GBIO 107 Ch. 12
Balanced polymorphism means that multiple _____________________ of a gene persist in a population at more or less constant frequencies indefinitely.
alleles
In the state of Hardy-Weinberg equilibrium, allele frequencies
are not changing.
What is responsible for the many breeds of domestic cats and dogs?
artificial selection
Broccoli, brussels sprouts, cauliflower, kale, and cabbage come from the wild mustard plant that humans have influenced over hundreds of years. The process that resulted in these five species is
artificial selection.
The genetic contribution of an organism to the next generation is referred to as
fitness.
Rock layers at the bottom of a geologic deposit are the
oldest.
What is the genotypic frequency of CC if 320 individuals have the genotype CC in a population of 2,000 individuals?
0.16
In a population of 1,000 individuals with a gene that has two alleles, there are 2,000 alleles total for this gene. If there are 800 copies of allele a, what is the frequency of allele a in the population?
0.4
Use the equation p^2 + 2qp + q^2 = 1.0 to solve the following problem. In a population of 100 squirrels there are 64 black ones, and the remaining are white. Black (B) is the dominant allele, and white (b) is the recessive allele. If the population is in Hardy-Weinberg equilibrium, what is the frequency of the black squirrels that are heterozygous (Bb) for their coat?
0.48
What factors limit the results of natural selection?
1. A population is limited by the alleles present in its gene pool. 2. Disasters such as floods, earthquakes, and volcanoes can indiscriminately eliminate allele combinations.
The average rate of mutation is around one DNA sequence change per ________ base pairs.
10^9
Independently of Charles Darwin, what other scientist proposed natural selection as a driving force for evolution?
Alfred Wallace
What occurs in natural populations and violates the assumptions of the Hardy-Weinberg equilibrium?
Allele frequencies can change due to chance events, mating is often nonrandom, and migration among populations occurs.
_________________ selection occurs when humans select for desirable characteristics in crosses of dogs, horses, or other organisms, where as _______________________ selection occurs when environmental factors select for adaptive traits.
Artificial; natural
As part of his voyage on the Beagle, Darwin spent about a month off the coast of Ecuador making observations on the
Galapagos Islands.
Darwin collected birds from the ___________________ Islands and took them back to England to study, where John Gould identified them as 13 species of birds called ______________.
Galapagos; finches
____________________ flow is the movement of individuals or gametes into or out of a population.
Gene
What did Darwin's ideas suggest about humans, which was hard for some people at the time to accept?
Humans are just another species subject to natural selection.
At the time On the Origin of Species was written, what ideas conflicted with Darwin's ideas about evolution?
Many people believed in the separate special creation of different species, and that species don't change after creation.
What occurs when environmental factors cause the differential reproductive success of individuals with particular genotypes?
Natural selection
What observations and inferences did Charles Darwin make in support of natural selection?
Natural selection can change the characteristics of a population over many generations, more individuals are born than can survive to reproduce, some individuals due to their inherited characteristics survive which makes them more likely to reproduce, organisms are varied and some variations are inherited, and there is competition among individuals for limited resources.
Human birth weight is an example of a type of natural selection called
Normalizing (stablizing) selection
What are examples of the bottleneck effect?
North American bison and greater prairie chickens
In some areas where cholera is common, why is the cystic fibrosis allele maintained in the population?
People heterozygous for the cystic fibrosis allele have a fitness advantage.
What are the key properties of evolutionary adaptations?
They are heritable, and they can confer reproductive success.
Whose essay, describing how factors limit human population size, influenced Charles Darwin's ideas about variation and survival among individuals in a population?
Thomas Malthus
True or false: Some features can persist in organisms even though they are not needed or used.
True
What describes the founder effect?
a small group of individuals establishes a new colony
The ability of an organism to camouflage with its environment is an example of a(n)
adaptation.
