Chapter 23 - Systematics, Phylogenies, and Comparative Biology

What is phylogeny?

A hypothesis about the evolutionary relationships among species.

What are ancestral traits?

Traits inherited from a distant common ancestor ex) ancestor passed on blue eyes

What are derived traits?

shared by a subset of group - makes species unique

What is a cladeogram?

A branching diagram that shows hypothesized evolutionary relationships.

What is a synapomorphy?

shared derived trait that indicates species share a recent common ancestor, makes group unique

What is a plesiomorphy?

An ancestral trait, also in outgroup

What is homoplasy?

A trait shared by species not because of a common ancestor, often due to convergent evolution. BAD, ex) wings of bats/ birds

What are homologous structures?

HOMO = SAME. derived from same common ancestor, which may differ in function. ex) human hand & bat hand evolve from same ancestor

What are analogous structures?

Traits with similar functions but difd evolutionary origins, often result of convergent evolution ex) the wings of birds, bats, and insects

What does Biological Species Concept (BSC) define?

interbreeding population reproductively isolated. ex) 2 diff dog breeds to create 1 dog

limitations of the Biological Species Concept?

It cannot be applied to allopatric populations, asexual organisms, fossil species, or geographically isolated populations. ex) 1 dog in US and same breed in Africa = cannot ever breed!

What is the Phylogenetic Species Concept (PSC)?

population/ set of populations that have 1+ shared derived characters/traits (if they look diff = ARE diff species)

Why is the Phylogenetic Species Concept useful?

It doesn’t rely on interbreeding & can be applied to asexual organisms, fossils, and geographically separated populations.

How does BSC differ from PSC?

BSC focuses on reproductive isolation, while PSC focuses on shared derived traits and evolutionary relationships.

what is homoplastic convergence

similar traits have evolved independently in diff. clades, through natural selection. ex) echolocation, opposable thumbs

what determines homologies

phylogenetic analysis

not all genetic characters evolve at the…

same speed. CAN calculate how fast species change if u estimate speed.

losing traits is helpful for …

figuring out a cladeogram

symplesiomorphies

shared ancestral states, more specific then plesiomorphies.

what is more specific then plesiomorphies

symplesiomorphies

outgroup

used to compare, relative position, related too but not member of group. BUT.. w/out it - hard to determine how others differ ex) Dr.T doesnt look tall next to siblings, but YES next to us

characters can be any aspect of the ..

phenotype (recognizable trait). need recognizable character states: YES or NO (no in-between)

cladistic methods

ancestral vs derived

ex of shared derived feature of mammals

presence of hair