Lecture Biology - Chapter 25: Reconstructing and using phylogenies. In this chapter, we will address the following questions: What is phylogeny? How are phylogenetic trees constructed? How do biologists use phylogenetic trees? How does phylogeny relate to classification? | Reconstructing and Using Phylogenies 25 Reconstructing and Using Phylogenies What Is Phylogeny? How Are Phylogenetic Trees Constructed? How Do Biologists Use Phylogenetic Trees? How Does Phylogeny Relate to Classification? 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. Figure How to Read a Phylogenetic Tree (Part 1) Figure How to Read a Phylogenetic Tree (Part 2) 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. What Is Phylogeny? A taxon (plural taxa) is any group of species that we designate (., vertebrates). A taxon that consists of all the descendents of a common ancestor is called a clade. 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. 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. 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. What Is Phylogeny? Features shared by two or more species that were inherited from a common ancestor are homologous. . | Reconstructing and Using Phylogenies 25 Reconstructing and Using Phylogenies What Is Phylogeny? How Are Phylogenetic Trees Constructed? How Do Biologists Use Phylogenetic Trees? How Does Phylogeny Relate to Classification? 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. Figure How to Read a Phylogenetic Tree (Part 1) Figure How to Read a Phylogenetic Tree (Part 2) 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. What Is Phylogeny? A taxon (plural taxa) is any group of species that we designate (., vertebrates). A taxon that consists of all the .
