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What are the two major points Darwin made in The Origin of Species?
He presented evidence that many species of organisms presently inhabiting Earth are descendants of ancestral species that were different from the modern species. And second, he proposed a mechanisms for this evolutionary process, natural selection.
The result of natural selection is an accumulation of inherited characteristics that enhance organisms' ability to survive and reproduce in specific environment, also called ____________.
Evolutionary adaptation
This is a change over time in the genetic composition of a population.
Evolution
Carolus Linnaeus founded this, which is the branch of biology concerned with naming and classifying organisms.
Taxonomy
Remains or traces of organisms from the past.
Fossils
Most fossils are found in these which are formed from the sand and mud that settle to the bottom of seas, lakes, and marshes.
Sedimentary rocks
The study of fossils was developed by Georges Cuvier.
Paleotology
Cuvier noted what about strata depth?
The deeper (older) the strata, the more dissimilar the fossils are from current life. He also observed that from one stratum to the next, some new species appear while others disappear. He inferred that extinctions must have been a common occurrence in the history of life.
A speculation observed by Cuvier that each boundary between strata represents a catastrophe, such as a flood or drought, that destroyed many of the species living at the time. He proposed that these periodic catastrophes were usually confined to local geographic regions, which were repopulated by species immigrating from other areas.
Catastrophism
The idea that profound change can take place through the cumulative effect of slow but continuous processes.
Gradualism
Charles Lyell incorporated Hutton's thinking into a more comprehensive theory ---- proposing that the same geologic processes are operating today as in the past, and at the same rate.
Uniformitarianism
A phrase that summarized Darwin's view of life. He perceived unity in life, with all organisms related through descent from an ancestor that lived in the remote past.
Descent with modification
Summary of Natural Selection
Natural Selection is the differential success in reproduction among individuals that vary in their heritable traits. These reproductive differences emerge as each individual interacts with its environment.

Over time, natural selection can increase the adaptation of organisms to their environment.

If an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.
Charles Darwin published this on November 24, 1859.
On the Origin of Species by Means of Natural Selection.
Darwin made two major points in The Origin of Species.
1. He presented evidence that the many species of organisms presently inhabiting earth are descendants of ancestral species that were different from the modern species.

2. He proposed a mechanism for this evolutionary process, which he termed natural selection.
The basic idea of natural selection is that a population can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals.
Natural Selection
An accumulation of inherited characteristics that enhance organisms' ability to survive and reproduce in specific environments.
Evolutionary adaptation
A change over time in the genetic composition of a population.
Evolution
The branch of biology concerned with naming and classifying organisms.
Taxonomy
Remains or traces of organisms from the past.
Fossils
Most fossils found in these formed from the sand and mud that settle to the bottom of seas, lakes, and marshes.
Sedimentary rocks
The study of fossils, was largely developed by French scientist Georges Cuvier.
Paleontology
Speculation that each boundary between strata represents a catastrophe, such as a flood or drought, that destroyed many of the species living at that time.
Catastophism
The idea that profound change can take place through the cumulative can take place through the cumulative effect of slow but continuous processes.
Gradualism
The same geologic processes are operating today as in the past, and at the same rate.
Uniformitarianism
Lamarck's Theory of Evolution
Two principles:

1. The first was use and disuse, the idea that the parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate. As an example, he cited a giraffe stretching its neck to reach leaves in high branches.

2. Inheritance of acquired characteristics, stated that an organism could pass these modifications to its offspring.
Which of the individuals discussed in this section viewed species as fixed, and which viewed species as being able to change over time?
Aristotle, Linnaeus, and Cuvier viewed species as fixed (though Cuvier noted that the species present in a particular location could change over time). Lamarck, Erasmus Darwin, and Charles Darwin thought species could change.
What was Lamarck's theory of evolution? Explain its significance.
Lamarck observed evidence of changes in species over time and noted that evolution could result in organisms' adaptations to their environments, though his theory was based on an incorrect mechanism for evolution: that modifications an organism acquires during its lifetime can be passed to its offspring.
A phrase that summarized Darwin's view of life. Perceived unity in life, with all organisms related through descent form an ancestor that lived in the remote past. As the descendants of that ancestral organism spilled into various habitats over millions of years, they accumulated diverse modifications, or adaptations, that fit them to specific ways of life.
Descent with modification
He dissected Darwin's theory of natural selection into three inferences based on five observations.
Ernst Mayr
Ernst Mayr's five observations of Darwin's theory.
1. For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully.

2. Nonetheless, populations tend to remain stable in size, except for seasonal fluctuations.

3. Resources are limited.

Inference 1: Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving each generation.

4. Members of a population vary extensively in their characteristics; no two individuals are exactly alike.

5. Much of this variation is heritable.

Inference 2: Survival depends in part on inherited traits. Individuals whose inherited traits give them a high probability of surviving and reproducing in a given environment have higher fitness and are likely to leave more offspring than less fit individuals.

Inference 3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations.
He contended that much of human suffering---disease, famine, homelessness, and war---was the inescapable consequence of the human population's potential to increase faster than food and other resources.
Thomas Malthus
Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits. This is a process called____________.
Artificial selection
Summary of Natural Selection:
1. Natural selection is the differential success in reproduction among individuals that vary in their heritable traits. These reproductive differences emerge as each individual interacts with its environment.

2. Over time, natural selection can increase the adaptation of organisms to their environment.

3. If an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.
Three subtle, but important points about evolution by natural selection:
1. Although natural selection occurs through interactions between individual organisms and their environment, individuals do not evolve. A population is the smallest unit of evolution.

2. Natural selection can amplify or diminish only heritable traits---that is, traits that are passed from organisms to their offspring. Though an organism may become modified through its own interactions with the environment during its lifetime, and these acquired characteristics may even adapt the organism to its environment, there is no evidence that such acquired characteristics can be inherited by offspring.

