ch 26 Flashcards
What is the relationship between systematics and taxonomy?
Systematics is a discipline within taxonomy.
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.
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
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
Why are phylogenetic trees considered hypotheses?
A phylogenetic tree can be used to make testable predictions.
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 __________.
1930s
Which of the following is a true statement concerning horizontal gene transfer?
Horizontal gene transfer is known to occur within both prokaryotes and eukaryotes.
The binomial system assigns to each organism a unique name that describes its __________.
genus and species
Rabbits and guinea pigs both belong to class Mammalia. This means they must also both belong to __________.
phylum Chordata
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?
homologous.
A taxon __________.
is a formal grouping at any given level
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
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.
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?
analogous
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
Sister taxa on a phylogenetic tree are defined as groups that __________.
share an immediate common ancestor and are each other’s closest relatives
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.
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 term polytomy refers to a situation in which __________.
there is a branch point on a phylogeny from which more than two descendent groups emerge
Which of the following would be the least useful in determining the relationships among various species?
Analogous structures
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
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.
A phylogenetic tree of bird families constructed by cladistic analysis would be a hypothesis about which of the following?
Evolutionary relationships among bird families
