[BIO 1306] Ch25_Lecture

[BIO 1306] Ch25_Lecture - 25 Reconstructing and Using...

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25 Reconstructing and Using Phylogenies
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25 Reconstructing and Using Phylogenies 25.1 What Is Phylogeny? 25.2 How Are Phylogenetic Trees Constructed? 25.3 How Do Biologists Use Phylogenetic Trees? 25.4 How Does Phylogeny Relate to Classification?
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25.1 What Is Phylogeny? Phylogeny is a description of the evolutionary history of relationships among organisms. This is portrayed in a diagram called a phylogenetic tree . Each split or node represents the point at which lineages diverged. The common ancestor of all organisms in the tree is the root .
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Figure 25.1 How to Read a Phylogenetic Tree (Part 1)
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Figure 25.1 How to Read a Phylogenetic Tree (Part 2)
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25.1 What Is Phylogeny? The timing of divergences is shown by the position of nodes on a time or divergence axis. Lineages can be rotated around nodes; the vertical order of taxa is largely arbitrary.
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25.1 What Is Phylogeny? A taxon (plural taxa ) is any group of species that we designate (e.g., vertebrates). A taxon that consists of all the descendents of a common ancestor is called a clade .
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25.1 What Is Phylogeny? Two species that are each other’s closest relatives are sister species . Two clades that are each other’s closest relatives are sister clades . Phylogenetic trees were used mainly in systematics (study of biodiversity); but are now used in nearly all fields of biology.
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25.1 What Is Phylogeny? One of the greatest unifying concepts in biology is that all life is connected through evolutionary history. The “Tree of Life” is the complete, 4- billion-year history of life. Knowledge of evolutionary relationships is essential for making comparisons in biology.
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25.1 What Is Phylogeny? Biologists determine traits that differ within a group of interest, then try to determine when these traits evolved. Often, we wish to know how the trait was influenced by environmental conditions or selection pressures.
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25.1 What Is Phylogeny? Features shared by two or more species that were inherited from a common ancestor are homologous . Example: The vertebral column is homologous in all vertebrates.
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25.1 What Is Phylogeny? A trait that differs from the ancestral trait is called derived . A trait that was present in the ancestor of a group is ancestral .
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25.1 What Is Phylogeny? Derived traits that are shared among a group and are viewed as evidence of the common ancestry of the group are known as synapomorphies . The vertebral column is a synapomorphy of all vertebrates.
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25.1 What Is Phylogeny? Similar traits can develop in unrelated groups of organisms: Convergent evolution —independently evolved traits subjected to similar selection pressures may become superficially similar. Example: the wings of bats and birds
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Figure 25.2 The Bones Are Homologous; the Wings Are Not
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25.1 What Is Phylogeny?
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[BIO 1306] Ch25_Lecture - 25 Reconstructing and Using...

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