Question 1

Which of the following best describes a monophyletic group in a phylogenetic tree?

Accepted Answer

A group that includes a common ancestor and all of its descendants.

Question 2

Which event is most closely associated with a rapid increase in the diversity of animal life during the Paleozoic era?

Accepted Answer

Cambrian explosion

Question 3

A paleontologist discovers a fossil in a sedimentary rock layer and uses radiometric dating to estimate its age. If the half-life of the isotope used is 5,000 years and only 25% of the original isotope remains, what is the approximate age of the fossil?

$$	ext{Number of half-lives} = \log_2$(\frac{100\%}{25\%})$$ 
$$	ext{Age} = 	ext{Number of half-lives} 	imes 5,000$$

Accepted Answer

10,000 years

Question 4

Which of the following is an example of homoplasy?

Accepted Answer

The wings of bats and birds, which evolved independently.

Question 5

Which bias in the fossil record is most likely to result in an overrepresentation of organisms with hard shells compared to those with soft bodies?

Accepted Answer

Taxonomic bias

Question 6

In a phylogenetic tree, what does a node (fork) represent?

Accepted Answer

A common ancestor of the descendant lineages.

Question 7

Which of the following best explains adaptive radiation?

Accepted Answer

The rapid diversification of a lineage into many new species, often following the opening of new ecological niches.

Question 8

Which statement about background extinction and mass extinction is correct?

Accepted Answer

Background extinction occurs at a relatively constant rate, while mass extinction is a rapid, widespread loss of species.

Question 9

A scientist is constructing a phylogenetic tree using a cladistics matrix. Which principle should they use to select the most parsimonious tree?

Accepted Answer

Choose the tree that requires the fewest evolutionary changes.

Question 10

Which of the following is a derived trait (synapomorphy) in mammals?

Accepted Answer

Presence of hair

Question 11

If two species share a trait due to common ancestry, this trait is called:

Accepted Answer

Homology

Question 12

Which of the following is NOT a limitation of the fossil record?

Accepted Answer

It provides direct evidence of extinct organisms.

Question 13

Which era is characterized by the dominance of dinosaurs and ends with a mass extinction event?

Accepted Answer

Mesozoic era

Question 14

A phylogenetic tree shows that whales and hippos share a recent common ancestor. What does this imply about their evolutionary relationship?

Accepted Answer

They are sister groups.

Question 15

Which of the following best describes a polyphyletic group?

Accepted Answer

A group that does not include the most recent common ancestor of its members.

Question 16

Which process is most likely to result in the preservation of soft tissues in fossils?

Accepted Answer

Rapid burial in anoxic (oxygen-poor) environments.

Question 17

Which of the following is an example of taxonomic bias in the fossil record?

Accepted Answer

More fossils of mollusks than jellyfish are found.

Question 18

Which major extinction event marks the boundary between the Mesozoic and Cenozoic eras?

Accepted Answer

End-Cretaceous extinction

Question 19

If a clade contains all descendants of a single common ancestor, but not the ancestor itself, what type of group is this?

Accepted Answer

Polyphyletic group

Question 20

Which of the following best explains why the Cambrian explosion is significant in evolutionary history?

Accepted Answer

It marks a period of rapid diversification and the appearance of most major animal phyla.

Chapter 25: Phylogeny and Fossils – Study Guide and Key Concepts

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