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BIOL 446 Study Guide - Final Guide: Melanin, Teleost, Drosophila Melanogaster

Course Code
BIOL 446
James Marden
Study Guide

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Course goals:
1. Learn to think and analyze from genes to ecosystems
2. Learn to recognize features of habitats that present
functional challenges to organisms
3. Learn the diversity of solutions to problems of
temperature, osmolarity, energy, etc..
4. Begin to understand how and why organisms work the
way they do
Topic 1: Adaptation
What is an adaptation?
1. Used as a noun to describe a trait or character:

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A trait that enhances fitness and that arose historically
as a result of natural selection for its current biological
role (Lauder 1996)
fitness: relative contribution of offspring to next generation(s)
historically: fitness effect must have been working in the past
natural selection: the process that determines fitness; not a
random process like genetic drift
2. Used to describe an evolutionary process
Over evolutionary time, organisms become adapted
to their environment
- infers increasingly good fit between organism and
environment brought about by the process of natural
selection acting on hertitable genetic variation that causes
evolutionary change
3. Used to describe a process of phenotypic adjustment
within individuals
Over the summer, trout become adapted to higher
water temperatures
- describes a non-heritable change (although the ability to
make such a change is usually heritable!!!)
- in order to avoid confusion, I will try to use the word
acclimate to refer to phenotypic changes within individuals

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How do we know an adaptation when we see one?
In the old days (pre-1980’s)
- observe a trait
- measure or speculate on its adaptive features
- voila: it’s an adaptation!
Problem: progress in the field of population genetics showed
us that not all traits are expected to be adaptive (because of
things like genetic drift, linkage, selection on correlated traits
[i.e. shared developmental pathway])
Also: With advent of gel electrophoresis came the discovery
of unexpectedly large degree of heterozygosity in metabolic
enzymes. Many polymorphisms began to look as if they are
selectively neutral.
An important paper: Gould and Lewontin (1979)
The Spandrels of San Marco and the Panglossian
Paradigm: A Critique of the Adaptationist Programme
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