i) GENETIC VARIATION & MUTATION & HARDY-WEINBERG PRINCIPLE

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1 Test 2 LOs: MICROEVOLUTION Define key terms: i) GENETIC VARIATION & MUTATION & HARDY-WEINBERG PRINCIPLE Population: all individuals of a single species that live together in the same place and time Microevolution: changes in genetic characteristics of a population over time (traits depend on genetics and environment); occurs in a shorter time compared to macroevolution; occurs when the allele frequencies in a population change Phenotypic Variation: differences in appearance or function between individual organisms Qualitative Variation: variation that exists in two or more discrete states, with intermediate forms often being absent Quantitative Variation: variation that is measured on a continuum (such as height in human beings) rather than in discrete units or categories Mean Value of Characteristic: average value of the characteristic Explain why variation in populations is important to evolution. In order for evolution to occur, there must be genetic variation that is heritable. e.g. fly experiment -variation in starvation resistance (variation) -after each generation, more flies survived longer (heritable) Classify a phenotypic character as exhibiting quantitative or qualitative variation. Examples of quantitative variation: height, weight, toe length, number of hairs on head Examples of qualitative variation: snow geese (either white or blue), blood type (A or B or AB or O) Explain how: - Two individuals of the same species can have different genotypes, but have the same phenotype This can occur due to the environment. If two individuals that have different genotypes, they may have the same phenotype if they live in similar environments. -And how two individuals could have the same genotype, but different phenotypes. This can also occur due to the environment. Although two individuals may have the same genotypes, their phenotypes may differ if they live in different environments. (e.g. ph of the soil can affect the colour of certain flowers)

2 Interpret from a graph of a quantitative character, the degree of variation for that character within the population. The width of the base of the graph is proportional to the degree of variation. (wider distribution) Describe, in simple terms, several ways in which variation is generated. Crossing over during meiosis Independent assortment during meiosis Fertilization may generate variation (half of chromosomes are from mom, half of chromosomes are from dad) Mutations are the ultimate source of variation (They can modify an allele to another allele that already exists in the population, they can create a new allele that doesn t exist in the population of interest and codes for the production of a new protein); mutations arise from random processes Explain: -The random nature of mutations; how mutations are passed on from one generation to the next (both vertically & horizontally) Vertically: (Meiosis) chromosomes may not segregate properly during anaphase I and/or anaphase II leading to mutations that may be passed on to the next generation. Horizontally: If a mutation occurs in the replication of a plasmid, it may be passed on to another bacteria and when that bacteria replicates, it will pass on the mutation to the next generation. -And the role of mutation in evolution Mutation can restore variation removed by other evolutionary processes. It also provides the raw material for evolution (mutation-random, natural selection-not random) Define: Gene Duplication: A portion of the genetic material is duplicated or replicated resulting in multiple copies of that region. Pseudogene: looks like a gene but doesn t act like one; not expressed (Dr. Kelly), a pseudogene is a DNA sequence that resembles a gene but has been mutated into an inactive form over the course of evolution. Gene family: genes similar to each other in structure and function (Dr. Kelly)

3 Explain how gene duplication can lead to evolutionary change. Outcome of gene duplication that could lead to evolution of novel traits: -may retain original function, but change in expression pattern (new tissues/developmental timing) -duplicated gene gains mutations altered protein product could perform valuable function e.g. copy B can bind new substrates Define: Evolutionary Developmental Biology ( evo-devo ): a field of biology that compares the genes controlling the developmental processes of different animals to determine the evolutionary origin of morphological novelties and developmental processes Genetic tool-kit (i.e., homeotic genes): Homeotic genes are regulatory genes that code for transcription factors that bind regulatory sites on DNA, either activating or repressing the expression of other genes that contribute to an organism s form; Comparisons of genome sequence data reveal that most animals, regardless of their complexity or position in the tree of life, share a set of several hundred homeotic genes that control their development. This genetic tool-kit governs the basic design of the body plan by controlling the activity of thousands of other genes. Explain, using a very general example, how changes in developmental regulatory genes can be a genetic switch between different morphologies. (Explain how small genetic changes could account for large changes in the characteristics of organisms and lead to new morphologies.) -Gene switches initial determinants of which genes are turned on/off in different body areas and cell types -By altering timing of a developmental gene (where/how long) can manifest huge changes to morphology -e.g. turn of ONE hox gene different set of wings (Dr. Kelly s insect example) Define: Gene Pool: the sum of all alleles at all gene loci in all individuals in a population Genotypic Frequency: the percentage of individuals in a population possessing a particular genotype Allele Frequency: the abundance of one allele relative to others at the same gene locus in individuals of a population Relative Abundance: the relative commonness of populations within a community

