Chapter 4: The Tree of Life: How Biologists Use Phylogeny to Reconstruct the Deep Past

What was the remarkable feature that made the dinosaur Zhenyuanlong different from most other dinosaurs and so exciting to scientists?

It had wings with quilled feathers.

The separation of middle ear bones from jaw bones during the evolution of the middle ear in monotremes and in therians is an example of _____.

homoplasy

Both lobe fin and fin ray appendages are connected to the shoulder girdle. What is the major difference between a lobe fin and a fin ray?

Only lobe fins have a chain of sturdy bones anchoring the fin.

Why was the category Reptilia paraphyletic?

Birds were not included in the group.

What is one thing needed to fully understand synapomorphies?

A fossil record that indicates the traits of the common ancestor of a group that shares a trait.

Once characters are scored, how do scientists use them?

The scores create a data matrix that are then used to build a hypothesis (i.e. a phylogenetic tree).

Which is the correctly phrased statement about lung fish?

Lung fish have shared derived traits that place them as the closest living relatives of tetrapods.

What would it likely mean if a scored character among many individuals of many species does not vary?

The character is not heritable.

What is convergent evolution?

The independent origin of similar traits in separate evolutionary lineages.

What is another term that means "shared and derived characters"?

Synapomorphies

Outgroups can be used to infer the ancestral states of characters when considering synapomorphic traits among species.

Outgroups can be used to infer the ancestral states of characters when considering synapomorphic traits among species.

What is one thing needed to fully understand synapomorphies?

A fossil record that indicates the traits of the common ancestor of a group that shares a trait.

Linnaeus' taxonomic organization showing the relationships among species used what types of data?

Shared traits among species

Outside group

Groups of organisms (e.g., species) that are outside of the monophyletic group being considered.

How can scientists discern that feathers are an example of an exaptation?

By studying the shared ancestors of birds and deriving behaviors that they had when feathers first evolved.

How can outgroups be used to understand phylogenetic relationships?

Outgroups can be used to infer the ancestral states of characters when considering synapomorphic traits among species.

Suppose scientists have discovered a new synapsid fossil. One of your friends is part of the team of paleontologists and she's just telling you about their preliminary findings on the phone when she has to end the call. You only learned that the fossil's body plan resembles that of a dog and that its jaw is capable generating some of the strongest chewing forces she has ever seen. Based on this information and your knowledge of the evolution of synapsids, what do you predict about this animal's hearing?

Its ability to detect airborne sound was excellent, similar to Didelphis.

The fact that _____ is one line of evidence supporting the hypothesis that middle ear bones _____.

middle ear bones develop as part of the jaw during embryonic development; evolved from jaw bones

Suppose scientists have discovered a new synapsid fossil. One of your friends is part of the team of paleontologists and she's just telling you about their preliminary findings on the phone when she has to end the call. You only learned that the fossil has wide shoulder and pelvic girdles and short legs, with head and body close to the ground, similar to an alligator. The force generated by its lower jaw during chewing is weak. Based on this information and your knowledge of the evolution of synapsids, what do you predict about this animal's hearing?

Its ability to detect airborne sound was fairly good but it was better at detecting substrate transmissions through its jaw, similar to Thrinaxodon.