Phylogeny and Systematics

Chapter 25

• Phylogeny – evolutionary history of a species or group of

species

• Systematics – study of biological diversity in evolutionary

context– Naming and classifying organisms

How do we know this stuff?

• Evidence of phylogeny– Fossil record– Morphology

• Homology – similarity due to shared ancestor• Analogy – similarity due to convergent evolution

– Molecular evidence (DNA)

Fossil Record & Geologic Time

• Sedimentary rocks are the richest source of fossils

Fossil Record: layers of fossils in sedimentary rocks – marks passing of geologic time

Geologic Time Scale

Methods to Date Fossils

• Relative Dating – location of fossils in layers of rock– Oldest layers are below newer layers

• Absolute Dating – age given in years– Radiometric dating

• Radioactive isotopes– Carbon, nitrogen, uranium

– L- and D- amino acids

Radiometric Dating

Plate Tectonics

History of Continental Drift

Mass Extinctions & Biodiversity

K-T Extinction

Systematics

Connecting Classification & Phylogeny

Classification

Classification & Phylogeny

CladogramsGrouping species based on similarities

Shared primitive character – shared beyond taxon we are trying to define

Shared derived character – evolutionary novelty unique to a particular clade

Clade: an ancestral species and all of its decendentcs (monophyletic group)

Cladistics and Taxonomy

Modern systematics is shaking up some phylogenetic trees

A phylogenetic tree is a hypothesis

Timing

• Molecular clocks– Mutations happen

at a steady rate