Figure 2

If two species descended from a common ancestral species differ by the presence of a chromosomal inversion, when must the inversion have occurred?

species often can be distinguished by the presence or absence of specific chromosomal inversions.

In Figure 2, one species descended from a common ancestral species has an inversion that the other does not. Where on this diagram must have the inversion have occurred?

This is the kind of analysis you will use to construct a more detailed evolutionary tree in this investigation.

Main Activity

In this part of the investigation, you will use the chromosomal inversion data from Table 1 to construct an evolutionary tree for the following four species: Drosophila heteroneura, D. hanaulae, D. substenoptera, and D. primaeva. You should indicate on the tree where the inversions occurred that can be used to determine the species’ evolutionary relationships.

Once the diagram is complete, compare the evolutionary relationships of the four species with the ages of the Hawaiian island on which they live (see Figure 3). What conclusions can you draw about how new species of flies appear in Hawaii?

The final part of this main activity is to construct a narrative account of how the four species of drosophilid flies might have evolved over time. Your account should address these points:

Figure 3

Radiometric dating has produced estimated ages for the major Hawaiian islands. The oldest islands are to the northwest and the youngest islands are to the southeast.

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