Because genes do not "know" when to mutate, it follows that bacterial species with a resistance to an antibiotic must have had a mutation _______________ exposure to the antibiotic.
before
What theory proposes that most geological formations were formed by brief, violent upheavals such as floods, earthquakes, and volcanic eruptions?
catastrophism
Genetic drift is a change in allele frequencies that occurs by _________________ and, unlike mutations, it tends to eliminate alleles from the population.
chance
The unity and diversity of life can be explained by
descent from a common ancestor.
Darwin reasoned that the variety of finch species found on the Galapagos Islands descended from a common ancestor. He used the phrase "__________________ with ______________________" to describe gradual genetic changes from the ancestral type.
descent; modification
Selection for one extreme phenotype in a population would be considered a type of natural selection called
directional selection.
When two phenotypic extremes of a trait are being selectively favored, then a natural population is undergoing _________________ selection.
disruptive
When two phenotypic extremes of a trait are being selectively favored, then a natural population is undergoing
disruptive selection.
In 1858, Darwin received a manuscript from Alfred Russel Wallace describing what similar idea of Darwin's?
evolution by natural selection.
If the environment changes, a trait that was adaptive may become nonadaptive or costly, demonstrating that
evolution continuously shapes populations.
A genotype's __________________ is the number of individuals with that genotype, divided by the total size of the population.
frequency
What describes how genetic drift occurs?
gain or loss of alleles by chance
While serving as a naturalist aboard HMS Beagle, Darwin
gathered many observations that would later help shape his theory of evolution.
What evolutionary forces has a greater effect on small populations?
genetic drift
Evolutionary theory
has developed over several centuries.
Carriers of cystic fibrosis have greater fitness in areas where cholera is common, which is an example of
heterozygote advantage.
In areas of Africa where malaria is common, the prevalence of the sickle cell allele is higher due to
heterozygote advantage.
What genotype for the "sickle cell gene" causes mild symptoms of sickle cell disease but confers resistance to malaria?
heterozygous
Although Darwin proposed that natural selection acted on heritable traits, Darwin did not understand
how heritable traits were shuffled and passed on between generations.
Gregor Mendel's main contribution was to solve the puzzle of
how traits are inherited
Your friend thinks that her dog can evolve into a new species because it is so different than any other dog she has ever seen. You know that this is not possible because
individual organisms cannot evolve.
Male bighorn sheep compete with other males for mating privileges and therefore exhibit _______________. Female peahens select one of many male peacocks to sire their chicks, which provides an example of ______________________.
intrasexual selection; intersexual selection
A ___________________ is a change in an organism's DNA sequence and is the raw material for evolution, because genes affect phenotypes and evolution acts on phenotypes.
mutation
A(n) _________________ is a change in a DNA sequence that occurs at random
mutation
What are mechanisms of evolution that can alter allele frequencies?
mutation, natural selection, and gene flow
Charles Darwin's book titled On the Origin of the Species proposed ________________ as an evolutionary mechanism.
natural selection.
What neither decreases nor increases reproductive success of an organism?
neutral variation
Sexual selection is a type of natural selection resulting from variations in the ability to
obtain mates.
The entire collection of the genes and their alleles in a population is called the gene
pool
After reading Malthus's essay, Darwin realized that
poorly adapted individuals would not survive if resources were limited.
Interbreeding members of the same species compose a
population.
Fitness of an organism depends on
reproduction.
What type of reproduction amplifies genetic variation by shuffling alleles and producing genetically different offspring?
sexual
A difference in the appearance between males and females of a species is called
sexual dimorphism
What increases genetic variability within a species through shuffling and reshuffling of parental alleles to produce genetically different offspring?
sexual reproduction
Genetic drift has a greater effect on
small populations.
An example of macroevolution would be the appearance of a new
species of finch
Once cause of genetic drift is _____________________, in which a small group of individuals leaves its home population and establishes a new, isolated settlement.
the founder effect
Suppose the migration of a subset of the human population to a new area leads to relatively low genetic diversity in the new population. This is an example of
the founder effect.
