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Question

Toxic mine waste is dumped halfway along a peninsula. All of the mice in the affected area die off and the area is instant death for any that enter it. The mice on the end of the peninsula eventually become a separate species from the mice at the beginning of the peninsula. Why might that happen?

Answer 1

The question: Toxic mine waste is dumped halfway along a peninsula. All of the mice in the affected area die off and the area is instant death for any that enter it. The mice on the end of the peninsula eventually become a separate species from the mice at the beginning of the peninsula. Why might that happen?

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We have several things coming into play here:

1. an environmental challenge
2. geographic isolation
3. behavioral modification
4. genetic modification

The environmental challenge is the dumping of toxic waste, our ground zero. This could cause different things to happen:

1. the mice on the fringe could develop resistance to the toxins while those farther from ground zero do not and continue to die when exposed (natural selection)
2. the mice might undergo genetic changes cause by the toxins (mutation)

Because the mice populations are found on a peninsula (a finger of land surrounded on three sides by water) and ground zero is in the middle of the peninsula, we now find ourselves with two zones:

1. the end of the peninsula which is its own little ecosystem because it is surrounded on three sides by water and the fourth side is a deadzone (geographic isolation)
2. the beginning of the pennisula which still has access to the mainland and an influx of new population members, predators and food items

We expect to see behavior modification in our mice on the end of the peninsula because they will probably experience pressure on food sources, which will cause them to try new food items. They may also avoid certain elements in the terrain because they have come to associate them with toxic waste and death, like leaving low ground for high ground to avoid toxins held in run off basins. Or some competitor species will have been more sensitive to the toxins and have been totally wiped out, opening up new opportunities in food and habitat for the mice.

Because of the natural selection and possible mutation cited above and also because the geographic isolation and potential behavioral modifications reduce the number of candidates available as mates, we expect to see genetic modifications over time.

Some or all of these factors combined produce what we call Speciation: the development of a new species from a subset of an existing species.