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Darwin and Evidence of Evolution
1 History of Evolutionary Thought
1.
In 1831, Charles Darwin, a 22-year-old naturalist, accepted a position aboard the ship HMS
Beagle that began a voyage around the world; his concept would eventually be known as
evolution.
2. Pre-Darwinian world-view was determined by intractable theological beliefs.
A. Mid-Eighteenth-Century Contributions
1. Carolus Linnaeus and Taxonomy. Taxonomy is the science of classifying organisms;
2. Georges Louis Leclerc, a French naturalist, wrote a 44-volume natural history of all known
plants and animals.
3. Erasmus Darwin
B. Late Eighteenth-/Early-Nineteenth Century Contributions
1. George Cuvier (1769–1832), a French vertebrate zoologist, was the first to use comparative
anatomy to develop a system of classifying animals.
2. Lamarck (1744–1829) was the first to state that descent with modification occurs.
2 Darwin’s Theory of Evolution
A. Darwin’s Background
1. His nature was too sensitive to pursue medicine; he attended divinity school at Cambridge.
2. He attended biology and geology lectures and was tutored by the Reverend John Henslow.
B. Geology and Fossils: His study of geology and fossils caused him to concur with Lyell that the
observed massive geological changes were caused by slow, continuous processes.
C. Biogeography
1. Biogeography is the study of the geographic distribution of life forms on earth.
2. Patagonian hares replaced rabbits in the South American grasslands.
3. The greater rhea found in the north was replaced by the lesser rhea in the south.
4. Comparison of the animals of South America and the Galápagos Islands caused Darwin to
conclude that adaptation to the environment can cause diversification, including origin of new
species.
5. The Galápagos Islands
a. These volcanic islands off the South American coast had fewer types of organisms.
b. Island species varied from the mainland species, and from island-to-island.
c. Each island had a variation of tortoise; long and short necked tortoises correlated with
different vegetation.
d. Darwin’s Finches
1) Finches on the Galápagos Islands resembled a mainland finch but there were more
types.
2) Galápagos finch species varied by nesting site, beak size, and eating habits.
3) One unusual finch used a twig or thorn to pry out insects, a job normally done by
(missing) woodpeckers (Darwin never witnessed this finch behavior).
D. Natural Selection and Adaptation
1. Darwin decided that adaptations develop over time; he sought a mechanism by which
adaptations might arise.
2. Natural selection was proposed by both Alfred Russel Wallace and Darwin as a driving
mechanism of evolution caused by environmental selection of organisms most fit to
reproduce, resulting in adaptation.
3. Because the environment is always changing, there is no perfectly-adapted organism.
4. There are three preconditions for natural selection.
a. The members of a population have random but heritable variations.
b. In a population, many more individuals are produced each generation than the
environment can support.
Some individuals have adaptive characteristics that enable them to survive and reproduce
better.
5. There are two consequences of natural selection.
a. An increasing proportion of individuals in succeeding generations will have the adaptive
characteristics.
b. The result of natural selection is a population adapted to its local environment.
6. Natural selection can only utilize variations that are randomly provided; therefore there is no
directedness or anticipation of future needs.
7. Extinction occurs when previous adaptations are no longer suitable to a changed environment.
E. Organisms Have Variations
1. In contrast to the previous worldview where imperfections were to be ignored, variations were
essential in natural selection.
2. Darwin suspected, but did not have today’s evidence, that the occurrence of variation is
completely random.
F. Organisms Struggle to Exist
1. Darwin and Wallace both read an essay by Thomas Malthus, a socioeconomist.
2. Malthus proposed that human populations outgrow food supply and death and famine were
inevitable.
3. Darwin applied this to all organisms; resources were not sufficient for all members to survive.
4. Therefore, there is a constant struggle for existence; only certain members survive and
reproduce.
