Chapter 25

Choose the best definition of a fossil. a. any trace of an organism that has been converted into rock 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.

True or false? 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. Speciation occurs extremely rapidly, and descendant populations occupy a large geographic area. b. A single lineage diversifies rapidly, and descendant populations occupy many habitats and ecological roles. e. 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.

Why is parsimony a useful tool for assessing which phylogenetic tree is most accurate? Why was parsimony misleading in the case of the astragalus during the evolution of artiodactyls?

Recommends 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?

Fossilization continues even today. If you wanted to increase the probability that your deceased favorite pet would become fossilized, what actions would you take? a. Place the corpse in an environment where decomposition is rapid (such as a forest). b. Place the corpse in an environment where decomposition is slow (such as a swamp or bog). e. Bury only the bones, since soft parts don't fossilize well. d. Place the corpse in an environment where plenty of oxygen is available.

Some researchers contend that the end-Permian extinction event was caused by an impact with a large extraterrestrial object. Describe three forms of evidence that you would like to see before you accept this hypothesis.

Are all the theropod dinosaurs extinct? a. Yes, all the theropod dinosaurs died out 66 million years ago. b. No, theropods are a monophyletic group that includes birds. c. \(\mathrm{No}\), theropods are a paraphyletic group that includes birds. d. No, theropods are a polyphyletic group that includes birds.