Deck 26: Evolutionary Genetics

Question 1

Of the various evolutionary forces, _____ is responsible for the origin of new genetic variation in a species.

A) natural selection
B) genetic drift
C) mutation
D) migration
E) nonrandom mating

Answer 1

C

Question 2

The balance hypothesis does NOT suggest that:

A) genetic variation in a population is mostly maintained by natural selection.
B) overdominance is one type of natural selection favoring the maintenance of genetic variation.
C) most molecular variants are not functionally equivalent.
D) levels of genetic variation are increased by the role of natural selection.
E) genetic drift and mutation are both important in determining levels of genetic variation within a population.

Answer 2

E

Question 3

The _____ concept defines a species as a group of organisms that are capable of exchanging genes.

A) morphospecies
B) phylogenetic species
C) biological species
D) cladogenic species
E) evolutionary species

Answer 3

C

Question 4

Before the advent of molecular techniques, researchers indirectly assessed genetic variation in populations through the study of _____ diversity.

A) protein
B) phenotypic
C) mutational
D) behavioral
E) fossil

Question 5

Evolution can be defined as _____ change that takes place in a(n) _____.

A) any; individual
B) a genetic; individual
C) any; group of organisms
D) a genetic; group of organisms
E) All of the answers are correct.

Question 6

Considering the strengths and weaknesses of molecular data, what could one NOT argue to be true?

A) Molecular methods can be used in all organisms since they all have proteins and DNA.
B) Molecular data are not easily quantifiable, making analysis somewhat subjective.
C) Molecular methods can access a large amount of data.
D) Molecular data can provide direct information on the process of evolution.
E) Molecular variation is clear and interpretable, even if the relationship between some traits and their underlying genes is complex.

Question 7

Alfred Roca and his colleagues used DNA sequencing to reassess the genetic relationships among African elephants. What did they conclude?

A) Genetic variation was uncommon in African elephants.
B) Cladogenesis occurred within African elephants.
C) There was extensive gene flow between forest and savannah elephants.
D) The genetic variation correlates with differences in phenotype that had been previously observed.
E) There was extensive difference in the mitochondrial genome between savannah and forest elephants.

Question 8

Can different species have very few visible morphological differences or none at all?

A) no, because different species must have distinct, visible morphological differences
B) yes, if they are not under selection to evolve such differences (cryptic species)
C) yes, if they are hybrids of other species
D) yes, when their DNA is identical
E) no, because their DNA is not identical, and phenotype must always reflect genotype

Question 9

The neutral-mutation hypothesis does NOT suggest that:

A) the evolution of most genetic variation in a population is influenced by genetic drift.
B) when natural selection is at work on protein variants, it will lead to little variation in the population.
C) most molecular variation is adaptively neutral-for example, most protein variants are functionally equivalent.
D) natural selection is still an important evolutionary force.
E) genetic variation in a population is maintained mainly by natural selection.

Question 10

How has molecular data helped resolve the evolutionary relationships among distantly related taxa?

Question 11

In most cases, different species are distinguished on the basis of:

A) genetic differences.
B) phenotypic differences.
C) time since anagenesis.
D) the absence of reproductive isolating mechanisms.
E) differences in ploidy level.

Question 12

Which reproductive isolating mechanism is exhibited by two different species of tree frogs when their males vocalize their distinct mating songs at the same time in the same forest?

A) prezygotic ecological
B) postzygotic
C) prezygotic behavioral
D) prezygotic temporal
E) prezygotic mechanical

Question 13

What characteristics of microsatellite markers make them useful in studying genetic variation?

Question 14

Support for evolution is NOT found in

A) comparative anatomy.
B) the fossil record.
C) the distributions of species (biogeography).
D) direct observation such as the evolution of pesticide resistance.
E) the change an organism undergoes as it ages.

Question 15

_____ is the splitting of one lineage into two distinct lineages.

A) Genesis
B) Anagenesis
C) Phylogenesis
D) Cladogenesis
E) Neogenesis

Question 16

Which reproductive isolating mechanism is exhibited by two different species of flowers, where one is pollinated by butterflies and another by bees?

A) prezygotic ecological
B) postzygotic
C) prezygotic behavioral
D) prezygotic temporal
E) prezygotic mechanical

Question 17

Protein electrophoresis was the first molecular technique to measure genetic variation. However, this technique normally underestimates the true amount of genetic variation. Why?

Question 18

The microsatellite study of bighorn sheep described in Section 26.1 was a study of:

A) anagenesis.
B) cladogenesis.
C) speciation.
D) proteins.
E) variation but not evolution.

Question 19

Which of the following markers is NOT used to investigate genetic variation in natural populations?

A) DNA sequence
B) RFLP
C) microsatellite
D) isotope
E) allozyme

Question 20

Which reproductive isolating mechanism is exhibited by two different Drosophila species where one species breeds in the early morning and the other in the afternoon?