Taking into account that natural selection resulted in the diversity of finches on the Galapagos Islands, what was the order of events that occured?
1. A few finches flew from the mainland to one island. 2. Most of the finches could only eat small seeds, but the island population outgrew the supply of small seeds. 3. Finches that could eat other foods survived and reproduced, while most of the birds that could only eat small seeds starved. 4. The finches that could eat other foods gradually made up more of the population.
Which two of the following was Charles Darwin not able to explain or understand with respect to his ideas on natural selection as a force of evolution?
1. How heritable traits were passed from one generation to the next. 2. The source of variation within populations.
What are all the effects of gene flow?
1. Introduce new alleles into a population. 2. Decrease regional differences in genetic diversity.
During his voyage on the Beagle, which of the following did Charles Darwin observe?
1. Land altered by forces, such as earthquakes and erosion. 2. Forest plant fossils mixed in with ocean sediments. 3. Plants and animals on the Galapagos Islands.
What are reasons why males usually show the greatest effects of sexual selection?
1. Males must compete for access to females. 2. Females have a high investment in reproduction.
What are examples of nonrandom mating?
1. Mate choice based on social position. 2. Mating only within a specific group. 3. Choosing mates based on certain characteristics.
What ideas were considered fundamental principles for the explanation of the diversity of life before the late 1800s?
1. Members of a particular species are identical in form and capacity. 2. Organisms arose by special creation and did not change.
What evidence supports the fact that descent from a common ancestor resulted in the diversity of life?
1. Most life forms use the same genetic code for gene expression. 2. Different species have similar proteins and enzymes. 3. A diversity of organisms use the same chemical reactions to extract energy from nutrients.
What are the five correct assumptions of the Hardy-Weinberg equilibrium that must be met to keep allele frequencies from changing?
1. No mutations occur. 2. Mating is random. 3. There is no migration into or out of the population. 4. No natural selection occurs. 5. The population is large.
What are implications of Conover's and Munch's studies on selective forces of fish harvesting?
1. Protecting the largest fish from harvest would help favor fast-growing fish. 2. Fisheries would benefit from both a minimum and maximum size limit for harvest.
Who was the naturalist on the five-year voyage of the HMS Beagle?
Charles Darwin
_______________________ is defined as a change in allele frequencies in a population over time.
Evolution
Geological processes that occurred today also occurred in the past, producing changes to Earth over time. This theory was proposed by _________________ and is referred to as _________________.
James Hutton; uniformitarianism
What is true about natural selection?
Results in differential reproductive success of individuals, and it occurs due to variation in environmental factors.
Natural selection requires
genetic diversity.
The appearance of a new species of oak tree would be called a(n)
macroevolutionary event.
What are examples that reflect a fitness greater than zero?
1. A male spider that is eaten by the female during mating, but that fathers 20 offspring. 2. A jellyfish with a thousand offspring, 50% of which reach adulthood. 3. A female salmon that lays over a million eggs, half of which hatch. 4. A penguin that has one chick that survives to reproduce.
What statements describe Lamarck's ideas about the origin of species?
1. Any physical changes that happen to the parents during their lives can be passed on to the next generation. 2. Organisms that use a body part repeatedly increase their abilities.
What are all the ways that the Hardy-Weinberg equations can be used?
1. Calculate allele frequencies if genotype frequencies are known. 2. Calculate genotype frequencies if allele frequencies are known. 3. Indicate if evolution is occurring.
What statements about Charles Darwin are correct?
1. Darwin proposed that natural selection was the driving force of evolution. 2. Darwin studied similarities and differences among organisms and related them to geological observations.
What are correct examples of artificial selection?
1. Darwin raised and developed several breeds of pigeons using artificial selection. 2. Broccoli, cauliflower, and kale were created by artificial selection of wild mustard.
As evolutionary theory was being developed prior to the mid-1700s, what fossil evidence conflicted with the idea that diversity of life was due to creation?