3. The environmental factors vary from place to place from time to time. A trait that is favorable in one situation may be useless or even detrimental in different circumstances.
A group of interbreeding individuals belonging to a particular species and sharing a common geographic area.
Population
Can be measured only as changes in relative proportions of heritable variations in a population over a succession of generations.
Evolution
Darwin's concept of descent with modification can explain why certain characteristics in related species have an underlying similarity even though they may have very different functions. Such similarity resulting from common ancestry is known as __________.
Homology
The arms, forelegs, flippers, and wings of different mammals are ______________ that represent variations on a structural theme that was present in their common ancestor.
Homologous structures
Some of the most intriguing homologous structures are ______________ , structures of marginal, if any, importance to the organism.
Vestigial organs
Darwin's observations of the geographic distribution of species, _____________, formed an important part of his theory of evolution.
Biogeography
Species of plants and animals that are found in one place and nowhere else in the world.
Endemic
Describe how the following concepts relate to Darwin's theory of evolution by natural selection: overreproduction of populations, limited resources, and heritable variation.
Species have the potential to produce more offspring than survive (overreproduction), leading to a struggle for resources, which are limited. Populations exhibit a range of heritable variations, some of which confer advantages to their bearers that make them more likely to leave more offspring then less well-suited individuals. Over time, this natural selection can results in a greater proportion of favorable traits in a population (evolutionary adaptation).
Explain why an individual organism cannot be said to evolve.
Though an individual may become modified during its lifetime through interactions with its environment, this does not represent evolution. Evolution can be measured only as a change in proportions of heritable variations from generation to generation.
Explain why the following statement is inaccurate: "Anti-HIV drugs have created drug resistance in the virus."
An environmental factor such as a drug does not create new traits such as drug resistance, but rather selects for traits among those that are already present in the population.
How does Darwin's theory account for both the similar mammalian forelimbs with different functions shown in Figure 22.14 and the similar lifestyle of the two distantly related mammals shown in Figure 22.17?
Despite their different functions, the forelimbs of different mammals are structurally similar because they all represent modifications of a structure found in the common ancestor. The similarities between the sugar glider and flying squirrel indicate that similar environments selected for similar adaptations despite different ancestry.
Explain how the fossil record can be used to test predictions of evolutionary theory?
If molecular biology or biogeography indicates a particular branching pattern of descent from a single group of ancestral organisms, representatives of the ancestral group should appear earlier in the fossil record than representatives of the later organisms. Likewise, the many transitional forms that link ancient organisms to present-day species are evidence of descent with modification.
Darwin's theory that life's diversity has arisen from fewer ancestral species through natural selection was a radical departure from the prevailing views of Western culture.
Resistance to the Idea of Evolution
Geologists Hutton and Lyell perceived that change in Earth's surface can result from slow, continuous actions still operating at the present time.
Theories of Gradualism
Lamarck hypothesized that species evolve, but the mechanisms he proposed unsupported by evidence.
Lamarck's Theory of Evolution
In _____________, Darwin proposed that species change through natural selection.
The Origin of Species
Darwin's research
Darwin's experiences during the voyage of HMS Beagle provided much of the background for his idea that new species originate from ancestral forms through the gradual accumulation of adaptations. After returning to England, he refined his theory and finally published it in 1859 after learning that Wallace had the same idea.
The Origin of Species
In his book describing his theory of descent with modification, Darwin recognized that there are heritable variations in populations and that some of those variations are better suited than others to a particular environment. Because organisms tend to produce many more offspring than the environment can support, there is competition for resources, and those that are better suited to the environment tend to have greater success in surviving and reproducing. Thus, these better-suited individuals leave more offspring than other individuals. Over time, this process of natural selection can result in adaptation of organisms to their environment.
Natural Selection in Action
Researchers have observed natural selection leading to adaptive evolution in wild guppy populations. In humans, the use of drugs selects for pathogens that through change mutations are resistant to drugs' effects. The ability of bacteria and viruses to evolve rapidly poses a challenge to our society.
Homology, Biogeography, and the Fossil Record
Evolutionary theory explains many kinds of observations, including structural and molecular similarities, geographic distribution of organisms, and the fossil record.
What is theoretical about the Darwinian's View of life?
Darwin's theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions.
Which of the following statements reflects aspects of Hutton and Lyell's ideas of gradualism that were incorporated into Darwin's theory of evolution?
Small changes accumulated over vast spans of time can produce dramatic results.
Which of the following is not an observation or inference on which natural selection is based?
Poorly adapted individuals never produce offspring.
Which of the following is an observation or inference on which natural selection is based?
1. There is heritable variation among individuals.

2. There is a struggle for limited resources, and only a fraction of offspring survive.

3. Individuals whose characteristics are best suited to the environment generally leave more offspring than those whose characteristics are less well suited.

4. Organisms interact with their environments.
Analysis of forelimb anatomy of humans, bats, and whales shows that humans and bats have fairly similar skeletal structures, while whales have diverged considerably int he shapes and proportions of their bones. However, analysis of several genes in these species suggests that all three diverged from a common ancestor at about the same time. Which of the following is the best explanation for these data?
Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.
Which of the following observations helped Darwin shape his concept of descent with modification?
South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.
Darwin synthesized information from several sources in developing his theory of evolution by natural selection. Which of the following did not influence his thinking?
Observations of molecular homologies.
Darwin synthesized information from several sources in developing his theory of evolution by natural selection. Which of the following did influence his thinking?
1. Linnaeus' hierarchical classification of species.

