DNA barcoding is used in species identification. To create a DNA barcode, a specific region of DNA is sequenced so that it can be compared to an online database of reference DNA. One region of DNA that is commonly used is 648 base pairs long within a mitochondrial gene, coding for the enzyme cytochrome c oxidase I.

1. (a)The solitary sandpiper, Tringa solitaria, is a migratory bird. DNA barcoding has shown that approximately 2.5 million years ago T. solitaria evolved into two subspecies, Tringa solitaria solitaria and Tringa solitaria cinnamomea. A subspecies is a genetically distinct population of a species that has some phenotypic differences but is not yet reproductively isolated. T. s. solitaria breed in eastern North America whereas T. s. cinnamomea breed in western North America. Suggest and explain how the two subspecies T. s. solitaria and T. s. cinnamomea could have evolved from the original T. solitaria population.[4]
2. (b)Fig. 3.1 shows an American oystercatcher, Haematopus palliatus. [Figure 3.1] The black oystercatcher, Haematopus bachmani, has all black feathers. DNA barcoding analysis suggests that the American oystercatcher and the black oystercatcher are not separate species. Suggest how DNA barcoding evidence could indicate that the American oystercatcher and black oystercatcher are not separate species.[2]
3. (c)Customs officers at airports can use a hand-held DNA barcoding device to identify biological specimens entering or leaving a country. Suggest how this helps protect endangered species.[2]

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