COEVOLUTION

= = SYMBIOSIS | COMMENSALISM | MUTUALISM | PARISITISM | AMENSALISM | COEVOLUTION = Coevolution =

**Definition**
Coevolution is the process by which two organisms evolve together, or "the change of a biological object triggered by the change of a related object".(2.)

Commensalism: Turtles and Algae
With commensalism there is one species that gains from the relationship and the other is not affected positively or negatively. An example of this is algae that is found on the shells of turtles. The algae benefits because it is given a substrate (the shell) and the algae doesn't affect the turtle at all. This is helpful to the algae because the algae has a way to move and prosper better, and this is nuetral for the turtle because it does not need to worry about an algae growing on it since nothing will happen.

Mutualism: Hummingbirds and ornithophilous flowers
Certain types of hummingbird have coevolved with certain flowers to form a mutualistic relationship. The flower produces nectar that provides the perfect nutrition for the bird, and exists in colors that the bird sees best. Meanwhile the bird's beak is perfectly shaped to drink from the flowers. The flower provides food for the bird, and the bird, by drinking from several different flowers spread pollen between flowers. A similar example would be the honey bee, another animal that has coevolved with a plant, the flower providing food, and the animal providing a means of pollination. There are actually several insects and plants that have coevolved in this manner.

Paristism: Tapeworms and vertebrates[[image:http://www.dobermann-review.com/info/health/worming/tapeworm.jpg width="336" height="303" align="right" caption="Life of a Tapeworm"]]
The coevolution of parasites and their hosts is positive for the parasite but usually bad for the host. It is good for the parasite because they can easily get the nutrients they need from their host. Their only disadvantage is getting out of their enclosed environment to continue reproduction, but they have mastered this by the fecal/oral route. Having a parasite is bad for the host because nutrients that it takes in to continue a healthy life is being taken away by the parasite and most of the time does not know it immediately. An example of this type of coevolution is when a tapeworm lives in the digestive tract of a vertebrate. The tapeworm takes the nutrients that are passing through the digestive tract and uses them for themselves while the vertebrate loses essential nutrients to survive.

[[image:zigzag2.jpg width="330" height="200" align="right" caption="Rough Skinned Newt"]]
Not all coevolution is the result of, or results in symbiosis. Coevolution can also occur in a predator prey relationship. Think of it as a sort of arms race, as the predator and prey each evolve new advantages to either pounce, or

keep from being pounced. A good example of this is the garter snake, and the rough skinned newt, it is exactly this predator prey relationship that has caused co-evolution. The newt has evolved an potent toxin in the skin, while the snake (which eats the newt) has developed a resistance to this poison.