Chapter 10: Evolution

• Evolution is the process of changing heritable traits in a population from one generation to the next.
• A research study of Darwin finches found that the average size of the bird's beak increased by 10% over the course of a year.
• It was evolution.

• There are many varieties of a gene.
• Individuals inherit alleles that code for certain characteristics.
• Over time, the frequencies of those alleles in the population change.

• The idea was correct, as it is often observed among athletes who train for competition.

• Changes in the genetic material of cells can only be passed on to offspring.

• Some species change over time, other species change and become new species, and other species become extinct.
• They propose theories for this.
• Lamarck thought that evolution happened through the inheritance of acquired characteristics.
• Darwin believed that evolution progresses through natural selection.
• The mechanisms responsible for the evolutionary patterns observed in nature are proposed by these theories.

• Changes in species can be studied.

• The oldest fossils are often found among the deepest deposits.
• Fossil oysters that have been removed from successive layers show gradual changes in the size of the oyster shell, with rapid changes in shell size.
• Changes produced new species.

• C-14 dating can be used to determine the age of fossils.
• The age of the fossil is determined by the decay rate of a radioactive isotope of carbon.

• The information shows that species in different parts of the world look the same.
• There is strong evidence for the role of natural selection in evolution.

• Humans introduced rabbits to Australia.
• A native Australian hare wallaby is similar to a rabbit.
• These two animals are not very similar.
• The rabbit and wallaby are mammals.
• The fetus of a mammal develops in the uterus, getting its sustenance from the mother.
• The fetus leaves the mother's uterus at an early stage of development and is attached to a teat in the abdominal pouch.
• Natural selection resulted in the great similarity of the rabbit and wallaby.

• Fish, chicken, pig, and human embryo have gliss and tails.

• Homogeneous structures may look different, but they will look the same in pattern.
• The forelimbs of cats, bats, whales, and humans all evolved from a common ancestral mammal.
• Evidence of evolutionary heritage can be found in the remnants of limbs in snakes, whales, and flightless birds.

• Plants in Africa have green stems and are similar to cacti in North America.
• The plants are similar, but they differ in their flower structures.

• Closely related species have higher percentages of sequences than distantly related species.
• All living things have the same genetic code and basic biochemical pathways.
• Modification of ancestral genetic information favors the evolution of different species.

• Humans and Chimpanzees have the same sequence of nucleotides.

• Some individuals have all genes that allow them to cope more successfully in their environment than other individuals.
• More offspring are produced by the more successful individuals.
• When the environment favors a trait, that is, when a trait increases the survival of its bearer, selection is said to act for that trait.
• It is said that selection acts against unfavorable traits.
• Favorable and unfavorable traits are different.

• Populations have a large reproductive potential.
• If all offspring survived to reproductive maturity and fostered their normal number of offspring, the population of two elephants would be 19 million.

• Population sizes are stable.
• Populations tend to change around a constant size.

• There are limited resources.
• As populations grow larger, resources do not increase.

• People compete for survival.
• The needs of a growing population will exceed the available resources eventually.
• Individuals have to compete for resources.

• There is variation in the population.
• There is a lot of variety in their form.

• There is a lot of variation.
• Darwin was unaware of the mechanism for heredity, but he did know that parents passed on their genes to their offspring.
• This is different from the characteristics acquired during the life of an organisms as a result of environmental influences.
• Exposure to pathogens or radiation can cause the amputation of a limb, but it is not heritable.
• The hereditary information that is passed from generation to generation is what we now know about most traits.

• The most fit people are the ones who survive.
• The term "Survival of the Fittest" refers to individuals who are able to out-compete other individuals for resources and mates.

• Favorable traits accumulate in the population, which leads to evolution.

• The offspring of the best adapted individuals inherit their parents' characteristics.
• The best offspring leave the most offspring.
• Over time, the best adapted for survival and reproduction will accumulate in the population.

• Populations may be affected by natural selection.

• New phenotypes may appear in the population as a result of new combinations of all genes, or new genes may be expressed with other all genes.

• Individuals with the most common form of a trait are the best adapted, while individuals who differ from the common form are poorly adapted.
• Selecting against all other trait variations maintains the population frequencies of common traits.

• The opposite extreme is chosen against.
• Favorable traits become more extreme, leading to distinct changes in the allele frequencies of the population, if directional selection continues for many generations.

• The Darwin finches were described at the beginning of the chapter.
• The beak size increased because of the shortage of large seeds.

