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Answer Key – LO 1.2 Which of the following is NOT a way in which natural selection affects the distribution of phenotypes? A) Directional selection Chance.

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Presentation on theme: "Answer Key – LO 1.2 Which of the following is NOT a way in which natural selection affects the distribution of phenotypes? A) Directional selection Chance."— Presentation transcript:

1 Answer Key – LO 1.2 Which of the following is NOT a way in which natural selection affects the distribution of phenotypes? A) Directional selection Chance events Stabilizing selection Disruptive selection Directional selection is most common wen a population’s environment changes or when members of a population migrate to a new habitat with different environmental conditions than their former one. Stabilizing selection acts against extreme phenotypes and favors intermediates variants. Disruptive selection occurs when environmental conditions favor individuals on both extremes of a phenotypic range over intermediate phenotypes. An example of directional selection is that black bears in Europe increase with size during the colder weather, only to decrease during the warmer weather. An example of stabilizing selection is the birth weights of most human babies lie in the range of 3-4 kg; babies who are much smaller or larger suffer higher rates of mortality. An example of disruptive selections is black- bellied seed cracker finches have two different beak sizes for cracking different types of seeds.

2 ANSWER KEY- LO 1.3 All members of an isolated village were genotyped for a particular RFLP. Of the 1000 individuals, 200 were homozygous for the presence of the restriction site, 700 were heterozygous, and 100 were homozygous for its absence. What is the frequency of the "restriction site present" allele, p? 0.45 B) 0.9 C) 0.2 D) 0.55 E) None of the above (A) How can the Hardy-Weinberg principle of genetic equilibrium be used to determine whether this population is evolving? (B) Identify a particular environmental change and describe how it might alter allelic frequencies in This population. Explain which condition of the Hardy-Weinberg principle would not be met. The Hardy-Weinberg principle can be used to determine if the population is evolving by a ratio. If the ratio of the dominant genotype to the recessive is 3:1 the population can be looked at as evolving. There are several environmental changes that could alter allelic frequencies in a population, thus causing certain conditions of the Hardy-Weinberg principal not to be met. An example of an environmental change would be the population decreasing in size due to a natural disaster. This would disrupt the Hardy-Weinberg condition of the population being large. Environmental changes can also cause mutation which would disrupt the Hardy-Weinberg condition. If the population changed due to Bottleneck or founder’s effect, then the population would become small and allele frequencies would change causing the principal not to be met.

3 L.O. 1.4 M.C. Question: From left to right in the picture shown, what 3 types of selection are shown? A) stabilizing, diversifying, directional B) directional, diversifying, stabilizing C) diversifying, directional, stabilizing D) directional, stabilizing, diversifying Learning Log/FRQ-style Question: Identify and describe each type of selection and provide an example of each. Directional selection is when one of the extremes is chosen, such as when a typically beige type of snail has offspring that are dark brown due to the rocks they live on changing from a lighter color to a dark brown. Stabilizing selection is when the middle trait is chosen, and this could result in the beige snails having almost all beige offspring due to all the rocks in their environment being beige. Diversifying selection is when both the extremes are chosen, so the snails would be either white or dark brown, and that could be caused by the rocks being brown with big white spots on them. Directional selection is when on of the extreme cases is chosen, so the graph goes to one side. Stabilizing is when the middle trait is shown, so the graph stays in the middle and gets slimmer. Diversifying selection is when both the extreme cases are chosen, so the middle of the graph drops and the two sides raise up.

