controlled by one gene: G is the allele for green feathers, g is the allele for blue feathers. Only 17 of the budgerigars have blue feathers.
Fig. 2.2 shows the Hardy-Weinberg equations: $p + q = 1$, $p^2 + 2pq + q^2 = 1$. Calculate the number of heterozygous individuals in the population. Show your working.
The Hardy-Weinberg principle does not apply to every population. State two conditions under which the Hardy-Weinberg principle cannot be applied.