Chapter 24

The evolutionary history of a group of organisms is called its: a. classification. b. taxonomy. c. phylogeny. d. domain. e. outgroup.

In the Linnaean hierarchy, the organisms classified within the same taxonomic category are called: a. a phylum. b. a taxon. c. a genus. d. a binomial. e. an epithet.

Which of the following does not help systematists determine whether a morphological character state is ancestral or derived? a. outgroup comparison b. patterns of embryonic development c. studies of the fossil record d. studies of the character in more related species e. dating of the character by molecular clocks

In a cladistic analysis, a systematist groups together organisms that share: a. derived homologous traits. b. derived homoplastic traits. c. ancestral homologous traits. d. ancestral homoplastic traits. e. all of the above.

A monophyletic taxon is one that includes: a. an ancestor and all of its descendants. b. an ancestor and some of its descendants. c. organisms from different evolutionary lineages. d. an ancestor and those descendants that still resemble it. e. organisms that resemble each other because they live in similar environments.

Which of the following is not an advantage of using molecular characters in a systematic analysis? a. Molecular characters provide abundant data. b. Systematists can compare molecules among species that are morphologically very similar. c. Systematists can compare molecules among species that are morphologically very different. d. Nucleotide sequences in DNA are generally not influenced by environmental factors. e. Systematists can easily determine whether base substitutions in the DNA of two species are synapomorphies.

Which of the following underlying assumptions allows differences in a particular molecular sequence to be used as a molecular clock? a. The sequence never experiences any mutations. b. The sequence codes for a protein. c. The sequence accumulates mutations at a reasonably constant rate. d. The sequence is part of a mitochondrial gene. e. The sequence codes for small subunit ribosomal RNA.

When systematists study morphological or behavioral traits to reconstruct the evolutionary history of a group of animals, they assume that: a. similarities and differences in phenotypic characters reflect underlying genetic similarities and differences. b. the animals use exactly the same traits to identify appropriate mates. c. differences in these traits caused speciation in the past. d. the adaptive value of these traits can be explained. e. variations in these traits are produced by environmental effects during development.

Which of the following pairs of structures are homoplastic? a. the wing skeleton of a bird and the wing skeleton of a bat b. the wing of a bird and the wing of a fly c. the eye of a fish and the eye of a human d. the bones in the foot of a duck and the bones in the foot of a chicken e. the toes on the foot of a lizard and the toes on the foot of a human

To construct a phylogenetic tree by applying the principles of parsimony to molecular sequence data, one would: a. start by making assumptions about variations in the rates at which different DNA segments evolve. b. group together organisms that share the largest number of ancestral sequences. c. group together organisms that share derived sequences, matching the groups to those defined by morphological characters. d. group together organisms that share derived sequences, minimizing the number of hypothesized evolutionary changes. e. identify derived sequences by studying the embryology of the organisms.

In the past, systematists commonly used the amino acid sequences of proteins and DNA sequences in phylogenetic analyses. Think about the genetic code (see Section 15.1 ), and explain why phylogenetic hypotheses based on DNA sequences may be more accurate than those based on amino acid sequences.

Create an imaginary phylogenetic tree for an ancestral species and its 10 descendants. Circle a monophyletic group, a polyphyletic group, and a paraphyletic group on the tree. Explain why the groups you identify match the definitions of the three types of groups.

Traditional evolutionary systematists identified Reptilia, not including birds, as one class of vertebrates, even though we know that this taxon is paraphyletic. Describe disadvantages of defining paraphyletic taxa in a classification.