Evolution of species

Cladistics

• A simple and objective way of constructing phylogenies (phylogenetic trees)

• Focus on shared derived characters• Clade – group of organisms related by descent• Synapomorphy – shared derived character of

a clade• Cladogram – the branching diagram

representing the phylogeny• plesiomorphy - ancestral traits• apomorphy - derived character evolved within a

clade

3

Mode of speciation

• Gradualism vs. punctuated equilibrium

Sympatry vs. allopatry

• Sympatry – species that co-occur in space and time

• Allopatry – species that do not overlap in distribution

• Speciation most readily occurs in allopatry

Islands

• Importance to speciation due to isolation

Ring species

Isolating mechanisms

The evolution of life

Angiosperms

Gymnosperms

Pteridophytes

Day 1 in the life of earth

Today

First Bacteria

Sudden increase inDiversity

Evolution of life

1 Billion

4 Billion

4.5 Billion

- 3500 Pre-Cambrian – protosynthesis, prokaryotes, first eucaryotes, multicelluar organisms.

- 545 Cambrian – huge increase in diversity, first algae, first vertebrates, invertebrates dominate.

- 500 Ordovician – plants colonize land

- 440 Silurian – fish, insects plus other inverts colonize land

- 410 Devonian – amphibians colonize land

- 355 Carboniferous – Extensive forests, amphibians dominate on land, first reptiles

- 290 Permian – Pangea forms, reptiles dominate land

- 250 Triassic – early dinosaurs, first mammals

- 205 Jurassic – continents begin to separate, first birds, flowering plants

- 145 Cretaceous – flowering plants dominate land, dinosaurs go extinct

- 65 Tertiary – continents near present position, flowering plants, birds and mammals, pollinating insects

- 1.8 Quaternary – repeated advance and retreat of glaciers, humans, large mammals and birds go extinct.