BIOL 3040 STUDY GUIDE II, PART A

BIOL 3040 STUDY GUIDE II, PART A Chapter 4 Synapomorphy: A character or trait that is shared by two or more taxonomic groups and is derived through evolution by a common ancestor. Homoplasy: Correspondence between parts or organs acquired as a result of parallel evolution or convergence. Homoplasy is analogous and can be due to convergent evolution 1. According to the tree below: a Species B is more closely related to species G than species A b Species B is equally related to species G and species A c Species B is more closely related to species A than to species G d Species B is the common ancestor of species A, H, F, and G e A and d are correct 2. Given the tree below, the similar body shape of Icthyosaurs and dolphins is best described as: (a) an example of convergent evolution (b) a homoplasious trait (c) an analogous trait (d) all of the above (e) none of the above 3. If species A and B are more closely related to each other than either is to species C, then species A and B must: (a) share a more recent common ancestor (b) be more similar physically overall (c) share more derived homologies (synapomorphies) (d) both a and c are correct (e) a, b, and c are all correct 4. Given the tree below, which statement(s) is/are correct? (a) The lineage leading from the ancestral primate to modern day lemurs is older than the lineage leading from the ancestral primate to modern day humans (b) The monkeys form a monophyletic group (c) a and b are correct (d) none are correct 5. In the tree below, assume that the ancestor was an herb (not a tree) without leaves or seeds. Which currently existing species has/have the same combination of trait as the ancestor? (a) fern (b) Psilotum (c) clubmoss (d) a and c are correct (e) b and c are correct 6. Which of the following is true of the most recent common ancestor of two currently living species? Family trees are made of the same species (a) it may still be alive (b) one of the two species can be more closely related to the common ancestor (c) one of the two species may morphologically resemble the common ancestor more than the other (d) all are true 7. The phylogeny below shows relationships between birds and four different dinosaur genera. Based on the logic of phylogenetic systematics, which of the following statement(s) is/are accurate? (a) Dinosaurs and birds form a monophyletic group (b) In order for dinosaurs to be a valid taxon, birds must also be called dinosaurs (c) Dinosaurs (not including birds) are a paraphyletic group (d) All of the above (e) None of the above 8. Given the tree above, which tree below is incorrect? Answer: C 9. Referring to the phylogenetic trees below which statement(s) is/are correct? (a) Tree A proposes that the camera eye of mollusks and vertebrates is homologous; Tree B proposes that the camera eye of mollusks and vertebrates arose through convergent evolution (b) Tree B proposes that the camera eye of mollusks and vertebrates is homologous; Tree A proposes that the camera eye of mollusks and vertebrates arose through convergent evolution (c) Tree B is more parsimonious (d) A and c are correct (e) B and c are correct 10. Referring to the tree below, which is an accurate statement about relationships? (a) a gorilla is more closely related to a human than it is to an orangutan (b) gorilla is more closely related to an orangutan than a human (c) a gorilla is equally related to a human and an orangutan (d) an orangutan is related to chimps and orangutans but not humans 11. Trap jaw ants have modified mandibles that function like a bear trap—when a potential prey item triggers the jaw it snaps shut with amazing speed (up to 145 mph!). The groups highlighted in the phylogeny below include species that have evolved trap jaws. With reference to this tree it appears that: (a) the trap jaw could be a homologous trait for Formicinae and Ponerinae (b) the trap jaw is homoplasious (analogous) for Myrmicinae and Ponerinae (c) the trap jaw is homoplasious (analogous) for Odontomachus and Myrmoteras (d) a and c are correct (e) b and c are correct 12. Given the tree below which of the following statements is correct? (a) A fish is more closely related to a frog than it is to a bird (b) The dog evolved before the turtle (c) A frog is the most recent ancestor of a dog (d) All of the above (e) None of the above 13. Considering the logic of phylogenetic systematics, which of the following statements is/are true? Valid taxonomic group if it is monophyletic (a) As depicted above the tree, the term “Anthropoids” is a valid taxonomical group (b) “Monkeys” are not a valid taxonomical group (c) “Monkeys” would be a valid taxonomical group if it also included tarsiers (d) a and b are correct (e) a and c are correct 14. You are constructing a phylogeny of a hypothetical group of insects. Several of the species have a pattern of four veins on the forewing while another group of species has a pattern of six veins. The three outgroups in your analysis all have a pattern of six veins. From this you can conclude: (a) the trait of having six veins is a synapomorphy (b) the group of species with six veins are more closely related to each other than they are to the any of the species with four veins (c) the trait of having four veins is a synapomorphy (d) a and b are correct (e) b and c are correct 15. According to the tree above, which of the following statement(s) is/are accurate? (a) species D, F, I, and A form a monophyletic group (b) species E, D, F form a paraphyletic group (c) Species C is equally related to species A and E (d) All of the above 16. Based on information provided in the tree above, which of the following statement(s) is/are accurate? (a) the frog, dog, turtle and lizard form a monophyletic group (b) the fish is the ancestor of the rest of the species in the tree (c) frogs are older than birds (d) all of the above (e) none of the above 17. Male pipefish have a brood pouch in which they carry and protect developing embryos. The gene patristacin plays a major role in the formation and function of the pouch. An evolutionary analysis revealed that patristacin is involved in liver and kidney function in all other fish (other male fish do not produce a brood pouch). This provides an example of: Where a new function takes over for an old function Co-option and recruitment are the same thing (a) co-option (b) irreducible complexity (c) group selection (d) tradeoffs Chapter 9 Coalescence: The process by which, looking back through time, the genealogy of any pair of homologous alleles merges in a common ancestor Maximum Parsimony: A statistical method for reconstructing phylogenies which identifies the tree topology; minimizes the total amount of change or the number of steps required to fit the data of the tree Maximum Likelihood: Approach used to estimate parameter values of a statistical model; they are used in phylogeny reconstruction to find the tree topologies that are most likely given a precise model for molecular evolution Purifying Selection: Negative Selection Bootstrap Value: Statistic for estimating the strength of evidence that a particular node on a phylogeny can exist Synonymous Substitution: Mutations that do not alter the amino acid sequence of a protein; since there is no effect, it is less prone to selection Replacement Substitution: Nonsynonymous; mutations that alter the amino acid sequence of the protein; can affect phenotype and are subject to selection Molecular Clock: A method used to determine time based on base pair substitutions; use the rates of molecular change to deduce the divergence time between two lineages in a phylogeny, for example. 1. Proponents of the Neutral theory of molecular evolution believe that most substitutions are fixed by . (a) sexual selection (b) natural selection (c) genetic drift (d) none of the above 2. The ratio of the rate of nonsynonymous to synonymous mutations (dN/dS) is equal to one if a gene is evolving . A dN/dS ratio greater than one indicates that the gene is evolving . (a) neutrally; purifying selection (b) under positive selection; neutrally (c) neutrally; under positive selection (d) under purifying selection; neutrally (e) under purifying selection; under positive selection 3. Synonymous mutations . The rate of synonymous substitutions in a gene serves as an estimate of the rate of . (a) change the amino acid sequence of the protein; neutral evolution by genetic drift (b) do not change the amino acid sequence of the protein; evolution by natural selection (c) change the amino acid sequence of the protein; evolution by natural selection (d) do not change the amino acid sequence of the protein; neutral evolution by genetic drift 4. A substitution that changes one of the first two bases in a codon (e.g. AGT) is called a mutation and will . (a) synonymous mutation; not change the resulting amino acid (b) nonsynonymous mutation; not change the resulting amino acid (c) nonsynonymous mutation; change the resulting amino acid (d) synonymous mutation; change the resulting amino acid (e) frameshift mutation; change the resulting amino acid 5. The codon TCA codes for serine. If a new mutation occurred that replaced the “A” with a “T,” this mutation would be and its fate would most likely be determined by . (a) nonsynonymous; genetic drift (b) nonsynonymous; natural selection (c) synonymous; genetic drift (d) synonymous; natural selection 6. New nonsynonymous mutations: (a) occur randomly with respect to fitness (b) are greater in number in a large population than a small population (c) are most often deleterious (d) all of the above 7. The synonymous substitution rate is often assumed to represent: (a) the rate of evolution by natural selection (b) the rate of evolution by genetic drift (c) the strength of purifying selection (d) the rate of adaptive evolution 8. Phylogenetic studies of mammals that used molecular clock estimates demonstrate that: (a) the largest peak in diversification rate occurred before dinosaurs went extinct (b) the largest peak in diversification rate occurred around the time dinosaurs went extinct (c) the largest peak in diversification rate occurred within the last 20 million years (d) mammals have diversified at more or less the same rate over time 9. Please explain why homoplasy is particularly problematic in the construction of molecular phylogenies from DNA sequence data. 10. Please explain why the average rate of evolution differs between introns and exons, and why this is important for choosing genetic markers to be used in phylogeny construction. • Introns