Phylogeny & Classification

Question 1

What is a monophyletic group?

Answer 1

A group that includes a collection of organisms, including those organisms’ most recent common ancestor, as well as all descendants of that common ancestor

Question 2

What are synonyms for a monophyletic group?

Answer 2

Taxon; clade

Question 3

What are the taxa most related to vertebrates?

Answer 3

Hemichordata, echinodermata, urochordata, and cephalochordata

Question 4

Phylogenies are _______ that approximate a pattern of descent based on fossil record, common traits, etc.

Answer 4

Hypotheses

Question 5

Why is the Linnaean system becoming obsolete?

Answer 5

It is open to each researcher’s opinion on how taxa should be classified. It also implies that some taxa are higher or lower on the evolutionary scale when they are equal.

Question 6

Give an example of a flaw of the Linnean system.

Answer 6

Separating birds into the Class Aves, excluding them from the Class Reptilia, when they are actually part of the Reptilia taxon.

Question 7

If two (or more) taxa share a unique characteristic, then we hypothesize that they share this feature because _________.

Answer 7

Of a common ancestor

Question 8

Homoplasy

Answer 8

When organisms evolve very similar characteristics independently; no common ancestors

Question 9

What groups are referred to as “protochordates?”

Answer 9

Hemichordata, urochordata, cephlachordata. This is not the monophyletic term.

Question 10

Plesiomorphic

Answer 10

Shared common ancestral trait(s)

Question 11

What is a flaw with classifying by plesiomorphic traits? Give an example.

Answer 11

They tell you that species have a common ancestor, but don’t give info on relationships between the descendants.
Ex) presence of vertebrae tell us all Vertebrata share a common ancestor, but don’t tell us how turtles, dogs, bears, are related evolutionarily