Phylogeny & the Tree of Life

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Why are phylogenetic trees considered hypotheses?

A phylogenetic tree can be used to make testable predictions.

Researchers can use molecular homologies to __________.

reveal the number of mutations in a particular sequence that has occurred in each species since they diverged from a common ancestor

Which of the following is a true statement concerning horizontal gene transfer?

Horizontal gene transfer is known to occur within both prokaryotes and eukaryotes.

Which of the following is an assumption that should be made when reading a phylogenetic tree?

None of the listed assumptions should be made.

Looking at the character table and phylogenetic tree above, which of the following is a true statement?

A backbone is a shared ancestral character in mammals (leopard).

A phylogenetic tree of bird families constructed by cladistic analysis would be a hypothesis about which of the following?

Evolutionary relationships among bird families

What is the basis for the use of a molecular clock to determine the absolute time of evolutionary change?

Nucleotide substitutions in a gene occur at a relatively constant rate.

Rabbits and guinea pigs both belong to class Mammalia. This means they must also both belong to __________.

phylum Chordata

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?

It consists of an ancestral species and some, but not all, of its descendants.

By applying a molecular clock, researchers have proposed that the first HIV-1 M invasion into humans occurred in the __________.


What is a primary reason why a three-domain taxonomic scheme has been adopted over the previous five-kingdom taxonomic scheme?

Phylogenies based on genetic data revealed that some prokaryotes (kingdom Monera) differ as much from each other as they differ from eukaryotes

Which of the following would be the least useful in determining the relationships among various species?

Analogous structures

A taxon __________.

is a formal grouping at any given level

The binomial system assigns to each organism a unique name that describes its __________.

genus and species

What is the relationship between systematics and taxonomy?

Systematics is a discipline within taxonomy.

Which of the following best summarizes the neutral theory?

Darwinian selection does not influence a lot of evolutionary change in genes and proteins because many of these changes do not affect fitness.

To which domain is the domain Eukarya (the domain to which humans belong) most closely related?

It is not clear whether eukaryotes are more closely related to bacteria or archaea.

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?


The term polytomy refers to a situation in which __________.

there is a branch point on a phylogeny from which more than two descendent groups emerge

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?


Sister taxa on a phylogenetic tree are defined as groups that __________.

share an immediate common ancestor and are each other’s closest relative

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?

The most likely tree is not always the most parsimonious

In a cladistic approach to systematics, an outgroup is __________.

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

Two genes are recognized as orthologous if __________.

they are homologous genes found in different species, and their divergence traces back to speciation events that produced the species

The principle of maximum parsimony is applied to the process of constructing a phylogenetic tree in what way?

The tree that requires the fewest evolutionary events, as measured by the origin of shared derived characters, is selected.

Which of the following is the correct order of taxonomic levels in the Linnean system of classification, from most to least inclusive?

Domain, kingdom, phylum, class, order, 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?

The fact that all mammals have hair

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?

It is important to use as many genes as possible. With this approach, fluctuations in evolutionary rate will tend to average out.

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 __________.

a paraphyletic group

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?


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