2. Lyell's Principles of Geology

3. Examples of major changes in domesticated species produced by artificial selection.

4. The distribution of species that he observed on the Galapagos Islands and during his journey around South America.
In science, the term theory generally applies to an idea that.....
Attempts to explain many related phenomena.
Within a few weeks of treatment with the drug 3TC, a patient's HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?
A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.
The smallest biological unit that can evolve over time is....
A population
Which of the following ideas is common to both Darwin's and Lamarck's theories of evolution?
Evolutionary adaptation results from interactions between organisms and their environments.
Which of the following pairs of structures is least likely to represent homology?
The brain of a cat and that of a dog.
We can define evolutionary change on its smallest scale, as change in the genetic makeup of a population from generation to generation.
Microevolution
Discoveries: quantitative characters are influenced by multiple genetic Ioci and that the alleles at each of these Ioci follow Mendelian patterns of inheritance. These discoveries helped reconcile Darwin's and Mendel's ideas and led to the formal founding of this, which is the study of how populations change genetically over time.
Population genetics
A comprehensive theory of evolution that integrated ideas form many other fields.
Modern synthesis
A localized group of individuals that are capable of interbreeding and producing fertile offspring.
Population
The aggregate of genes in a population at any one time is called the population's ___________.
Gene pool
Concepts for Ch. 23:
Population genetics provides a foundation for studying evolution

Mutation and sexual recombination produce the variation that makes evolution possible.

Natural selection, genetic drift, and gene flow can alter a population's genetic composition.

Natural selection is the primary mechanism of adaptive evolution.
The theorem states that the frequencies of alleles and genotypes in a population's gene pool remain constant form generation to generation provides that only Mendelian segregation and recombination of alleles are at work. Named for the two scientists who independently derived the principle in 1908.
Hardy-Weinberg Theorem
Population having the same allele frequencies from one generation to the next, but its genotype frequencies can be predicted from the allele frequencies.
Hardy-Weinberg equilibrium
Conditions for Hardy-Weinberg Equilibrium:
1. Extremely large population size. The smaller the population, the greater the role played by chance fluctuations in allele frequencies from one generation to the next, known as genetic drift.

2. No gene flow. Gene flow, the transfer of alleles between populations, can alter allele frequencies.

3. No mutations. By introducing or removing genes from chromosomes or by changing one allele into another, mutations modify the gene pool.

4. Random mating. If individuals preferentially choose mates with certain genotypes, including close relatives (inbreeding), random mixing of gametes does not occur.

5. No natural selection. Differential survival and reproductive success of individuals carrying different genotypes will alter allele frequencies.
What did Mendel's findings about genetics add to Darwin's theory of evolution by natural selection?
Mendel showed that inheritance is particulate, and subsequently it was shown that this type of inheritance can preserve the variation on which natural selection acts.
Suppose a population of organisms with 500 gene Ioci is fixed at half of these Ioci, and has two alleles at each of the other Ioci. How many alleles are found in its gene pool? Explain.
750. Half the Ioci (250) are fixed, meaning only one allele exists for each locus; 250 x 1 = 250. There are two alleles each for the other Ioci: 250 x 2 = 500. 250 + 500 = 750.
Which parts of the Hardy-Weinberg equation

