BIOL1030 Topic 1 Phylogeny and Cladistics

Define taxonomy

the discipline of naming and categorizing organisms.

How are taxa categorized?

Based on shared traits.

What are the 3 types of shared traits that taxa are categorized by?

• Morphological traits

• Molecular (e.g., gene/protein sequences)

• Developmental features/processes

What is the Mneomic for classification?

Dear King Philip Came Over For Good Soup

Soup

Define phylogeny

the evolutionary history of a species or a group of related species.

What does a node on a phylogenetic tree depict?

Common ancestors.

What does each branch point represent on a phylogenetic tree?

The divergence of two species (speciation event).

True/False: Tree branches can be rotated around a branch point.

True.

What is a sister taxa?

groups that share an immediate common ancestor

What is a rooted phylogenetic tree?

includes a branch to represent the last common ancestor of all taxa in the tree.

What is an out group on a phylogenetic tree?

A more distantly related group of organisms that serves as a reference.

What is a polytomy?

a branch from which more than two groups emerge

Why do polytomys occur?

Usually because there is an unresolved level of divergence among them.

Phenotypic and genetic similarities due to shared ancestry are called...

homologies.

Are organisms with similar morphologies or DNA sequences more or less likely to be related than organisms with different structures or sequences?

More likely.

Define homologous structures

Same structure, different function.

What type of evolution results in homologous structures?

Divergent evolution.

Define analogous structures.

Different structure, same function.

What type of evolution results in analogous structures?

Convergent (independent) evolution.

Does a phylogeny have to show similarities due to homology or analogy?

Homology.

Define cladistics.

classification based on common ancestry

What is a clade?

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

What is a monophyletic clade?

a clade that consists of the ancestor species and all its descendants.

What is a polyphyletic clade?

A clade that includes distantly related species but does not include their most recent common ancestor.

What is a paraphyletic clade?

A clade that includes an ancestral species and some, but not all, of the descendants.

What is a shared ancestral character?

a character that originated in an ancestor of the taxon.

What is a shared derived character?

a character novel to a particular clade. The character is not found in an ancestor.

Can a character be both ancestral and derived? Why or why not?

Yes. Because it depends on the context.

If an ancestor lacks a characteristic shared by all descendants, what do we define it as?

An out group.

What in an organisms genome can you use to infer relatedness?

Nucleic acid sequences or other molecules.

Does DNA coding for rRNA change relatively quickly or slowly?

Slowly.

Why is DNA coding for rRNA useful for investigating branch points hundreds of millions of years ago?

Because the evolutionary changes are slow.

What type of DNA evolves rapidly and can be used to explore recent evolutionary events?

mitochondrial DNA.