• When the rains came back, the direction of the selection changed to favor smaller beaks.

• Some individuals in a population may have resistance to the insecticide.
• Most of the offspring of these few individuals will inherit the insecticide-resistance trait.
• After several generations of selection, the population will consist of all resistant individuals.

• The light form of the moth was hidden among the light-colored lichens that grew on tree barks in London before the industrial revolution.

• The dark form of the moths was never seen because it was easy to spot and eaten by birds.
• soot killed the pollution-sensitive lichens, exposing the dark tree bark below.
• As a result, the dark form of the moth became the better camouflaged of the two forms.
• The first dark moths were discovered a hundred years ago.
• In unpolluted areas outside London, the light form of the moth continued to dominate.
• Changes in environmental conditions promote evolution.

• There is a selection for plants that flower earlier.
• Invasive plant species seem to be favored.

• Many species of weeds occur in a range of heights, but tall forms are the majority.
• Only very short forms of the same weeds are found in lawns.
• Short weeds are beneficial on lawns.
• Tall weeds are better competitors for sunlight.

• Males who have physical qualities that allow them to increase their mating frequencies have an advantage over males who don't.

• The evolution of large stature or musculature are examples of sexual selection.

• The peacock's tail is an extreme example.

• Sexual selection is a form of disruptive selection.

• It is not "natural" selection since it is carried out by humans.

• Humans have bred animals with certain desirable qualities in order to create the various breeds of dogs.

• The offspring of a single species of wild mustard are all varieties of broccoli, cabbage, and cauliflower.

• There must be variation in the population in order for natural selection to work.

• rearranging existing alleles into new combinations is one of the contributions to variation listed here.
• There are alleles that never existed before in the gene pool.

• Antibiotics and pesticides can be introduced into populations.
• The genetic variation of the population may already have these alleles.
• The nonsusceptible individuals can reproduce quickly without competition if antibiotics or pesticides are applied.

• When two different alleles for a single gene are present, the allele is hidden from natural selection, allowing variation to be "stored" for future generations.
• There is more variation in the pool.

• The best adaptation is provided by a single phenotype.
• The alleles for the beneficial trait increase in frequencies.
• Many populations have examples of the coexistence of two or more different phenotypes.

• Alleles and phenotypes are maintained in the population by selection.

• A hybrid of corn developed by crossing two different corn strains that were highly inbred is more resistant to disease and produces larger corn ears than either of the inbred strains.

• The common phenotypes are selected against each other.
• Since rare phenotypes have an advantage, they increase in frequency and become common.
• They lose their advantage when they become common.
• Polymorphism is maintained with this type of selection, as the phenotypes alternate between low and high frequencies.

• A search image is a standard representation of a predator's prey.
• The predator's search effort is maximized by standardizing on the most common form of its prey.
• The prey that escapes is rare.

• Not all variations have the same value.
• neutral variation is represented by the differences in fingerprints among humans.
• The environment to which the variation is exposed determines whether it is neutral or not.

• Humans impact the evolutionary potential of many species by reducing the size of their populations.
• Populations lack the variation necessary to respond to selection pressures when genetic variation decreases.

• Wild varieties in their native habitats are lost due to human impacts.
• A monoculture is extremely susceptible to changing environmental conditions and has no genetic variation.
• In the middle of the 19th century in Ireland, widespread crop failures and famine were caused by potato diseases.

• In the absence of susceptible individuals, nonsusceptiblebacteria increase in number and dominate the population, causing new outbreaks of disease.

• Darwin proposed natural selection as the mechanism for evolution.

• With the understanding of genetics, it became evident that factors other than natural selection can cause evolution.

• Some alleles may increase or decrease by chance.
• The effect of genetic drift can be very strong when populations are small.

• The chances of flipping a coin can be compared to genetic drift.
• If a coin is flipped 100 times, the number of heads obtained would approach the expected probability.

• If the coin is flipped only 5 times, one can get all tails.
• Gene frequencies may change by chance.

• One of the founding members of the small group of Germans that began the Amish community in Pennsylvania had an allele for polydactylism.
• The number of cases of this trait among the 8,000 Amish exceeded the number of cases in the rest of the world.

• The small population that results is vulnerable to genetic drift regardless of the cause.
• Gene frequencies may change due to chance when there are forces that strike individuals randomly.
• Floods, volcanic eruptions, and ice ages have caused genetic drift for many populations of plants and animals.

