Speciation occurs through the process of evolution and natural selection, creating new species. It happens when a common group of organisms becomes reproductively isolated into two or more separate groups. There are three main mechanisms for reproductive isolation: geographical isolation caused by physical barriers; behavioral isolation through different mating rituals or signals; and temporal isolation where populations mate at different times. Speciation can happen gradually over long periods of time or rapidly within 10,000 years or less, which would be reflected differently in the fossil record.

1. Speciation: Creation of Different Species

11. Darwin’s Finches

13. Organ pipe cactus (l) and Euphorbia (R): fleshy bodies, no leaves