Question 1

Which of these would, if it had acted upon a gene, prevent this gene from acting as a reliable molecular clock?
A)neutral mutations
B)genetic drift
C)mutations within introns
D)natural selection
E)most substitution mutations involving an exonic codon's third position

Accepted Answer

Natural selection would prevent a gene from acting as a reliable molecular clock because it would cause changes in the gene's sequence that are not due to neutral mutations and would therefore disrupt the gene's rate of evolution over time.

Question 2

A monophyletic group
A)is the basal taxon.
B)includes the groups that form the nodes on a phylogenetic tree.
C)is an ancestral species and includes all of its descendants.
D)is an ancestral species and includes some of its descendants.
E)includes species that show convergent evolution.

Accepted Answer

A monophyletic group is a taxonomic group that includes an ancestral species and all of its descendants, therefore option C is the best choice.

Question 3

A researcher wants to determine the genetic relatedness of several breeds of dog (Canis lupus familiaris). The researcher should compare homologous sequences of this type of biochemical-________-which can be described as ________.
A)fatty acids; highly conserved
B)lipids; poorly conserved
C)proteins; highly conserved
D)amino acids; highly conserved
E)nucleic acids, poorly conserved

Accepted Answer

To determine genetic relatedness, the researcher should compare homologous sequences of nucleic acids, such as DNA or RNA, which can be variable among different breeds and thus poorly conserved. Comparing conserved sequences would not reveal differences that could be used to identify genetic relatedness. Comparing non-homologous sequences, such as lipids or fatty acids, would not provide information about genetic relatedness. Although proteins are also variable among different breeds, comparing them may not be as informative as comparing nucleic acids, since changes in the DNA sequence can ultimately affect the protein sequence. Comparing homologous sequences of amino acids is also an option, but since this usually implies comparing protein sequences, the explanation still applies.

Question 4

The lakes of northern Minnesota are home to many similar species of damselflies of the genus Enallagma that have apparently undergone speciation from ancestral stock since the last glacial retreat about 10 000 years ago. Sequencing which of the following would probably be most useful in sorting out evolutionary relationships among these closely related species?
A)nuclear DNA
B)mitochondrial DNA
C)small nuclear RNA
D)ribosomal RNA
E)amino acids in proteins

Accepted Answer

Mitochondrial DNA (mtDNA) is often used for studying evolutionary relationships within species and among closely related species. mtDNA is maternally inherited and evolves at a faster rate than nuclear DNA, making it useful for distinguishing between closely related species that may have diverged relatively recently.

Question 5

Which kind of DNA should provide the best molecular clock for determining the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?
A)that coding for ribosomal RNA
B)intronic DNA belonging to a gene whose product performs a crucial function
C)paralogous DNA that has lost its function (i.e., no longer codes for functional gene product)
D)mitochondrial DNA
E)exonic DNA that codes for a noncrucial part of a polypeptide

Accepted Answer

Ribosomal RNA (rRNA) genes are highly conserved across different species due to their essential role in protein synthesis. This conservation makes them excellent molecular clocks for studying evolutionary relationships over long periods, including those species whose common ancestors became extinct billions of years ago.

Question 6

A phylogenetic tree constructed using sequence differences in mitochondrial DNA would be most valid for discerning the evolutionary relatedness of
A)archaeans and bacteria.
B)fungi and animals.
C)chimpanzees and humans.
D)sharks and dolphins.
E)mosses and ferns.

Accepted Answer

Mitochondrial DNA is inherited maternally and is therefore particularly useful for studying evolutionary relatedness among closely related species, such as chimpanzees and humans.

Question 7

The most important feature that permits a gene to act as a molecular clock is
A)having a large number of base pairs.
B)having a larger proportion of exonic DNA than of intronic DNA.
C)having a reliable average rate of mutation.
D)its recent origin by a gene-duplication event.
E)its being acted upon by natural selection.

Accepted Answer

A gene can act as a molecular clock only if it has a reliable average rate of mutation. This allows for the estimation of divergence times between species based on differences in their DNA sequences. Without a consistent rate of mutation, the gene could not be used as a reliable clock.

Question 8

Which statement represents the best explanation for the observation that the nuclear DNA of wolves and domestic dogs has a very high degree of sequence homology?
A)Dogs and wolves have very similar morphologies.
B)Dogs and wolves belong to the same order.
C)Dogs and wolves are both members of the order Carnivora.
D)Dogs and wolves shared a common ancestor very recently.

