2 - The Tree Of Life

Question 1

Clade/monophyletic group def

Answer 1

a piece of phylogeny that includes an ancestral lineage of an organism and all the descendants of that ancestor

Question 2

Homology def

Answer 2

any similarity between traits that is due to the organisms’ shared ancestry

Question 3

Synamorphies def

Answer 3

derived form of a trait shared by a group of related species

Question 4

Molecular evidence for evolution

Answer 4

DNA similarities between certain species can indicate a close relationship, or a common ancestor
- bases sequences of some other proteins can also indicate relationships, e.g. cytochrome C

Question 5

Phylogeny def

Answer 5

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

Question 6

node def (in phylogenetic trees)

Answer 6

points in phylogeny where a lineage splits

Question 7

Tips def (phylogeny trees)

Answer 7

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

Question 8

what does a phylogenetic tree consist of

Answer 8

consist of nested clades

Question 9

characters def

Answer 9

heritable aspects that can be compared

Question 10

Taxa def

Answer 10

group of organisms that form a cohesive taxonomic unit, such as ‘order’ or ‘phylum’

Question 11

homology def

Answer 11

similarity of traits in different species resulting from their inheritance from a common ancestor

Question 12

Phylogenetic interference principles

Answer 12

1. assume similar features are homologous until proven otherwise
2. use shared derived features, not shared ancestral ones

Question 13

synapomorphy def

Answer 13

shared derived character

Question 14

why may microorganisms share genes

Answer 14

sharing of genes by horizontal gene transfer

Question 15

autapomorphy def

Answer 15

a derived trait unique to one group of organisms

Question 16

Root def (phylogeny tree)

Answer 16

ancestral population from which all other species originate in a evolutionary tree

Question 17

why phlogeny useful

Answer 17

• organise knowledge of biological diversity
• structuring classifications
• providing insights into events that occurred during evolution

Question 18

why some lineages often split during evolution

Answer 18

when groups of populations become genetically isolated from one another
- migration of individuals from one area to another - called founder event
- geological or climatic events - e.g. natural disaster - called vicariance

Question 19

founder effect def

Answer 19

migration of a few individuals to a new isolated region (e.g. an island)

Question 20

what does genetic isolation cause (founder effect or vicariance)
- why

Answer 20

reproductive isolation as:
- can lead to new selective pressures in new environments
- so isolated group will start evolving differences from one another
- as a mutation in one group has no way to get to the other population

Question 21

vicariance def

Answer 21

when population or group split by geological or climatic events - natural disasters

Question 22

what can be assumed when two lineages diverge (by founder effect or vicariance)

Answer 22

the two sets of descendants will remain distinct - may develop reproductive isolation between one another, etc.

Question 23

what do branching points in a tree correspond to

Answer 23

correspond to nodes - inferred speciation events

Question 24

importance of phylogenetic trees

Answer 24

• efficient structure for organizing knowledge of biodiversity
• easily visualise evolutionary history (phylogeny) of an organism

Question 25

branches def

Answer 25

are lineages evolving through time that connect successive speciation or other branching events.

Question 26

internal nodes def

Answer 26

nodes that occur within a phylogeny and represent ancestral populations or species

Question 27

Monophyletic def

Answer 27

describes a group of organisms that form a clade

Question 28

Polyphyletic def

Answer 28

describes a taxon that does not include the common ancestor of all the members of the taxon

Question 29

Paraphyletic def

Answer 29

describes a group of organisms that share a common ancestor although the group does not include all the descendants of that common ancestor.

Question 30

Outgroups def

Answer 30

groups of organisms (e.g., a species) that are outside of the monophyletic group being considered

Question 31

Homoplasy def

Answer 31

describes a character state not due to shared descent

Question 32

Convergent evolution def

Answer 32

independent origin of similar traits in separate evolutionary lineages

Question 33

Evolutionary reversal def

Answer 33

describes the reversion of a derived character state to a form resembling its ancestral state

Question 34

Polytomy def

Answer 34

describes an internal node of a phylogeny with more than two branches (i.e., the order in which the branchings occurred is not resolved)