4 Genetic Equilibrium: the point at which neither the allele frequencies nor the genotype frequencies in a population change in succeeding generations Loci/locus: the particular site on a chromosome at which a gene is located Fixation/Loss: If there is only 1 allele, frequency=1; fixed (Dr. Kelly); In population genetics, fixation is the change in a gene pool from a situation where there exist at least two variants of a particular gene (allele) to a situation where only one of the alleles remains. Differentiate between genotype frequency and allele frequency. Genotype frequency is the percentage of individuals (relative abundance) in a population possessing each genotype for a given locus (gene). Allele frequency is the relative abundance of different alleles for a gene within a population. Calculate frequencies of alleles or genotypes given information on the number of individuals with specific genotypes. p 2 +2pq+ q 2 = 1 e.g. There are 2 alleles in a population: A 1 and A 2. There are 4 A 1 A 2, 3 A 2 A 2, and 3 A 1 A 1. Calculate the allele frequencies. Total number of alleles=20 Frequency of A 1 =10/20=0.5, Frequency of A 2 =10/20=0.5 Explain how the Hardy-Weinberg (HW) principle acts as a null model/hypothesis for evolution. (Using the 5 assumptions describing population) -If evolution was NOT occurring, there would be no mutations because they are mechanisms of evolution. -If evolution was NOT occurring, the population would be isolated from other populations which would prevent gene flow-another mechanism of evolution. -If evolution was NOT occurring, there would be no natural selection (mechanism of evolution) with respect to the gene of interest; all genotypes in the population survive and reproduce equally well. -If evolution was NOT occurring, there would a population that is infinite in size (extremely large) meaning that the effects of genetic drift (mechanism of evolution) are minimal.

5 List the 5 conditions of the HW principle under which a population of diploid organisms can reach genetic equilibrium. 1. No mutations are occurring 2. The population is closed to migration from other populations 3. The population is infinite in size 4. All genotypes in the population survive and reproduce equally well 5. Individuals in the population mate randomly with respect to genotypes Explain why microevolution will not occur under the conditions of HW. Under the conditions of HW, frequencies of alleles (and genotypes) are preserved from generation to generation in populations and thus microevolution will not occur. ii) NATURAL SELECTION & ADAPTATION Define: natural selection, artificial selection, adaptation, fitness, relative fitness, stabilizing selection, directional selection, disruptive selection, fitness trade-off, adaptive radiation. [Knowledge] Natural Selection: evolutionary process by which alleles increase likelihood of survival and the reproductive output of the individuals that carry them become more common in subsequent generations. Artificial Selection: selective breeding of animals or plants to ensure certain desirable traits appear at higher frequency in successive generations. Adaptation: characteristic(s) that helps an organism survive longer or reproduce more under a particular set of environmental conditions. Fitness: an organism s ability to survive and reproduce in a particular environment. Relative fitness: The number of surviving offspring that an individual produces compared with the number left by others in population. Stabilizing selection: a type of natural selection in which individuals expressing intermediate phenotypes have the highest relative fitness. Directional Selection: a type of selection in which individuals near one end of the phenotypic spectrum have the highest relative fitness. Disruptive selection: a type of selection in which extreme phenotypes have higher relative fitness than intermediate phenotypes. Fitness trade-off: compromise between traits. An advantageous trait also has a disadvantage side to it. See examples at bottom. Adaptive Radiation: the diversification of a group of organisms into forms filling different