4 Answer Key - LO 1.5 M.C. Question: A large assemblage of land snails is subdivided into two populations (A and B) by a river that effectively isolates the populations for an indefinitely long period. From an evolutionary standpoint, which of the following is the LEAST likely to occur in the two populations? A) Populations A and B will eventually differ in their ecological requirements. B) Population A may ultimately breed at a different time of the year that population B does. C) Population A may undergo instantaneous speculation by the doubling of its chromosome numbers (polyploidy). D) Under laboratory conditions, cross-fertilization between members of the two populations may be successful even after a long period of geographical separation. E) The two populations may become morphologically very dissimilar. Learning Log/FRQ-style Question: Suppose a population of mice live on the side of a volcanically active mountain. The population of mice has a dominant gene for white fur, and a recessive gene for black fur. At the moment the mice are hunted at the same rate; what would the population look like ten months after a volcanic eruption? Why? What kind of selection is this? Draw and label a graph depicting the two populations. Label the original population and the population after natural selection. Example of a given diagram (labels included) : The recessive gene of black fur would be naturally favored because these mice better fit their new environment. The new, dark, habitat created by the volcanic eruption will hide the mice from predators and white mice populations with decline. This is know as disruptive selection; the environmental factors changed and favored one phenotype over another.

5 ANSWER KEY LO 1.6 M.C. Question: Supposed in a large colony of isolated beetles, where the allelic frequencies used to be equal a few generations ago, the frequency of the recessive allele was now nearly double that of the dominant allele, and the frequency is still increasing. Which of the following is most likely true concerning the scenario stated above? A) It follows the Hardy-Weinberg equation because the population is large enough to counteract the climbing recessive allelic frequency. B) Genetic drift is occurring in the population. C) Something recently has changed in their environmental surroundings that has caused natural selection to favor the recessive allele over the dominant allele. D) The beetles with the dominant allele will emigrated out of the colony. a)Discuss the difference between the founder effect and the bottleneck effect and b) describe how natural selection is more “predictable” than genetic drift The bottle neck effect is when you have destruction of the environment that results in a few of the population remaining to repopulate, and they may not be representative of the original population. The founder effects has similar effects, except that instead of an environmental disaster, it results from a portion of the original population settling in a different area. Natural selection is more predictable because the environment weeds out those who are not as best fitted (reproduction of the fittest). Genetic drift, however, happens completely by chance.

6 L.O. 1.7 Which of the following would not cause genetic drift in a population?
a) Immigrants from Asia coming to a town on the west coast of the US b) Mating in a population of butterflies is dependent on the most colorful wings c) A population squirrels is very large with several traits for tail shape d) A drought occurs that allows only plants with water conservation techniques to survive e) A mutation occurs in a population of rabbits which causes more padded feet for crossing snow FRQ-Style Question: Name three factors involved in achieving Hardy Weinberg equilibrium and explain how it may impact genetic drift. Describe how these influences on genetic drift may lead to evolution in a population. A factor which may disrupt equilibrium is the occurrence of selection for a specific trait in the population. If one trait is favored by the environment, then it will alter the gene pool as this will impact the potential for reproduction and thus the frequency of the alleles which shall lead to drift in future generations. The equilibrium may also be hampered by the occurrence of gene flow within the population. The movement of organisms in and out of the population would alter the allelic frequency and may lead to further drift in later generations. Another influence on equilibrium is the requirement of maintaining a large population to prevent genetic drift. This is due to the fact that a larger gene pool would minimize any alteration to the gene pool and will provide greater stability for future generations. These instances of genetic drift would cause alterations to the gene pool of a population and act as a mechanism of evolution. Evolution occurs through drift as the population begins to express a certain trait more frequently, and speciation may occur for the population expressing this gene leading to a new step of evolution for the population.

