Choose the best definition of a fossil.

a. A rock that contains information about an organism

b. A bone, tooth, shell, or other hard part of an organism that has been preserved

c. Any trace of an organism that lived in the past

d. Any part of a dead organism

Critique the following statement: The absence of a trait cannot be used as a synapomorphy in phylogenetic analysis; only shared derived traits that are present in the clade can be used.

Which of the following best characterizes an adaptive radiation?

a. Descendant species occupy a large geographic area.

b. A single lineage diversifies rapidly, and descendant species occupy many habitats and ecological roles.

c. Natural selection is particularly intense, because disruptive selection occurs.

d. Species recover after a mass extinction.

Which of the following is an example of homoplasy?

a. Hair in humans and fur in mice

b. Astragalus ankle bones in hippos and deer

c. Hox genes in humans and flies

d. Streamlined bodies in dolphins and ichthyosaurs

What important assumption does parsimony make when assessing which phylogenetic tree is most accurate? Why was parsimony misleading in the case of the astragalus during the evolution of artiodactyls?

You can use a 'one-snip test' to identify monophyletic groups—meaning that if you 'cut' any branch on a tree, everything that 'falls off' is a monophyletic group. Why is this valid?

Describe one similarity between the End-Cretaceous Extinction and the Sixth Mass Extinction, and one difference.

Use the fossil evidence shown in Figure 25.6 to determine whether flight evolved earlier in insects or in birds. Is flight an example of homology or convergent evolution? Explain.

The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today. Why are there so many species in some phyla, such as Cnidaria, but so few in others, such as Ctenophora? Based on your reading of this chapter, propose at least five traits that you think might have been most important in triggering diversification within phyla (examples: origin of hearing, origin of internal fertilization).

The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today. Why are there so many species in some phyla, such as Cnidaria (see photo), but so few in others, such as Ctenophora? Jezkova and Wiens used a type of graph called a linear regression to find correlations between variables such as the proportion of species per phylum with legs (on the y-axis) and the diversification rate per phylum (on the x-axis). Sketch a graph to show what a strong positive correlation between these two variables would look like and what the absence of a correlation would look like.

The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today. Why are there so many species in some phyla, such as Cnidaria (see photo), but so few in others, such as Ctenophora? A sample of Jekova and Wiens' results is shown here. The R2 value represents the strength of the correlation (where 0.00 is lowest and 1.00 is highest). The P value represents the statistical significance. Which five traits look most important?

Which traits do not correlate strongly with diversification rate within phyla but are likely to have been important in the original diversification of animal phyla during the Cambrian? Select True or False for each trait.

T/F presence of a head

T/F mobile lifestyle

T/F terrestrial lifestyle

T/F bilateral symmetry

The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today. Why are there so many species in some phyla, such as Cnidaria (see photo), but so few in others, such as Ctenophora? The researchers know that correlation does not equal causation. However, can the absence of a correlation enable you to reject a hypothesis of causation? How would the R2 values be different in a scenario where a single trait was important to diversification in many phyla versus a scenario where different traits were important to diversification in different phyla?