The collared flycatcher, Ficedula albicollis, and the pied flycatcher, F. hypoleuca are two closely related species of bird. DNA analysis has shown that speciation from a common ancestor occurred approximately 1 million years ago. A study was carried out on the island of Öland, Sweden. In Öland, the breeding areas of the two bird species overlap and small numbers of hybrid flycatchers are produced. • Birds were captured and their DNA was analysed to identify whether each bird was F. albicollis, F. hypoleuca or a hybrid. • Sperm samples were taken from the male birds. Table 3.1 shows the percentage of males of each bird type with normal sperm. Table 3.1 bird type | percentage of males with normal sperm ---|--- F. albicollis | 68 F. hypoleuca | 78 male hybrid | 0 • The researchers observed that female birds mostly choose mates of their own species based on plumage (feathers) and song. • Hybrid flycatchers are produced when female F. albicollis mate with male F. hypoleuca that have a song that is similar to F. albicollis. • Analysis showed that all female hybrids were sterile. The group of eggs a female bird lays at a single time in its nest is called a clutch. The offspring in the nest are looked after by a male-female pair. Sometimes the male in the male-female pair does not provide the sperm that fertilise the eggs of the female. Table 3.2 shows: • the percentage of clutches with eggs that hatched • the percentage of extra-pair nestlings (offspring in the nest fathered by a male that was different from the male of the male-female pair). Table 3.2 parents of nest | percentage of clutches with eggs that hatched | percentage of extra-pair nestlings male | female | | ---|---|---|--- F. albicollis | F. albicollis | 94.5 | 17.2 F. hypoleuca | F. hypoleuca | 89.3 | 22.4 hybrid | F. albicollis or F. hypoleuca | 38.0 | 100.0

1. (a)(i)Discuss the pre-zygotic and post-zygotic isolating mechanisms that maintain F. albicollis and F. hypoleuca as separate species.[4]
2. (a)(ii)Explain how the two species F. albicollis and F. hypoleuca could have evolved from one original ancestral population.[5]
3. (b)(i)A single-nucleotide polymorphism (SNP) is caused by a base pair substitution mutation in a specific region of DNA. One method of identifying whether two individuals have the same SNP is to: • use a specific primer and polymerase chain reaction (PCR) • add a restriction enzyme • carry out gel electrophoresis • stain with a dye to compare banding patterns. Explain why: a specific primer is used a restriction enzyme is added gel electrophoresis is carried out.[3]
4. (b)(ii)The method of identifying whether two individuals have the same SNP method was carried out to compare species A and species B. Fig. 3.1 shows the banding patterns that were observed. [Figure 3.1] Describe and suggest an explanation for the results obtained in Fig. 3.1.[2]

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