Chapter 4: The Tree of Life

Question 1

phylogeny

Answer 1

a visual representation of the evolutionary history of populations, genes, or species

Question 2

tips

Answer 2

terminal ends of an evolutionary tree, representing species, molecules, or populations being compared

Question 3

branches

Answer 3

lineages evolving through time between successive speciation events

Question 4

node

Answer 4

a point in a phylogeny where a lineage splits (a speciation event)

Question 5

internal node

Answer 5

nodes within a phylogeny representing ancestral populations or species

Question 6

clade

Answer 6

an organism and all its descendants

Question 7

monophyletic

Answer 7

a term used to describe a group of organisms that form a clade

Question 8

characters

Answer 8

heritable aspects of organisms that can be compared across taxa

Question 9

taxon

Answer 9

a group of organisms that are a taxonomic unit, such as a species or order (can be species, family, or class)

Question 10

synapomorphy

Answer 10

shared derived character evolved in the immediate common ancestor of a clade & was inherited by all its descendants

Question 11

cladistics

Answer 11

phylogenetic methods that construct trees by grouping taxa into nested hierarchies (clades) according to their synapomorphies

Question 12

homoplasy

Answer 12

character state similarity not due to shared descent (unreliable way to build phylogeny b/c trait came from convergent evolution/evolutionary reversal)

Question 13

convergent evolution

Answer 13

the independent origin of similar traits in separate evolutionary lineages; the same solution to an evolutionary problem (ex: dolphins and sharks are both streamlined)

Question 14

evolutionary reversal

Answer 14

the reversion of a derived character state to its ancestral state (ex: snakes lost limbs which was a characteristic of vertebrate common ancestor)

Question 15

exaptation

Answer 15

a trait that originates performing one function, and which is later co-opted for a new function

Question 16

australopithecines

Answer 16

members of the hominin genus Australopithecus

Question 17

polyphyletic

Answer 17

referring to a taxon which does not contain the most recent common ancestor of all members of the group; results when you focus on just one or two traits (like having all “flying things”)ex: pachyderms are a polyphyletic group b/c having thick skin evolved separately but they do all have it

Question 18

paraphyletic

Answer 18

referring to a taxon which includes most recent common ancestor and some, but not all of its descendents; a really bad classification

Question 19

rooted tree

Answer 19

straightforward progression with a clear indication of the direction of time

Question 20

unrooted tree

Answer 20

bush-like tree which is #NotClearOn progression of time; branch tips more recent than interior nodes but can’t tell recency of branch vs branch

Question 21

ingroup

Answer 21

the various species being studied or included in a phylogeny

Question 22

outgroup

Answer 22

close relative of members of the ingroup which provides a basis of comparison

Question 23

homoplasy

Answer 23

analogous trait in a tree; can’t figure out exact sequence (bad way to determine tree)

Question 24

symplesiomorphy

Answer 24

new trait in a lineage that appears in one taxon (bad way to determine tree)

Question 25

divergent evolution

Answer 25

closely related populations became different species because selection operated differently on them (creates homologous traits)