are normally cleaved off and not shown in the protein, therefore, a non-coding region can be under evolution but show no effect • Exons are in the coding region and therefore, are subject to selection if a nonsynonymous (deleterious) mutation occurs, but will most likely be lost due to genetic drift 11. You are studying the source of new virus that has recently infected humans. You suspect that the virus was transferred from other primates (they exhibit a similar infection), specifically chimpanzees, gorillas, or orangutans. You sample blood from several infected humans and sequence some viral genes. You then build a phylogenetic tree with the human sequences and all the known strains from each primate. Draw a hypothetical phylogenetic tree that would suggest that the virus came from gorillas, and this transfer occurred twice independently. Label chimp sequences (c), gorilla (g), orangutans (o), and humans (h). H and g should share a common ancestor 12. In 2002, Trask et al. published a study showing that a high frequency of HIV transmissions in Lusaka, Zambia occurred between marriage partners. Specifically, they studied a cohort of married couples where, at the beginning of the study, one partner was infected and the other was not. Later, the uninfected partner became infected. If you were doing this study, how could you use phylogenetic methods to determine whether the newly infected individual was likely infected by his/her partner? Briefly describe your study design and results that would support and results that would refute (you can use drawings if you wish) the partner-partner transmission scenario. 13. Balancing selection tends to coalescence times because in the population. a. increase, older alleles are maintained b. decrease, new alleles are fixed rapidly c. not affect, no single allele is favored d. increase, new alleles are fixed rapidly e. none of the above 13. A few years ago, the avian influenza virus (H5N1) swept from Asia, across, Russia, to Europe. Nigeria was the first African country to report detection of the virus in chickens. The phylogeny below depicts the relationships between H5N1 from Nigeria and samples from other parts of Asia and Europe. Samples from Nigeria are labeled either as Lagos or northern Nigeria. Given the phylogeny below, what is the minimum number of times H5N1 was introduced to Nigeria? 3 monophyletic trends 14. This is a true story. A gastroenterologist from Lafayette, LA was accused of infecting his girlfriend with HIV by injecting her with a syringe containing HIV infected blood from one of his patients. The victim (the girlfriend) claimed that the doctor injected her during an argument. However, the victim was also a nurse, and so conceivably may have had contact with HIV infected blood through her job. Given below is a phylogenetic tree constructed using HIV sequences from the victim (denoted with a “V” in the label), HIV sequences from the patient whose blood was allegedly in the syringe that the doctor injected into the victim (denoted by a “P” in the label), and HIV sequences representing much of the diversity of HIV strains from the Lafayette area during the time of the incident (denoted by “LA” in the label). Is the tree to the right consistent with the prosecution’s case that the doctor injected the victim with HIV infected blood from his patient? Why or why not? • Yes, there is a shared ancestor between the strain of the nurse and the strain of the patient that is recent 15. Please explain why synonymous sites typically evolve faster than nonsynonymous sites. • Most new mutations that change a protein sequence will be deleterious and will be removed by natural selection • Synonymous sites evolve more quickly due to drift because they are not constrained • Nonsynonymous changes the amino acid sequence o Normally a negative effect because most things in your body work really well o Almost everything is fixed by natural selection o Lower evolution rate because most changes are deleterious and will be removed from the population o Evolution wouldn’t have a chance to change anything o The more important a coding region is the less likely it is to change o Positive selection will happen rapidly, but is SUPER RARE • Synonymous is just drift o Doesn’t change phenotype o Drift is a better 16. What is coalescence? What is the effect of balancing selection on coalescence times? What is an example of a gene with a long coalescence time, and why is that gene under balancing selection? • Coalescence: o Looking back in time and tracing the common ancestor of the allele • The farther back in time you go the more mutations might have occurred because there was more time for mutations to accumulate • Balancing o Natural selection almost always removes variation o Human blood groups and MHC are 2 examples 17. Explain how phylogenetics supported the innocence of the doctors and nurses accused of transmitting HIV to children in a Libyan hospital. • The common ancestor of the children’s viral strain predated the doctors’ arrival 18. A phylogeny of mammals based on DNA sequences of alpha-globin and cytochrome oxidase I might yield different topologies because: • Cytochrome oxidase evolves more rapidly so that evolutionary reversals may lead to homoplasies. 