(p^2 + 2pq + q^2) = 1

correspond to the frequency of individuals that have at least one PKU allele?
2pq + q^2; 2pq represents heterozygotes with one PKU allele and q^2 represents homozygotes with two PKU alleles.
Changes in the nucleotide sequence of DNA
Mutations
A change of as little as one base in a gene - a _____________ - can have a significant impact on phenotype.
Point mutation
Gene __________ is an important source of variation. ____________ of the chromosome segments, like other chromosomal mutations, are almost always harmful.
Duplication
This is far more important than mutation on a generation-to-generation time scale in producing the variations that make adaptation possible. Nearly all phenotypic variations based on genetic differences result from recombinational shuffling of the existing alleles in the gene pool.
Sexual recombination
Of all the mutations that occur, why do only a small fraction become widespread in a gene pool?
Most mutations occur in somatic cells that do not produce gametes and so are lost when the organism dies. Of mutations that do occur in cell lines that produce gametes, many do not have a phenotypic effect on which natural selection can act. Others have a harmful effect and are thus unlikely to spread in a population from generation to generation because they decrease the reproductive success of their bearers.
How does sexual recombination produce variation?
A population contains a vast number of possible mating combinations, and fertilization brings together the gametes of individuals with different genetic backgrounds. Sexual reproduction reshuffles alleles into fresh combinations every generation.
The three major factors that alter allele frequencies and cause most evolutionary change are:
Natural selection, genetic drift, and gene flow
Similar deviations from the expected results --- which occur because real populations are finite in size rather than infinite --- explain how allele frequencies can fluctuate unpredictably from one generation to the next. Such fluctuations are called ___________.
Genetic drift
In effect, the survivors have passed through a restrictive area of survival, and their gene pool may no longer be reflective of the original population's gene pool.
Bottleneck effect
When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool is not reflective of the source population.
Founder effect
A population may gain or lose alleles by _________, genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes.
Gene flow
In what sense is natural selection more "predictable" than genetic drift?
Natural selection is more "predictable" in that it tends to increase or decrease the frequency of alleles that correspond to variations that increase or decrease an organism's reproductive success in its environment. Alleles subject to genetic drift all have the same likelihood of increasing or decreasing in frequency.
Distinguish genetic drift and gene flow in terms of (a) how they occur and (b) their implications for future genetic variation in a population.
Genetic drift results from chance fluctuations of allele frequencies from generation to generation; it tends to decrease variation over time. Gene flow is the exchange of alleles between populations; it tends to increase variation within a population but decrease allele frequency differences between populations.
Classified as an either-or basis. Often determined by a single gene locus with different alleles that produce distinct phenotypes.
Discrete characters
Vary along a continuum. Heritable variation results from the influence of two ore more genes on a single phenotypic character.
Quantitative characters
When individuals differ in a discrete character, the different forms are called _________.
Morphs
A population is said to display _____________ for a character if two or more distinct morphs are each represented in high enough frequencies to be readily noticeable.
Phenotypic polymorphism
The heritable component of height (example) is the result of such ______________ for alleles at the several loci that influence height. (example): height variation in the human population does not show phenotypic polymorphism because it does not consist of distinct and separate morphs - heights vary. Nonetheless, polymorphisms play a role in such characteristics at the genetic level.
Genetic polymorphisms
Measured as the average percent of these Ioci that are heterozygous.
Average heterozygosity
Most species exhibit ______, which are differences between the gene pools of separate populations or population subgroups.
Geographic variation
Some examples of geographic variation occur as a ___________, a graded change in a trait along a geographic axis.
Cline
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals.
Fitness
The contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus.
Relative fitness
Most comment when a population's environment changes or when members of a population migrate to a new habitat with different environmental conditions than their former one.
Directional selection
Occurs when conditions favor individuals on both extremes of a phenotypic range over individuals with intermediate phenotypes.
Disruptive selection
Acts against extreme phenotypes and favors intermediate variants. This mode of selection reduces variation and maintains the status quo for a particular phenotypic character.
Stabilizing selection
Selection favors:
Certain heritable traits through differential reproductive success.
____________ occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population, a state called _________________. This type of selection includes heterozygote advantage and frequency-dependent selection.
Balancing selection; balanced polymorphism.
If individuals who are heterozygous at a particular gene locus have a greater fitness than the homozygotes, natural selection will tend to maintain two or more alleles at that locus.
Heterozygote advantage
Some of the genetic variation in populations probably has little or no impact on reproductive success, and thus natural selection does not affect these alleles.
Neutral variation
Genes that have become inactivated by mutations, genetic "noise" is free to accumulate in all parts of the gene.
Pseudogenes
Darwin was the first to explore the implications of ________________, which is natural selection for mating success.
Sexual selection
Marked differences between the sexes in secondary sexual characteristics, which are not directly associated with reproduction.
Sexual dimorphism
Meaning selection "within the same sex", is a direct competition among individuals of one sex for mates of the opposite sex.
Intrasexual selection
Also called mate choice, individuals of one sex (usually females)are choosy in selecting their mates from the other sex.
Intersexual selection
Nature abounds with examples of organisms that seem to be less than ideally "engineered" for their lifestyles, for several reasons:
1. Evolution is limited by historical constraints. Each species has a legacy of descent with modification from a long line of ancestral forms. Evolution does not scrap ancestral anatomy and build each new complex structure from scratch; it co-opts existing structures and adapts them to new situations.

