BIS 2C Study Guide - Winter 2019, Comprehensive Midterm Notes - Synapomorphy, Speciation, Phylogenetic Tree

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Published on 14 Feb 2019
School
UC-Davis
Department
Biological Sciences
Course
BIS 2C
Professor
BIS 2C
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Lecture 1
Why phylogeny?
How do we organize the diversity of life?
Current estimate of described species ~8.7m with up to 80% yet to be named.
Up to 86% of species are undescribed, with many discovered each year.
Our discoveries are biased towards macroscopic life; new technology has accelerated the discovery of microbes.
Phylogenies are powerful tools that help us make predictions about evolution, including topics related to
human health
We can use phylogenies to map characteristics of organisms to better understand evolutionary process
We can understand our origins, make better decisions as a society, and realize our place on the tree of life
Anatomy of phylogenetic trees
Phylogenies are figures that represent the ancestor-descendant relationships among a group of organisms.
Basic model of speciation; an ancestral lineages (A) splits into exactly two descendants (B and C).
Successive speciation (splitting) events lead to more complex patterns of ancestor-descendant relationships.
Phylogenetic trees
Taxa are at the tips; a taxon is any named group; taxa refers to multiple taxons.
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Nodes represent the most recent common ancestor (MRCA) of two (or more) descendant taxa.
Branches represent the evolution of taxa over time.
The root branch leads to the root node which is the MRCA of all descendent taxa on the phylogeny. (When a root
branch is present, phylogeny is rooted)
Time is represented on phylogenies; preceding nodes represent earlier speciation events.
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Oversimplifications of trees
Phylogenetic trees are oversimplifications of more complex evolutionary history.
1. Populations within species are usually not shown
a. Phylogenies are simplifications of complex, population-level processes that extend far back in time.
2. Many branches may not be shown
a. Only a subset of species are used for some lineages
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Document Summary

Current estimate of described species ~8. 7m with up to 80% yet to be named. Up to 86% of species are undescribed, with many discovered each year. Our discoveries are biased towards macroscopic life; new technology has accelerated the discovery of microbes . Phylogenies are powerful tools that help us make predictions about evolution, including topics related to human health. We can use phylogenies to map characteristics of organisms to better understand evolutionary process. We can understand our origins, make better decisions as a society, and realize our place on the tree of life. Phylogenies are figures that represent the ancestor-descendant relationships among a group of organisms. Basic model of speciation ; an ancestral lineages (a) splits into exactly two descendants (b and c). Successive speciation (splitting) events lead to more complex patterns of ancestor-descendant relationships. Taxa are at the tips; a taxon is any named group; taxa refers to multiple taxons.

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