19. What parts of the genome are most likely to show “clock-like” evolution? Why? 20. What are kA and ks? What patterns would you expect kA and ks to show if a gene was undergoing positive selection? Purifying selection? Neutral evolution? • KA = Number of replacement substitutions in replacement • KS = Number of synonymous substitutions per synonymous site • Purifying: o KA < KS • Neutral: o KA = KS • Positive Selection: o KA > KS 21. Explain the evidence for positive selection on the gene FOXP2 in the lineage leading to modern humans. • In all other mammals, the FOXP2 gene is identical • In humans, 2 amino acids are changed, causing us to have the ability to have speak 22. You are studying the evolution of a gene involved cuticle pigmentation in Drosophila. Comparing two species, you collect the following data: Fixed differences (between species) Polymorphisms (within species) Synonymous 10 20 Non-synonymous 5 10 Is natural selection acting on this gene? Neutrally Dn/Ds compared to Pn/Ps 5/10 = 10/20 (neutral selection) 0/10 10/20 (purifying/directional selection) 10/10 10/20 (positive selection) 23. In the tree below, the numbers in red represent bootstrap values. Which of the following statements has the best statistical support? a. Sheep are more closely related to pigs than to dogs b. Dogs are more closely related to sheep than to humans c. Guinea pigs are more closely related to dogs than to mice d. Humans are more closely related to chimps than to owl monkeys Chapter 10 Paralog: Genes related by duplication within a genome; evolve new functions, even if these are related to the original one. Ortholog: Genes in different species that evolved from a common ancestral gene by speciation; retain the same function in the course of evolution normally. Gene Recruitment (Co-Option): The placement of a new gene under a foreign regulatory system. Such re-arrangement of pre-existing regulatory networks can lead to an increase in genomic complexity. This reorganization is recognized as a major driving force in evolution. 1. Some evolutionary biologists argue that changes in the regulation of genes rather than changes in the coding sequence are more likely to be involved in adaptation. Which of the following statements forms part of the basis for this argument: (a) coding sequence changes are constrained because most genes perform multiple functions (b) regulatory mutations are more likely to occur than coding sequence mutations (c) regulatory changes likely affect all processes that a gene is involved in (d) all of the above 2. Some evolutionary biologists argue that, overall, regulatory mutations are more likely to result in adaptation than changes in the protein coding sequence of genes. Considering the logic underlying their argument, in which case below would this expectation not apply to a particular gene involved in adaptation: a the gene is involved in multiple functions b the gene is involved in only one function c the gene is expressed in different tissues d the protein encoded by the gene performs an important function 3. Gene duplication: (a) result in genes that are paralogs (b) leads to functional redundancy (c) can result in one of the copies gaining a new function (d) all of the above 4. Which of the following statements accurately describes Hox genes: (a) they code for traits such as legs or wings in the developing embryo (b) their expression gives positional information to other genes (c) they are transcription factors (d) a and b are correct (e) b and c are correct 5. Which of the following statements about venom evolution is accurate? (a) the earliest venoms evolved after fangs and other parts of the venom delivery system (b) the earliest venoms evolved before fangs and other parts of the venom delivery system (c) all reptiles produce venom even if they do not have fangs or other components of the venom delivery system (d) b and c are correct 6. Male pipefish have a brood pouch in which they carry and protect developing embryos. The gene patristacin plays a major role in the formation and function of the pouch. An evolutionary analysis revealed that patristacin is involved in liver and kidney function in all other fish (other male fish do not produce a brood pouch). This is an example of: (e) gene recruitment (f) irreducible complexity (g) gene duplication (h) antagonistic pleiotropy 7. Longer hind limbs in crickets appear to result from what type of perturbation to a patterning network: (a) blocked pathway (b) change in signal level of pathway element (c) deployment of a patterning pathway in a new location (d) deployment of a patterning pathway at a new time 8. Based on the development of snakes, which lack forelimbs, hypothesize about how you could genetically engineer a chicken that lacks wings. • By expressing limb expanding genes to the neck or legs in the embryo. 