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