Chapter 26

Which of the following is a true statement concerning horizontal gene transfer? ANSWER Horizontal gene transfer is known to occur within both prokaryotes and eukaryotes. Horizontal gene transfer occurs only in certain prokaryotes. Horizontal gene transfer is a hypothetical means of transferring genes between organisms for which evidence has been observed only in laboratory animals. There is evidence that horizontal gene transfer has occurred rarely in the evolutionary history of life. Horizontal gene transfer has only negative consequences for a lineage.

A phylogenetic tree of bird families constructed by cladistic analysis would be a hypothesis about which of the following? ANSWER Evolutionary relationships among bird families Characteristics shared by all bird families Families that look most alike Analogous structures shared by various species Relative ages of living species of birds

Which of the following is an assumption that should be made when reading a phylogenetic tree? ANSWER None of the listed assumptions should be made. Species in taxa arising from the same branch point should appear most similar to each other. The sequence of branching in a tree indicates the absolute ages of the particular species. A taxon on a phylogenetic tree evolved from the taxon next to it. All of the listed assumptions should be made.

In cladistics, biologists attempt to place species into groups that each include an ancestral species and all of its descendants. A group that is paraphyletic fails to accomplish this goal in what way? ANSWER It consists of an ancestral species and some, but not all, of its descendants. It includes species with different ancestors. It includes species grouped based only on phenotypic similarities. The ancestral member is identified only by fossil evidence. All members of the group are extinct.

Rabbits and guinea pigs both belong to class Mammalia. This means they must also both belong to __________. ANSWER phylum Chordata order Rodentia genus Cavia family Caviidae All of the listed responses are correct.

What is the basis for the use of a molecular clock to determine the absolute time of evolutionary change? ANSWER Nucleotide substitutions in a gene occur at a relatively constant rate. DNA degrades at a known rate following the death of an organism. The rate of mutation increases following divergence in a lineage. Natural selection occurs at a constant rate. Rates of nucleotide substitutions have increased throughout the history of life on Earth.

By applying a molecular clock, researchers have proposed that the first HIV-1 M invasion into humans occurred in the __________. ANSWER 1930s 1830s 1890s 1950s 1980s

What is a primary reason why a three-domain taxonomic scheme has been adopted over the previous five-kingdom taxonomic scheme? ANSWER Phylogenies based on genetic data revealed that some prokaryotes (kingdom Monera) differ as much from each other as they differ from eukaryotes. The three-domain taxonomic scheme was necessary to further partition each kingdom as new species were discovered. The five-kingdom taxonomic scheme was never widely accepted. The five-kingdom system failed to distinguish between prokaryotes and eukaryotes. More detailed analysis of the phenotypes of unicellular eukaryotes indicated that they did not belong in any of the five kingdoms.

Which of the following would be the least useful in determining the relationships among various species? ANSWER Analogous structures A comparison of DNA base sequences Homologous structures Fossils Amino acid sequences of proteins

A taxon __________. ANSWER is a formal grouping at any given level is a formal grouping in any level from phylum to species is a clade is a species of one type of organism at one level is comparable to another type of organism at the same level

The binomial system assigns to each organism a unique name that describes its __________. ANSWER genus and species order and family body plan and habitat family and species evolutionary history

What is the relationship between systematics and taxonomy? ANSWER Systematics is a discipline within taxonomy. Systematics and taxonomy are the same thing. Systematics and taxonomy are alternative approaches to the same goal. The development of systematics preceded that of taxonomy. Systematics has replaced taxonomy.

Which of the following best summarizes the neutral theory? ANSWER Darwinian selection does not influence a lot of evolutionary change in genes and proteins because many of these changes do not affect fitness. Most harmful mutations are removed from a population quickly. Differences in the rate of the clock in different genes are a function of how important each gene is. If a particular sequence of amino acids is critical for survival, most new mutations will be harmful and fewer will be neutral. These genes will change slowly over time. Most mutations lead to dramatic changes in the evolution of a species.

To which domain is the domain Eukarya (the domain to which humans belong) most closely related? ANSWER It is not clear whether eukaryotes are more closely related to bacteria or archaea. Bacteria Fungi Archaea Protista

Why are phylogenetic trees considered hypotheses? ANSWER A phylogenetic tree can be used to make testable predictions. Darwinian evolution is a hypothesis, and therefore a phylogenetic tree representing evolutionary history is necessarily also hypothetical. The fossil record is not an adequate source of evidence in drawing conclusions about evolutionary histories. Current genetic analyses are not yet accurate enough to permit conclusions about evolutionary histories. There are competing ideas about the evolutionary history of any taxonomic group.