6 ecological niches (status of organism within its environment). Explain the importance of genetic variation to the process of natural selection. [Comprehension] Because of genetic variation, certain alleles are more favored than others (natural selection). If there s no genetic variation, how can an allele be favored amongst others, if there s only one allele in the population. No genetic variation means they are all equally fit. Explain how natural selection acts on phenotypic variation to alter the genetic structure of a population. [Comprehension] When certain phenotypes are favored, they are passed on more to the next generation, which is changing the genetic structure of a population. Phenotypes result of genes, so if phenotypes are favored, those genes that produce those phenotypes are favored as well. Differentiate between artificial selection and natural selection. [Knowledge, Comprehension, Analysis] Artificial selection is selecting certain alleles to be greater in the next generation (selective breeding) and natural selection is process by which favorable heritable traits become more common in successive generations of a population of reproducing organisms, and unfavorable heritable traits become less common, due to differential reproduction of genotypes. Basically, we can control artificial selection but not natural selection. EX: Artificial selection: Breeding for a small dog such as a chihuahua. Natural selection: Bird whose beak after a generation or more changes so it can feed on the food available to survive. Explain how artificial selection provides evidence for natural selection. [Comprehension] It demonstrates conclusively that if individuals in a population consistently have differences in reproductive success based on *inherited* traits, generation after generation, then that population will slowly change over time and those traits will become more universal. That is precisely the essential claim of natural selection. Describe what is meant by descent with modification. *Comprehension+ Descent with modification refers to the passing on of traits from parent organisms to their

7 offspring. Explain why individuals do not evolve and why evolution is considered a population process. [Comprehension] Evolution and natural selection is a long process covering many hundreds, thousands, even millions of generations. The evolutionary process cannot take place in an individual because the individual represents only one generation. Differentiate between evolution and natural selection. [Comprehension, Analysis] Evolution is a gradual process in which something changes into a different and usually more complex or better form whereas natural selection is a mechanism in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated. Explain why reproduction is more important than survival to an old age in terms of evolution by natural selection. [Comprehension, Analysis] For natural selection to occur, the parent has to pass on its favorable traits to its offspring, if it does not reproduce it is not contributing to their next generation. Survival of the fittest means surviving to reproduce. Describe how the process of natural selection is non-random. [Comprehension] Natural selection is non random because of the fact that favorable traits are passed on, not any trait. It is because these traits helped them (population) to survive that they are passed on, there is a reason. Explain why evolution is not progressive (e.g., moving towards perfection ). [Comprehension] Evolution is progressive in the sense that it keeps a population of organisms "tuned" to its environment. If the environment changes too rapidly for a population of organisms to genetically adapt, they lose their fitness and go extinct no matter strong they are. Describe how natural selection results in adaptation of populations. [Comprehension] Adaptation is/are trait(s) that allow individuals to out produce individuals without those traits. Natural selection passes on these traits because their parents had used these traits to out

8 produce as well. Describe why there are limits to adaptive evolution (i.e., why organisms can never be perfectly adapted to their environment). [Comprehension] An organism can never be perfectly adapted to the environment because environment changes sometimes due to chance events (hurricanes) and etc. Explain why a character that is strongly influenced by the environment would not respond to selection (either artificial or natural). [Comprehension] ummm.. Idk:S Explain why natural selection usually exerts little effect (i.e., weak selection) on a geneticallydetermined phenotype that appears in post-reproductive life. [Comprehension/Analysis] When you are in your post-reproductive life, you do not contribute to the next generation. If anything happens to you, it won t matter because your not passing any traits on to the next generation anyway, not in stage to reproduce. Example Huntington s disease affect females after 40 yrs. of age, but that will not matter because natural selection will only affect the offspring not the parent because it wont contribute to the next generation. Compare and contrast the different types of selection (e.g., directional, etc.), discussing their effects on genetic variation and mean character value within a population. [Comprehension/Analysis] 1) Directional selection: when individuals near one end of phenotypic spectrum have the highest relative fitness. The mean value shift towards the extreme, either lower or higher than before Decreases genetic variation. 2) Stabilizing selection: when individuals expressing intermediate phenotypes (middle) have the highest relative fitness. Eliminates phenotypic extremes (at ends of phenotypic spectrum) Decrease genetic and phenotypic variation and increases frequency of intermediate phenotypes 3) Disruptive selection: when extreme phenotypes (both ends) have higher relative fitness. Alleles producing extreme phenotypes become more common promoting polymorphism. Genetic variation higher than other types of selection. Identify, given a scenario, which form(s) of natural selection is/are at work. [Analysis] don t know how to explain this :S

