Classification and phylogenyEdexcel A-Level Biology A: Flashcards

Exam questions on Classification and phylogeny

1. A taxonomist is studying two populations of lizards that live in separate valleys. The lizards look very similar and she is unsure whether they are one species or two. She has tissue samples from both populations.
   Describe how DNA could be used to help decide whether the two populations of lizard are the same species.2 marks
2. Cytochrome c is a protein used in respiration and is found in all aerobic organisms. A biologist compares the amino acid sequence of human cytochrome c with that of other species. The numbers of differences from the human sequence are: rhesus monkey 1, horse 12 and tuna 21.
   Explain how the data suggest that humans are more closely related to horses than to tuna.2 marks
3. Until the 1970s living things were classified into five kingdoms, and all prokaryotes were placed in one kingdom because of their similar cell structure. In 1977 Carl Woese and colleagues compared the base sequences of ribosomal RNA from many organisms. They found that some prokaryotes, later called Archaea, had ribosomal RNA sequences very different from those of both bacteria and eukaryotes. Later, other scientists found that archaeal cell membranes contain different lipids from bacterial membranes. In 1990 a classification with three domains, Bacteria, Archaea and Eukaryota, was proposed.
   Explain how the comparison of ribosomal RNA sequences led to a new classification of living organisms.3 marks