Phylogenetics

Question 1

Parsimony

Answer 1

Describes how the simplest explanation is the best info based on the given evidence. In an evolutionary perspective, the most complicated path is rare and unlikely to occur because evolution is difficult and time-consuming

Ex. If all animals in 4 different branches lay amniotic eggs, it would be the best to put this trait in position 1 (the node where all 4 branches met) rather than having 4 different mapping of the same trait

Question 2

2 types of homologies

Answer 2

Synapomorphy - shared derived and unique trait

Symplesiomorphy - shared ancestral trait

“syn/sym” = shared
“apo” = derived, unique
“plesio” = old, ancestral
“morphy” = shape or form

Question 3

Monophyletic group

Answer 3

“mono” = one evolutionary history. Consists of any group that contains a common ancestor and ALL of its descendants

Question 4

Polyphyletic group

Answer 4

Excludes the common ancestor. Usually occurs when a convergent of traits occurs that wasn’t recognized as independently evolved

Ex. Bats vs. birds

Question 5

Paraphyletic group

Answer 5

Consists of the common ancestor and SOME of its descendants

Question 6

Phylogenetic tree

Answer 6

Hypothesis of the evolutionary relationships between different organisms

Question 7

Taxon

Answer 7

Named group of organisms

Ex. Homo sapiens, Phylum Mollusca, and Class Hexactinellida

Question 8

Phenotypic character

Answer 8

Feature of an organism that can be observed, like eye colour or jointed appendages. A character must have more than one character state

Question 9

Character state

Answer 9

Minimum is 2 (presence or absence)

Ex.
Jointed appendages can be present or absent
Eye colour can be blue, brown, etc.
Anatomical structures, like a muscle or gill

Question 10

Shared character

Answer 10

When two or more taxa have the same character state for a character

Question 11

Homologous

Answer 11

When a shared character can be traced to the same character state in the most recent common ancestor

Ex. If structure X in one taxon and structure Y in a different taxon both arose from the same structure in the common ancestor of these two taxa, then X and Y are homologous

Question 12

Convergent characters

Answer 12

Shared characters that have evolved independently in two or more taxa, therefore, the shared character is not inherited from their most common ancestor

Question 13

Ancestral character state

Answer 13

A character state that was inherited by a taxon from a relatively ancient ancestor, meaning the character state evolved a relatively long time ago

Question 14

Derived character state

Answer 14

A character state that has evolved relatively recently

Question 15

Plesiomorphic character state

Answer 15

The character state before an evolutionary change (the ancestral character state)

Question 16

Apomorphic character state

Answer 16

The character state after this evolutionary change (the derived character state)

Question 17

Synapomorphy

Answer 17

An apomorphy (derived character state) that is shared by two or more taxa and their most recent common ancestor. It’s a homologous character

Ex. mammary glands evolved in the common ancestor of all mammals, therefore, they are a synapomorphy for mammals

Question 18

Symplesiomorphy

Answer 18

A plesiomorphy (ancestral character state) that is shared by two or more taxa. It’s a homologous character