Intro to Phylogeny and Cladistics

Question 1

What is taxonomy and what is it based on?

Answer 1

Taxonomy is the discipline of naming and categorizing organisms based on shared morphological/developmental/molecular traits.

Question 2

Who developed taxonomy and what else did they develop?

Answer 2

Carolus Linnaeus developed a formal hierarchal system of taxonomy as well as Binomial scientific naming.

Question 3

What is phylogeny?

Answer 3

Phylogeny is the evolutionary history of a species or a group of related species.

Question 4

What is systematics?

Answer 4

Systematics is a discipline of classifying organisms and determining their evolutionary relationships.

Question 5

What are nodes?

Answer 5

Nodes, or branch points, on a phylogenetic tree depict the divergence of two species from their common ancestor.

Question 6

What does systematics use to infer evolutionary relationships?

Answer 6

Fossils, morphological data, biochemical data (usually in proteins) and genetic data.

Question 7

What are sister taxa?

Answer 7

Sister taxa are groups that share an immediate common ancestor of all the taxa in the tree.

Question 8

What is a rooted phylogenetic tree?

Answer 8

It is a phylogenetic tree that branches out from a common ancestor chronologically to show evolutionary relationships.

Question 9

What is an outgroup?

Answer 9

A more distantly related group of organisms that serves as a reference.

Question 10

What is a polytomy?

Answer 10

A branch on a phylogenetic tree where more than two groups emerge due to an unresolved level of divergence.

Question 11

What is homology?

Answer 11

Phenotypical similarities due to divergent evolution.

Question 12

What are analogous structures?

Answer 12

Phenotypical similarities due to convergent evolution.

Question 13

What is a clade? What are the types of clades?

Answer 13

A group of species that includes an ancestral species and all its descendants. Include monophyletic, polyphyletic, and paraphyletic grouping.

Question 14

What is the difference between monophyletic, polyphyletic and paraphyletic groups?

Answer 14

Monophyletic groups consist of the ancestor species and its descendants.

Polyphyletic groups consist of distantly related species, but does not include their most recent common ancestor.

Paraphyletic groups consist of ancestral species and some but not all of the descendants.

Question 15

What is the difference between a shared ancestral character and a shared derived character?

Answer 15

Shared ancestral characters are traits that originated in an ancestor of a clade.

Shared derived characters are traits that are novel to a particular clade.

Question 16

How is an organism’s evolutionary history documented? Give an example.

Answer 16

Evolutionary history is found by comparing nucleic acids or other molecules of different organisms. For example, DNA coding for rRNA changes relatively slowly and is useful for investigating branching points.

Question 17

What is the difference between a clade and a grade?

Answer 17

Clades are related groups that share ancestry due to divergent evolution.

Grades are unrelated groups that only share biological features due to convergent evolution.