phylogenies

Linnaeus’s taxonomy

Kingdom, phylum, class, order family, genus species

Taxon

Major groupings of organisms

Sister taxa

Two or more closely related taxa

How do systematics studies group species?

With common evolutionary descent

What do taxonomic groups include?

The most recent common ancestor

Claude

A group of taxa that share a common ancestor

What is the major goal of systematics?

To infer an evolutionary tree

Phylogeny

The evolutionary history of a group of species

Phylogenetic tree

The graphical representation of this history

What do evolutionary trees describe?

Pattern (cladograms) and in some cases the timing of events (phylograms) that occurred as species diversified

What does a phylogenetic trees show?

Terminal taxa, monophyletic group, root, branch, nodes

Why are nodes important?

Indicate most recent common ancestors (before lineages split), can indicate speciation points

Monophyletic group

Includes the moon ancestor and all the descendants of that ancestor

What types of characters are common in related taxa?

• sequences of nucleotides in a particular gene (DNA data)

• Presence of absence of specific skeletal elects or flower parts (morphological characters)

• Mode of embryonic or larval development (developmental traits)

• Physiological, behavioural, biochemical

Homologous characters

Similarities in biological structures or sequences in different species that are due to common ancestry

What are traits that can be inherited from a common ancestor?

DNA sequences, protein, anatomical structure, behaviour pattern

Synapomorphies

A homologous trait that is shared among certain species and is similar because it was modified in a common ancestor (a shared, derived trait, inherited by descendants)

What do synapomorphies identify?

Monophyletic groups (clades)

How can synapomorphies be identified?

At the level of population, species, genera, phyla, etc

Monophyletic group

Includes the common ancestor and all the descendants of that ancestor (they share synapomorphies)

Paraphyletic group

Includes the common ancestor and some, not all, of the ancestor’s descendant

Polyphyletic group

Does not include the common ancestor of the group

Convergent evolution

The independent evolution of similar feature by 2 or more groups

Process where unrelated species independently evolve similar traits due to adapting to similar environmental pressures or ways of life

How do you distinguish between homoplasious and homologous characters?

Homologous - similarities in traits due to shared ancestry

Homoplasious - similarities that evolved independently in different lineages

Molecular clocks

To estimate the timing of evolutionary events (measures number of changes, mutations, which accumulate in gene sequences of different species over time)