Accepted Answer

The high degree of sequence homology seen in the nuclear DNA of wolves and domestic dogs indicates that they shared a common ancestor very recently. This is because DNA sequences diverge over time, so the more similar two sequences are, the more recently they diverged from a common ancestor. Morphology, order membership, and even carnivore status do not directly relate to DNA sequence homology, so options A-C are not as appropriate explanations for this observation.

Question 9

When it acts upon a gene, which of the following processes consequently makes that gene an accurate molecular clock?
A)transcription
B)directional natural selection
C)mutation
D)proofreading
E)reverse transcription

Accepted Answer

Mutation is the process that causes changes in the DNA sequence of a gene. These changes may accumulate over time and can provide information about the evolutionary history of a species. Mutations occur randomly and are not affected by natural selection, making them an accurate molecular clock. Transcription, proofreading, and reverse transcription do not cause changes in the DNA sequence, and directional natural selection may cause certain changes to be favored over others, disrupting the accuracy of the clock.

Question 10

Species 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
A)plasmids.
B)mitochondrial genomes.
C)homologous genes that are poorly conserved.
D)homologous genes that are highly conserved.

Accepted Answer

The answer of Species that are not closely related and...

Question 11

Nucleic acid sequences that undergo few changes over the course of evolutionary time are said to be conserved. Conserved sequences of nucleic acids
A)are found in the most crucial portions of proteins.
B)include all mitochondrial DNA.
C)are abundant in ribosomes.
D)are proportionately more common in eukaryotic introns than in eukaryotic exons.
E)comprise a larger proportion of pre-mRNA (immature Mrna)than of mature mRNA.

Accepted Answer

The answer of Nucleic acid sequences that undergo few changes...

Question 12

Concerning growth in genome size over evolutionary time, which of these is least associated with the others?
A)orthologous genes
B)gene duplications
C)paralogous genes
D)gene families

Accepted Answer

Orthologous genes refer to genes that diverged through speciation events and are found in different species. The size of the genome does not necessarily have to increase with the presence of orthologous genes. On the other hand, gene duplications, paralogous genes, and gene families are all associated with an increase in genome size.

Question 13

The reason that paralogous genes can diverge from each other within the same gene pool, whereas orthologous genes diverge only after gene pools are isolated from each other, is that
A)having multiple copies of genes is essential for the occurrence of sympatric speciation in the wild.
B)paralogous genes can occur only in diploid species; thus, they are absent from most prokaryotes.
C)polyploidy is a necessary precondition for the occurrence of sympatric speciation in the wild.
D)having an extra copy of a gene permits modifications to the copy without loss of the original gene product.

Accepted Answer

Paralogous genes are those that arise through gene duplication events that result in multiple copies of a gene within a genome. Because these duplicates remain in the same gene pool, modifications to the duplicate copy may occur without loss of the original gene product. This can lead to divergence between the copies, as functionally equivalent mutations can accumulate independently in each gene copy. In contrast, orthologous genes are those that diverge from each other only after gene pools are isolated from each other, typically as a result of speciation events. In this case, mutations that arise in one gene copy will not be shared with the other copy, so the two genes will diverge more slowly.

Question 14

Paralogous genes that have lost the function of coding for any functional gene product are known as "pseudogenes." Which of these is a valid prediction regarding the fate of pseudogenes over evolutionary time?
A)They will be preserved by natural selection.
B)They will be highly conserved.
C)They will ultimately regain their original function.
D)They will be transformed into orthologous genes.
E)They will have relatively high mutation rates.

Accepted Answer

Pseudogenes are non-functional and do not contribute to the organism's fitness. Therefore, they are not subject to selection pressure, and mutations can accumulate relatively quickly. Over time, this can lead to significant sequence divergence and pseudogenization.

Question 15

Since all organisms share a common ancestor, it comes as no surprise that some characteristics are shared while others are not. If we consider the backbone and feathers, respectively, of birds, we can say that the former is a ________ while the latter are a ________.
A)monophyletic characteristic, paraphyletic characteristic
B)monophyletic characteristic, polyphyletic characteristic
C)shared derived character, shared ancestral character
D)shared ancestral character, shared derived character
E)ingroup, outgroup

Accepted Answer

The backbone is a shared ancestral character because it is a trait shared by birds and their ancestors, while feathers are a shared derived character specific to birds and not present in their distant ancestors.

