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Modern examples


It is possible to mathematically predict how a colony of bacteria will react to a change in its environment. The growth and distribution of individuals of a single generation will be constrained by certain limiting factors, and across generations, these limits will change as the metabolism evolves to adapt to new conditions.

Higher organisms, certainly vertebrates, often adapt to new conditions by a change in behaviour. Thus, many birds migrate south for the winter. Moreover, a single organism can itself transform its environment. Beavers create ponds from creeks, and so are not constrained even by the landscape that they move into.

It is a truism to say that humans are less affected by natural selection than bacteria are. In the same time, it is rarely recognized that other animals also avoid selective pressures by adaptive (migrating birds) or transformative behaviour (beaver) (Day 2004).

Burrowing is one such behaviour, one that is extremely common in terrestrial vertebrates (e.g. Reichman and Seabloom 2002).


Fossil examples


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