G. Organisms Differ in Fitness
1. Organisms whose traits enable them to reproduce to a greater degree have a greater fitness.
2. Darwin noted that humans carry out artificial selection.
H. Organisms Become Adapted
1. An adaptation is a trait that helps an organism be more suited to its environment.
2. Unrelated organisms living in the same environment often display similar characteristics.
3. Because of differential reproduction, adaptive traits increase in each succeeding generation.
I. On the Origin of Species by Darwin
1. After the HMS Beagle returned to England in 1836, Darwin waited over 20 years to publish.
2. He used the time to test his hypothesis that life forms arose by descent from a common
ancestor and that natural selection is a mechanism by which species can change and new
species arise.
3. Darwin was forced to publish Origin of Species after reading a similar hypothesis by Alfred
Russel Wallace.
c.
3 The Evidence of Evolution
A. Common Descent
1. The hypothesis of common descent is supported by many lines of evidence.
2. The more varied the evidence, the more certain it becomes.
3. Darwin synthesized much of the current data but biochemical research was yet to come.
B. Fossils Evidence
1. The fossil record is the history of life recorded by remains from the past.
2. Fossils are at least 10,000 years old and include skeletons, shells, seeds, insects trapped in
amber, and imprints of leaves.
3. The fossil record traces history of life and allows us to study history of particular organisms.
4. Fossil evidence supports the common descent hypothesis; fossils can be linked over time
because they reveal a similarity in form, despite observed changes.
5. Transitional forms reveal links between groups.
6. The fossil record allows us to trace the history of the modern-day horse Equus.
C. Biogeographical Evidence
1. Biogeography studies the distribution of plants and animals worldwide.
2. Distribution of organisms is explained by related forms evolving in one locale and spreading
to other accessible areas.
a. Darwin observed South America had no rabbits; he concluded rabbits originated
elsewhere.
b.
Biogeography explains the abundance of finch species on the Galápagos Islands lacking
on the mainland.
3. Physical factors, such as the location of continents, determine where a population can spread.
D. Anatomical Evidence
1. Organisms have anatomical similarities when they are closely related because of common
descent.
2. Vestigial structures are remains of a structure that was functional in some ancestors but is no
longer functional in the organism in question.
3. Embryological development reveals a unity of plan.
E. Biochemical Evidence
F. Because it is supported by so many lines of evidence, evolution is no longer considered a hypothesis.
Evolution is one of the great unifying theories of biology, similar in status to the germ theory of
disease in medicine.
Process of Evolution
1 Microevolution
1.
A.
B.
C.
D.
It was not until the 1930s that population geneticists were able to apply the principles of
genetics to populations and thus to recognize when evolution had occurred.
2. A population is all of the members of a single species occupying a certain area at the same
time.
3. Evolution that occurs within a population is called microevolution.
4. Population genetics studies the variation in alleles in a gene pool.
5. The gene pool is the total of all the alleles in a population; it is described in terms of gene
frequencies.
6. Neither dominance nor sexual reproduction changes allele frequencies.
7. The Hardy-Weinberg principle
a. This principle states an equilibrium of allele frequencies in a gene pool (using a formula
p2 + 2pq + q2) remains in effect in each succeeding generation of a sexually reproducing
population if five conditions are met.
1) No mutation
2) No gene flow
3) Random mating
4) No genetic drift
5) No selection
Genetic Mutations
1. Many traits in organisms are polymorphic, i.e., two or more distinct phenotypes are
present in the population due to mutated genes.
2. Analysis of Drosophila enzymes indicates they have multiple alleles at least at 30% of
their gene loci.
3. In humans, freckles are an example of polymorphism, as are the ABO blood types.
4. Mutations may not immediately affect the phenotype.
5. Mutations can be beneficial, neutral, or harmful; a seemingly harmful mutation that
requires Daphnia to live at higher temperatures becomes advantageous when the
environment changes.
6. Specific recombinations of alleles may be more adaptive than other combinations.
Gene Flow
Nonrandom Mating
Genetic Drift
1.
2.
The bottleneck effect
The founder effect
2 Natural Selection
 Natural selection 3. Relative fitness compares the fitness of one phenotype to
another.
Types of Selection.
