Phylogenies

Question 1

Phylogeny

Answer 1

the evolutionary history of a group of organisms

Question 2

Phylogenic tree

Answer 2

graphical summary of this history, showing the evolutionary relationships among genes, populations, species, or higher taxa

Question 3

Tree of life

Answer 3

the most universal of all phylogenetic trees, depicting the evolutionary relationships among all living organisms on Earth

Question 4

nodes

Answer 4

forks in the tree

represent hypothetical common ancestors

Question 5

Where are taxa located?

Answer 5

At the tips of the tree, never in the middle, even if some of the taxa are extinct

Question 6

Sister groups

Answer 6

share a recent common ancestor at the node where their branches meet

Question 7

What happens once species diverge?

Answer 7

Both species continue to evolve

Question 8

Outgroup

Answer 8

a taxon that diverged prior to the taxa that are the focus of the study

a sister group

helps to root the tree

Question 9

Polytomy

Answer 9

a node that depicts an ancestral branch dividing into 3 of more (rather than two) descendant branches

usually indicates where there was insufficient evidence to determine which taxa are more closely related

Question 10

Are the number of nodes important?

Answer 10

No

Question 11

Are phylogenetic trees exact?

Answer 11

No. They must be estimated through using a variety of data.

Phylogenetic trees are like hypotheses that can be tested and are often revised as new data becomes available

Question 12

What is the first step in inferring evolutionary relationships?

Answer 12

Decide which taxa to compare

Decide which characteristics to use to compare

Question 13

character or trait

Answer 13

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

Question 14

Willi Henning

Answer 14

developed the cladistic approach

Question 15

Cladisitic approach

Answer 15

a way to estimate a phylogenetic tree

based on the principle that relationships among species can be reconstructed by identifying shared derived traits, called synapomorphies

Question 16

synamorphy

Answer 16

a trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors

can include gaining and loosing characteristics

Question 17

monophyletic group

Answer 17

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

Question 18

paraphyletic group

Answer 18

a group that includes an ancestral population and some of its descendants, but not all

can be if a trait was lost in one of the descendants, not all have it

Question 19

parsimony

Answer 19

the most likely explanation or pattern is the one that assumes the fewest steps to reach a particular result

Question 20

In cladistics are the length of the branches important?

Answer 20

No

Question 21

How is parsimony implemented?

Answer 21

through computer programs

Question 22

homoplasy

Answer 22

occurs when traits are similar for reasons OTHER than common ancestry

Question 23

convergent evolution

Answer 23

the independent evolution of similar traits in distantly related organisms due to adaptation to similar environment and lifestyles

not due to common ancestry

Question 24

What is a cause of homoplasy?

Answer 24

Convergent evolution

Question 25

The whale example

Answer 25

Does not follow parsimony because the whale had to gain the pulley shaped astragalus and then loose it, but it is supported by fossils and DNA data

Question 26

An example of a homoplasy

Answer 26

Cell walls in plants and fungi

They are made out of different materials

Question 27

the best classification system…

Answer 27

most closely reflects evolutionary history

Question 28

molecular systematics

Answer 28

the use of molecular genetics to study the evolution of relationships among individuals and species

Question 29

Four chambered hearts of birds and mammals example

Answer 29

Their common ancestor only had a 3 chambered heart, so the four chambered heart in birds and mammals had to have evolved independently after they split from the common ancestor

Question 30

Note: figure out how to do the last problem with most parismonous tree

Answer 30

do practice taking data and constructing the most parismonious tree