Ch.26 - Phylogeny and Tree of Life

Question 1

Goals of chapter 26:

Become familiar w vocab relating to systematics and phylogenetics.

Correctly interpret relationships shown on phylo trees.

Have a basic understanding of how phylo trees:

• are constructed using parsimony
• can be used to test hypotheses

Answer 1

Goals of chapter 26:

Become familiar w vocab relating to systematics and phylogenetics.

Correctly interpret relationships shown on phylo trees.

Have a basic understanding of how phylo trees:

• are constructed using parsimony
• can be used to test hypotheses

Question 2

Which field of biology is devoted to the ordered division and naming of organisms

Answer 2

Taxonomy: a field of biology devoted to the ordered division and naming of organisms

Question 3

___________ is a field of biology focused on determining evolutionary relationships among different groups.

Answer 3

Systematics: a field of biology focused on determining evolutionary relationships among diff groups.

• Use data fr fossils, genes, and behavior to infer evol relationships
• Illustrate relations in branching phylogenetic trees.

Question 4

What is phylogenetics?

Answer 4

Phylogenetics: a method for det evol relationships

• Phylogeny: evolutionary history of a species or group of species

Question 5

A phylogenetic tree represents a hypothesis about ______________.

Answer 5

A phylogenetic tree represents a hypothesis about evolutionary relationships.

Question 6

What does each branch in a phylo tree rep?

Answer 6

Each branch point represents the split of two species

Question 7

_________ are groups that share an immediate common ancestor

Answer 7

Sister taxa are groups that share an immediate common ancestor

I.e. share a unique common ancestor not shared by any other groups.

Question 8

What is meant by a rooted tree? Polytomy?

Answer 8

Rooted tree: has branch representing the last common ancestor of all taxa in the tree.

Polytomy is a branch from which more than two groups emerge

Question 9

T/F: phylo trees show patterns of descent and indicate absolute age.

Answer 9

FALSE

Phylo trees DO show patterns of descent

Phylo trees DO NOT indicate absolute age

It shouldn’t be assumed that a taxon evolved from the taxon next to it

Question 10

Describe how to create a phylogenetic tree

Answer 10

Gather data on groups of interest:

• Morphology, genes, biochem, behavior
• Use only traits that result fr common ancestry (homologies)
• Avoid traits that are result of convergent evolution (analogous traits)

Question 11

Analogous structures or molecular sequences that evolved independently are also called _________

Answer 11

Analogous strucs or molecular seqs that evolved indep are also called homoplasies

• Result of convergent evol, NOT common ancestry.

Question 12

How might fossil evidence and degree of complexity be used to distinguish homologous structures from analagous/homoplasies?

Answer 12

The more complex two similar structures are, the more likely it is that they are homologous

Question 13

What is a clade?

Answer 13

Clade: group of species wh incl a common ancestor and all species that descended from that ancestor

Aka monophyletic groups

Can be nested w/i larger clades

Question 14

What is contained w/i a paraphyletic group?

Answer 14

Paraphyletic group contains a common ancestor and some, BUT NOT ALL, of its descendents

Question 15

What differentiates a polyphyletic group from a mono- or paraphyletic group?

Answer 15

Polyphyletic group: includes taxa with a different common ancestor

Question 16

Differentiate shared ancestral vs shared derived traits.

Answer 16

Shared ancestral: character that originated in common ancestor of a taxon

• All members of the taxon have that trait
• Ex: all vertebrates (incl mammals) have a backbone

Shared derived: an evolutionary novelty unique to a partic clade

• Ex: w/i vertebrates, only mammals have hair

Question 17

Describe how to infer phylogenies (evol relationships)

Answer 17

Ask: in wh clade did a shared derived character first arise?

Make table listing shared derived traits

• For ea group of interest, note whether character is present (1) or absent (0)

Include an outgroup: group known to have diverged fr evol lineage before any groups of interest.

Most common trait reps first branch point on phylo tree → repeated for next most common trait.

Question 18

What is the principle of max parsimony?

Answer 18

Investigate the simplest explanation that is consistent with the facts

Most parsimonious tree reqs fewest evol events:

• Simplest pattern of morphological changes
• Fewest # of DNA base changes
• Utilizes computer programs

Question 19

Principle of Maximum Likelihood

Answer 19

Some DNA base changes are more likely than others

Question 20

Explain why phylogenetic trees are considered relative and not absolute.

Answer 20

Can det wh traits occurred earlier and wh occurred later relative to other trait

Question 21

Length of a branch reflects _____________

Answer 21

Length of a branch reflects number of genetic changes

May also rep time—det by fossil record. Always check if indicated.

Question 22

______________ allows us to predict features of an ancestor from features of its descendents

Answer 22

Phylogenetic bracketing allows us to predict features of an ancestor from features of its descendents

• “In-reverse” inference
• E.g. used to infer features of dinosaurs from their descendents (birds and crocodiles)

Question 23

T/F: The animal kingdom in monophyletic

Answer 23

TRUE

The animal kingdom in monophyletic

Question 24

Given a phylogenetic tree, describe how to det:

• Closest relatives
• Sister groups
• Clade/monophyletic groups

Answer 24

Given a phylogenetic tree, describe how to det:

• Closest relatives - anything conn to shared node
• Sister groups
• Clade/monophyletic groups - includes node
• Sister taxa
• common ancestor
• taxon closely related

Question 25

Each branch tip on a phylogenetic tree represents a specific group of organisms known as a(n) _______

Answer 25

Each branch tip on a phylogenetic tree represents a specific group of organisms known as a taxon.