The work of charles darwin and alfred wallace on the origin of the earth's species extended the ideas of lyell's uniformitarianism into the biological sciences. the theory of evolution is based on the principle that the diversity seen in the earth's species can be explained by the

The correct answer will be- uniform modification of genetic traits for a long period of time.

Explanation:

The concept of uniformitarianism explains that everything on the earth can be explained by the scientific method.  This concept has always influenced the development of the disciplines of science like in science the theory of evolution represents the extended ideas of the uniformitarianism.

The diversity of the species on the earth is explained by the uniform modifications of the genetic traits passed to offspring for a long period of time in a population.

Thus, uniform modification of genetic traits for a long period of time is the correct answer.

that is wrong, its not thymus.