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Quote of the week: "Intelligent life on a planet comes of age when it first works out the reason for its own existence." Richard Dawkins, The Selfish Gene. (pg. 1)

The Role of Predators in Evolution
By Branden Holmes on September 6, 2010

The evolutionary arms race between predator and prey is virtually universal. As such, it is vital to have a grasp of how predators can drive evolution in prey species. Of course, the arms race is run in evolutionary time rather than real time; adaptation and counter-adaptation, separated by a lag of several or many generations in genetic response. Adaptation is a long and steady process of replacement: maladapted individuals give way to adapted individuals, and adapted individuals give way to better adapted individuals. But the adaptations that are beneficial to an individual which lives free from predators are, as we shall see, diametrically opposed to those that individuals which experience the constant threat of being eaten, find to help aid survival.

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What is fitness?
By Branden Holmes on November 28, 2010

When evolutionary biologists speak of the "fitness" of an individual, what they usually mean these days is what is called reproductive success (RS): the extent to which some of their genes will still survive in the population x number of generations later. Because it is not enough just to only consider the contribution of offspring into the next generation. It is good that an individual may have many offspring, even twice as many as the average. But if none of those offspring are likewise endowed with fecundity, it doesn't matter how many offspring that individual has because they will not be disproportianally represented in terms of genes many generations later. How durable a species or gene is (the probability that that species or gene will still be extant after many generations) is what really counts in evolution. This is simply a temporal extension of reproductive success, where the period concerned is many, many generations later, and the entity concerned is the population as opposed to the individual, because individuals do not live for many generations. So, inheritability of fecundity is essential, otherwise the gene pool will simply be diluted and directional selection of fecundity will be impossible. But a number of other definitions for fitness are in wide use, somewhat confounding the problem of multiple definitions, which also partially overlap in meaning:

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Genetic drift as cause of evolutionary change
By Branden Holmes on November 22, 2010

There are two ways in which evolutionary change may occur. The first is of course natural selection, made famous by Darwin in the Origin (he coined the phrase). The second process is random sampling, better known by its popular name genetic drift. Natural selection deals with advantageous and disadvantageous mutations, whereas genetic drift governs how neutral and nearly neutral mutations will be inherited from one generation to the next. However, genetic drift is only an evolutionary force in small populations. This is because it is the random changing of the frequencies of different alleles at a given locus, or position where a gene resides upon a chromosome. For alleles to become fixated (where every individual in the population possesses that particular allele) by coincidence is much more probable given a small initial population because there are less individuals for the allele to spread to.

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