1. Fossils showed that species were extinct. 2. Different layers of rock contained different groups of fossilized organisms. 3. Fossils depicted organisms never seen before.
What can limit the actions of natural selection?
1. Traits that affect survival but not reproduction. 2. An organism's evolutionary history. 3. Low variation among alleles in the population.
What important ideas did the following scientists propose about evolution: Buffon, Lyell, Darwin, and Lamarck?
Buffon: Closely related species arise from a common ancestor and are changing. Lyell: Natural processes are slow and steady, and the Earth is much older than 6,000 years. Darwin: Variation exists in a population and new species arise when natural selection acts on the variation. Lamarck: Repeated use of a body part increases an organism's abilities, and this change during a lifetime passes to the next generation.
What is true about the heterozygous genotype in the situation of heterozygote advantage?
Can contain harmful alleles and has greater fitness than homozygous genotypes
In 1859, ________________ published his book titled On the Origin of Species that underlies many principles of modern life science.
Charles Darwin
True or false: The goal of natural selection is to produce perfect organisms.
False
What are mechanisms of evolution and can alter allele frequencies?
Gene flow, natural selection, and mutation
The idea that organisms could change their body form by repeated use of their body parts and that these changes could be passed to the next generation was introduced by
Lamarck.
What are all of the reasonings of Charles Darwin that were influenced by Thomas Malthus's essay?
More individuals are born into a population than the habitat can support, there is variation in a population, and some individuals in a population are better able to obtain resources than others.
What is an example of a mutation that could result in evolutionary change?
Mutation in the chromosome structure of an egg cell before fertilization.
Fitness depends on what?
Number of successful reproductive efforts in lifetime, proportion of offspring that survive to reproduce, and the ability to survive long enough to successfully reproduce.
Before the late 1800s, how did some scientists explain the presence of fossils without denying a creator?
The fossils could be explained using religious stories.
To calculate an allele frequency, you should divide the number of copies of that allele by the total number of _______________ in the population for that gene.
alleles
When a population's size drops rapidly over a short period, resulting in a loss of many alleles that were present in the larger ancestral population, this is referred to as the
bottleneck effect.
If two species that live on opposite sides of the planet share common characteristics and live in similar habitats, then these two species have undergone
convergent evolution.
If a predator is more likely to prey upon fish that are the brightest in color, then natural selection in this environment will favor
drabber fish.
Natural selection, mutation, genetic drift, nonrandom mating, and gene flow are all mechanisms of ____________ and can change allele frequencies in populations.
evolution
One definition of __________________ is "changes in traits from generation to generation."
evolution
How does natural selection act to change allele frequencies?
favors adaptive phenotypes
Disruptive selection is a mechanism of natural selection that
favors two or more extreme phenotypes in a population.
In evolutionary terms, fitness of an organism is defined as an organism's
genetic contribution to the next generation.
A chance change in a population's allele frequencies, such as after a drastic reduction in population size, is the root of what force of evolution?
genetic drift
A change in allele frequencies that occurs by chance and that tends to eliminate alleles in a population rather than increase diversity is called
genetic drift.
The modern evolutionary synthesis connects natural selection and
genetic variation that arises by mutation.
In the Hardy-Weinberg equilibrium, the terms p^2, 2pq, and q^2 refer to
genotype frequencies in a population.
Lyell's idea about fossils and the age of the Earth led to the conclusion that
gradual changes occurred in some organisms and that these could be preserved in the fossil record.
As proposed by James Hutton, the theory of uniformitarianism states that
gradual geological processes such as erosion and sedimentation that act in modern times also occurred in the past.
Mate choice, such as in sexual selection
leads to nonrandom mating.
The principle of superposition explains the idea that _____________ layers of rock, along with the fossils they contain, are older than the layers ___________ them.
lower; above
The small, genetic changes that occur from generation to generation within a population or species are called
microevolution.
A mutation can affect evolution in a species only if
subsequent generations inherit it.
Cuvier thought that lower layers of rock were older than those above him. This principle describes
superposition.
