Science 25

Evolution is a theory that assumes organisms change over time. Two biologists argue about the process of evolution.

Scientist 1

Evolution is a steady, gradual process. Populations are constantly being shaped into idealists, adapted best to the environment in which they are found. Because environments endure continual fluctuations in temperature, precipitation and the effects of human impact, environments are unstable. Therefore, there is never a single ideal to be reached, and populations of species are continually evolving. This slow, continual evolution can be termed gradualism, and is evidenced by the fossil record, which shows the small changes have accumulated over time to result in larger changes.

Scientist 2

Evolution occurs in rapid bursts. Environments, although fluctuating in temperature, precipitation and other qualities, are relatively stable. Only when a major disruption to the environment, such as a fire, volcanic eruption or Ice Age, is suffered, will populations be subjected to evolution. This evolution occurs quickly, resulting in major changes over a short period of time. Once the environment stabilizes again, evolution slows, if not altogether ceases. This process is termed punctuated equilibrium and explains the gaps in the fossil record as well as the evolution of major morphological (structural) changes, such as bones in animals and seeds in plants.