7 Answer Key – LO 1.8 M.C. Question: A scientist studying birds on two adjacent islands discovers that the Bingle Bird, which has a short and strong beak, on the Island of Seuss and the Hephalump Bird, which has a long and narrow beak, on Winnie Island have a common ancestor, but can no longer reproduce together. Which of the following predictions correctly explains this phenomena by using a theory that incorporates the Bottleneck Effect and the Founder Effect? A drought on the Island of Seuss caused only the birds with short and strong beaks that could open hard seeds to be able to survive on the island, while the birds with long and narrow beaks had to find another habitat where they could feed on flowers. The extended separation of the birds led to the development of two different species. A tsunami destroyed Winnie Island, killing many birds and forcing several of the ancestral birds to move to the Island of Seuss. By chance, the alleles for a short and strong beak were represented more on the Island of Seuss and the alleles for a long and narrow beak were represented more on Winnie Island. Eventually, the separated populations became too genetically different to reproduce. Winnie Island has many plants with long flowers from which it is easier to obtain nectar if a bird has a long and narrow beak. The food source on the Island of Seuss is mostly hard seeds that are easily opened with a short and strong beak. The once homogenous population went through natural selection to create two new populations that were better suited for the food sources. Foreign predators were introduced on the Island of Seuss and Winnie Island. The predators of the Island of Seuss preferred to eat birds with long and narrow beaks while the predators on Winnie Island ate birds with short and strong beaks. The abundant predators caused their respective prey to become extinct, creating a population of short and strong beaked birds on the Island of Seuss and a population of long and narrow beaks on Winnie Island. FRQ: Darwin’s research on finches in the Galapagos Islands led to his theory of evolution and its mechanism, natural selection. Describe TWO mechanisms of genetic drift and explain how each can result in a new species. Migration can be one mechanism of genetic drift. Members of a species can become isolated from the population due to geography, and the new colonizing population represents alleles in different ratios than represented in the original population. This causes genetic drift and can eventually result in populations that are so genetically different that they can no longer reproduce. Another mechanism of genetic drift is the bottleneck effect. When a natural disaster like a tsunami or a forest fire occurs, random members of a populations are killed. The surviving individuals represent alleles in different frequencies than they were in the original population. The population can have such different alleles that the gene pool shifts entirely and a new species evolves.

8 L.O. 1.9 M.C. Question: Analysis of forelimb anatomy of human, bats, and whales shows that humans and bats, and whales shows that humans and bats have fairly similar skeletal structures, while whales have diverged considerably in the shapes and proportions of their bones. However, analysis of several genes in the species suggests that all three diverged from a common ancestor at about the same time. Which of the following is the best explanation for these data? a. Humans and bats evolved by natural selection, and whales evolved by Lamarckian mechanisms? b. Evolution of human and bat forelimbs was adaptive, but not for whales. c. Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy. d. Genes mutate more rapidly in whales than in humans or bats. e. Whales are not properly defined as mammals. Describe the modern theory of evolution and show how it is supported by evidence from two of the following areas: population genetics, molecular biology, and comparative anatomy and embryology. In modern terms, evolution is a change over time in the genetic composition of a population. In molecular biology, comparisons of nucleic acid sequences are often used. If the species are very closely related, the sequences likely differ at only one or a few locations. In contrast, comparable nucleic acid sequences in distantly related species usually have different bases at many sites and may even have different lengths. The arms, forelegs, flippers, and wings of different mammals are homologous structures that represent variations on a structural theme that was present in their common ancestor. One kind Of homologous structure is vestigial organs, structures of marginal, if Any, importance to the organism. Vestigial organs are remnants of Structures that served important functions in the organism’s ancestor.

9 Answer Key: LO 1.10 Learning Log/ Free Response Question:
MC Question: All of the following pairs of structures are homologous structures except which? The wings of a bat and the wings of a butterfly The arm of a human and the leg of panther The hooves of a camel and the hooves of a sheep The scales on the foot of a chicken and the scales on a lizard Learning Log/ Free Response Question: A paleontologist on an expedition in Hong Kong finds the remains and fossils of an extinct species of supposed city dwelling rodent. The scientist expects to find organisms of common ancestry in an area close to New York city. Explain why the scientists prediction is either valid or invalid and describe the scientific evidence that supports your reasoning. The paleontologist’s prediction is invalid; the extinct species of rodent would most likely share common ancestry with other rodent species in the surrounding area. Based on evidence supported by biogeography, closely related species tend to be located in the same geographic region, whereas the same ecological niches in distant regions are occupied by very different species even though they may be similar looking.

