Speciation worksheet 1 a How does the length of time required to fix a new mutation by positive selection compare with that by genetic drift b How does your answer to a explain why most polymorphisms result from selectively neutral mutations 2 Below are DNA sequences from part of the 16S ribosomal RNA gene for 4 vertebrate species T G G C T G A C C T G G C A Woodpecker T G G C T G A C C A G G C A T G C C T G A C C A G A C A T G C C C A A T C A G G C A Owl Crocodile Snake Count the genetic differences in this gene between the following pairs of species a woodpeckers and owls b woodpeckers and crocodiles c crocodiles and snakes 3 The table below gives estimates from the fossil record of the time at which the evolutionary lineages from 2 diverged woodpeckers and owls woodpeckers and crocodiles crocodiles and snakes 80 MYA 250 MYA 300 MYA a Draw a graph of genetic distance fixed differences vs time since divergence b Is your graph consistent with the statement Divergence occurs according to a molecular clock Explain what property of the graph allowed you to come to your conclusion 4 In apple maggot flies the divergence process has progressed to the extent that the flies now exist as two reproductively isolated populations that have distinct host plant preferences One population has evolved to feed and mate on the introduced apple tree This population emerges at a time that is optimal for mating and laying eggs on this introduced tree The other population has continued to lay eggs on the native hawthorne tree and has the ancestral emergence time For each of the four evolutionary forces listed below explain whether and why that force may have been important in causing reproductive isolation and or divergence in apple maggot flies a Mutation b Gene flow c Genetic Drift d Selection host tree e Why is it significant to the speciation process that apple maggot flies mate on their 5 Give an example of an adaptive radiation that occurred after a colonization event a mass extinction and a morphological innovation In each case provide a hypothesis for why the adaptive radiation occurred