Question 16

Which of the following pairs is incorrectly matched?
A)orthologous genes - speciation with divergence of genes
B)paralogous genes - gene duplication and divergence
C)orthologous and paralogous genes - both lead to speciation
D)paralogous genes - divergence within a species

Accepted Answer

Only paralogous genes lead to divergence within a species, while both orthologous and paralogous genes can lead to speciation. Therefore, C is incorrectly matched.

Question 17

Neutral theory proposes that
A)molecular clocks are more reliable when the surrounding pH is close to 7.0.
B)most mutations of highly conserved DNA sequences should have no functional effect.
C)DNA is less susceptible to mutation when it codes for amino acid sequences whose side groups (or R groups)have a neutral pH.
D)DNA is less susceptible to mutation when it codes for amino acid sequences whose side groups (or R groups)have a neutral electrical charge.
E)a significant proportion of mutations are not acted upon by natural selection.

Accepted Answer

Neutral theory proposes that a significant proportion of mutations are not acted upon by natural selection, and instead occur randomly and persist in the population due to genetic drift. This challenges traditional evolutionary theory which suggests that natural selection is the primary driving force of evolution.

Question 18

Members of which kingdom have cell walls and are all heterotrophic?
A)Plantae
B)Fungi
C)Animalia
D)Protista
E)Monera

Accepted Answer

Members of the Fungi kingdom have cell walls and are all heterotrophic. Plantae have cell walls and are autotrophic, Animalia lack cell walls and are heterotrophic, Protista may or may not have cell walls and can be either autotrophic or heterotrophic, and Monera have cell walls but can be either autotrophic or heterotrophic.

Question 19

What important criterion was used in the late 1960s to distinguish between the three multicellular eukaryotic kingdoms of the five-kingdom classification system?
A)the number of cells present in individual organisms
B)the geological stratum in which fossils first appear
C)the nutritional modes they employ
D)the biogeographic province where each first appears
E)the features of their embryos

Accepted Answer

The important criterion used in the late 1960s to distinguish between the three multicellular eukaryotic kingdoms of the five-kingdom classification system was the nutritional modes they employ. The three kingdoms were Plantae (producers), Animalia (consumers), and Fungi (decomposers). This distinction was based on the organisms' modes of acquiring nutrients.

Question 20

What kind of evidence has recently made it necessary to assign the prokaryotes to either of two different domains, rather than assigning all prokaryotes to the same kingdom?
A)molecular
B)behavioural
C)nutritional
D)anatomical
E)ecological

Accepted Answer

Recent molecular evidence has shown that prokaryotes can be divided into two domains: Bacteria and Archaea, which are genetically distinct from each other. Therefore, it is necessary to assign prokaryotes to two different domains rather than assigning them all to the same kingdom.

Quiz 26: Phylogeny and the Tree of Life

Which of these would, if it had acted upon a gene, prevent this gene from acting as a reliable molecular clock?

A monophyletic group

A researcher wants to determine the genetic relatedness of several breeds of dog (Canis lupus familiaris) . The researcher should compare homologous sequences of this type of biochemical--which can be described as .

Which kind of DNA should provide the best molecular clock for determining the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?

A phylogenetic tree constructed using sequence differences in mitochondrial DNA would be most valid for discerning the evolutionary relatedness of

The most important feature that permits a gene to act as a molecular clock is

Which statement represents the best explanation for the observation that the nuclear DNA of wolves and domestic dogs has a very high degree of sequence homology?

When it acts upon a gene, which of the following processes consequently makes that gene an accurate molecular clock?

Species 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

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

Concerning growth in genome size over evolutionary time, which of these is least associated with the others?

The reason that paralogous genes can diverge from each other within the same gene pool, whereas orthologous genes diverge only after gene pools are isolated from each other, is that

Paralogous genes that have lost the function of coding for any functional gene product are known as "pseudogenes." Which of these is a valid prediction regarding the fate of pseudogenes over evolutionary time?

Since all organisms share a common ancestor, it comes as no surprise that some characteristics are shared while others are not. If we consider the backbone and feathers, respectively, of birds, we can say that the former is a while the latter are a .

Which of the following pairs is incorrectly matched?

Neutral theory proposes that

Members of which kingdom have cell walls and are all heterotrophic?

What important criterion was used in the late 1960s to distinguish between the three multicellular eukaryotic kingdoms of the five-kingdom classification system?

What kind of evidence has recently made it necessary to assign the prokaryotes to either of two different domains, rather than assigning all prokaryotes to the same kingdom?