10 ANSWER KEY– LO 1.11 M.C. Question: Which of the following is not a scientific argument for the theory evolution. Chimpanzees and Humans share 98% of their DNA. B) Fossils of species with both lungs and gills have been found in Nunavut. C) Africans and Asians have similar physical features. D) Species in different parts of the globe with similar environments share many behaviours/ physical features. Learning Log/FRQ-style Question: How can homologous structures and biochemistry be used to explain the changes of organisms over time? Use specific examples. The evolution of organism overtime is an effect of changes in habitat, changes in food, geographical isolation, etc. In convergent evolution, genetically unrelated species share a set of common traits. For example, sharks and dolphins both have flippers, yet they belong to a different biological class. This is due to their shared food source and habitat. Similarly, similar genetic makeup serves in divergent evolution to show how two genetically close species can have different features. For example, the finches of the Galapagos all have different beaks because of their different food sources and habitats (they were isolated geographically from each other- a natural hindrance to reproduction/ genetic variation). However, their strikingly similar DNA shows that they share a common ancestor.

11 ANSWER KEY-LO 1.12 M.C Question: If Darwin had been aware of genes, and of their typical mode of transmission to subsequent generations, with which statement would most likely have been in agreement? Somehow if natural selection can change one gene’s frequency in a population over the course of generations then, given enough time and enough genes, natural selection may cause sufficient genetic change to produce new species from old ones If an individual somatic cell genes change during its entire lifetime, supposedly making it more fit, then it will be able to pass these genes on to its offspring. If an individual’s acquires new genes by engulfing, or somehow being infected by, another organism, then a new genetic species will possibly be the result. A single mutant gene in a single gamete will, if perpetuated, will produce a new species within just two generations. Of all mutations that occur, why do only a small fraction become widespread in a gene pool? Most mutations occur in somatic cells that do not produce gametes and so are lost when the organism dies. Of mutations that do not occur in cell lines that produce gametes, many do not have a phenotypic effect on which natural selection can act. Others have a harmful effect and are thus unlikely to spread in a population from generation because they decrease the reproductive success of their barriers

12 Answer Key- L.O. 1.13 There are 100 students in a class. Ninety-six did well in the course whereas four blew it totally and received a grade of F. In the highly unlikely event that these traits are genetic rather than environmental, if these traits involve dominant and recessive alleles, and if the four (4%) represent the frequency of the homozygous recessive condition, calculate the frequency of the recessive allele. a.) 40% c.) 20% b.) 4% d.) 2% *We know that the 4% represent the homozygous recessive condition, therefore, we know that q2 = 0.04 (which is 4%) and √0.04 = .2 (q) .2 = 20% A large population of Biology teachers have 396 red-sided individuals and 557 tan-sided individuals. Red is completely recessive. Calculate the following: a.) The allele frequencies of each allele. b.) The expected genotype frequencies. c.) The number of heterozygous individuals you would predict. d.) The expected phenotype frequencies. a.) First, calculate the total number of people: = 953. Recessive (q2 )=all red. 396 ÷ 953 = (q2 ) √0.416 = recessive p-q= – = dominant b.) AA= p2 (0.355)2 = Aa= 2pq = 2(0.355)(0.645) = 0.458 aa = q2 = (0.645)2 = 0.416 c.) (Aa calculated in part b) × 953 (total population) = 436 teachers d.) A phenotype= = 0.584 a phenotype= (calculated in part b)

