Chapter 26

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The legless condition that is observed in several groups of extant reptiles is the result of __________.

Several instances of the legless condition arising independently of each other.

The scientific discipline concerned with naming organisms is called __________.


The various taxonomic levels (e.g. genera, classes, etc.) of the hierarchical classification system differ
from each other on the basis of __________.

Their inclusiveness

A phylogenetic tree that is "rooted" is one __________.

At whose base is located the common ancestor of all taxa depicted on the tree.

The correct sequence from the most to least comprehensive, of the taxonomic levels listed here is

Kingdom, phylum, class, order, family, genus, and species

The common housefly belongs to all of the following taxa. Assuming you had access to textbooks or
other scientific literature, knowing which of the following should provide you with the most specific
information about the common housefly?

Genus Musca

Darwin analogized the effects of evolution as the above-ground portion of a many-branched tree, with
extant species being the tips of the twigs. The common ancestor of two species is most analogous to
which anatomical tree part?

A node where two twigs diverge

Dozens of potato varieties exist, differing from each other in potato-tuber size, skin color, flesh color,
and shape. One might construct a classification of potatoes based on these morphological traits. Which of
these criticisms of such a classification scheme is most likely to come from an adherent of the phylocode
method of classification?

The only biologically valid classification of potato varieties is one that accurately reflects their genetic and evolutionary relatedness.

The term "homoplasy" is most applicable to which of these features?

The legless condition found in various types of extant lizards

If organisms A, B, and C belong to the same class but to different orders and if organisms D, E, and F
belong to the same order but to different families, which of the following pairs of organisms would be
expected to show the greatest degree of structural homology?

D and F

If, someday, an archaean cell is discovered whose SSU-rRNA sequence is more similar to that of
humans than the sequence of mouse SSU-rRNA is to that of humans, the best explanation for this
apparent discrepancy would be __________.


The best classification system is that which most closely __________.

Reflectes evolutionary history

Which of the following pairs are the best examples of homologous structures?

Bat wing and human hand

Some molecular data place the giant panda in the bear family (Ursidae) but place the lesser panda in
the raccoon family (Procyonidae). Consequently, the morphological similarities of these two species are
probably due to __________.

Possession of analogous structures

Which mutation should least require realignment of homologous regions of a gene that is common to
several related species?

1-base substitution

The common ancestors of birds and mammals were very early reptiles, which almost certainly had 3-
chambered hearts (2 atria + 1 ventricle). Birds and mammals are alike in having 4-chambered hearts (2
atria + 2 ventricles). The 4-chambered hearts of birds and mammals are best described as __________.


Generally, within a lineage, the largest number of shared derived characters should be found among
two organisms that are members of the same


A common ancestor for both species C and E could be at position number __________.


The two extant species that are most closely related to each other are __________.

D and E

Which species are extinct?

A and E

If this evolutionary tree is an accurate depiction of relatedness, then which of the following should be
1. The entire tree is based on maximum parsimony.
2. If all species depicted here make up a taxon, this taxon is monophyletic.
3. The last common ancestor of species B and C occurred more recently than the last
common ancestor of species D and E.
4. Species A is the direct ancestor of both species B and species C.
5. The species present at position 3 is ancestral to C, D, and E.


Which of the following is not true of all horizontally oriented phylogenetic trees, where time advances
to the right?

Each branch point represents a point in absolute time.

Ultimately, which of these serves as the basis for both the principle of maximum parsimony and the
principle that shared complexity indicates homology rather than analogy?

The laws of probablity

Shared derived characters are most likely to be found in taxa that are __________.


A taxon, all of whose members have the same common ancestor, is __________.


The term that is most appropriately associated with clade is __________.


If birds are excluded from the class Reptilia, the term that consequently describes the class Reptilia is


If the eukaryotic condition arose, independently, several different times during evolutionary history,
and if ancestors of these different lineages are extant and are classified in the domain Eukarya, then the
domain Eukarya would be __________.


When using a cladistic approach to systematics, which of the following is considered most important
for classification?

Shared derived characters

The four-chambered hearts of birds and the four-chambered hearts of mammals evolved
independently of each other. If one were unaware of this independence, then one might logically conclude
that __________.

The common ancestor of birds and mammals had a four-chambered heart

Phylogenetic hypotheses (such as those represented by phylogenetic trees) are strongest when

they are supported by more than one kind of evidence, such as when fossil evidence corroborates molecular evidence.

Cladograms (a type of phylogenetic tree) constructed from evidence from molecular systematics are
based on similarities in __________.

Mutations to homologous genes

A researcher wants to determine the genetic relatedness of several breeds of dog (Canis familiaris).
The researcher should compare homologous sequences of __________ that are known to be __________.

Proteins or nucleic acids; poorly conserved

Concerning growth in genome size over evolutionary time, which of these does not belong with the

Orthologous genes

Nucleic acid sequences that undergo few changes over the course of evolutionary time are said to be
conserved. Conserved sequences of nucleic acids ____________.

Are abundant in ribosomes

pecies that are not closely related and that do not share many anatomical similarities can still be
placed together on the same phylogenetic tree by comparing their __________.


If the sequence of Species A differs from that of the other four species due to simple misalignment,
then what should the computer software find when it compares the sequence of Species A to those of the
other four species?

The nucleotide sequence of Species A should have long sequences that are nearly identical to those of the other species, but offset in terms of position number.

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