I need help to understand this? 1. Most island species are closely related to sp

Question

I need help to understand this?

1. Most island species are closely related to species from the nearest mainland neighbouring island.

2. Islands colonized by species from the nearest mainland.

3. Two islands with similar environments in different parts of the world are populated not by closely related species but rather by species that resemble those of the nearest mainland.

What IS BEING SAID HERE?? p. 465 Campbell I took excerpts from Biogeography paragraph.. I am trying to understand this please.

Explanation / Answer

In the first 2 examples you have forms of geographical isolation. The species found on the island are distantly related to ancestors from the mainland. In this example you have species moving to the island from the mainland then will continue to evolve on heir own path due to differences in habitat conditions. This is known as Homology. This is most famously known in Darwin's Finches. Each island Darwin visited had a finches with unique features due to the type of food each island offered but each different species was distantly related. In the 3rd example we have two isolated populations with similar growing conditions. Here we see Homoplasy. This is where 2 separate species have developed the same traits through evolution. For example Fish and Whales, though not related both have fins. This is because their habitat can be best transverses with fins instead of feet.

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