Ch 20: Phylogeny

Question 1

What is an outgroup on a phylogeny or evolutionary tree?

Answer 1

It’s the species or group from an evolutionary lineage that is closely related to but not part of the group of species we are studying.

p. 409

Question 2

A taxon is equivalent to a _____ only if it is monophyletic (from the Greek, meaning “single tribe”), signifying that it consists of an ancestral species and ALL of its descendants.

Answer 2

clade

Question 3

A __________ group (meaning “beside the group”), consists of an ancestral species and some but not all of its descendants.

Answer 3

paraphyletic

p. 408

Question 4

What is a polyphyletic group?

Answer 4

A group which includes distantly related species, but does not include their most recent common ancestor.

p. 408

Question 5

Describe the Linnaean system.

Answer 5

Related species are placed into genera, genera into families, families into orders, orders into classes, classes into phyla, phyla into kingdoms, and kingdoms into domains.

Question 6

Which hierarchies of taxa have their name italicized?

Answer 6

Species names and genera names only.

p. 402

Question 7

What are sister taxa?

Answer 7

Groups of organisms that share a common ancestor that is not shared by any other group.

p. 403-404

Question 8

Define phylogeny.

Answer 8

The actual evolutionary history of a species or group of species.

Question 9

__________ is defined as a discipline focused on classifying organisms (to genera, families, species, etc.) and determining their evolutionary relationships.

Answer 9

Systematics

Question 10

Which of the following statements about descent with modification is true?

a. ) An organism is likely to be more similar to organisms with which it shares a distant common ancestor than to those with which it shares a more recent common ancestor.
b. ) Two species whose common ancestor lived a long time ago are unlikely to share any characteristics.
c. ) Over time, evolution by natural selection causes species to accumulate differences from their ancestors.
d. ) All similarities between organisms result from descent from a common ancestor.

Answer 10

c

Question 11

The genome of an organism…..

a. ) …of one species is identical to the genome of an organism of a closely related species.
b. ) includes all of the organism’s DNA.
c. ) only includes the organism’s genes.
d. ) only includes segments of the organism’s DNA that do not encode proteins.

Answer 11

b.) An organism’s genome consists of the complete collection of its genes along with all of its noncoding DNA sequences.

Question 12

Define taxonomy.

Answer 12

The ordered division and naming of organisms.

Question 13

_________ _________ –> grouping species according to their evolutionary history. Taxonomy (naming) should reflect evolution.

(It wasn’t always like this. Linnaeus didn’t necessarily do it like this.)

Answer 13

Phylogenetic systematics

Question 14

A _________ is a hypothesis about the phylogeny.

Answer 14

cladogram

There is one evolutionary history (phylogeny), the cladogram represents our hypothesis about it.

Question 15

__________ is a synonym for phylogenetic systematics.

Answer 15

Cladistics

Question 16

Define a polytomy on a cladogram.

Answer 16

-tomy refers to split. A place where one line splits into more than 2.

Question 17

Suppose that two distantly related species live in similar environments and share a distinctive characteristic that facilitates survival in their environment but is not found in their immediate ancestors. Based on this information, this distinctive feature most likely represents

a. ) a character that arose by chance in each species.
b. ) a homologous character.
c. ) a character that spread from one species to the other by matings between species.
d. ) an analogous character

Answer 17

d.

Analogous characters arise by convergent evolution and have similar functions, but not common ancestry.

Question 18

How are phylogenetic trees constructed?

Answer 18

Fossil record
Morphology of living organisms; bones muscles, etc.
Molecules, DNA, RNA, proteins

Question 19

There are specific rules about what kinds of characteristics can be used to build a phylogenetic tree:

• -Use only shared _______ characteristics.
• -Use only most parsimonious tree (fewest changes; simplest explanation).
• -Lineages branch from 1 –> 2 (if a polytomy is present, it’s a lack of data problem).

Answer 19

derived

Question 20

What is the evolutionary pattern of leglessness in reptiles?

Answer 20

It evolved twice, as a result of convergent evolution.
Leglessness is an analogous trait in this case.

This is the most parsimonious explanation for the available data.

Question 21

Adding time scale to a cladogram with fossils. Position in layers gives un relative dating.
Numerical dating , dating of volcanic ash

Question 22

Carbon-14 dating only helpful for 60,000 years ago.

See Ch 23

Question 23

Radioisotope dating methods can’t be used with sedimentary rocks.

Question 24

adding time scale using genetic changes (mutations).

Answer 24

*** # of changes proportional to the time since a lineage split.
Degree of genetic difference.
Compare number of mutations to divergence time (millions of years) from fossil record.

Question 25

What is the difference between a cladogram and a phylogenetic tree?

Answer 25

A cladogram is a hypothesis (or current understanding) about the phylogeny. Remember there is only one true evolutionary history (phylogeny).

Question 26

A homoplasy is a similar (analogous) structure or molecular sequence that has evolved _____________ in two (or more) species.

Answer 26

independently

Question 27

An homology is a similarity in characteristics resulting from…

Answer 27

….shared ancestry, or shared evolutionary history.