13 Answer Key- LO 1.14 Learning Log/FRQ-style Question: Among the varied forms of life on earth, many organisms share common life processes despite other enormous functional and taxonomical differences. Identify and describe two processes shared across multiple kingdoms, examine their differences between kingdoms while listing at least two of the taxonomical kingdoms that share them. Light dependent reactions of photosynthesis are instrumental in the conversion of environmental sunlight, water, and carbon dioxide into sugars that can be hydrolized for energy. In plants, such reactions occur in the thylakoid membrane within the membrane-bound chloroplast, but in photosynthetic bacteria light dependent reactions take place in the plasma membrane of the cell. Sexual reproduction is the method developed by eukaryotes to introduce genetic diversity into populations by combining the genetic materials of partnered organisms into unique offspring. Although performed in some capacity in animals, plants, and fungi, sexual reproduction has many variations. In animals, the process typically occurs when two diploid organisms combine their respective haploid gametes to create a new, genetically unique, diploid organism. In plants and fungi, however, this can occur differently such as in the case of self-fertilization, the sexual generation of an organism using only the sex organs of a single parent. Additionally, plants, fungi, and animals often exhibit varying life cycles with prominent example such as mosses existing as haploid organisms even when fully mature. M.C. Question: Which of the following characteristics is not exclusive to eukaryotic life? A) cell wall composed of either chitin or cellulose B) flagella or other external structures used in locomotion C) cytoskeleton of microtubules, microfilaments, and/or intermediate filaments D) presence of the Golgi apparatus E) genetic material wrapped into chromosomes

14 Answer Key- LO 1.15 Based on your knowledge of membrane bound organelles, which of the following statements is true? Plants are more closely related to protists than fungi Bacteria developed before protists The earliest cells were eukaryotic Animals were the last kingdom to evolve You are an evolutionary biologist comparing the genetic codes of a species of animal and a species of plant. Using conserved core biological processes or features in your answer, explain why the two species’ genetic codes are so similar. Even though the two species are dissimilar on the macroscopic level, they are both eukaryotes, and therefore share all of the structures common to eukaryotes, such as a cytoskeleton and a nuclear envelope. Animal and plant cells also use similar processes to function, like hormonal signaling and sexual reproduction. These structures and functions account for a large portion of any given organism’s genetic code, and therefore any two organisms who share these traits can be expected to have much of the same DNA.

15 Several analogous characteristics shared by all the fishes
Answer Key- LO 1.16 Which of the following would be most useful for constructing a phylogenetic tree for several fish species? Several analogous characteristics shared by all the fishes A single homologous characteristic shared by all the fishes The total degree of morphological similarity among various fish species Several characteristics thought to have evolved after different fishes diverged from one another A single characteristic that is different in all the fishes Darwin is considered the “father of evolutionary biology.” One of his contributions to the field of evolutionary biology is branching evolution, which implies the common descent of all species. Discuss one example of supporting evidence. One explanation of common ancestry is homology, which is similarity in characteristics resulting from a shared ancestry. This could be embryological, structural, molecular, or processes. For example, vestigial organs are remnants of structures that served important functions in the organisms ancestors.

16 ANSWER KEY 1.17 What can be inferred from a species that is on a clade above a specific characteristic? A) The species does not possess this characteristic. B) The characteristic was lost through natural selection and no longer possessed by the species. C) The species has evolved so that it possesses that characteristic. D) An ancestor of the species possessed this characteristic. A group of scientists predict that two types of birds evolved from one common ancestor. One species of bird was found in Alaska while the other was discovered in the northeast region of Russia. What visual diagram could be used to display the relationship between the two species in relation to their ancestor? The two birds look almost identical, but one type on bird can fly while the other cannot, and when face postzygotic barriers when scientists attempt to mate them together. Between which two classification groups does this suggest divergence occurred? What does this suggest about each bird species’ binomial? A phylogenetic tree could be used to display the divergence that occurred between the two species of a common ancestor. Because species that appear to be closely related are grouped into the same genus, these two birds have most likely evolved from the same genus into different species. This suggest that the first part of their binomials are the same because they belong to the same genus group, but that they have two different specific epithets.