2. Adaptations are often compromises. Each organism must do many different things.

3. Chance and natural selection interact. Chance events affect the subsequent evolutionary history of populations.

4. Selection can edit only existing variations. Natural Selection favors only the fittest phenotypes among those currently in the population, which may not be the ideal traits. New alleles do not arise on demand.
Does nucleotide variability in a population always correspond to phenotypic polymorphism? Why or why not?
No; many nucleotides are in noncoding portions of DNA or in pseudogenes that have been inactivated by mutations. A change in a nucleotide may not even change the amino acid encoded because of the redundancy of the genetic code.
What is the relative fitness of a sterile mule? Explain.
Zero, because fitness includes reproductive contribution to the next generation, and a sterile mule cannot produce offspring.
How does sexual selection lead to sexual dimorphism?
In sexual selection, organisms may compete for mates through behaviors or displays of secondary sexual characteristics; only the competing sex is selected for these characteristics.
Explain what is meant by the "reproductive handicap" for sex.
Only half of the members (the females) of a sexual population actually produce offspring, while all the members of an asexual population can produce offspring.
The Modern Synthesis:
The modern synthesis integrates Mendelian genetics with the Darwinian theory of evolution by natural selection and focuses on populations as the basic unit of evolution.
Gene Pools and Allele Frequencies:
A population, a localized group of organisms that all belong to the same species, is united by its gene pool, the aggregate of all alleles in the population.
The Hardy-Weinberg Theorem:
The Hardy-Weinberg theorem states that the frequencies of alleles and genotypes in a population will remain constant if Mendelian segregation and random mating are the only processes that affect the gene pool. If p and q represent the relative frequencies of the only two possible alleles at a particular locus, then p^2 + 2pq + q^2 =1, where p^2 and q^2 are the frequencies of the homozygous genotypes and 2pq is the frequency of the heterozygous genotype. Although many populations approximate Hardy-Weinberg equilibrium, the equilibrium in its strictest sense applies only if the population is large, mating is random, mutation is negligible, there is no gene flow from other populations, and all individuals have equal reproductive success.
Mutation:
New genes and new alleles originate only by mutation. Most mutations have no effect or are harmful, but a few increase adaptation.
Sexual Recombination:
Genetic recombination between sexually reproducing organisms produces most of the variation in traits that makes adaptation possible.
Natural Selection:
Differential success in reproduction results in certain alleles being passed to the next generation in greater proportions than others.
Genetic Drift:
Chance fluctuations in allele frequencies from generation to generation tend to reduce genetic variation in populations.
Gene Flow:
Genetic exchange between populations tends to reduce differences between populations over time.
Genetic Variation:
Genetic variation includes variation among individuals within a population in discrete and quantitative characters, as well as geographic variation between populations.
A Closer Look at Natural Selection:
One organism has a greater relative fitness than another if it leaves more descendants. Selection favors certain genotypes in a population by acting on the phenotypes of individual organisms. Natural selection can favor relatively rare individuals at one end of the phenotype range (directional selection), can favor individuals at both extremes of the range rather than intermediate phenotypes (disruptive selection), or can act against extreme phenotypes (stabilizing selection).
The Preservation of Genetic Variation:
Diploidy maintains a reservoir of concealed recessive variation in heterozygotes. Balanced polymorphism may maintain variation at some gene Ioci as a result of heterozygote advantage or frequency-dependent selection.
Sexual Selection:
Sexual selection leads to the evolution of secondary sex characteristics, which can give individuals an advantage in mating.
The Evolutionary Enigma of Sexual Reproduction:
Enhanced disease resistance based on genetic variation is one possible explanation for the persistence of sexual reproduction despite its lesser reproductive output compared to asexual reproduction.
Why Natural Selection Cannot Fashion Perfect Organisms
Structures results from modified ancestral anatomy, adaptations are often compromises, the gene pool can be affected by genetic drift, and natural selection can act only on available variation.
In the gene pool of a population with 100 individuals, a fixed allele for a particular gene locus has a frequency of ...
1
Researchers examining a particular gene in a fruit fly population discovered that the gene can have either of two slightly different sequences, designated A1 and A2. Further tests showed that 70% of the gametes produced in the population contained the A1 sequence. If the population is at Hardy-Weinberg equilibrium, what proportion of the flies carries both A1 and A2?
0.42
At a locus with a dominant and a recessive allele in Hardy-Weinberg equilibrium, 16% of the individuals are homozygous for the recessive allele. What is the frequency of the dominant allele in the population?
0.4
The average length of jackrabbit ears decreases gradually with increasing latitude. This variation is an example of:
Directional selection
Which of the following is a polymorphic trait in humans?
Variation in the number of fingers
Natural selection changes allele frequencies in populations because some ____________ survive and reproduce more successfully than others.
Individual organisms
Longer tails of male barn swallows evolve because female barn swallows prefer to mate with the males that have the longest tails. This process is best described as:
Intersexual selection for traits, such as long tails, that help males attract mates.
No two human individuals are alike, except for identical twins. The chief cause of the variation among individuals is:
Sexual recombination
Road construction has isolated a small portion of a beetle population from the main population. After a few generations, this new population exhibits dramatic genetic differences from the old one, most likely because:
Allele frequencies among the stranded beetles differed by chance from those in the parent population's gene pool and subsequent genetic drift caused even more divergence from the original gene pool.
Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating:
Stabilizing selection
In the gene pool of a population with 100 individuals, a fixed allele for a particular gene locus has a frequency of
1
Adult male vervet monkeys have red penises and blue scrotums. Males use their colorful genitalia in dominance displays wherein they compete with each other for access to females. The coloration of the male genitalia is best explained as the result of ________, and specifically of ________.
sexual selection; intrasexual selection
Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
In evolutionary terms, the more closely related two different organisms are, the
more recently they shared a common ancestor.
During drought years on the Galpagos, small, easily eaten seeds become rare leaving only large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, then what should one expect to result from natural selection?
More small-beaked birds dying than the larger-beaked birds. The offspring produced in subsequent generations have a higher percentage of birds with large beaks.
During a study session about evolution, one of your fellow students remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Which statement would you use to correct this student's misconception?
Characteristics acquired during an organism's life are generally not passed on through genes.
In a population with two alleles, B and b, the allele frequency of b is 0.4. What would be the frequency of heterozygotes if the population is in Hardy-Weinberg equilibrium?
0.48
Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. This adaptation of the poppies to their new environment is due to _____.
directional selection
Through time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing
Gene flow
If a population has the following genotype frequencies, AA=0.42, Aa=0.46, and aa=0.12, what are the allele frequencies?
A=0.65; a=0.35
In a hypothetical population of 1,000 people, tests of blood-type genes show that 160 have the genotype AA, 480 have the genotype AB, and 360 have the genotype BB.

What is the frequency of the B allele?
0.600
At a locus with a dominant and a recessive allele in Hardy-Weinberg equilibrium, 16% of the individuals are homozygous for the recessive allele. What is the frequency of the dominant allele in the population?
0.6
Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, these bones having developed from the same embryonic tissues. How do biologists interpret these similarities?
by identifying the bones as being homologous and by proposing that humans, bats, and dolphins share a common ancestor
Road construction has isolated a small portion of a beetle population from the main population. After a few generations, this new population exhibits dramatic genetic differences from the old one, most likely because
allele frequencies among the stranded beetles differed by chance from those in the parent population's gene pool and subsequent genetic drift caused even more divergence from the original gene pool.
Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. Which information would shed the most light on whether these structures are homologous or whether they are, instead, the result of convergent evolution?
The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 36% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.


