Biology 10 Tree of Life

What are shared ancestral characters?

Characteristics or features that are present in a group because they were present in the ancestors of the group. Shared accumulated history.

What is synapomorphy?

An evolutionary novelty shared by a particular clade (shared derived character)

What is a clade?

A group of species that includes an ancestral species and all of its descendants

What is a cladogram?

A branching diagram used to show phylogenetic relationships among organisms.

What is homology?

Similarity in characteristics due to a shared ancestor

What is a homoplasy?

Similar (analogous) structures that evolved independently in two separate species

What is Maximum Parsimony?

When exploring explanations for an observation, one should investigate the simplest explanation that is consistent with the facts

Why is parsimony important to cladograms?

The most parsimonious cladogram is the one that requires the smallest number of evolutionary events.

What is an outgroup?

An organism very distantly related to the rest of the organisms in the cladogram through a common ancestor. Closely related to the ingroup. Characters shared by outgroup and ingroup are ancestral.

What is a branch point?

Where lineages diverge in a cladogram

What are shared derived characters?

Evolutionary novelties unique to a particular clade. Not originated in the ancestor of a taxon.

What are taxa?

The units used in biological classification of organisms. They are grouped based on morphological and molecular homologies.

What is maximum likelihood?

Given certain rules about how DNA changes overtime, a tree can be found that reflects the most likely sequence of evolutionary events.

What are phylograms?

They depict the amount of evolutionary change. Branch length is proportional to the change. Scale determined from fossil record and/or molecular clock calculations based on changes in DNA sequences.

What is a molecular clock?

Determined by amount of DNA change, calibrated against branches whose dates are known from the fossil record.