Now consider the environment

Now consider the environment - indication of the amount of...

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Now consider the environment: certain physical properties of the environment can be described by the mean (average) value or the range of values (highest - lowest). Which aspect of an organism (the trait itself or the plasticity for that trait) will evolve in response to which measure? It may be that the plasticity for a trait will evolve in response to the range of values the environment throws at an organism (e.g., coldest - hottest, driest-wettest days), whereas the trait itself (e.g., thickness of fur) will evolve in response to the mean. This is not a rule! but would be an interesting thing to test and/or think about. The idea of plasticity is interwoven with the notion of canalization . In light of the ball rolling down the trough of a developmental pathway (previous lecture), one can consider the width of the trough as an
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Unformatted text preview: indication of the amount of plasticity "tolerated" in the organism in question. A highly canalized organism (or developmental program) would have low plasticity . Another variant form of the plasticity issue is that some organisms may exhibit threshold effects where there is not a clear gradual transition between forms, but a stepwise change of phenotype in response to a gradual environmental change. See fig. 9.11, pg. 242, but note that these graphs do not have an environmental axis, so a distinct from a norm of reaction. One example of this are plants that have distinctly different growth forms in different environments. Question: is there an "environment" that is half way in between air and water?, and if so would these plants exhibit a graded response to such an environmental gradient?...
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