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Evolution

20 21 the red QUeen evolutionary arms race All species are in constant competition with others for resources, and one result of this is that they all need to keep evolving just to maintain the status quo. In species that relate as predator and prey, sharper teeth or greater speed in a predator may result in thicker armor or faster legs in its prey. The concept was first described by Leigh Van Valen in 1976, and termed the Red Queen effect, after Lewis Carrolls Through the Looking Glass, when the Red Queen remarks to Alice, it takes all the running you can do, to keep in the same place, It turns out that perpetual motion is a prerequisite of evolution. Because environmental conditions are always in flux, so too are the organisms that populate them see examples opposite. One example is the role of sex in fighting disease. Diseases break into cells, either eating them fungi and bacteria or taking over their genetic machinery viruses. They get in by using protein keys, and successful breakins can lead to the key spreading fast. Sex, as opposed to cloning, creates children who are different to one another, and have a variety of different locks to keep the parasites guessing. For example the flax plant has 27 versions of 5 different genes that help resist rust fungus, and different individuals have different combinations. Resistance genes that work become widespread, but then so do parasites that unlock them, and then new corresponding resistance genes, then new keys, and so on. The pace of evolutionary change varies. Saltation emphasises the role of mutations in the sudden morphological changes that result in branching of the evolutionary tree, while gradualism emphazises natural selection and the subtle adaptation of species over time. Above Many predatorprey systems engage in arms races. For example, over millions of years many mollusks have evolved thick shells and spines to avoid being eaten by animals such as crabs and fish. These predators have, in turn, evolved powerful claws and jaws that compensate for the snails thick shells and spines. Left In the arms race between plants and insects, plants that evolve a chemical that is repellent or harmful to insects will be favored by natural selection. But the spread of this gene puts pressure on the insect population, favoring insects that evolve the ability to overcome this defense. This, in turn, puts pressure on the plant population, and any plant that evolves a stronger chemical defense will be favored. This, in turn, puts more pressure on the insect population ... and so on. The levels of defense and counterdefense perpetually escalate, without either side ever winning.
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