9. Please describe Lamb et al.’s hypothesis for the evolution of the vertebrate eye. 10. Describe the prevailing hypothesis (Lamb et al) for the steps involved in the evolution of vertebrate eyes. 11. How did crotamine evolve? What is the evidence for this? • Beta-defensins evolved into crotamine via a duplicated gene that experienced regulatory mutation effecting where it was made (pancreasmouth) • It under went further mutations in shape and took on new functions like damaging muscles 12. Give an example of an evolutionary change that occurred through a change in a protein coding sequence. Give an example of an evolutionary change that occurred through a mutation in a regulatory sequence. Why might evolution be more likely to occur through changes in protein coding sequences? Why might it be less likely to occur this way? 13. What are opsins? Describe how the study of opsins supports the hypothesis that the common ancestor of cnidarians and bilaterians had the ability to sense light • Opsins: molecule that sits on the photoreceptors of the eyes; is hit by the light entering eye; mediates conversion of a photon of light into electrochemical signal • Discovered species of cnidarians have opsin genes in sensory neurons • When Cnidarians and Bilaterians diverged, cnidarians inherited both types of opsins, and bilaterians evolved further into new forms 14. Describe the evolution of lenses in vertebrate eyes • Opsins evolve from serpentine proteinsOpsins duplicate into two forms C and r-likeAnother duplication greats re-opsins and RGR/Go opsins in bilateriansBilaterians now carry 3 types of opsinsC-opsins evolve into primary photo-receptors while the other 2 types aid in sight 15. In the tree below, grey boxes show clades of dart frogs that are toxic, and the ants show the evolution of diet specialization. What is the evidence that the evolution of toxicity is associated with the evolution of diet specialization? • May aid in the development of toxicity however some toxic frogs are present without a diet containg ants. 16. Use the distance matrix below to reconstruct the best –fit phylogenetic tree via UPGMA: B C D E A 1 3 5 7 B 2 3 4 C 2 5 D 4 E C D E A+B 2.5 4 5.5 C 3 5 D 4 E C+D E A+B 3.25 5.5 C+D 4.5 E Chapter 13 Phylogenetic Species Concept: Species are the smallest possible groups whose members are descended from a common ancestor and who all possess defining or derived characteristics that distinguish them from other such groups. Biological Species Concept: Species are groups of actually interbreeding natural populations that are reproductively isolated from other groups. Allopatry: Occurs when populations are separated non-overlapping geographic areas. Sympatry: Occurs when populations are in the same areas. Reproductive Isolation: Occurs when reproductive barriers prevent reproduction between populations. Prezygotic Reproductive Barriers: Aspects of genetics, behavior, physiology, or ecology of a species that prevent the sperm of 1 species from fertilizing the egg of another species; reduced zygote formation. Postzygotic Reproductive Barriers: Aspects of genetics, behavior, physiology, or ecology of a species that prevent fertilized zygotes from successfully developing and reproducing themselves. Gametic Incompatibility: Occurs when sperm or pollen from a species fails to penetrate/fertilize the egg of another. Reinforcement: Increase in reproductive isolation between populations through selection against hybrid offspring. Ring Species: A connected series of populations where each one can interbreed with neighboring species that have diverged sufficiently across their ranges so eventually they too are different to breed. Allopolyploidy: Polyploidy resulting from interspecific hybridization; hybrid becomes distinct sexually; reproducing asexually species 1. In the monkeyflowers studied by Bradshaw and Schemske reproductive isolation results from: (a) gametic incompatibility between pollen and ovule (b) sterility of hybrid offspring (c) color preferences of hummingbirds and bees (d) asynchrony in time in which plants reach reproductive maturity 2. Which of the following would provide evidence for reinforcement? (a) Premating isolation between the two species is higher in areas where they are sympatric vs. areas where they are allopatric; postzygotic isolation is strong in all crosses (b) Postzygotic isolation between two species is higher in areas where they are sympatric vs. areas where they are allopatric; premating isolation is the same in allopatric and sympatric populations (c) Premating isolation between the two species is higher in sympatry than allopatry; there is no postzygotic isolation in any cross (d) Both a and c 3. Many butterflies in the genus Heliconius are mimetic, which means that they closely mimic the wing patterning and color of highly poisonous species even though they themselves are not poisonous. This is a benefit because many predators (such as birds) learn to avoid poisonous species by identifying their wing patterns/colors. Some closely related Heliconius species mimic different poisonous species. Although they can successfully hybridize and produce viable/fertile offspring that have high fitness in the laboratory, the hybrids are intermediate in wing patterning/color and are not good mimics. Consequently, they have low fitness in nature. This is an example of: (a) Intrinsic postzygotic isolation (b) Haldane’s rule (c) Extrinsic postzygotic isolation (d) Habitat isolation (e) Prezygotic isolation 4. Under the biological species concept: (a) a species represents a group of interbreeding (or potentially interbreeding) populations that are reproductively isolated from other such groups (b) species are evolutionary independent units (c) different species do not exchange genes (d) a and c are correct (e) a, b, and c are correct (Phylogenetic B and C; Biological A) 5. You are studying a potential case of incipient sympatric speciation involving two morphs of a cichlid fish in a crater lake that feed at different depths and differ in morphology. If true, which of the following statements would make sympatric speciation more likely (or at least possible)? 