1. Directional selection
2. Stabilizing selection
3. Disruptive selection
3. Macroevolution


Macroevolution refers to any evolutionary change at or above the species level.
Speciation is the splitting of one species into two or more species or the transformation of one species
into a new species over time; speciation is the final result of changes in gene pool allele and genotypic
frequencies.
A. What is a Species?
Reproduce viable and fertile offsprings
B. Reproductive Isolating Mechanisms
Prezygotic (“before formation of a zygote”) isolating mechanisms are anatomical or
behavioral differences between the members of two species that prevent mating or make it
unlikely fertilization will take place if mating occurs.
a. Habitat isolation
b. Temporal isolation
c. Behavioral isolation
d. Mechanical isolation
e. Gamete isolation
2. Postzygotic (“after formation of a zygote”) isolating mechanisms prevent development of a
hybrid after mating has taken place.
a. Zygote mortality is when hybrids (offspring of parents of two different species) do not
live to reproduce.
b. Hybrid sterility occurs when the hybrid offspring are sterile (e.g., mules).
c. In F2 fitness, the offspring are fertile but the F2 generation is sterile.
C. Modes of Speciation
1. Allopatric speciation occurs when new species result from populations being separated by a
geographical barrier that prevents their members from reproducing with each other.
2. Sympatric speciation would occur when members of a single population develop a genetic
difference (e.g., chromosome number) that prevents them from reproducing with the parent
type.
D. Adaptive Radiation
1.
1. Which of the following would change the gene frequencies of a population?
A. DNA is stable from generation to generation and does not change.
B. Tall people in a population marry other tall people and do not marry people who are
short or average height.
C. A population on an island remains isolated and no one leaves or moves onto the island.
D. None of the choices would change the gene frequencies of a population.
2. Which of the following would be a cause of microevolution?
A. A flood kills almost all the wild strawberry plants in a particular area.
B. The largest and strongest male lion chases away other males and is the only male to
mate with females and produce offspring.
C. Wolves are moved from Canada and introduced into the wild in Wyoming.
D. All of the choices can lead to microevolution.
3. A certain species of butterfly in colors ranging from white to dark blue is found. The
birds found in the same area feed on the white or lightly colored butterflies, leaving
butterflies that are darkly colored. This is an example of:
A. stabilizing selection
B. disruptive selection
C. directional selection
4. Which of the following is/are a biological "population?"
A. all of the corn plants in a cornfield
B. all of the variable-colored ladybird beetles of the species Harmonia axyridis in a forest
C. all male and female English sparrows that reside in your community
D. all of the human population of a rural western town
E. All of the choices are correct.
5. What is the term used to describe the accumulation of small changes in the gene pool
of a species over time?
A. genetic drift
B. founder effect
C. microevolution
D. directional selection
6. Which of these conditions is NOT among the requirements of the Hardy-Weinberg
equilibrium?
A. no net mutations
B. no net migration of alleles into or out of the population
C. small population with genetic drift
D. no selection of one genotype over another
E. sexually reproducing and random mating population
7. If the Hardy-Weinberg equilibrium is met, what is the net effect?
A. evolution leading to a population better adapted to an unchanging environment
B. evolution leading to a population better adapted to a changing environment
C. very slow and continuous evolution with no increased adaptation
D. no evolution because the alleles in the population remain the same
8. A student proposes that left-handedness is a recessive trait that is therefore hidden in
much of the human population. A survey of a class of 36 students finds that 27 (0.75) are
right-handed and 9 (0.25) are left-handed. Using the Hardy-Weinberg formula, what
would the expected genotype and allele frequencies be in this theoretical population?