• They can always choose mates with similar or different characteristics.
• When mates choose only nearby individuals, nonrandom mating also occurs.
• mate selection is not random, and only the alleles of the individuals who are most compatible with each other are passed on to the next generation.

• There is no evolution at genetic equilibrium.
• The factors that change the frequencies of the genes do not occur in order for equilibrium to occur.

• All traits are neutral.

• There are no changes that occur.

• The population is large.

• Mating is random.

• An example would be a plant population of 84% plants with red flowers and 16% plants with white flowers.

• You can determine the percentage of individuals with the dominant and heterogeneous condition.

• The conditions of the equilibrium are not obeyed in most natural populations.
• The starting point for the calculations is how allele frequencies are changing, which equilibrium conditions are being violated, and what mechanisms are driving the evolution of a population.

• Barriers include mountain ranges or rivers, but any region that excludes vital resources, such as a region devoid of water, a burned area devoid of food, or an area covered with volcanic lava, can act as a barrier because individuals cannot survive its crossing.
• Gene frequencies in the two populations can differ due to natural selection and other factors.
• Interbreeding between the populations will not happen if the geographic barrier is removed.
• Interbreeding is prevented by reproductive barriers created by differential evolution.
• New species have formed.

• A population of insects has a polymorphism for color.
• If not camouflaged, the insect is eaten.
• Only insects with the same color can mate.
• Similar colored insects are reproductively isolated from other subpopulations and their genes differ as in allopatric speciation.

• Two viable diploid gametes and two sterile gametes with no chromosomes were produced as a result of polyploidy.
• A diploid sperm canfertilize a diploid egg.
• In a single generation, reproductive isolation with other individuals in the population occurs since normal meiosis in the individual will continue to produce diploid gametes.

• In some cases, the genetic variation of the hybrid is greater than that of either parent, and this allows the population of hybrid to evolve beyond the range of either parent.
• The hybrid is exposed to different selection pressures.

• It happens when the ancestral species is introduced to an area that has a lot of diversity.
• The populations specialize for each set of conditions.

• The colonization of Australia began with a single ancestral species.

• The 14 species of Darwin's finches on the Galapagos Islands are descended from a single ancestral South American mainland species.

• The five mass extinctions resulted in adaptive radiations.
• The periods following extinctions provided numerous opportunities for species to colonize.
• Colonization followed by competition promoted speciation.

• Various mechanisms exist to maintain reproductive isolation if a species is not physically separated.

• There are two types of mechanisms.

• The mule is a sterile hybrid of a donkey and a horse.

• This can happen as a result of allopatric or sympatric speciation.

• The species share a common ancestor, but that's not the reason for the similarities.

• There are torpedo-shaped bodies in sharks, porpoises, and penguins.
• These animals have adapted to aquatic life and not from a recent common ancestor.

• The eyes of fish and squids are similar.
• These animals do not have a common ancestor.
• The eyes in these two groups of animals are from different parts of the body.

• The adaptations of the two groups of mammals, the marsupial mammals and the placental mammals, have been the same since their ancestors encountered similar environments.

• A prey species can escape its predator by gaining an adaptation.
• The majority of the predator population will fail to catch prey.

• The immune systems of animals and plants are affected by coevolution.

• Microevolution is the subject of the previous chapters.

• The pace of macroevolution and the development of evolutionary history have different interpretations of the fossil evidence.

• Major changes in lineages occur over long periods of time, from hundreds of thousands to millions of years.
• snapshots of the evolutionary process are provided by fossil evidence.
• The incompleteness of the available fossil record shows that the intermediate stages of evolution are not represented by fossils.

• Most of the fossils in the fossil history should be from the extended periods of stasis with few, if any, fossils from the short bursts of evolution.
• This theory considers the absence of fossils to be data that confirms rapid evolutionary events.

• The processes that are believed to have contributed to the formation of the first living things are described in this kind of evolution.

• The earth and its atmosphere were formed.

• The earth is thought to have formed 4.5 billion years ago.
• For billions of years, the earth was inhospitable to life.

• The primordial atmosphere was formed from outgassing of the molten interior of the planet.

• The primordial seas were formed.

• The primordial seas consisted of water and minerals.

• The organic molecule were synthesised.

• The formation of organic molecules is catalyzed by energy.
• An organic soup was formed.

• UV light provided most of the energy, but also lightning, radioactivity, and heat.