A bald eagle and a black bear both have four limbs with digits because they are both tetrapods, descendants of a four-limbed ancestor. In this comparison, the limbs of the eagle and the bear are what type of structure? ANSWER Homologous Analogous Paralogous Vestigial Exaptations

The term polytomy refers to a situation in which __________. ANSWER there is a branch point on a phylogeny from which more than two descendent groups emerge any lineages on a phylogeny diverge a branch point within a phylogenetic tree represents the most recent common ancestor of all the taxa in the tree separate lineages independently evolve similar structures multiple common names apply to one species

If you wanted to determine the lineage of plants that have evolved on a relatively young archipelago—approximately 15,000 years old—what type of nucleic acid should you compare? ANSWER mtDNA mRNA rRNA tRNA Nuclear DNA miRNA

Sister taxa on a phylogenetic tree are defined as groups that __________. ANSWER share an immediate common ancestor and are each other's closest relatives arise from different branches at the same time appear most similar due to convergent evolution compete for resources in the same habitat

Birds and mammals have a four-chambered heart, but most reptiles have a three-chambered heart. How does this fact affect the construction of phylogenetic trees for these groups? ANSWER The most likely tree is not always the most parsimonious. It shows that the common ancestor of birds and mammals must have had a four-chambered heart. This represents a problem with the principle of parsimony, rather than a problem with the analogy-homology issue. The most likely tree is always the most parsimonious. None of the listed responses is correct.

In a cladistic approach to systematics, an outgroup is __________. ANSWER a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes all the species under study the group of the most closely related species determined from the output of the cladistic analysis the most recent common ancestor of all the species under study the most recently evolved descendant or group of descendants to have come from the species under study a species or group of species, including all of the species under study, incorrectly assigned to the lineage

Two genes are recognized as orthologous if __________. ANSWER they are homologous genes found in different species, and their divergence traces back to speciation events that produced the species they are homologous genes found in the same species due to gene duplication they are analogous genes found in different species, representing independent mutations producing similar phenotypes they are analogous genes found in the same species, representing independent mutations producing similar phenotypes they are genes present in the same species that have opposing effects on the phenotype

The principle of maximum parsimony is applied to the process of constructing a phylogenetic tree in what way? ANSWER The tree that requires the fewest evolutionary events, as measured by the origin of shared derived characters, is selected. The process of constructing a phylogenetic tree is kept simple by including few species in the study. A phylogenetic tree is constructed using only the characters that can be measured in living organisms. The tree that requires the fewest branch points is selected. Whenever possible, biologists continue to use previously constructed phylogenies.

Researchers can use molecular homologies to __________. ANSWER reveal the number of mutations in a particular sequence that has occurred in each species since they diverged from a common ancestor estimate how long ago the common ancestor lived hypothesize about the morphological structures of a common ancestor hypothesize about the behavior of a common ancestor All of the listed responses are correct.

Which of the following is the correct order of taxonomic levels in the Linnean system of classification, from most to least inclusive? ANSWER Domain, kingdom, phylum, class, order, family, genus, species Kingdom, domain, phylum, order, class, family, genus, species Phylum, domain, kingdom, class, order, family, genus, species Phylum, domain, kingdom, family, class, order, genus, species Kingdom, domain, order, phylum, class, family, genus, species

Using cladistic analysis, a taxonomist wishes to construct a phylogenetic tree showing the relationships among various species of mammals. Which of the following would be the least useful for this purpose? ANSWER The fact that all mammals have hair Descriptions of various types of limbs (wings, legs, flippers, etc.) Data about skull bones The fact that teeth vary among types of mammals DNA base sequences

The idea of using molecules as clocks to time evolutionary events is very attractive, but there are many problems in actually applying the technique. What seems to be the best way to get reliable results? ANSWER It is important to use as many genes as possible. With this approach, fluctuations in evolutionary rate will tend to average out. It is important to use a gene that has been affected by natural selection to ensure that evolution will be observed. It is important to use one gene in which the changes are clearly neutral. It is best to use a gene that is essential to survival because they change more slowly. All of the listed responses are correct.

The separate lineages leading to dolphins and sharks both evolved streamlined bodies, dorsal fins, and broad tail fins as adaptations to efficient locomotion in a marine environment. In this comparison, the bodies and fins of dolphins and sharks are what type of structures? ANSWER Analogous Homologous Paralogous Vestigial Exaptations

Three living species X, Y, and Z share a common ancestor T, as do extinct species U and V. A grouping that consists of species T, X, Y, and Z (but not U or V) makes up __________. ANSWER a paraphyletic group a valid taxon a monophyletic clade an ingroup, with species U as the outgroup a polyphyletic group