What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time?
The two phenotypes are about equally adaptive under laboratory conditions.
DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. What would need to be true for pest eradication efforts to have been successful in the long run?
All individual insects should have possessed genomes that made them susceptible to DDT.
The Galpagos archipelago appeared about 2 million years ago, when submerged volcanoes (seamounts) rose above the ocean's surface. A single hypothetical colonization event introduced a species of finch to one island in the distant past. Today, several islands in the archipelago contain unique species of finches. What must have happened following the initial colonization event to account for the current situation?
Cladogenesis, Allopatric speciation, Adaptive speciation
In which of the following groups has sympatric speciation been most important?
plants
Successfully breeding two individual organisms at a zoo and obtaining fertile offspring for several generations is no guarantee that the same could occur in nature (i.e., in the wild). Which species concept becomes difficult to confirm because of this fact?
biological
Some species of Anopheles mosquito live in brackish water, some in running fresh water, and others in stagnant water. What type of reproductive barrier is most obviously separating these different species?
habitat isolation
A defining characteristic of allopatric speciation is
geographic isolation.
Plant species A has a diploid number of 24. A new species, B, arises as an autopolyploid from A. The diploid number of B would probably be
48
Which of the following must occur during a period of geographic isolation in order for two sibling species to remain genetically distinct following their geographic reunion in the same home range?
reproductive isolation
Two species of frogs belonging to the same genus occasionally mate, but the offspring do not complete development. What is the mechanism for keeping the two frog species separate?
the postzygotic barrier called hybrid inviability
The origin of new species is at the focal point of evolutionary theory, because the appearance of new species is the source of biological diversity.
Speciation
Evolutionary change above the species level.
Macroevolution
Two basic patterns of evolutionary change:
anagenesis and cladogenisis
Phyletic evolution; the accumulation of changes that gradually transform a given species with different characteristics.
Anagenesis
Branching evolution; the splitting of a gene pool into two or more separate pools, which each give rise to one or more new species.
Cladogenesis
Proposed in 1942 by biologist Ernst Mayr, this defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are unable to produce viable, fertile offspring with members of other populations.
Biological species concept
The existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids.
Reproductive isolation
Before the zygote; impede mating between species or hinder the fertilization of ova if members of different species attempt to mate.
Prezygotic barriers
After the zygote; often prevent the hybrid zygote from developing into a viable, fertile adult.
Postzygotic barriers
Two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers such as mountain ranges.
Habitat isolation
Species that breed during different times of the day, different seasons, or different years cannot mix their gametes.
Temporal isolation
Courtship rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species.
Behavioral isolation
Morphological differences can prevent successful mating.
Mechanical isolation
Sperm of one species may not be able to fertilize the eggs of another speices. Many mechanisms can produce the isolation. For instance, sperm may not be able to survive in the reproductive tract of females of the other species, or biochemical mechanisms may prevent the sperm from penetrating the membrane surrounding te other species' eggs.
Gametic isolation
The genes of different parent species may interact and impair the hybrid's development.
Reduced hybrid viability
Even if hybrids are vigorous, they may be sterile. If chromosomes of the two parent species differ in number or structure, meiosis in the hybrids may fail to produce normal gametes. Since the infertile hybrids cannot produce offspring when they mate with either parental species, genes cannot flow freely between the species.
Reduced hybrid fertility
Some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring of the next generation are feeble or sterile.
Hybrid breakdown
Concept that characterizes a species by its body shape, size, and other structural features.
Morphological species concept
Concept that focuses on morphologically discrete species known only from the fossil record.
Paleontological species concept
Concept that views a species in terms of its ecological niche, its role in biological community.
Ecological species concept
Concept that defines a species as a set of organisms with a unique genetic history -- that is, one branch on the tree of life.
Phylogenetic species concept
Gene flow is interrupted when a population is divided into geographically isolated subpopulations - speciation.
Allopatric "other country"
Takes place in geographically overlapping populations - speciation.
Sympatric "same country"
Some plant species have their origins in accidents during cell division that result in extra sets of chromosomes, a mutational change that results in this condition.
Polyploidy
An individual that has more than two chromosome sets, all derived from a single species.
Autopolyploid
In subsequent generations, various mechanisms can change a sterile hybrid into a fertile polyploid known as ___________
Allopolploid
In ______________ speciation, a new species forms while geographically isolated from its parent population.
Allopatric
In _____________ speciation, requires the emergence of a reproductive barrier that isolates a subset of a population without geographic separation from the parent population.
Sympatric
The evolution of many diversely adapted species from a common ancestor upon introduction to various new environmental opportunities and challenges.
Adaptive radiation
Term to describe periods of apparent stasis punctuated by sudden change.
Punctuated equilibrium
It is the cumulative change during thousands of small speciation episodes that accounts for sweeping evolutionary changes.
Macroevolution
Structures that evolve in one context but become co-opted for another function are sometimes called _____________ to distinguish them from the adaptive origin of the original structure.
Exaptations
Offers one explanation for how novel features can arise gradually through a series of intermediate stages, each of which has some function in the organism's current context.
Concept of exaptation
The interface between evolutionary biology and developmental biology.
Evo-devo
Genes that program this control the rate, timing, and spatial pattern of changes in an organism's form as it develops from a zygote into an adult.
Development
An evolutionary change in the rate or timing of developmental events.
Heterochrony
This proportioning that helps give a body specific form is called ______________.
Allometric growth
If reproductive development accelerated compared to somatic development, the sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species --- a condition called ____________.
Paedomorphosis
Affects the evolution of morphology by altering the rates at which various body parts develop or by changing the time of onset or completion of a particular part's development.
Heterochrony
Determine such basic features as were a pair of wings and a pair of legs will develop on abird or how a plant's flower parts are arranged.
Homeotic genes
The produce of this _____ gene provides positional information about how far digits and other bones should extend form the limb.
Hox
Evolution can result in an evolutionary trend even if some new species counter the trend.
Branching
The species that endure the longest and generate the most new offspring species determine the direction of major evolutionary trends. The species selection model suggests that "differential speciation success" plays a role in macroevolution similar to the role of differential reproductive success in microevolution.
Species selection
The appearance of an evolutionary trend does not imply that there is some intrinsic drive toward a particular phenotype. _________ is the result of the interactions between organisms and their current environments.
Evolution
Two bird species in a forest are not known to interbreed. One species feeds and mates in the treetops and the other on the ground. But in captivity, the two species can interbreed and produce viable, fertile offspring. What type of reproductive barriers most likely keeps these species separate? Explain.
Since the birds are known to breed successfully in captivity, the reproductive barrier in nature must be prezygotic. Given the species differences in habitat preference, the reproductive barrier is most likely to be habitat isolation.
A. Which species concept can be used for bother asexual and sexual species?