A) prezygotic ecological
B) postzygotic
C) prezygotic behavioral
D) prezygotic temporal
E) prezygotic mechanical

Question 21

_____ characteristics evolved from the same character in a common ancestor.

A) Similar
B) Paralogous
C) Homologous
D) Phylogenetic
E) Parsimonious

Question 22

What two factors are thought to play a critical role in sympatric speciation? Explain how they lead to sympatric speciation.

Question 23

_____ is BEST known for developing the concept of biological species.

A) Mendel
B) Darwin
C) Mayr
D) Fisher
E) Linnaeus

Question 24

How much genetic differentiation is required for reproductive isolation to take place?

Question 25

How does speciation by polyploidy occur?

Question 26

A(n) _____ tree is one that contains a node representing the common ancestor to all other nodes in the tree.

A) gene
B) phylogenetic
C) outgroup
D) most parsimonious
E) rooted

Question 27

In Darwin's finches (Figure 26.6, below), the species Geospiza magnirostris is MOST closely related to which species?

A) Geospiza scandens
B) Geospiza fortis
C) Geospiza conirostris
D) Geospiza difficilis
E) Certhidea olivacea

Question 28

Problems with using the biological species concept do NOT include that:

A) it is sometimes difficult to determine if reproductive isolation exists.
B) reproductive isolation does not apply to asexual organisms.
C) the concept of reproductive isolation does not work for fossils.
D) reproductive isolation is not a mechanism that ensures that species are evolving independently.
E) All of these are problems with the biological species concept.

Question 29

In the phylogeny of Darwin's finches (Figure 26.6, below), which species serves as an outgroup?

A) Pinaroloxias inornata
B) Geospiza fortis
C) Geospiza conirostris
D) Geospiza difficilis
E) Certhidea olivacea

Question 30

The diagram below represents the ranges of three closely related species (A, B, and
C), which are separated by a mountain range and river. As an expert geologist, you hypothesize that the area was originally occupied by a single species. Its range was split first by the mountain range. Later, the river formed, separating populations on the eastern side of the mountains. If your hypothesis is correct, what should the phylogenetic relationships be among the three species? Draw a phylogeny as your answer.

Question 31

All of the following are examples of postzygotic reproductive isolating mechanisms EXCEPT:

A) a sheep adapted to mountains mating with a sheep adapted to desert producing offspring maladapted to either habitat.
B) two plant species flowering at different times.
C) the hybrid offspring of two species dying before birth.
D) the hybrid offspring of two species being sterile.
E) the hybrid offspring of two species being fertile but their offspring being inviable or sterile.

Question 32

What is the first step in cladogenesis? Give an example of how this might occur.

Question 33

_____ is the idea that, if postzygotic isolating mechanisms exist between two species, then natural selection will favor traits that lead to the evolution of prezygotic isolating mechanisms.

A) Hybrid breakdown
B) Reinforcement
C) Gametic isolation
D) Phylogenetic species
E) Hybrid inviability

Question 34

Why is sympatric speciation thought to be so rare in nature? Specifically, which evolutionary forces act against sympatric speciation, and what evolutionary forces might act to allow sympatric speciation?

Question 35

All of the following are examples of prezygotic reproductive isolating mechanisms EXCEPT:

A) a cat trying to mate with a lion.
B) a male fiddler crab waving its claw to attract a mate.
C) the hybrid offspring of two species dying before birth.
D) fireflies flashing their light-emitting organs.
E) two plant species flowering at different times.

Question 36

Is the buildup of reproductive barriers in two allopatric populations the result of natural selection for reproductive isolation?

Question 37

_____ represent the evolutionary relationships among groups of organisms.

A) Alignments
B) Nodes
C) Synonymous rates of substitution
D) Phylogenetic trees
E) Species concepts

Question 38

The construction of a phylogeny from DNA sequence data requires:

A) the identification of monophyletic groups prior to analysis.
B) a proper alignment of nucleotide bases from homologous genes.
C) the use of the fossil record to calibrate rates of nucleotide substitution.
D) removing any sequences with insertions or deletions from the analysis.
E) the use of genes that influence traits associated with reproductive isolating mechanisms.

Question 39

_____ speciation arises in the absence of any geographic barrier to gene flow.

A) Autocratic
B) Allopatric
C) Sympatric
D) Parapatric
E) Peripatric

Question 40

One example of _____ speciation is when a small group of individuals colonizes an island.

A) autocratic
B) allopatric
C) sympatric
D) parapatric
E) peripatric

Question 41

Which of the following are homologous?

A) bat wings and fly wings
B) bat wings and bird legs
C) bat wings and human hands
D) bat wings and human feet
E) bat wings and bird wings

Question 42

According to the molecular clock data in Figure 26.14 (below), approximately what proportion of differences (per amino acid site) has accumulated between the common ancestor of all vertebrates (including fish) and the common ancestor of humans and kangaroos?

