Chapter 26 terms / concepts

Question 1

Phylogeny

Answer 1

The evolutionary history of a species or group of species

Question 2

Systematics

Answer 2

A discipline focused on classifying organisms and determining their evolutionary relationships

Question 3

Hierarchial classification

Answer 3

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 4

Phylogenetic tree

Answer 4

a branching drawing/diagram that indicates the evolutionary history of a group of organisms

Question 5

How do phylogenetic trees describe evolutionary relationships?

Answer 5

They are depicted into a series of dichotomous branch points, with illustrate a divergence of two lineages from a common ancestor

Question 6

Evolutionary lineage

Answer 6

A sequence of ancestral organisms leading to a particular taxon; represented by a branch (line) in a phylogenetic tree

Question 7

Sister taxa

Answer 7

Groups of organisms that share an immediate common ancestor that is not shared by any other group

Sister groups do not just describe the relationship between two organisms, but all organisms that are linked to a common ancestor.

Question 8

Basal taxon

Answer 8

A lineage that diverges from all other members of its group early in the history of the group

Question 9

How are computer programs used to evalulate molecular homologies?

Answer 9

First, aligning comparable DNA sequences. If there are many matches, species are closely related. If the sequences are different in many ways, they may be more distantly related

But if there is a base pair deletion to a single nucleotide, it would shift the whole sequence over, no longer aligning the two (still very similar) genetic sequences

Computer programs help analyze comparable genetic sequences by re-aligning the genetic sequences in their correct locations while also noting insertions or deletions.

They can also be used to search for parsimonious trees

Question 10

Cladistics

Answer 10

An approach to systematics in which organisms are placed into groups called clades, which are based primarily on descent.

Question 11

Clade

Answer 11

a group of species that includes an ancestral species and all of its descendants. it is the same as a monophyletic group

Question 12

Monophyletic

Answer 12

a group of taxa that consists of an ancestral species and all of its descendants (equivalent to a clade)

Question 13

Paraphyletic

Answer 13

consists of an ancestral species and some, but not all of its descendants

Question 14

Polyphyletic

Answer 14

Includes distantly related species but does not include most recent common ancestor

Question 15

Differentiate between derived and ancestral traits and explain how they are used to construct phylogenetic trees

Answer 15

a shared ancestral character: a character/trait that is shared by the members of a particular clade that originated from an ancestor that is NOT a member of that clade. (eg. backbone in mammals)

A derived ancestral character: an evolutionary novelty that is unique to a particular clade (eg. hair in mammals)

Question 16

Outgroup

Answer 16

A species or group from an evolutionary lineage that is closely related to but not part of the group of species being studied (ingroup).

Question 17

Phylogenetic trees have proportional branch lengths

Answer 17

Some lengths indicate the amount of genetic changes that have occurred in a species’ genome

While others can be proportional to time, and branching points can be determined from the fossil record

Question 18

What is the principle of maximum parisomy and how can it be applied to phylogenetic trees?

Answer 18

When considering multiple explanations for an observation, the simplest explanation consistent with the facts should be investigated first

The most parsimonious tree, therefore, requires the fewest evolutionary events measured by derived morphological characters. For phylogenies on DNA, the most parsimonious tree relies on the fewest base changes between species.

This strategy helps narrow down the correct tree when studying a lot of different species and trying to group them correctly. The least amount of “acquired trait events” wins

Question 19

What is the principle of maximum likelihood and how can it be applied to phylogenetic trees?

Answer 19

It identifies the tree that is most likely to have been produced given the set of DNA data and probability rules about how DNA sequences change over time.

Question 20

Orthologous genes

Answer 20

Homologous genes that are found in different species because of speciation

Question 21

Paralogous genes

Answer 21

Homologous genes that are found in the same genome as a result of gene duplication

Question 22

Which of the homologous genes are better at inferring phylogeny, orthologous and paralogous genes, and why?

Answer 22

Orthologous

The differences among orthologous genes reflect the history of speciation events, making them well-suited for inferring phylogeny, since they can only diverge AFTER speciation has taken place.

Question 23

What is a molecular clock, and how can it infer phylogenetic relationships?

Answer 23

Molecular clocks is an approach to measuring the absolute time of evolutionary change by referencing certain regions of the genome that appear to evolve at constant rates (which are more than likely going to be neutral as they will not be impeded or quickened by natural selection)

(eg. the number of nucleotide substitutions is proportional to the amount of time since an orthologous gene diverged from an ancestor, and nucleotide substitutions for paralogous genes are proportional to the amount of time since duplication)