Nikolai Vavilov was a Russian botanist, geneticist and agronomist. He was one of the great minds of the 20th century, but tragically died of starvation in prison under the Stalin regime.
Ronald Fisher was an evolutionary biologist and statistician. He is perhaps best known for inventing an array of revolutionary statistical procedures that could be used within the natural sciences, but his contribution to our understanding of evolution goes far beyond the statistical tests with which he most widely and commonly associated.
D’Arcy Wentworth Thompson (1860-1948) was a Scottish biologist, and a gifted mathematician, naturalist and classical scholar. His work provides a quintessential example of how seemingly disparate disciplines can be combined to develop novel approaches to understanding evolution.
Although this is intended as a light-hearted guide to areas of science that might interest you, it serves to illustrate the inter-disciplinary nature of science.