BIO 370 Lecture Notes - Lecture 27: Phylogenetic Tree, Spectral Sensitivity, Color Vision
Branch lengths represent actual time rather than amount of evolutionary change.
Rooted trees can be drawn up to down, down to up, left to right, right to left, and even
circularly.
Just as we can generate and test hypotheses using evolutionary relationships indicated by the
structure of a phylogenetic tree, we can also generate and test hypotheses using the branch
lengths on a phylogenetic tree.
One such hypothesis is that species with shorter generation times experience more rapid rates
of evolution as measured by changes in DNA sequence.
With regard to this hypothesis, how do think short-lived plants (e.g., herbs) would compare
with long-lived plants (e.g., shrubs and trees)?
Short-lived species have higher mutation change in germ line per year.
Long-lived plants have slower rate of DNA sequence change
Tree species generally are on short branches; herb species branches more variable, but the
longest are always herbs.
Traits on Trees
If a phylogenetic tree represents a hypothesis about the evolutionary history of a set of
populations based on their traits, then by looking at where a given trait appears on a tree, we
can generate a hypothesis about when and how that trait has evolved.
As an example, we will examine the presence of opsins, the visual pigments that facilitate color
vision.
Spectral sensitivity of the human cone opsins.
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Document Summary
Branch lengths represent actual time rather than amount of evolutionary change. Rooted trees can be drawn up to down, down to up, left to right, right to left, and even circularly. Just as we can generate and test hypotheses using evolutionary relationships indicated by the structure of a phylogenetic tree, we can also generate and test hypotheses using the branch lengths on a phylogenetic tree. One such hypothesis is that species with shorter generation times experience more rapid rates of evolution as measured by changes in dna sequence. Short-lived species have higher mutation change in germ line per year. Long-lived plants have slower rate of dna sequence change. Tree species generally are on short branches; herb species branches more variable, but the longest are always herbs. As an example, we will examine the presence of opsins, the visual pigments that facilitate color vision. Homology: shared with 2+ species and inherited from ancestor.
