Evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

he processes of evolution’ introduces the main causal processes of evolution. Evolutionary change ultimately relies on the mutations of organisms. These are caused by stable changes in the genetic material, transmitted from parent to offspring.

Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable

- Mutation generates variation
- Evolution by genetic drift causes changes in populations by chance alone
- Evolution by gene flow (migration) makes two different populations more similar to each other
- Non-random mating results from mate choice

375 million-year-old transitional species between fish and the first legged animals, reveals that the evolution of hind legs actually began as enhanced hind fins.Clues to the seminal moment in the history of life were found in the bones of Tiktaalik.