Many of these now-freshwater lineages independently evolved the same sort of genetic changes which produce a lightly armored body form. However, several stickleback lineages invaded new, freshwater environments. The ancestral stickleback fish was marine-living and heavily armored by sturdy plates. A real-life example of parallel evolution also involves fish. 5b in which two closely related fish lineages evolve in the same way, resulting in two lineages with a striped body pattern.

In this process, two traits that are already similar (usually because of common ancestry) independently evolve the same set of changes-generally meaning that the same set of underlying genes are involved. 5a, fish lineages that originally had different body patterns might independently evolve analogous vertical stripes, perhaps because of selection for a particular camouflage pattern. For example, two distantly related plant lineages might evolve analogous tubular red flowers under selection from hummingbird nectar feeders. Two lineages that begin with different traits evolve a similar characteristic independently of one another, often because both lineages face similar environmental challenges and selective pressures. This process produces analogies, as discussed above. Homoplasies can evolve in three ways (though the lines between these categories are often blurry):Ĭonvergent evolution. A homoplasious trait is a similarity among organisms that was not inherited from the common ancestor of those organisms. The counterpart of homology is usually considered to be homoplasy, a much broader concept than analogy. However, biologists often depart from high school texts in their analysis of analogies (e.g., Hall 2007 Gregory 2008).

This is the view presented by standard biology textbooks.

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