Lecture 22- Phylogenetics

Question 1

What is the difference between taxonomy and phylogeny?

Answer 1

Taxonomy classifies organisms into categories and phylogeny reflects the evolutionary history of these organisms

Question 2

What is a phylogenetic tree?

Answer 2

Hypothetical diagram that represents evolutionary relationships among organisms

Question 3

What is the phylogenetic species concept?

Answer 3

Concept that a species is the smallest set of organisms that can be distinguished on a phylogenetic tree (species are based on evolutionary history- species are independent lineages)

Question 4

With regards to phylogeny, what is a dichotomy?

Answer 4

A branch point on a tree that has two (di) immediate descendants

Question 5

What is a monophyletic group (clade)?

Answer 5

A group on a phylogenetic tree which includes the ancestor and all descendants (all members of group share a common ancestor- true evolutionary relationship)

Question 6

What is an extant species?

Answer 6

A species that is still alive (opposite of extinct)

Question 7

What is the difference between homologous traits and analogous traits?

Answer 7

Homologous traits are derived from a common ancestor, whereas analogous traits are similar due to convergent evolution (independently acquired due to similar evolutionary pressures)

Ex Homologous structures: The forelimbs of mammals, such as humans, cats, whales, and bats, are considered homologous structures. Despite having different functions (walking, grasping, swimming, and flying), they all share a common skeletal structure, indicating a common ancestry

Ex Analogous structures: The wings of bats and the wings of birds are considered analogous structures. While both are used for flying and have a similar function, they have different underlying structures. Bats have wings with a membrane stretched over elongated fingers, while birds have wings with feathers supported by a rigid skeletal structure.

Question 8

What does a rooted tree represent?

Answer 8

The most recent common ancestor of all taxa on the tree

Question 9

What is a basal taxon?

Answer 9

A lineage (displayed on a phylogenetic tree) that evolved early from the root and from which no other branches have diverged

Question 10

What are shared derived traits?

Answer 10

Characteristics which are unique to a particular clade (present in all members of ingroup)

Question 11

What are sister taxa?

Answer 11

Any two taxa derived from an immediate common ancestor

Question 12

What is the difference between a monophyletic group and a paraphyletic group?

Answer 12

A monophyletic group (clade) includes the most recent common ancestor and all descendants, whereas a paraphyletic group includes the common ancestor and some but not all descendants

Question 13

What is convergent evolution?

Answer 13

Process by which organisms not closely related (not monophyletic) independently evolve similar traits as a result of having to adapt to similar environments or ecological niches

Question 14

What is a polytomy?

Answer 14

A branch point on a phylogenetic tree with more than two groups (evolutionary relationships not fully clear)

Question 15

What is cladistics?

Answer 15

Method of biological classification in which organisms are categorized in groups based on their most recent common ancestor

Question 16

What does a node represent on a phylogenetic tree?

Answer 16

Divergence of two lineages from a common ancestor

Question 17

What is the difference between the ingroup and the outgroup?

Answer 17

The ingroup refers to the taxa being studied, whereas the outgroup refers to the taxa that diverged before the lineage that is being studied

Question 18

What is a polyphyletic group?

Answer 18

A group on a phylogenetic tree in which organisms are grouped together but do not share an immediate common ancestor

Question 19

What is the difference between ancestral traits and derived traits?

Answer 19

Ancestral (evolutionary) traits are homologous within a group of organisms (descended from a common ancestor in which the trait first evolved) whereas a derived trait is present in an organism but absent in the most recent common ancestor