B. Which can only be applied to sexual species?

C. Which would be more useful for identifying species in the field?
A. All species concepts except the biological species concept can be applied to both asexual and sexual species because they define species on the basis of characteristics other than ability to reproduce.

B. The biological species concept can be applied only to extant sexual species.

C. The easiest species concept to apply in the field would be the morphological species concept because it is based only on the appearance of the organism. Additional information about its ecological habits, evolutionary history, and reproduction are not required.
Explain why allopatric speciation would be less likely to occur on an island close to a mainland than on a more isolated island of the same size.
Continued gene flow between mainland populations and those on a nearby island reduces the chance that enough genetic divergence will take place for allopatric speciation to occur.
Normal watermelon plants are diploid (2n=22) but breeders have produced tetraploid (4n=44) watermelons. If tetraploid plants are hybridized with their diploid relatives, they produce triploid (3n=33) seeds. These offspring can produce triploid seedless watermelons and can be further propagated by cuttings. Are the diploid and tetraploid watermelon plants different species? Explain.
The diploid and tetraploid watermelons are separate species. Their hybrids are triploid and as a result are sterile because of problems carrying out meiosis.
In the fossil record, transitional fossils linking newer species to older ones are relatively rare. Suggest an explanation for this observation.
According to the model of punctuated equilibrium, in most cases, the time during which speciation (that is, the distinguishing evolutionary changes) occurs is relatively short compared with the overall duration of the species' existence. Thus, on the vast geologic time scale of the fossil record, the transition of one species to another seems abrupt, and instances of gradual change in the fossil record are rare. Furthermore, some of the changes that transitional species underwent may not be apparent in fossils.
How can the Darwininan concept of descent with modification explain the evolution of such complex structures as the vertebrate eye or heart?
Such complex structures do not evolve all at once, but in increments, with natural selection selecting for adaptive variants of the earlier versions.
Explain why the concept of exaptation does not mean that a structure evolves in anticipation of some future environmental change.
Although an exaptation is co-opted for new or additional functions in a new environment, it existed in the first plant because it worked as an adaptation to the original environment.
How can heterochrony cause the evolution of different body forms?
The timing of different developmental pathways in organisms can change in different ways (hterochrony). This can result in differential growth patterns, such as those producing different patterns of webbing in salamander feet.
The Biological Species Concept:
A biological species is a group of populations whose individuals have the potential to interbreed and produce fertile offspring with each other but not with members of other species. The biological species concept emphasizes reproductive isolation through prezygotic and postzygotic barriers that can result in separating the gene pools of different populations.
Other definitions of Species:
Although particularly helpful in thinking about speciation processes, the biological species concept has some major limitations. For instance, it cannot be applied to organisms that are known only as fossils or to organisms that reproduce only asexually. Thus, scientists maintain alternative species concepts, such as the morphological species concept, that are useful in various contexts.
Allopatric "other country" speciation
Allopatric speciation may occur when two populations of one species become geographically separated from each other. One or both populations may undergo evolutionary change during the period of separation. Should they come into contact once more, they may be separated by the prezygotic and postzygotic isolating mechanisms that have accumulated.
Sympatric "same country" speciation
A new species can originate while remaining in a geographically overlapping area with the parent species. In particular, many plant species have evolved sympatrically through polyploidy (multiplications of the chromosome number). Autopolyploids are species derived this way from one ancestral species. Allopolyploids are species with multiple sets of chromosomes derived from different species. Sympatric speciation can also result from the appearance of new ecological niches and from nonrandom mating in polymorphic populations.
Allopatric and Sympatric Speciation: Summary
In allopatric speciation, a new species forms while geographically isolated from its parent population. In sympatric speciation, a reproductive barrier isolates a subset of a population without geographic separation.
Adaptive Radiation:
Adaptive radiation can occur when a population encounters a multiplicity of new or newly available ecological niches. This may happen during colonization of a new environment, such as newly formed volcanic islands, or after an environmental change that has resulted in mass extinctions of other species in an area.
Studying the Genetics of Speciation:
The explosion of genomics is enabling researchers to identify specific genes involved in some cases of speciation.
The Tempo of Speciation:
Eldredge and Gould's punctuated equilibrium model draws on fossil evidence showing that species change most as they arise from an ancestral species, after which they undergo relatively little change for the rest of their existence. This model contrasts with a model of gradual change throughout a species' existence
Evolutionary Novelties
Most novel biological structures evolve in many stages from previously existing structures. Some complex structures, such as the eye, have had similar functions during all stages of their evolution. The most important functions of others, such as feathers, have changed.
Evolution of the Genes That Control Development
Many large evolutionary changes may have been associated with mutations in genes that regulate development. Such changes can affect the timing of developmental events (heterochrony) or the spatial organization of body parts. Some of these changes result from mutational changes in homeotic genes and in the genes that regulate them.
The largest unit within which gene flow can readily occur is a _________.
Species
Males of different species of the fruit fly that live in the same parts of the Hawaiian islands have different elaborate courtship rituals that involve fighting other males and stylized movements that attract females. What type of reproductive isolation does this represent?
Behavioral isolation
According to the punctuated equilibrium model,
most new species accumulate their unique features as they come into existence, then change little for the rest of their duration as a species.
An analytical approach to understanding the diversity and relationships of organisms, both present and extinct.
Systematics
Uses comparisons of DNA, RNA, and other molecules to infer evolutionary relationships between individual genes and even between entire genomes.
Molecular systematics
The evolutionary history of a species or a group of species.
Phylogeny
Based on the sequence in which fossils have accumulated in such strata.
Fossil record
Genes or other DNA sequences are _______ if the nature of their similarity suggests that they are descended from the sequences carried by a common ancestor.
Homolgous
Similarity due to convergent evolution
Analogy
Analogous structures that have evolved independently
Homoplasies
Two DNA sequences that resemble each other at many points along their length are most likely _______.
Homologous
Scientists have sequenced more than __________ bases' worth of nucleic acid data from thousands of species.
20 billion
Published Systam natura, his taxonomic classification of all plants and animals known at the time.
Carolus Linnaeus
An ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences.
Taxonomy
The two-part format of the scientific name.
Binomial, scientific epithet
The first part of the species' name
Genus
The second part of the species' name
Species
Hierarchical Classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Branching diagrams used to depict their hypotheses about evolutionary relationships.
Phylogenetic trees
Two-way branch plants, each branch plant represents the divergence of two species from a common ancestor.
Dichotomies
Patterns of shared characteristics can be depicted in a diagram called a __________.
Cladogram
Defined as a group of species that includes an ancestral species and all its descendants.
Clade
The analysis of how species may be grouped into clades.
Cladistics
A valid clade is _________, signifying that it consists of the ancestral species and all its descendants.
Monophyletic
Grouping that consists of an ancestral species and some, but not all, of the descendants.
Paraphyletic
Grouping of several species that lack a common ancestor.
Polyphyletic
A character that is shared beyond the taxon we are trying to define.
Shared primitive character
An evolutionary novelty unique to a particular clade.
Shared derived character
A flexible rod running the length of the animal.
Notochord
A homologous structure that predates the branching of a particular clade from other members of that clade.
Shared primitive character
An evolutionary novelty unique to a particular clade
Shared derived character
Systematists use this method to differentiate between shared derived and shared primitive characters.
Outgroup comparison
Based on the assumption that homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor. Also enables us to focus on just those characters that were derived at the various branch points in the evolution of a clade.
Outgroup comparison
A valuable tool for tracing organisms' evolutionary history
Comparing nucleic acids or other molecules to infer relatedness
One of the most important types of mutation in evolution because it increases the number of genes in the genome, providing further opportunities for evolutionary changes.
Gene duplication
Genes found in a single copy in the genome; can diverge only once speciation has taken place
Orthologous genes
Results from gene duplication, so they are found in more than one copy in the genome; can diverge within the clade that carries them, often adding new function.
Paralogous genes
The widespread consistency in total gene number in organisms of varying complexity indicates that
genes in complex organisms are extremely versatile and that each gene can perform many functions
Earth is about __________ years old.
4.6 billion
Life arose about ________ BYA
3.8
Chemical traces in rock arose __________ BYA
3.8
Fossil bacteria in rocks arose ________ BYA
3.5
Earth's atmosphere consists of:
Carbon dioxide (CO2)
Methane (CH4)
Ammonia (NH3)
Hydrogen sulfide (H2S)
Water (H2O)
Abundant energy to drive reactions were from:
1. Frequent storms with much lightening

