Topic 1.7: Classification and Cladistics (HL) Questions

State one named example of a group of organisms that has been reclassified because of cladistic evidence, and give the type of group it had wrongly been.

Cladistics groups organisms primarily on the basis of which type of evidence?

Modern cladograms are built mainly from which type of evidence?

What is a clade?

State what a single node (branch point) on a cladogram represents.

Two species' DNA base sequences for the same gene show MANY differences. What does this suggest about the two species?

Define the term monophyletic group.

Which phrase best defines a clade?

State the term used for a group that consists of a common ancestor together with all of its descendants.

On a cladogram, what does a node (branch point) represent?

Two groups on a cladogram are MOST closely related when their branches meet at which point?

State two types of molecule whose sequences can be compared between species to provide molecular evidence of how closely they are related.

What does the root of a cladogram represent?

On a cladogram of four groups, one group's branch joins the others only at the root, while the other three share more recent nodes. What does this tell you about that group?

Outline why two species that diverged from a common ancestor long ago show more sequence differences than two species that diverged recently.

The cladogram shows four groups. The spotted skink and the banded skink meet at the node nearest the tips. Which statement about these two groups is correct? [Diagram: bio-cladogram]

A traditional group called 'reptiles' that deliberately leaves out the birds is best described as:

Cladograms are increasingly constructed from molecular evidence rather than from physical features. Outline how the base sequences of genes or the amino-acid sequences of proteins are used to determine how closely two species are related.

Distinguish between a tip and a node on a cladogram.

The amino-acid sequence of the same protein in a test species is compared with three other species, giving 6 differences with species J, 19 differences with species K, and 31 differences with species L. Deduce the order of the three species from the most closely to the most distantly related to the test species, and justify your ranking.