A. 0.75 right-handed homozygous dominant and 0.25 recessive homozygous for 3-to-1
right-to-left handed alleles in the population
B. 0.25 right-handed homozygous, 0.50 heterozygous, and 0.25 recessive homozygous
for a 3-to-1 right-to-left handed alleles in the population
C. 0.25 right-handed homozygous, 0.50 heterozygous, and 0.25 recessive homozygous
for a 0.5 allele frequency for each allele
D. 0.50 right-handed homozygous, 0.25 heterozygous, and 0.25 recessive homozygous
for a 0.5 allele frequency for each allele
E. They cannot be estimated using these limited data.
9. Another student proposes that handedness could just as easily be passed to children by
how the parents carry the child and interact with it, a learning process that may perpetuate
the parents' handedness. Assuming all parents and children are expressing their "true
handedness," the occurrence of which case below would cast the most serious doubt on a
simple genetic basis for handedness, with left-handedness recessive?
A. Two right-handed parents have a left-handed child.
B. Two left-handed parents have a right-handed child.
C. Left-handed parents only have left-handed children.
D. Right-handed parents only have right-handed children.
E. None of the choices is correct.
10. A random alteration in the sequence of DNA nucleotides that provides a new variant
allele is
A. gene mutation.
B. polymorphism.
C. gene frequency.
D. disruption.
11. Which of the following reflect(s) the likely presence of (a) gene mutation(s)?
A. Fruit flies subjected to intense radiation breed a wider array of variable offspring.
B. A chemical leaking from the surface of an old abandoned coal mine alters a regulatory
gene so that a cricket nymph develops an extra set of eyes.
C. The bacteria that cause gonorrhea, a common sexually transmitted disease, have
previously been killed by penicillin; however, after continuous usage of the antibiotic,
penicillin-resistant strains are now becoming prevalent.
D. Radiation causes an alteration in a DNA nucleotide sequence, which is discovered
when mapped, but which appears to be neither increasing nor decreasing in successive
generations.
E. All of the choices are correct.
12. Drug-resistance mutations occur in bacteria
A. only when they are exposed to the drug to which they become resistant.
B. more often when they are exposed to the drug.
C. at any time, even when they are not exposed to the drug.
D. only when they are exposed to radiation or other mutagens.
13. A mutation to a _______ form is more likely to be recognized than any other because
______.
A. beneficial, individuals with a beneficial mutation are much better adapted and survive
longer in their environment
B. beneficial, individuals with a beneficial mutation will always be healthier and have
more offspring than others
C. neutral, these mutations make up the majority of changes in the species
D. harmful, these allow the individual to survive better in a different environment
E. harmful, species are already well adapted and few beneficial changes are possible—
but many damaging changes are possible and cause death or poor adaptation by the
individual
14. Which of the following conditions contributes to evolution?
A. mutations
B. gene flow
C. genetic drift
D. natural selection
E. All of the choices are correct.
15. The most common source of genetic variation in sexually reproducing organisms is
A. mutation.
B. recombination of alleles.
C. duplication of chromosomes.
D. duplication of genes.
16. If the mutation rate of individual genes is taken to be about one in 100,000 genes per
cell cycle across many organisms, we might expect evolution to proceed at an even rate
for various forms of life. Which factor could make the accumulation of gene mutations
faster or slower among different organisms?
A. Organisms with more genes will likely have more mutations per generation.
B. More selection of mutations can occur in a shorter period of time for bacteria that
replicate each ten minutes than for humans with a (roughly) 20-year generation span.
C. Organisms vary in the proportion of DNA that is active and in the percent of loci that
have multiple alleles.
D. All of the choices are correct.
17. Our domesticated honey bee—originally from Europe—is slow to sting, requires
abundant flower nectar, gets up late in the morning, and stores much honey but only
produces enough new brood to swarm once a year. Because the European honey bee was
performing poorly as a honey producer in South America, the African subspecies was
imported in a breeding experiment. The African honey bee formed small nests, foraged
earlier and on smaller nectar sources, produced less honey stores and more brood,
swarmed four or five times a year, and was fast to sting. However, when the African
queens escaped, the two populations interbred and the African genotype spread several
hundred miles north each year. Surprisingly, a hundred miles behind the expanding range
of the African honey bees, the European and hybrid strains died out and the bees were
essentially 100 percent African. How would this be explained in evolutionary genetics
terms?
