25 Phylogenetics

Question 1

Phylogeny

Answer 1

the evolutionary history of a group of organisms

Question 2

Phylogenetic tree

Answer 2

a branching diagram that depicts the evolutionary relationships among species or other taxa

Question 3

Tree of life

Answer 3

most universal phylogenetic tree that includes all organisms

Question 4

Branches

Answer 4

a part of a phylogenetic tree that represents populations through time

Question 5

Root

Answer 5

the most ancestral branch in a phylogenetic tree

Question 6

Nodes (forks)

Answer 6

a point within a phylogenetic tree where two branches spit, representing the point in time when a hypothetical ancestral group (the most recent common one) split into two or more descendant groups

Question 7

Tips (terminal nodes)

Answer 7

endpoint of a branch in a phylogenetic tree that represents a living or extinct group of genes, species, families, phyla, or other taxa

Question 8

Where are taxa located in a phylogenetic tree?

Answer 8

On the branch tips, never within a tree, because none of the taxa (living or extinct) are presumed to be ancestors of others

Question 9

Sister groups

Answer 9

two or more lineages that share a recent common ancestor at the node where their branches meet

Question 10

Speciation event

Answer 10

two populations within the ancestral species become genetically isolated and diverge over a long or short time due to mutation, natural selection, and genetic drift, leading to different species

Question 11

Polytomy

Answer 11

a node in a phylogenetic tree that depicts an ancestral branch dividing into 3 or more descendant branches, indicating insufficient data is available to know which taxa are more closely related

Question 12

Character or trait

Answer 12

any observable characteristic (genetic, morphological, physiological, developmental, or behavioral) to be studied

Question 13

Outgroup

Answer 13

a taxon that is closely related to the taxa being studied (a sister group) but that diverged earlier used to establish the relative timing of evolution of each character

Question 14

Ancestral trait

Answer 14

trait found in the ancestors of a particular group

Question 15

Derived trait

Answer 15

a trait that is a modified form of an ancestral trait, found in a descendant, and originates via mutation, selection, and genetic drift

Question 16

Cladistic approach or cladistics

Answer 16

a method for constructing a phylogenetic tree that is based on identifying shared, derived traits called synapomorphies

Question 17

Synapomorphy

Answer 17

a shared, derived trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors i.e. a monophyletic group

Question 18

Monophyletic group or clade or lineage

Answer 18

an evolutionary unit that includes an ancestral population and all of its descendants but no others

Question 19

Principle of Parsimony

Answer 19

logical principle that the most likely explanation of a phenomenon is the most economical or simplest (the one with the fewest character changes)

Question 20

Homology “same source” or Homologous traits

Answer 20

similarity among organisms of different species due to shared ancestry (e.g. all mammals have hair); used to determine monophyletic groups

Question 21

Homoplasy “same form”

Answer 21

Similarity among organisms of different species due to reasons other than common ancestry like convergent evolution

Question 22

Convergent evolution

Answer 22

the independent evolution of similar traits in different species due to adaptation to similar environmental conditions and a similar way of life

Question 23

What is the evidence that all organisms share a common ancestor?

Answer 23

(1) All organisms are made of cells (2) DNA is the genetic material of all cells (3) Basic chemical building blocks are common to all cells (4) Genetic code

Question 24

Cladogram

Answer 24

phylogeny where only the order of the nodes matter and the length of the branches is meaningless

Question 25

Phylogram

Answer 25

phylogeny where branch length represents change; usually includes a scale bar to indicate rate of change

Question 26

What are the 2 types of phylogenies?

Answer 26

cladogram and phylogram