roadmap 5&6

What is the ultimate source of genetic variation?

Mutation, which creates new alleles.

How does recombination create variation?

Crossing over during meiosis creates new allele combinations on chromosomes.

How does independent assortment contribute to variation?

Random segregation of chromosomes shuffles alleles into unique combinations.

How does sexual reproduction increase variation?

Combines alleles from two parents to create novel genotypes.

What is gene flow?

Migration of individuals or gametes that introduces alleles into a population.

What are single-gene differences?

Discrete Mendelian traits that can create dramatic phenotypic variation subject to selection.

Which of the following contributes to genetic variation: mutation, recombination, sex, or gene flow?

All of the above.

What does the root of a phylogenetic tree represent?

The common ancestor of all taxa in the tree.

What do nodes represent in a phylogenetic tree?

Points of divergence (speciation events).

What do tips (leaves) represent?

Current species or taxa.

What is a clade?

A monophyletic group (ancestor + all descendants).

What is a cladogram?

A tree showing branching relationships only; branch lengths arbitrary.

What is a phylogram?

A tree where branch length is proportional to amount of genetic change.

What is a chronogram?

A tree where branch length is proportional to time since divergence (calibrated with molecular clock).

What can branch length represent in phylogenetic trees?

Time since divergence, amount of genetic change, or number of mutations—depends on the method.

How do you identify sister taxa on a tree?

Two taxa that share a more recent common ancestor with each other than with any other group.

What does an outgroup do in a phylogeny?

Helps root the tree and polarize character changes.

What species concept matches the statement: "a group sharing a more recent common ancestor with each other than with others"?

The Phylogenetic Species Concept.