Heating at the tropics lead to rising air masses, which sets up the primary Hadley circulation cells. The spinning of the earth breaks up the circulation cells into three units in both the northern and southern hemispheres. Surface winds at mid-latitudes move away from the equator. These prevailing winds tend to blow our storms in from the west. Pick one of the six main terrestrial biomes.
Various answers are possible.
Genetic similarities among related species. Shared developmental pathways among related species. Fossil record showing changes in organisms over time, consistent with evolution from common ancestors.