1. The two morphs specialize on different food types; matings between the morphs produce offspring that are intermediate and can efficiently utilize both food types. 2. The two morphs feed on different food types and there is strong disruptive selection operating such that individuals that are intermediate are very strongly selected against (basically none survive). 3. Mating occurs in the area of the lake where each morph feeds. Also, females choose males based on jaw morphology, preferring males that have the same jaw morphology as the female. 4. The two morphs feed at different depths, but both morphs come to a rocky area near the shore to mate. Females prefer to mate with males of the other morph. 5. Genes for habitat preference and jaw morphology are very tightly linked to one another on a chromosome. (a) 1, 2, 3, 4, 5 (b) 1, 4 (c) 2, 3, 5 (d) 2, 3, 4, 5 (e) 1, 5 6. Extrinsic postzygotic isolation is most likely when: e parental populations are adapted to similar environments f parental populations are adapted to divergent environments g Genetic drift is strong h Gene flow between parental populations is high 7. The process of reinforcement requires: (a) genetic variation for mating discrimination (b) preexisting postzygotic isolation (c) preexisting prezygotic isolation (d) a and b (e) all are correct 8. Which of the following conditions are thought to be necessary for sympatric speciation to occur? (a) Disruptive selection (b) Stabilizing selection (c) Positive assortative mating (d) A and c are correct (e) B and c are correct 9. Which of the following is required to designate populations as separate species under the phylogenetic species concept : (a) each population forms a monophyletic group (b) the populations do not exchange genes (c) there is strong reproductive isolation between the populations (d) a and b are correct (e) a, b, and c are correct 10. Which of the following scenarios would result in a different species designation for two populations under the phylogenetic and biological species concepts: (a) there is no gene flow; all hybrids are sterile (b) each population forms a monophyletic group; populations mate during different seasons (c) there is no gene flow; fertile hybrids are produced when bred in the lab (d) each population is paraphyletic; fertile hybrids are produced when bred in the lab 11. You are studying speciation in crickets. You find that males and females from different populations will mate, but few eggs get fertilized. This is an example of what type of reproductive isolating barrier: (a) premating (b) postmating-prezygotic (c) intrinsic postzygotic (d) extrinsic postzygotic 12. The idea that different giraffe populations represent six different species is based on: (a) the biological species concept (b) the general lineage species concept (c) the phylogenetic species concept (d) all of the above 13. If two plant species with different numbers of chromosomes interbreed: (a) the offspring will be unable to produce sexually (b) the offspring might be able to produce asexually (c) the offspring will be capable of breeding with one of the parental species but not the other (d) none of the above 14. Describe a situation where biologists using the phylogenetic species concept and the biological species concept would reach different conclusions on whether two populations represent different species. • Humans and Primates • Humans can breed with any population of humans 15. Please provide a real or hypothetical example of a (a) premating, (b) postmating-prezygotic, (c) intrinsic postzygotic, and (d) extrinsic postzygotic reproductive isolating barrier. • Premating: Physical/neurological difference from other species causes inability to breed • B – Sperm is unable to fertilize the egg • C – Hybrid inviability (dies before/after birth) • D – Able to reproduce, but can’t get mate 16. Explain the Dobzhansky-Muller model for the evolution of reproductive isolation. What is the evidence that multiple Dobzhansky-Muller incompatabilities are involved in speciation in Drosophila? • Took Drosophila related species; paired males and females of different species; observed if they produced any hybrids. 17. Why is sympatric speciation rare? Difference in phenotypes reduces the chances of breeding between populations. 18. What is the evidence for sympatric speciation in crater lake cichlids? 19. Explain Haldane’s rule. • States that if a species’ hybrids of one sex are only inviable or sterile, the afflicted sex is much more likely to be heterogametic (XY) than homogametic (XX) • Takes more than one to make hybrids sterile • Things must occur on X and W • X linked might not have something that is compatible Chapter 14 1. Which of the following factors contribute to species diversity observed at a particular point in time: a. Extinctions b. Originations c. Initial Diversity d. All of the Above