• A complex molecule formed.
• These kinds of Molecules would later be used in the synthesis of the Molecules are used in the synthesis of the Molecules are used in the synthesis of the Molecules are used in the synthesis of the Molecules are used in the synthesis of the Molecules are used in the synthesis of

• Oxygen wasn't present so simple molecule were able to form.

• Oxygen, a very reactive molecule, would have prevented the formation of organic molecules if it had been present.

• The water contained various organic compounds after a week.

• There were self-replicating molecule that were synthesised.

• Monomers are combined to form something.
• Some of the reactions may have been caused by dehydration condensation, in which the water molecule is removed.

• This is based on recent discoveries.
• The functions of both genes can be performed by RNA.

• The organic molecule was isolated into the Protobionts.

• They were able to carry out chemical reactions that could be exchanged.
• Borders formed in the same way as conjugates aggregate to form conjugates and form conjugates and form conjugates and form conjugates and form conjugates and form conjugates and form conjugates and form conjugates and form conjugates and form

• Both have borders that form when the same molecule with the same chemical properties is separated from another molecule with different chemical properties.

• The prokaryotes formed around 3.8 bya.

• Heterotrophic prokaryotes are Pathogenicbacteria.

• The organic soup was a source of organic material.
• Competition for organic material increased as these cells reproduced.
• Heterotrophs that are most successful at obtaining food would be favored by natural selection.

• The primitive autotrophic prokaryotes were formed.

• A Heterotroph gained the ability to make its own food.

• Light energy is used to manufacture organic compounds by autotrophs.
• The autotrophic prokaryotes that obtain energy and manufacture organic compounds are called cruciobacteria.

• Oxygen was released as a result of the activity of autotrophs.
• The ozone layer was created by the interaction of UV light and oxygen.

• The formation of the ozone layer prevented incoming UV light from reaching the surface of the earth.

• The major source of energy for the abiotic synthesis was terminated.

• The eokeryotes formed a theory.

• Mitochondria, chloroplasts, and other organelles established residence inside another prokaryote.

• There is a lot of evidence for the theory.

• Mitochondria and chloroplasts have their own genes.
• bacteria and cyanobacteria have the same circular and without histone genes.

• The size and sequence of the ribosomes are similar to those ofbacteria.

• Mitochondria and chloroplasts reproduce independently of their host cell.

• Mitochondria and chloroplasts have two different types of cells.
• When the prokaryote is surrounded by a vesicle, the second membrane could be acquired.

• The thlakoid membranes of the chloroplasts are similar to those of the cyanobacteria.

• A review of the material presented in this chapter is provided by the questions that follow.
• They can be used to evaluate how well you understand the concepts.
• AP multiple-choice questions are often more general, covering a broad range of concepts.
• The two practice exams in this book are for these types of questions.

• Four possible answers or sentence completions are followed by each of the following questions or statements.
• The one best answer or sentence is what you choose.

• Europe and other regions of the world probably started with the B blood-type allele.

• The results of the test-cross experiments showed that the frequencies of dominant, Heterozygous, and Homozygous individuals were 32%, 64%, and 4%, respectively.

• Individual snails have dark bands on a yellow, pink, or dark brown background.

• The key is used for questions 9-12.
• The answer in the key can be used more than once.

• Populations of most whale species are decreasing because of human predation.

• There are more than 750,000 species of insects.

• A numerical answer is required for the following questions.
• You can use a calculator with a square root capability.

• The questions that follow are typical of an entire AP exam question or just that part of a question that is related to this chapter.

• There are two types of questions on the AP exam.
• It takes about 20 minutes to answer a long free-response question.
• Sometimes they offer you a choice of questions to answer.
• 6 minutes is the time it takes to answer a short free-response question.
• diagrams can be used to supplement your answers, but a diagram alone is not adequate.

• Few people can actually use the muscles that attach their ears to the skull.

• If the muscles serve no purpose, explain why in one or two sentences.

• Explain why this statement is false in two or three sentences.

• neutral variation can be seen in the creation of fingerprints, which are created by ridges on fingers.
• The differences have no value.

• Discuss the following as they relate to speciation.

• Discuss the importance of Darwin's theory of natural selection.

• Discuss how each of the following affected the origin of living organisms.

• Highly reactive oxygen was not present to cause chemical evolution.
• Oxygen interfered with the abiotic chemical reactions and ended abiotic synthesis.
• The oxygen interacted with the UV light to form the ozone layer.

• Changes in gene frequencies from other factors may contribute to increases in fitness.
• If the population increases as a result of natural selection, the allele will lead to an adaptation.