9 Predict, given a description, the outcome of a scenario/experiment if selection is acting. [Comprehension, Analysis, Application] There is selection if certain traits are passes on more than others. Will notice a change in genetic frequency, and phenotypic frequency. Discuss adaptations, commenting on why: there are limits to adaptation; not all traits are adaptive; why adaptation is not universally good; adaptations always represent compromises (how an organism s phenotype represents a compromise or trade-off between the adaptive value of multiple traits. [Comprehension] An adaptation is a feature that is common in a population because it provides some improved function. Adaptations are well fitted to their function and are produced by natural selection. Limits to adaptions because the environment is always changing. Adaptions are not universally good because one adaption may be good for some function but not another. May not be good in all environments. Provide an example of a fitness trade-off. [Knowledge] One example is an organism being slower in order to have a larger body size. The larger body size may be beneficial for fighting predators but it makes the organism slower. Example in class: gill guppies like longer gonopodia in males but that increases their chances of getting eaten by predators. iii) MAINTENANCE OF GENETIC VARIATION (HETEROZYGOTE ADVANTAGE, ETC) Explain why alleles coding for dominant traits don t, through natural selection, always replace recessive or rare alleles. [Comprehension, Analysis] Dominant traits don replace them because recessive or rare alleles will come up because of genetic drift (chance) Describe how diploidy can hide harmful recessive alleles from natural (or artificial) selection. [Comprehension] Haploid can only have one allele so it cannot hide the harmful recessive allele.

10 **In diploid harmful recessive alleles are disadvantageous in a homozygous state, but in a heterozygous state, the recessive allele can be masked because of the expression of the dominant allele. Diploid state preserves recessive allele at low frequency in large population, doesn t eliminate them. In small population, the combination of natural selection and genetic drift can eliminate them. Describe how spatial and temporal environmental variability can influence population variation. [Comprehension, Analysis] In temporal variability different alleles will be favored in different environment. At a different time of the year, a different phenotype selected. Ex: camouflage white fox will be good in winter, but not in spring. In spatial variability, there will be a greater change in characteristics along the geographic line. Describe heterozygote advantage and frequency-dependent selection. [Comprehension] Heterozygote advantage: describes a mechanism by which a recessive allele, though harmful in the homozygous condition, is maintained in a population because it provides some adaptive advantage in heterozygotes. Example is sickle-cell disease. Individuals homozygous recessive (ss) for the sickle-cell allele are inflicted with the devastating effects of the disease. However, in heterozygotes (Ss), it is believed that the sickle-cell allele provides some protection against malaria. Frequency-dependent selection: evolutionary process where the fitness of a phenotype is dependent on its frequency relative to other phenotypes in a given population. Example: rare phenotypes have higher relative fitness than more common phenotypes, until it will increase until common and loses its advantage. Predator-prey interactions. iv) GENE FLOW, GENETIC DRIFT, AND NON-RANDOM MATING. List and define the agents of microevolutionary change: mutation, gene flow, genetic drift (including founder effect and genetic bottleneck), and natural selection, as well as non-random mating. [Knowledge] Mutation: is a heritable change in DNA Gene flow: the transfer of genes from one population to another through the movement of individuals or their gametes (ex. flowers) Genetic drift: a Random fluctuation in allele frequencies as a result of chance events; usually reduces