17 Answer Key- LO 1.18 MC Answer
The underlying premise of cladistics and phylogeny is that Taxa that share many homologous traits are more closely related than species that share few. The more recently that taxa have branched from a common ancestor the less similar should they be in morphology and in their DNA sequences Taxa that share many derived traits are likely to be most closely related. A and C only Learning Log/FRQ Answer The more recently a species diverged the more closely related they are as they still share genetic material and the organisms will look more similar and share more DNA. If the species underwent speciation longer ago, the branches are further apart and they are more distantly related as share less genetic material as organisms have evolved over time. The more branches a phylogenetic tree has the more speciation has occurred and the less branches it has, the less speciation has occurred and the more similar the organisms are to the other organisms that share that branch.

18 ANSWER KEY- LO 1.19 M.C. Question: Which of the following would be a constructive reason for creating a phylogenetic tree for leopards? A) Several analogous characteristics shared with similar animals B) A single characteristic is shared with several animals C)Several characteristics predicted to have evolved from other species over the years D) A single characteristic shared with all leopards. Learning Log/FRQ Question: Hierarchical classification is reflected in the continuous branching of phylogenetic trees. Species that appear to be closely related are put in the same group. Name TWO ways phylogeny can be traced. Draw and label THREE of the hierarchical classifications in the correct order. Hierarchical classification involves similar species being placed in certain groups. The bottom three categories are domain also known as Eukarya, Kingdom also known as animalia, and phylum also known as chordata. Domain being the first classification, and the other two following behind. Phylogeny can be traced by relative dating and absolute dating. Relative dating is based on the layer of fossil found. Either it is older or younger. Absolute dating is also known as radiometric dating that involves isotopes. It uses the decay of radioactive isotopes to determine the age of the rocks or fossils.

19 M.C. Question: Which situation below would ENCOURAGE speciation?
ANSWER KEY- LO 1.20 M.C. Question: Which situation below would ENCOURAGE speciation? A) A large population of animals. B) Population exhibits zero net mutation. C) Animals mate randomly. D) A small population of animals. Explanation: The smaller a population is, the easier it is for it to be subject to genetic drift. This may been seen in phenomena such as the bottleneck effect or the founder effect. FRQ: To the left is a hypothetical graph following the populations of dingoes and thylacines (a striped wolf much like the dingo) on the Australian mainland. Given what you know about extinction, give TWO reasons why the thylacine might have gone extinct. Also give TWO reasons why over 4,000 years, the dingo and thylacine might have become two different species descendant from wild dogs while together on mainland Australia. The thylacine might have gone extinct due to loss of food source. If the dingoes were larger and had more muscular jaws, they could have easily stolen food from thylacines or outhunted them. They might have also been more adapted to the environment with their camouflaged light-colored coats, making it harder to hunt them than the thylacines. Two reasons they may have sympatrically speciated are sexual selection of similar partners or natural selection that favored dogs with characteristics on extreme ends of the spectrum. plain coat striped coat discouraged

20 ANSWER KEY – LO 1.21 What is a leading cause of extinction among species? Competition Natural Selection Habitat loss Increasing disease A type of modern evidence of speciation is molecular biology or blasting DNA sequences to make comparisons amongst species. This new type of data looks directly at the chromosomes to give a molecular ‘proof’ of a common ancestor. Fossils were an original piece of proof as it was visual and made a rebuttal to the proposed theory very difficult. Fossils in modern times now work as a backbone, so to speak, providing more support and evidence for the theory of evolution. It provides evidence of homologous structures between different species which can then be blasted for molecular comparison. One of Darwin’s key pieces of evidence in proving his theory of evolution was fossils. Compare and contrast modern evidence of speciation with the fundamental observation of fossils. Why were fossils originally so significant in comparison to other types of evidence and why do they still hold merit?