• Gene flow is the transfer of genes from one population to another.

• It's usually harmful when there is a random variation in the population.
• Natural selection, genetic drift, gene flow, and nonrandom mating are some of the causes of the variation in the population.

• Male lions have long hair.
• The result of sexual selection is differences in appearance between males and females.

• The population is not in equilibrium.

• The nonrandom nature of a test cross can cause this.

• The maintenance of patterned shells in the snail population is an example of balanced polymorphism.
• There is good evidence that it is maintained by natural selection, genetic drift, and other factors.
• This does not apply because convergent evolution refers to two or more species not of the same ancestral origin.
• The question deals with variation within a single species.

• The structures in different species are related.
• The insects are not related to the other animals.
• Birds and mammals are related by descent from an early reptile.
• The insect wings are similar structures.

• When population size falls, there is a problem.

• Surviving individuals may have a limited amount of genetic variation.
• When populations are small, the effect of genetic drift increases.

• When crossing over during prophase I of meiosis, mixing of maternal and paternal chromosomes, and random union of gametes, new combinations of alleles are produced.
• No two people will ever have the same genetics.

• Somebacteria are resistant to antibiotics as a result of genetic variation.
• Extensive use of antibiotics can cause resistant strains to survive and reproduce.
• Most survivingbacteria are antibiotic resistant after many generations of selection.

• The variety of insects and their range of habitat and ecological influence is an example of adaptive radiation.

• Evolution doesn't happen for an individual.
• Group of individuals of the same species are the only ones to evolve.

• You should enter 0.7 into the answer grid if the question asks for the Frequency rounded to the nearest tenth.

• To find the size of the population, add up all the individuals.
• You should enter your answer in the answer grid with a percentage in decimal form.

• Ancestors of the ear muscles served a function.
• These muscles are still used for rotation of the ear to capture different sounds.

• Adaptives are part of the family.
• An individual can either inherit an advantage or not.
• He will survive and produce offspring with the same trait.

• The ridges have some value.
• The ridges allow for a better grip.
• It is not the pattern of ridges that is important, but the presence of the ridges that provide the value.

• In a group of interbreeding organisms, allele frequencies change from generation to generation.
• When evolution occurs as a result of natural selection, all of the individuals with certain characteristics are passed on to the next generation.
• The best alleles in the population accumulate over time.
• Natural selection takes into account the available characteristics in the population.
• New alleles, increase variation, and the introduction of more successful traits may be achieved through the use of genetic alterations.

• Variation can be introduced into the population by mixing up existing alleles through genetic recombination, but it is the raw material for variation.
• It is the only way that new alleles can be introduced.

• Genetic drift can cause allele frequencies to change.
• Random changes in frequencies are described by genetic drift.
• This is important in evolution when populations are small.
• The small surviving population may change due to genetic drift when there is a population shortage.
• The effects of genetic drift may affect a founder population.
• If a small group of individuals are separated from the mother population, the allele frequencies of the founder group may be different.

• The movement of alleles between populations can cause evolution.
• Gene flow occurs when individuals emigrate or bring alleles into the population.
• Gene flow can cause a change in the relative frequencies of alleles.

• Changes in allele frequencies can be caused by nonrandom mating.
• The frequencies of alleles increase when there is random mating.

• In sexual selection, the frequencies of alleles increase if they give people a better chance of getting a mate.

• Males that win contests that make them more attractive to females have a advantage.
• Another form of nonrandom mating is inbreeding.

• The question is about how evolution occurs, so make sure that your answer is clear about how the mechanism causes evolution.
• Don't just define the mechanisms.

• When a river or mountain range divides the population into two, it's called allopatric speciation.

• The two populations are separate and reproductively isolated.
• Changes in frequencies in one population may not happen in the other.
• Natural selection may favor different characteristics in the two populations if the environment is different.
• The founder effect and the small population may cause differences in allele frequencies.
• Allele frequencies are strongly influenced by chance.
• Natural selection can act upon the introduction of new alleles absent in the other population.

• In the absence of a geographic barrier, sympatric speciation occurs.
• One of several other causes causes reproductive isolation.
• Polyploidy creates reproductive isolation in a single generation.
• All of the chromosomes are contained in gametes, instead of half of them.
• If a gamete is fertilized by a similar gamete, the resulting zygote has twice the number of chromosomes and is immediately reproductively isolated from people with the same chromosomes as its parents.
• Polyploidy is common in plants.

