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The Five Fingers of Evolution.
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A thorough understanding of biology requires
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a thorough understanding of the process of evolution.
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Most people are familiar with the process of natural selection.
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However, this is just one of five processes that can result in evolution.
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Before we discuss all five of these processes,
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we should define evolution.
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Evolution is simply change in the gene pool over time.
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But what is a gene pool? And for that matter, what is a gene?
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Before spending any more time on genetics,
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let us begin with a story.
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Imagine that a boat capsizes, and 10 survivors swim to shore on a deserted island.
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They are never rescued, and they form a new population that exists for thousands of years.
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Strangely enough, five of the survivors have red hair.
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Red hair is created when a person inherits two copies of the red gene from their parents.
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If you only have one copy of the gene, you won't have red hair.
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To make this easier, we will assume
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that the five non-redheads are not carriers of the gene.
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The initial frequency of the red hair gene
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is therefore 50 percent, or 10 of 20 total genes.
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These genes are the gene pool.
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The 20 different genes are like cards in a deck
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that keep getting reshuffled with each new generation.
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Sex is simply a reshuffling of the genetic deck.
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The cards are reshuffled and passed to the next generation;
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the deck remains the same, 50 percent red.
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The genes are reshuffled and passed to the next generation;
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the gene pool remains the same, 50 percent red.
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Even though the population may grow in size over time,
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the frequency should stay at about 50 percent.
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If this frequency ever varies, then evolution has occurred.
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Evolution is simply change in the gene pool over time.
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Think about it in terms of the cards.
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If the frequency of the cards in the deck ever changes,
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evolution has occurred.
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There are five processes that can cause the frequency to change.
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To remember these processes, we will use the fingers on your hands,
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starting from the little finger and moving to the thumb.
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The little finger should remind you that the population can shrink.
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If the population shrinks, then chance can take over.
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For example, if only four individuals survive an epidemic,
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then their genes will represent the new gene pool.
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The next finger is the ring finger.
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This finger should remind you of mating, because a ring represents a couple.
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If individuals choose a mate based on their appearance or location,
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the frequency may change.
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If redheaded individuals only mate with redheaded individuals,
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they could eventually form a new population.
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If no one ever mates with redheaded individuals,
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