A. Gene flow is not occurring and therefore these are two separate species.
B. This is a natural consequence of the Hardy-Weinberg equilibrium.
C. Obviously the African bee genes are dominant over the European honey bee alleles.
D. Gene flow is occurring between these subspecies but the African bee is "ecologically
better."
E. This can be understood as a classic case of genetic drift.
18. Occasionally, "living fossils" such as the coelacanth are found; these organisms
appear to be little changed from their ancestors preserved in rock strata many millions of
years ago. Such organisms often occur in ocean deeps and in soil and desert
environments that change less often over time. This is an indication that
A. although gene mutations may be common, there may be little selection among
individuals already well adapted to a uniform environment.
B. these organisms do not have the same high mutation rate of most organisms.
C. by chance, these organism's mutations are all in alleles that do not affect morphology.
D. the Hardy-Weinberg equilibrium prevents these organisms from evolving very fast.
E. there is extensive inbreeding in such organisms.
19. Social research indicates that a person is most likely to marry someone from the same
village or city, or a high school or college classmate. Therefore, the Hardy-Weinberg
equilibrium does not apply well to human populations because
A. allelic changes in one direction are balanced by changes in the opposite direction.
B. there is no directional trend in selection of mates since most individuals marry
someone.
C. individuals are not pairing up by chance across the whole population, and genetic drift
is more likely to change gene frequencies.
D. this increases gene flow.
E. we accumulate adaptive traits that improve the population.
20. Which statement is NOT true about nonrandom mating?
A. Inbreeding is mating between relatives more often than by chance.
B. Inbreeding is a change in allele frequencies that increases the proportion of
heterozygotes in the population.
C. An example of assortative mating is when a tall man marries a tall woman.
D. Assortative mating tends to cause subdivision into two phenotypic classes with
reduced gene flow between them.
21. If two adjacent populations of the same species show gene flow, then the two
populations will
A. become more similar in their gene pools.
B. become isolated from each other.
C. develop into different species.
D. adapt to different conditions and become separate.
22. Which of the following is true about genetic drift?
A. It is more likely to occur in a large population than in a small population.
B. It may lead to an allele's becoming fixed in a population when its alternative allele is
lost from the population.
C. It increases the number of heterozygotes in a population.
D. It increases the level of rare alleles in a population.
23. Which statement is NOT true about the founder effect?
A. It is a form of genetic drift.
B. It produces a high frequency of some rare alleles in a small isolated population.
C. Founding members contain a tiny fraction of the alleles found in the original
population.
D. The founder effect occurs when a population is subjected to near extinction and then
recovers so that only a few alleles are left in survivors.
24. If early Viking explorers in Greenland and North America had survived and become
the main ancestors of early North American settlers, rather than the mixture of
immigrants from across Europe and other continents, today there would be a much higher
incidence of Nordic traits in the U.S. population. Such a scenario would demonstrate
A. gene flow from continent to continent.
B. the founder effect.
C. genetic drift among the original Viking explorers.
D. directional selection.
E. fitness for the North American environment.
25. In the case of the peppered moths in England, when Kettlewell set up cameras to
document that more white or black moths were eaten by birds on clean or sooty trees, he
was verifying which factor involved in evolution by natural selection?
A. The organisms vary in traits.
B. The variation is inherited.
C. More young are born than can survive.
D. Some individuals are better adapted to the environment.
26. Which of the following is required for natural selection to occur in a population?
A. variation in the population
B. inheritance of variation through genetic differences
C. differential reproduction so that more fit individuals have more offspring
D. accumulation of adaptive traits so that they increase in the population
E. All of the choices are required.
27. Which of the following would result in reproductive isolation?
A. Two populations of crickets are indistinguishable in physical features, but the females
in each group only come to the different songs of their males.
B. Fruit flies on one Hawaiian island live for hundreds of generations and do not come in
contact with fruit flies on another island except when blown there by rare tropical storms.
