AP Biology 05/03/23

Chapter 25.Phylogeny & Systematics

An unexpected family tree. What are the evolutionary relationships among a human, a mushroom, and a tulip? Molecular systematics has revealed that—despite appearances—animals, including humans, and fungi, such as mushrooms, are more closely related to each other than either are to plants.

AP Biology 05/03/23

Building phylogenies Morphological & molecular homologies

similarities based on shared ancestries bone structure DNA sequences

beware of analogous structures convergent evolution

“Homoplasies” marsupial mole

placental mole

AP Biology 05/03/23

Evaluating molecular homologies Aligning DNA

sequences more bases in

common = more closely related

analyzed by software

beware of molecular homologies

AP Biology

Orthologous genes

05/03/23

Common genes:

differences due to

speciation; diverged after a speciation

event

AP Biology

Paralogous Genes

Common genes; differences due to a duplication event

Examples: next page

05/03/23

AP Biology

Ortho/Para Genes example:

05/03/23

AP Biology 05/03/23

Connection between classification & phylogeny

Tracing possible evolutionary relationships between some of the taxa of the order Carnivora, a branch of the class Mammalia.

Building trees

AP Biology 05/03/23

Illustrating phylogeny Cladograms

patterns of shared characteristics

Classify organisms according to the order in time at which branches arise along a phylogenetic tree

AP Biology 05/03/23

Illustrating phylogeny Cladograms

patterns of shared characteristics

Shared Primitive Character

AP Biology 05/03/23

Illustrating phylogeny Cladograms

patterns of shared characteristics

Shared Derived Character

AP Biology 05/03/23

Parsimony & analogy vs. homology

Phylogenetic trees are hypothesesWhich is the most parsimonious tree?

AP Biology 05/03/23

Parsimony & analogy vs. homology

Maximum Parsimony

Maximum Liklihood

AP Biology 05/03/23

Modern Systematics Shaking up some trees!

Crocodiles are now thought to be closer to birds than other reptiles

AP Biology 05/03/23

Molecular clocksTrace variations in genomes to date evolutionary changes

Rate of change is calculated and then extrapolate back

What does this assume?

HIV-1M samples were collected from patients between early 1980s & late 1990s. The gene evolved at a relatively constant rate. Concluded that HIV-1M strain first infected humans in 1930s.

AP Biology

Trees: Phylogram (Primates)

05/03/23

AP Biology

Tree: Phylogram (Giraffe species)

05/03/23

AP Biology

Tree: Ultrametric

05/03/23

AP Biology 05/03/23

Universal Tree of Life 3 Domains

Bacteria Eukarya Archaea