Question

will rate

Part III Chapter 5 Evolution can be observed directly, as in the famous example of natural selection and adaptation to drought in Darwin's finch populations on Daphne Major in the Galápagos archipelago. Answer the following questions, referring to these graphs: 90 Before the drought 1976 All Daphne birds N 751 60 30 8 10 11 12 13 14 7 12 After the drought 1978 Survivors N =90 6 13 7 8 10 11 12 14 Beak depth (mm) Source: understandingevolution.org Number of finches Number of finches CO 9. Based on these limited data, which mode of selection seems to have operated on the finches? What evidence supports this idea? 10. Assume the drought continues for another 2 years. If natural selection is occurring, what would you expect to see in future generations? If the changes in beak size are not due to natural selection, but to genetic drift, then what would you expect to see in future generations?

Answer 1

9) The natural selection in this case occur is balancing selection because you find that on this graph before drought there are found birds from 6cm beak depth to the14 cm beak depth. Now look in the graph after drought. You found that the birds having beak depth from 7cm to 11.5 cm are found only. This depicts that the intermediate beak depth birds can survive in the conditions which are alter by drought.

---;-----------

10)

If the drought condition continues for two years, then there will be found more intermediate beak depth size. Now, in this case the beak size become 9 cm to 11 cm ( hypothetically).

If the change in beak size occurs due to genetic drift, then there will be not found so much variation in beak size. There is random fixation of one allele in a gene encoding beak size. That's why there will be found only those birds which have similar size of beak's depth. For example :if fixation occurs for 10 cm, then there will be all birds of 10cm beak depth in case of genetic drift.