Vertebrate Diversity & Phylogeny

Question 1

A point of divergence in a phylogenetic tree. Where 2-3 lineages spilt a part from the common ancestor

Answer 1

Node

Question 2

A common ancestor and all of its descendents

Answer 2

Monophyletic group

Question 3

A common ancestor and some of the descendents

Answer 3

Paraphyletic

Question 4

Two lineages that share a common ancestor

Answer 4

Sister groups

Question 5

The least related and the furthest lineage seen on the phylogenetic tree

Answer 5

Outgroup

Question 6

Includes all living relatives

Answer 6

Crown group

Question 7

Extinct relatives of the crown group

Answer 7

Stem group

Question 8

Many lineages that share a common ancestor

Answer 8

Polytomy

Question 9

Who were the conodonts, Haikouella, and Metaspriggina?

Answer 9

• Conodonts: extinct group of vertebrates
• Haikouella & Metaspriggina are primitive chordates
• They are related to vertebrates but are not vertebrates

Question 10

Draw a cladogram showing the relationships of the following animals: tunicate, amphioxus, hagfish, lamprey, cephalaspid ostracoderm, placoderm, shark, acanthodian, sturgeon, Amia, salmon, tuna, coelacanth, lungfish, osteolepiform fish (e.g. Eusthenopteron), human. Which of these animals is a vertebrate? A gnathostome? An actinopterygian? A teleost? A sarcopterygian? A tetrapod? Make sure you know where to plot the evolution of the following characters on your cladogram: gills, jaws, internal nostrils (choanae).

Question 11

Draw a cladogram showing the relationships of the following animals: osteolepiform fish (e.g. Eusthenopteron), Tiktaalik, Ichthyostega, frog, salamander, turtle, lizard, snake, dinosaur, crocodile, bird, platypus, kangaroo, opossum, rat, human. Which of these animals is/are a sarcopterygian? Which is/are a tetrapod? A lissamphibian? An amniote? A diapsid? A lepidosauromorph? An archosauromorph? A synapsid? A monotreme? A eutherian? Make sure you know where to plot the evolution of the following characters on your cladogram: loss of operculum, digits (of hand and foot), keratinized skin, amniote egg, feathers, hair, mammary glands.

Question 12

What is the difference between Linnaean and Cladistic classification of vertebrates?

Answer 12

Linnaean Classification
* Hierarchical
* Subclass, subphylum, etc.
* Morphological characteristics

Cladistic Classification
* No levels of hierarchical classification
* Indentations instead of titles such as subclass
* Phylogenetic classification
* Recognizes monophyletic groups

Question 13

In particular, what is the only kind of group recognized in Cladistic classifications?

Answer 13

Monophyletic groups

Question 14

Give an example of a group that is recognized in the traditional Linnaean classification that does not meet this criterion, and therefore does not appear in the Cladistic classification.

Answer 14

• Many vertebrate groups are not monophyletic (reptiles)
• Why? Birds are related to reptiles as well but not grouped together.