Lecture 6

Question 1

What is adaptive radiation?

Answer 1

an event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations (i.e. cichlids, or Darwin’s finches)

Question 2

What are the mechanisms of adaptive radiation?

Answer 2

1. key-innovation: a novel trait (adaptation) that allows organisms to evolve to exploit a new niche or resource - i.e. evolution of vascular tissue in plants allowed them to shift from aquatic to terrestrial organisms
2. release from competition (vacated niches): occurs on islands or from extinctions; lineages that invade islands are free from competition with other species on the mainland, which may have species that fill all possible ecological niches, which prevents the lineage from splitting into new forms and diversifying - i.e. Hawaiian Honeycreepers invading islands, dinosaurs at the end of the Cretaceous period
3. specialization: can subdivide a single niche into many new niches - i.e. cichlid fishes take advantage of different foods

Question 3

What is phylogeny?

Answer 3

the evolutionary history of a lineage or lineages (populations, genes, or species)

Question 4

What is a phylogenetic tree?

Answer 4

a visual representation of a phylogeny

Question 5

Define the structures associated with a phylogenetic tree.

Answer 5

nodes: represent common ancestors for all descendent lineages
clades: a common ancestor and all of its descendants
taxa: hierarchies found in taxonomy; can be rotated around nodes and still depict the same relationships; the use of characters can be used to define groups nested within the phylogeny

Question 6

How should a phylogenetic tree be read?

Answer 6

look for common ancestry instead of reading along the tips

Question 7

True or False: Accurate phylogenetic trees can be constructed with varying scales and without all related species included.

Answer 7

true

Question 8

What are monophyletic groups?

Answer 8

clades; have the most recent common ancestor; can be separated from the phylogenetic tree with a single cut

Question 9

What are paraphyletic groups?

Answer 9

do not have the most recent common ancestor

Question 10

Are all Linnaean taxa monophyletic?

Answer 10

no (i.e. fish)

Question 11

What are characters and character states in phylogeny?

Answer 11

identifiable heritable traits and character states
i.e. in insects, wings is a character, and ‘present’ or ‘absent’ are character states
‘derived’ and ‘ancestral’ are also character states

Question 12

What are synapomorphies?

Answer 12

derived character states shared by the descendants of a common ancestor; homologous characteristics

Question 13

What is an outgroup in phylogeny?

Answer 13

used to infer approximate ancestral character states