Phylogeny

Question 1

What is a Phylogeny?

Answer 1

A hypothesis concerning the evolutionary history of relationships among organisms. Portrayed in a diagram called a phylogenetic tree. Each split represents speciation from a common ancestor.

Question 2

Is there such thing as a reptile?

Answer 2

No, because reptiles would have to include birds to be monophyletic.

Question 3

Clade

Answer 3

Monophyletic Group. Group of species diverged from a common ancestor.

Question 4

Paraphyletic

Answer 4

Phylogenetic grouping that purposefully excludes one or more species (reptiles, fish, invertebrates).

Question 5

Polyphyletic

Answer 5

Grouping together things that have other closer relatives because they look similar (worms).

Question 6

Taxonomic classifications

Answer 6

nested clades.

Question 7

How do we reconstruct evolution?

Answer 7

Synapomorphy… look at shared and derived traits, physical or genetic.

Question 8

Homology vs Convergence

Answer 8

Convergent evolution is when two things independently evolve traits that seem homologous but aren’t. One has to look closely at structure to determine which is which.

Question 9

Homoplasy

Answer 9

Confusing situations in which character states are due to convergence or reversal rather than common ancestry.

Question 10

Parsimony Principle

Answer 10

The simplest explanation for data is preferred.

Question 11

Why use an outgroup when building a phylogeny?

Answer 11

Comparison with the outgroup shows which character states are derived and which are ancestral. Allows us to “root the tree”