A species will develop according to the environment it exists in. Predators, climate changes, and other environmental factors can all create reasons for a species to adapt. These adaptations are part of the evolution of the species, allowing it to change in a way that will increase its chances of survival. There are three types of evolution: divergent, convergent, and parallel.

Divergent evolution is the most commonly known of the three types of evolution. It involves one species that eventually separates into two separate species. For example, a flock of migratory birds, heading for a warmer climate, gets divided in a storm. One half of the flock continues on to the original destination. The other half lands on a new island, and decides to stay. Over time, they develop characteristics that allow them to better survive on the island, and become a different species their ancestors who were initially separated from the larger flock. What was once one species has now been separated into two.

The second type of evolution -- and usually the hardest to understand -- is convergent evolution. Convergent evolution explains two or more species that develop similar traits in separate types of environments. Animals developing wings is one example of convergent evolution. There was no one common ancestor for all winged animals. Due to their individual environments, these animals all developed wings on their own, through generations of evolution. Wings were developed based on the physics of flying, not on a pre-programmed internal blueprint handed down from a similar ancestor.

Convergent and parallel evolution are very similar, and are easily confused. When two separate species in the same environment develop the same adaptations for survival, it is called parallel evolution. This type of evolution begins with two similar species that exist in similar environments. Over time, these species will evolve in very similar ways. One example of parallel evolution is the North American Cactus and the African euphorbia. These two plants belong to different plant families, but share the same sort of environment. Because of that, they have developed the same adaptations for survival -- the ability to store water in their thick stems and sharp quills to ward off predators. Both plants can survive in hot, dry climates.

Evolution is a process. Species adapt and evolve to better survive in their environments. Similar environments can cause similar adaptations in different species, and different environments can cause different adaptations in similar species. Studying the affect of environmental factors on the evolution of a species is the best way to make educated guesses on both the history and the future of a species. By considering all three types of evolution, it is possible to get a very accurate idea of how a species of plant or animal has developed into its current form.