A) 0.1
B) 0.3
C) 0.5
D) 0.7
E) 0.9

Question 43

Horizontal gene transfer is most common:

A) among bacteria.
B) among eukaryotes.
C) among viruses.
D) from eukaryotes to bacteria.
E) from plants to animals.

Question 44

Based on careful inspection of the genetic code, why might the second position of a codon have the lowest rate of substitutions in a gene?

Question 45

The relatively small amount of genetic differentiation among some species suggests that many phenotypic differences reflect changes in _____, rather than the evolution of new genes.

A) gene expression
B) gene duplication
C) exon shuffling
D) whole-genome duplication
E) horizontal gene transfer

Question 46

Based on the gene tree in Figure 26.11 (below), which of the following pairs of genes are MOST similar?

A) tilapia PRL1 and cherry salmon SOMA
B) human SOMA and human PRL
C) alligator PRL2 and chicken PRL
D) catfish PRL and chicken SOMA
E) whale PRL and catfish PRL

Question 47

Discuss the role of the availability of whole-genome sequences in understanding the evolutionary process.

Question 48

(a) What are pseudogenes? (b) Why might homologous pseudogenes in a group of closely related species be more useful than "real" genes for elucidating phylogenetic relationships between those species?

Question 49

In Darwin's finches (Figure 26.6, below), which genera have the LATEST common ancestor in common?

A) Geospiza and Certhidea
B) Pinaroloxias and Camarhynchus
C) Geospiza and Camarhynchus
D) Geospiza and Pinaroloxias
E) Pinaroloxias and Platyspiza

Question 50

(a) What is a molecular clock? (b) In what situation(s) would it be especially useful? (c) Explain how a molecular clock is calibrated. (d) What are some known problems with using molecular clocks?

Question 51

Based on Figure 26.11 (below), which pair of genes was the EARLIEST to diverge?

A) sea bass PRL and tilapia PRL2
B) sea bass PRL and eel PRL
C) sea bass PRL and tilapia PRL1
D) eel PRL and catfish PRL
E) catfish PRL and carp PRL

Question 52

A phylogenetic tree for three species, A, B, and C, is shown below. A particular DNA region that is shared by all three species is cloned from each species and sequenced. There are about 100 nucleotide substitutions between A and C and between B and C. There are only 20 differences between A and B. The fossil record indicates that the ancestor to A and B diverged from the ancestor to C around 10 million years ago. What is the best estimate of the divergence between A and B based on this information, assuming a constant rate of mutation and the same rate of mutation on all branches?

A) 1 million years ago
B) 2 million years ago
C) 5 million years ago
D) 10 million years ago
E) 20 million years ago

Question 53

How might gene duplication provide a mechanism for the addition of new genes with novel functions?

Question 54

_____ are sets of genes that are similar in sequence but encode different products.

A) Codons
B) Genomes
C) Exons
D) Pseudogenes
E) Multigene families

Question 55

Phylogenies can be used to reconstruct the evolutionary history of a group of species. The DNA sequences of genes are frequently used to construct such phylogenetic trees. Will the phylogenies of genes always match the history of the organisms that the genes come from?

Question 56

The _____ approach to inferring relationships among species selects the phylogeny that minimizes the number of evolutionary changes.

A) maximum likelihood
B) Bayesian
C) maximum parsimony
D) distance
E) rooted tree

Question 57

Which region of a gene should have the HIGHEST rates of substitution?

A) first position of a codon
B) second position of a codon
C) third position of a codon
D) 5' flanking region
E) 3' untranslated region

Question 58

For most protein-coding genes, the rate of substitution in _____ is considerably higher than in _____.

A) synonymous sites; nonsynonymous sites
B) nonsynonymous sites; synonymous sites
C) nonsynonymous sites; introns
D) 3' untranslated regions; synonymous sites
E) 3' untranslated regions; introns

Question 59

The observation that some genes are mosaics of other genes can be explained by:

A) evolution.
B) horizontal gene transfer.
C) exon shuffling.
D) gene duplication.
E) pseudogenes.

Question 60

The underlying assumptions of using a molecular clock to date evolutionary events are based on:

A) the neutral mutation hypothesis.
B) the balance hypothesis.
C) rates of exon shuffling.
D) the model of allopatric speciation.
E) maximum parsimony analyses.

Question 61

For most protein-encoding genes, the synonymous rate of change is considerably higher than the nonsynonymous rate. In comparing two taxa, how might you interpret the evolutionary history of a gene if the nonsynonymous rate of change was higher than the synonymous rate?

Question 62

(a) What is horizontal gene transfer? (b) How does horizontal gene transfer generate incongruity between phylogenetic (species) trees and gene trees?

Question 63

Suppose that there are three species that are closely related as indicated by the phylogenetic tree below. Each species contains only one copy of a particular gene. The version in Species A is designated Gene_A, and so on. The relationships among the three versions of the gene in the different species are shown below. Explain in terms of duplications and/or deletions the incongruity between the phylogenetic (species) tree and the gene tree.