11 genetic variation. Founder effect: a phenomenon in which a few individuals colonize and start their own population, they carry only a small sample of the parent population s genetic variation. Genetic bottleneck: a stressful factor (disease, drought, and hurricane) kills many individuals and eliminates some alleles from a population. Natural Selection: an evolutionary process in which alleles that increase survival and reproductive output of the individual that carry them become more common in future generations. Non-random mating: mating that has not occurred due to chance (ex. People who look alike mate more often than they would under random conditions) Compare and contrast the different microevolutionary process\es, commenting on their impact on a population s genetic structure. *Comprehension, Analysis+ Mutations introduces new genetic variation into a population Gene flow may introduce genetic variation from another population Genetic drift reduces genetic variation especially in small populations; can eliminate alleles Natural selection one allele can replace another or allelic variation can be preserved Non-random mating does not directly allele frequencies, but usually prevents genetic variability Describe how gene flow between two populations results in the populations becoming similar. [Comprehension] If there is no gene flow, then they will be completely genetically independent, on the other hand if there is gene flow then you will see an increase in the similarity between the two populations as they start mating. Describe how organism mobility and gamete mobility influence rates of gene flow between populations. [Comprehension] Organisms mobility and gamete mobility increase the rates of gene flow between populations because since the organisms is able to move this increases the chances of them entering into other populations and breeding. Gamete mobility can refer to the movement of fish s eggs and sperm and this can cause an increase in gene flow Describe how population bottlenecks and founder events can lead to genetic drift. [Comprehension] Bottlenecks can lead to genetic drift because when there is a chance and many individuals die then there is a reduction in genetic variation, even if the population numbers rebound later. Founder effect can lead to genetic drift because when the new population is formed by chance there could be alleles that may be missing from the population. Compare and contrast between population bottlenecks and founder events. [Comprehension] Both founder effect and bottleneck effect cause a decrease in allele frequencies as well as genetic variation. Also in both there is a random sample of the genes from the original population. Whereas

12 the differences are that in founder effect a new population is formed and in bottleneck a population size is decreased because of a catastrophic event. Explain why the effects of genetic drift increase as the population size decreases. [Comprehension] The effects of genetic drift are higher in small population sizes because smaller populations have less variation and therefore a lower ability to adapt to changing conditions. Describe the implications that genetic drift has for conservation biology. [Comprehension] Endangered species experience severe population bottlenecks, which results in the loss of genetic variability. The small number of individuals that are used in captive breeding programs may not fully represent a species genetic diversity. With such little variation, no matter how large a population becomes in the future, it will be less resistant to diseases or less able to cope with environmental change. Define terms of non-random mating: sexual selection, intrasexual selection, intersexual selection, inbreeding, inbreeding depression, honest signals, sexual dimorphism, monogamy, polygamy (polygyny and polyandry), handicap hypothesis. [Knowledge] Sexual selection: A form of natural selection established by male competition for access to females and by the female s choice of mates. Intrasexual selection: The selection within the same sex (ex. Males compete against each other) Intersexual selection: Selection between the two sexes (ex. Bright plumage of a male peacock does not help it physically overcome rival males, but females prefer male peacocks with bright plumage) inbreeding: a form of non-random mating in which genetically related individuals mate with each other. Inbreeding depression: A decrease in fitness in a population as a result of mating with related individuals. Honest signals: sexual dimorphism: Differences in the size or appearance of males and females. Monogamy: The practice or state of having a sexual relationship with only one partner. Polygamy: A pattern in mating in which an animal has more than one mate of the opposite sex. Polygyny: Polygamy in which a man has more than one wife. Polyandry: Polygamy in which a woman has more than one husband. Handicap hypothesis: Describe the negative effects of inbreeding on a population s genetic variation. *Comprehension+ Inbreeding causes recessive phenotypes to be expressed more often and causes genetic variation to decrease. Describe the effects of inbreeding on recessive phenotypes and heterozygosity. [Comprehension]

