Preview - Selection in Action: Natural Selection

Selection in Action: Natural Selection

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Selection in Action: Natural Selection (20:00)

Item# 809
©1981

This program provides arguments in favor of continental drift and the one-time existence of a supercontinent, shows how isolation can give rise to different species and how species develop in response to their environments, and explains clines and suggests the reason for their existence. After viewing the program, students should understand the significance of the continental drift theory, the purpose of studying inherited variation in isolated populations, and the conclusions about an isolated environment in a species’ ancestry that can be drawn from the presence or absence of variation. (20 minutes)

Segments in this Video - (5)

1. Evidence Supports Continental Drift (02:57)

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The San Andreas Fault, the magnetism of exposed rock in England, and the sand layers below that rock all provide evidence that supports the theory of plate tectonics, the idea of continental drift.

2. Fossil Evidence for a Supercontinent (04:56)

Continental drift explains many features of plant and animal distribution. Fossil evidence from Antarctica supports the theory that the continents we know were once parts of a supercontinent.

3. Isolation and Evolution: Field Mice (03:57)

Continental drift has relevance to the study of evolution, as isolation is an important factor in the process. Differences among field mice from different islands illustrate the effects of isolation.

4. Isolation and Evolution: Voles (02:20)

A study of voles from different islands finds differences that illustrate how animal populations, in isolation, have evolved differences from their ancestral stock.

5. Genetic Variability: Mice and Seabirds (05:40)

Living things must be able to transmit variations to their progeny in order to evolve new subspecies. Genetic differences among arctic skuas in the Shetland Islands are determined by behavior.