21 Answer Key – LO 1.22 An orange tiger is heterozygous for the white fur and orange fur gene, it mates with another tiger with the exact same genotype in the snowy mountains of Nepal. After multiple matings between tigers of the same genotype occur in the same area, the majority of offspring seem to be white. This is due to an adaptation for camouflage purposes, what kind of natural selection is this? Stabilizing selection Directional selection Disruptive selection Super selection For each type of natural selection (directional, disruptive and stabilizing), list an example, and define the type of natural selection. Give an advantages and disadvantage of one of the types of natural selection. Directional selection is when a population’s trait distribution shifts to another extreme. An example of this could be when a bird with a narrow beak mates with a bird with a wide beak, but the population needs a narrow beak to survive in the habitat. The beak distribution would shift to the narrow beak to help aid survival. Disruptive selection is when the two extreme phenotypes are mainly seen in a population, mostly homozygous dominant or recessive. Stabilizing selection is when the extreme phenotypes of a population are rarely seen, the opposite of disruptive selection. An advantage of stabilizing selection is that the unfavored genotypes could be selected against, such as an albino offspring. A disadvantage of stabilizing selection would be a decrease of the population diversity.

22 L.O. 1.23 Which of the following does not tend to promote speciation?
A) founder effect B) reproductive isolation C) natural selection D) gene flow Describe a method of speciation that can lead to the development of separate species from one common specie? Give an example. One method of speciation is allopatric speciation (geographic isolation). This occurs when a population of one species becomes physically separated by some geographic barrier. Some geographic barriers could be a mountain range, river, ocean, lake, etc. Once the species are separated they start to adapt to their new environments. The long the species are apart the more they change causing two new species to form. An example of this are the Galapagos turtles.

23 Answers- L.O. 1.24 M.C. Question: More epic and manly manes on lions have evolved to be so magnificent due to the fact that lady-lions love the scruffy, neck-scarf mane. The process by which these lion’s manes have evolved is best described as Genetic drift that changes the frequencies of the alleles for mane manliness Natural selection for sexual reproduction that maintains variations in the genes that influence sexy manes. Intersexual selection for traits, such as long flowing manes, that help males attract mates. Intrasexual selection for traits, such as long flowing manes, that help males win contests for access to females. Directional selection for traits, such as long flowing manes, that improve males’ ability catch food and stun onlookers. Suppose a population of 1000 unicorns experience a bottle neck where 50% of the population is wiped out. The original population was 55% red, 35% pink and 10% white; homo. Dominant, heterozygous, and homo. Recessive, respectively. What would likely be the most common phenotype? Least common? Why? What would likely happen to the white unicorn phenotype? The likely outcome of this bottle neck effect on this population of majestic creatures would be a shortage of the infamous white unicorn. Obviously the new populations would approximately reach 275 red unicorns, 175 pink unicorns, and only about 50 white unicorns. Red would still maintain the majority of the new population while white would likely hold the smallest representation, meaning red would be the most common phenotype while white was the least common phenotype. This is because a bottle neck effect that kills every other unicorn, assuming color has no effect on death selection, would be equally distributed across the population. If the white unicorn population where reduced to such low numbers they could have a chance of becoming extinct due to the fact that white is the recessive gene in this scenario.


25 Answer Key- L.O. 1.26 Analysis of forelimb anatomy of humans, bats, and whales shows that humans and bats have fairly similar skeletal structures, while whales have diverged considerably in the shapes and proportions of their bones. However, analysis of several genes in these species suggests that all three diverged from and common ancestor at about the same time. Which of the following is the best explanation of these data? a. Humans and bats evolved by natural selection, and whales evolved by Lamarckian mechanisms. b. Evolution of human and bat forelimbs was adaptive, but not for whales. c. Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy. d. Genes mutate more rapidly than in humans or bats. e. Whales are not properly defined as mammals. Using your knowledge of evolution, describe how the following concepts relate to Darwin’s theory of evolution by natural selection: Over reproduction of populations: more offspring than strictly necessary, some of which won’t survive. Limited resources: 2 or more organisms are in need of the same limited resource and are forced to compete for it. The stronger/ more equipped of the two will survive. Heritable variation: This is the differences among individuals in morphology, behavior, and reproductive performance that have a genetic basis. Species have the potential to produce more offspring than survive (over reproduction), leading to a struggle for resources, which are limited. Populations exhibit a range of heritable variations, some of which confer advantages to their bearers that make them more likely to leave more offspring than less well-suited individuals. Over time this natural selection can result in a greater portion of favorable traits in a population (evolutionary adaptation).