13 Since relatives often carry the same alleles, inbreeding generally increases the frequency of homozygous genotypes and decreases the frequency of heterozygotes. Thus, recessive phenotypes are often expressed. Explain, using an example, how non-random mating may not result in evolution. [Comprehension, Analysis] Differentiate between intersexual and intrasexual selection. [Comprehension] Intrasexual selection is when two individuals of the same sex compete with each other for an individual of the other sex. Whereas intersexual selection between the two sexes. Predict, given a scenario, which sex will show the greater variation in reproductive success (and be able to explain why). In the example in class with the elephant seals, the males shows greater variation in reproductive success because some males can be able to father 1-10 offspring and some will father offspring, whereas females on average only mother 1-3 offspring. Predict, given a scenario, the extent of sexual dimorphism within a species. Sexual dimorphism are the differences in the size of males and females. One example of sexual size dimorphism is the bat Myotis nigricans. In this species, females are substantially larger than males. They differ in body weight, skull measurement, and forearm length. The difference in size is believed to be caused by natural selection for a large female size due to a fecundity advantage. The interaction between the sexes and energetic needs such as time and energy required to produce viable offspring make it favorable for females to be larger in this species. Explain, using an example, how sexual selection has resulted in showy structures in males, commenting on what these might indicate about the males (relate this to fitness trade off, handicap hypothesis, etc.). [Comprehension] In some bird species, a brighter plumage is more attractive to females, but has a negative effect on fitness because it allows the individual to be more easily by predators (known as the handicap hypothesis). Explain using an example, how all or some microevolutionary processes might act simultaneously on a population. [Comprehension, Analysis] Explain, given what we ve discussed about evolutionary mechanisms, why variation is beneficial to a population. [Comprehension, Analysis] Variation is beneficial to a population because if there is an event that eliminates only one type of allele and there is no variation then the chance of the population going extinct increases.

14 Compare and contrast genetic drift and natural selection in terms of how they work and their potential outcomes with respect to fitness, adaptation, genetic variation, & random vs. non-random processes. [Knowledge, Comprehension] Genetic drift is a random event that occurs and has no effect on the fitness of a species. No matter how fit an individual is during a hurricane they will not have a better advantage than other individual. Whereas the higher your fitness the better natural selection will be a benefit to you. Explain why natural selection is the only mechanism of evolution to result in adaptation. [Comprehension] Relate the 5 conditions of the HW principle to the various mechanisms of evolution (microevolutionary processes). [Analysis] Explain, using an example, how natural selection can alter/shape complex traits. [Comprehension] Define key terms: v) SPECIATION Speciation: the process of species formation Macroevolution: descent of different species from a common ancestor over many generations; occurs over a longer period of time than microevolution (Dr. Kelly) Hybrid: An offspring resulting from the cross between parents of different species or sub-species. Hybridization: when two species interbreed and produce fertile offspring Compare and contrast microevolution versus macroevolution, and the linking role of speciation. -Both involve a change in genetic characteristics in a population over time. -Microevolution involves changes in allele frequency from generation to generation within a species. Macroevolution involves the origin and divergence of major taxonomic groups; involves speciation- split from common ancestor Explain why differentiation of two similar looking organisms as different species might be useful. This may be useful because these different species may have become so similar in appearance due to convergent evolution (similar environments develop similar traits) Describe the definition of a species according to the: -Biological Species Concept: group of organisms that can successfully interbreed and produce fertile offspring -Phylogenetic Species Concept: group of organisms bound by a unique ancestry

15 -Ecological Species Concept: group of organisms that share a distinct ecological niche -and Morphological Species Concept: the idea that all individuals of a species share measurable traits that distinguish them from individuals of other species Compare and contrast the four species concepts (listed above), addressing their uses and limitations. SPECIES CONCEPT USES LIMITATIONS Biological Determine if two organisms can interbreed and produce fertile offspring -It does not deal well with the many species that reproduce asexually -Can t classify fossils -Can t identify whether geographically isolated populations belong to the Phylogenetic Ecological Morphological Determine if two organisms have a common ancestor Determine if two organisms share a distinct ecological niche Determine if a certain organism has traits that distinguish them from others same species -Determination of the degree of difference required for separate species - Many taxa exploit overlapping resources, or can suddenly switch if a resource becomes scare. -Relies on subjective criteria -Organisms that have the same phenotype/ look the same may not have the same genotype/ genetic makeup (not the same species) -Male and female individuals of the same species may be mistaken for being different species Given a scenario, determine which species concept would be most appropriate to determine if two organisms were the same species. Use each concept s definition of a species to determine which one would be most appropriate. Explain why the Biological Species Concept is not useful for classifying -Asexual organisms: they do not reproduce sexually and therefore cannot interbreed -Fossil organisms: the are no longer living and therefore cannot be classified using the biological species concept; failure or success of interbreeding cannot be observed -Hybrids: The definition of species does not apply where there is hybridization, when two species interbreed and produce fertile offspring Hybridization between species tat produces sterile offspring does not pout them outside the definition of the Biological Species Concept (textbook doesn t really

