Unit 26 Part 2

Define Cladistic analysis

Classifies organism according to the order in time that branches arose along a dichotomous phylogenetic tree

• Clad is an evolutionary branch

• use novel homologies to define branch points on phylogenetic trees

Define outgroup comparison

The one most closely related to the ancestor

What is principle of maximum parisnary

Sometimes referred to as the KISS principle

• Keep It Simple Stupid

• Find the simplest explanation that is consistent with the facts

What is the phylogenic tree hypothesis?

They’re guesses backed by evidence

used to make predictions about the past

Explain how an organisms evolutionary history is documented in its genome

Molecular systematics helps us to uncover evolutionary relationships

Important for organisms where we have fossils

Different genes evolve at different rates

DNA that codes for rRNA changes relatively slowly

• used to study divergence hundred of millions years ago

Mitochondrial DNA, mtDNA, evolves relatively rapidly

• used for more recent divergences

Define molecular clocks

Measuring the absolute time of evolutionary change based on the observation that same genes evolve at a regular rate

• calibrated by comparing the number of genetic differences against the dates of the evolutionary branch points that are known in fossil record