2. Frequent volcanic eruptions

3. Frequent meteor impacts

4. UV light from the sun
How to assemble a living thing:
1. Abiotic synthesis of small organic molecules

2. Joining these molecules into polymers

3. Packaging these molecules into "protobionts"

4. The origin of self-replication molecules
Miller and Urey Experiments:
1. Electric spark simulates lightening

2. Gases of primeval atmosphere

3. Organic molecules appear after only a few days
Alternative hypothesis for origin:
First organic compounds may have been synthesized over hydrothermal vents; extraterrestrial origin
Abiotic synthesis of polymers
Small organic molecules polymerize when they are converted on hot sand or clay
Protobionts
Groups of abiotically produced molecules surrounded by a membrane; liposomes can form when lipids or other organic molecules are added to water
Ribozymes found to catalyze many different reactions including:
Self-splicing, making complimentary copies of short-stretches of RNA
Can determine absolute ages of fossils; Potassium 40 (40K) naturally decays to Argon 40 (40Ar)
Radiometric dating
Shows time scales involved in the history of life on earth
Clock Analogy
First organisms were:
Anaerobic
Prokaryotes
Bacteria & Archaea
Fed on organic molecules = hetertropic

Fed on their own, made their own food = autotrophic
Correct sequence of events
Anaerobic cells > photosynthesis > O2 > Aerobic metabolism
Oxygenic prokaryotes
Photosynthetic bacteria evolved 3.5 BYA

CO2 + H2O = Food + O2
Accumulates in the atmosphere 2.7 BYA
Oxygen
Were earth's sole inhabitants from 3.5 to about 2 BYA.
Prokaryotes
Common to all life forms
Electron transport systems
Probably evolved about 3.5 BYA
Oxygenic photosynthesis
O2 accumulates in the atmosphere:
Posed a challenge for life

Provided new ecological niches to exploit, ie. Aerobic metabolism

Without oxygenic photosynthesis, the present oxidizing atmosphere wouldn't exist
The first eukaryotes, the oldest, are ______ BYA.
2.1
Theory that states:

Mitochondria and plastids were formerly small prokaryotes living with larger host cells; were possibly undigested prey or internal parasites or mutualists.
Endosymbiotic theory
The first multicellular organism were about _________ BY. Animals - soft-bodied marine invertebrates.
1.5-1.2
The first multicellular organisms were colonies, specialization of cell within colonies followed.
Colonial connection
542 MYA - almost all modern forms of animals arose at this time
Cambrian explosion
Early classification systems had two kingdoms:
Plants and animals
Robert Whitaker proposed a system with five kingdoms:
1. Monera
2. Protista
3. Plantae
4. Fungi
5. Animalia
Modern Classification System; molecular data has provided new insights regarding the deepest branches of the tree of life; Three domain system has replaced the five kingdom system:
1. Arachaea
2. Bacteria
3. Eukarya
Current debates about the number and boundaries of the kingdoms of life center mainly on which group of organisms?
Prokaryotes and single-celled eukaryotes.