16 make sense..) -And those organisms that can reproduce both sexually and asexually (e.g., Daphnia pulex): When observing if these types of organisms can interbreed successfully, they may choose to reproduce either sexually or asexually. If they choose to reproduce asexually, the biological species concept cannot be used. (Refer to Asexual organisms above.) Explain why the Biological Species Concept is not useful for classifying asexual organisms, fossil organisms, hybrids, organisms, and those organisms that can reproduce both sexually and asexually (e.g., Daphnia pulex). [Comprehension] The biological species concept is not useful for classifying a number of different organisms because the definition of species is a group of organisms that can successfully interbreed and produce fertile offspring. This definition doesn t apply to individuals that reproduce asexually but that doesn t mean that they are not species. Describe how Biological Species Concept could explain why individuals of a species typically look alike. [Comprehension] The biological species concept could explain why individuals of a species look alike because in order to be classified in the B.S.C the two organisms must be able to interbreed and therefore they will look alike as the DNA is passed on. Identify the one evolutionary mechanism that could not occur if two groups of organisms are identified as separate species according to the Biological Species Concept. [Synthesis/Evaluation] One evolutionary mechanism that could not occur if two groups of organisms are identified as separate species according to the Biological Species Concept is that they cannot interbreed. Describe a ring species and its pattern of gene flow, the concept of subspecies, and how it can pose a challenge to the Biological Species Concept. [Comprehension] A ring species is one in which species with a geographic distribution forms a ring and overlaps at the ends. The many subspecies of Ensatina salamanders in California exhibit subtle morphological and genetic differences all along their range. They all interbreed with their immediate neighbors with one exception: where the extreme ends of the range overlap in Southern California, 2 subspecies do not interbreed. This possesses a challenge to the B.S.C because if all the subspecies that were able to interbreed went extinct and the only 2 subspecies left were the 2 that could interbreed would that now make them 2 different species? Define a cline and explain how a species could vary over its geographic range. [Comprehension] A gradual change in a character or feature across the distributional range of a species or population, usually correlated with an environmental or geographic transition. A species can vary over it s geographic range because of environmental factors.

17 Define prezygotic and postzygotic isolating mechanisms. [Knowledge] Prezygotic Isolating Mechanisms: a reproductive isolating mechanism that acts prior to the production of a zygote, fertilized egg Postzygotic isolating mechanisms: barriers after fertilization Define and recognize examples of prezygotic isolating mechanisms: ecological/habitat isolation, temporal isolation, behavioural isolation, mechanical isolation, and gametic isolation. [Knowledge/Application] Ecological/habitat isolation: live in same geographic region but in different habitats Temporal Isolation: Same habitat but mate at different times of day or year Behavioural Isolation: when signals used by one species not recognized by another Mechanical Isolation: differences in structure of copulatory (sex) organs preventing successful mating between individuals of different species. Gametic Isolation: incompatibility b/w sperm and eggs of another Identify which prezygotic isolating mechanisms inhibit mating attempts, and which limit fertilization, but not mating attempts. [Application/Analysis] Inhibit mating attempts: temporal, behavioural and ecological isolation Limit fertilization: mechanical (not sure about this one) and gametic isolation Define and recognize examples of postzygotic isolating mechanisms: hybrid inviability, hybrid sterility and hybrid breakdown. [Knowledge/Application] Hybrid inviability: 2 different set of instructions from parents, may not intercat properly so dies as embryo or at early stage. Hybrid Sterility: not able to produce functional gametes b/c of difference in # or structure of chromosome (cannot pair properly during meiosis). Hybrid breakdown: First generation (F1) hybrids are viable and fertile, but further hybrid generations (F2 and backcrosses) are inviable or sterile (not able to produce children). Explain how hybrid breakdown can be a reproductive isolating mechanism if the F1 (hybrid offspring of two species) is viable and fertile. [Comprehension, Analysis] Hybrid breakdown can be a reproductive isolating mechanism because even if the F1 offspring is fertile and viable the F2 offspring may exhibit reduced survival or fertility. Define allopatric speciation. [Knowledge] Allopatric Speciation: speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration.

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