Bio 202 Tree Thinking Ch26

What do we call a tree diagram with an explicit time scale?

A chronogram.

The part of the figure being pointed to by the upper red arrow represents _____

A contemporary species

What do we call a tree diagram with an explicit scale for the amount of evolutionary change?

A phylogram

What is the definition of a polyphyletic group?

A set of species that does NOT include the common ancestor of the set.

What is the definition of a monophyletic group?

A set of species that includes the common ancestor of the set & all of the species descended from that common ancestor.

What is the definition of a paraphyletic group?

A set of species that includes the common ancestor of the set and some but not all of the species descended from that common ancestor.

What is the definition of a symplesiomorphy?

A shared ancestral character similarity.

What is the definition of a synapomorphy?

A shared derived character similarity.

The earliest vertebrates from > 500 million years ago had a tail, and most living vertebrates have retained this feature. Among amphibians, salamander have a tail but frogs & toads have lost it. Among mammals, monkeys have a tail but the great apes have lost it. The shared similarity between salamanders and monkeys in having a tail is an example of _____.

A symplesiomorphy (shared ancestral similarity).

The part of the figure being pointed to by the lower red arrow represents _____.

An ancestral species

What can we say about the relative ages of the branching events marked with "b" and "c" ?

Branching event "b" occurred about 23 million years ago (mya) and branching event "c" occurred about 32 mya, so "b" is younger than "c".

Draw a line around a part of this diagram that would represent a polyphyletic taxon.

Here are 2. There are others

Draw a line around a part of this diagram that would represent a paraphyletic taxon

Here are 3 of several possibilities.

Draw a line around a part of this diagram that would represent a monophyletic taxon.

Here are 4. How many more can you find ?

The red arrow in this figure points to a "thread" that represents _____.

One population in a lineage

What can we say about the relative ages of the branching events marked with "b" and "a" ?

Speciation event "b" is younger (occurred more recently) than speciation event "a"

Suppose species B & D share a derived character state, but A & C retain the ancestral state of the character. How might this pattern of character states have evolved ?

The derived character state may have evolved 2 times independently. This is called homoplasy.

All mammals share the similarity of having hair & mammary glands but these characters are not present in the other 4-limbed vertebrates (amphibians, reptiles & birds), including the reptiles from which mammals evolved. What do we call these 2 similarities between any 2 mammals, if the frame of reference is the 4-limbed vertebrates?

They are synapomorphies (shared derived similarities).

What can we say about the relative ages of the branching events marked with "b" and "c" ?

We can't say anything about their relative ages. "b" could be younger than "c" or older or the same age.

This structure, which we called a _____, was used to represent a section of a branch of a tree diagram.

lineage