• When the habitats of two different species meet, another source of reproductive isolation can occur.
• Some individuals may mate because of incomplete prezygotic or postzygotic reproductive mechanisms in the zone where the two populations meet.
• If the hybrid form is better adapted to the features of the hybrid zone than either of the parent populations, then a population that is isolated from either parent population may result.

• A third source of reproductive isolation can occur when a population has a balanced polymorphism.
• A balanced polymorphism occurs when multiple forms of a trait are maintained in the population at higher frequencies than would be expected.
• One or more of the forms have an adaptation that has a greater value to a specific feature of the environment than other forms.
• In some cases, the adaptation may create an isolating mechanism.
• In response to seed size, a population consists of birds with large and small beaks.

• When a population is introduced to an area with many conditions, adaptive radiation occurs.
• When the introduced species enters new habitats, selection pressures will vary.
• Larger animals may be favored for insulation.
• Fruit-eating abilities among the animals may be favored in a habitat with many fruit producing plants.
• There is adaptive radiation among plants.
• In a rain forest habitat, individual plants that have adaptation to wet conditions are favored, whereas in dry regions, plants with water conservers are favored.

• Darwin's finches are a good example of adaptive radiation.
• The finches are found on the islands of the Galapagos Islands.
• Descendants from a single mainland species spread to the various islands.
• The bodies of water between the islands provided a barrier that led to allopatric speciation.
• As finches competed for resources, sympatric speciation occurred on each island.
• The ability to obtain food, an important characteristic for survival, led to specialization in sizes and shapes of beaks.
• There are 14 species of finches, each adapted for obtaining different kinds of food and different sizes of food, because of allopatric speciation of populations on separate islands and each individual island.

• Divide your answer into two parts, a and b.
• Define a prezygotic isolating mechanism, list the different forms that it can take, and give an example of each.
• Define postzygotic mechanism, follow with different forms, and provide an example of each.

• A geographic barrier separates a population into groups.
• The evolution of the two new populations may differ.
• Natural selection in one group may be different from natural selection in the other group.
• Food or water may be different.
• There may be differences in the group.
• Even if the barrier is removed, the two groups may become so different that they can't reproduce with each other.
• They are reproductively isolated and each is a separate species.

• Polyploidy is the possession of more than one set of chromosomes.

• During meiosis, gametes have double the normal number of chromosomes.
• The diploid zygote contains twice the normal number of chromosomes when a spermfertilizes an egg.
• A polyploid individual is the result.
• When this new individual undergoes a normal meiosis, gametes will contain twice the number of chromosomes as their parent and will be able to fertilize only similarly produced gametes.
• The polyploid individual and its offspring are not part of the original population.
• A speciation event occurs in a single generation.
• Plants and animals have rare polyploidy.

• Sexual selection is the process of selecting males.

• Only males that win contests with other males are able to mate.
• A male's success in these two areas can be improved by certain characteristics.
• Sexual selection results in attributes that improve success in contests, such as large size, or increased musculature, as well as features that are attractive to females, such as good nest-building ability, large territories, or long or colorful feathers.
• Sexual selection can change allele frequencies over time, but it is not possible to form a new species.

• Natural selection favors individuals with certain characteristics that increase their fitness, such as their ability to survive and leave fertile offspring.
• No one individual in the population would be more capable of leaving offspring than anyone else.
• There can't be natural selection without variation.

• If a trait is not heritable, it doesn't matter how much it increases fitness because it can't be passed on to the next generation.
• The acquired characteristics do not contribute to evolution.
• It's not possible to count any changes that occur in the tissues.
• In order for a trait to contribute to evolution, it must be included in gametes.

• Differences among individuals won't affect their ability to produce offspring if there are unlimited resources and unlimited availability of mates.
• Resources will become limited as the population grows.
• Individuals have to compete for resources.
• The offspring of individuals with the traits that increase their ability to obtain resources will be passed on to the next generation.
• There is no evolution without competition.

• This question asks you to explain how it is important to Darwin's theory of natural selection.
• Don't stray from the target.
• If you wanted to explain how alack of variation can cause genetic drift, you wouldn't get any points because Darwin's theory isn't part of it.
• No points would be given for describing howmutations contribute to variation because they are not part of histheory.

• The major step leading to the origin of life is the part of the question that corresponds to it.
• Specific information can be found in the discussion on "The Origin of Life"presented earlier in this chapter.
• You should separate your answers into paragraphs that correspond to each part of the question.