C. One brood of the seventeen-year cicada emerged in 1987 (and will do so every 17
years) and lives a few months as adults; another brood emerged in 1992 (and will do so
every 17 years); the larvae of both feed side-by-side on tree roots.
D. A lion and a tiger mate in the artificial confines of a zoo but the offspring is infertile.
E. All of the choices are correct.
28. An insect population lives along the edge of a north-south mountain range. The
populations from the east and west slope eventually join in a low northern pass and
interbreed, producing fertile offspring, but they do not circle around the southern edge
because of a desert barrier. When glaciers move southward, the populations are pushed
south of the northern pass and are isolated. While isolated, the two populations develop
enough differences over time that when the glaciers retreat north and the insects again
share the same pass, they no longer mate at the same time, nor can they produce fertile
offspring. These insects
A. began as one species and therefore remain one species.
B. were originally two species and remain two species.
C. were originally two species but are now one species.
D. were originally one species but are now two species.
E. The number of species cannot be determined from the information given.
29. An insect population lives along the edge of a north-south mountain range. The
populations from the east and west slope eventually join in a low northern pass and
interbreed, producing fertile offspring, but they do not circle around the southern edge
because of a desert barrier. When glaciers move southward, the populations are pushed
south of the northern pass and are isolated. While isolated, the two populations develop
enough differences over time that when the glaciers retreat north and the insects again
share the same pass, they no longer mate at the same time, nor can they produce fertile
offspring. Insect populations on the mountain slopes were
A. always allopatric.
B. always sympatric.
C. first allopatric, then sympatric, then allopatric.
D. first sympatric, then allopatric, then sympatric.
E. There is not enough information to determine sympatry or allopatry.
30. In the case of Darwin's finches, an ancestral finch species from the mainland arrived
on the Galápagos Islands and soon developed into many new species via adaptive
radiation. The finches did NOT undergo adaptive radiation back on the mainland. What is
the most plausible biological explanation?
A. Directional selection works better on islands.
B. Competition from many other birds species on the mainland provided stabilizing
selection that was absent on the islands.
C. The environment on the mainland was completely uniform.
D. The founder effect greatly expanded the variation in alleles in the Galápagos finch
gene pool.
E. The ancestral mainland finch was reproductively isolated.
31. While we have seen how natural selection and the use of pesticides can lead to the
development of resistant varieties of insects, two economically important flies, the
Mediterranean fruit fly (Medfly) and the screwworm fly, can be driven to local extinction
by the continuous release of sterile flies of those species. The critical factor is that the
female of these species only mates once. But which of the following is/are also necessary
for sterile release to work?
A. The target species is truly just one species.
B. The insect can be raised artificially in large numbers.
C. The insects to be released can be sterilized with radiation without affecting their
ability to attract a mate in the wild.
D. All of the choices are correct.
32. Throughout the chapter, a wide range of evidence has been brought together to
describe what constitutes a species. From all of this you can conclude that
A. some day we could theoretically finalize a list of all species on earth and, if correct, it
could remain unchanged.
B. once mating experiments have been conducted and fertile offspring detected, a species
can be defined with absolute certainty.
C. a species can be definitively described by DNA hybridization, DNA sequencing, or
enzymes.
D. just as organisms recognize their own species, all levels of taxa [class, order, family,
genus] are naturally occurring entities.
E. None of the choices is correct.
33. Based on the text's coverage of the rate of mutation, adaptive radiation, etc., you can
conclude that the rate of evolution progresses at
A. a fairly constant rate and would produce the same outcome if "re-run."
B. an uneven rate but would produce the same outcome if "re-run."
C. a fairly constant rate but would produce different outcomes if "re-run."
D. an uneven rate and would produce different outcomes if "re-run."
34. Reproductive isolation mechanisms for a species include all of the following
EXCEPT
A. habitat isolation
B. temporal isolation of reproduction
C. mechanical isolation of copulation
D. hybrid sterility
E. All of the choices are mechanisms.
35. Microevolution is due to
A. genetic Flow.
B. gene mutations.
C. genetic drift.
D. non-random mating.
E. All of the choices applies.