26 ANSWER KEY – LO 1.27 The most compelling evidence that RNA evolved before DNA is… A) RNA is copied by ribozymes, which evolved before DNA Polymerase. B) RNA’s single stranded coding allows it to assume different shapes to interact and adapt better. C) DNA was too complex for such primitive cells. D) RNA uses nucleotides that evolved before those in DNA. Using the picture to the right, Explain why Miller and Urey might have used certain features in their experiment and what they represent in Earth as it was billions of years ago. Every part of Miller and Urey’s experiment simulated something in the primitive Earth. The water with a flame under it would have represented the ocean being heated by the earth. This water would have evaporated. The spark emitted by the electrodes represents lightning, which scrambled atoms to bind in different ways. The gases used in the experiment are the same as what the primitive Earth’s atmosphere would have had. The cooling and condensing of the water simulates rain.

27 ANSWER KEY– LO 1.28 M.C. Question: Scientists agree that the first molecules on earth were: A) Proteins B) Nucleic acids C) RNA D) None of the above Explain the Primordial (Organic) Soup theory. Does this process involve reduction or oxidation, and why? Primordial Soup is the collection of Amino Acids and organic molecules that were used to make other compounds. The elements were all mixed together in the primitive earth, inspiring the soup analogy. This is a reduction reaction because electrons are added. (Drawings could be added to help demonstrate student’s knowledge of the subject.)

28 the same amount of UV radiation as early
L.O Miller and Urey created and performed an experiment using the Primordial Soup theory. Their experiment proved that this theory was a possibility for the origin of life. According to their experiment, which statement is false? A) Life could start through chemical reactions B) Organic compounds are capable of being made through extreme conditions C) Used known gases on primitive earth D) It was done using a closed environment like primitive earth Compare and contrast the early Earth vs. Earth today, be specific about the environment and conditions that existed. Early Earth’s atmosphere did not consist of oxygen and today’s atmosphere does. Early Earth experienced heavy amounts of UV radiation and although UV radiation is becoming a problem for us today, we do not experience the same amount of UV radiation as early Earth did. Early Earth did not initially contain any life forms, but over time life forms have evolved and have reached very complex levels today. The primeval sea consisted of only the basic monomers and today our oceans contain great life forms.

29 Answer Key- LO 1.30 Multiple Choice: RNA is most likely the first genetic material on Earth because __________. A. RNA is structurally simpler than DNA. B. RNA has simpler reproduction. C. RNA is able to assume a variety of 3D shapes mandated by nucleotide sequences. D. All of the above. Explanation: All these characteristics of RNA contribute to the hypothesis RNA was the first genetic material. The simplicity of RNA is easier for the simple organisms of the time to. Free Response Discuss the elements and conditions of early Earth and how the combination contributes to the creation of early life. reproduce. Describe the most widely accepted theory for the early evolution of life. Remember to discuss protbionts, genetic materials, and scientific experiments in the explanation Early Earth consisted of high levels of CO2, methane, ammonia, hydrogen, and hydrogen sulfide. The combination of these elements with the violent lightening storms and thick atmosphere with water vapor gave way to the creation of life. As Earth cooled, the water vapor condensed into oceans, and much of the hydrogen escaped to space. Early oceans were a solution of organic molecules from which life arose. The Miller- Urey experiment found the simulation of early Earth produced a variety of amino acids found in organisms today along with other compounds. Protobionts are also a part of the early evolution of life. Protobionts exhibit some of the properties associated with life, like simple reproduction and metabolism, as well as the maintenance of an internal chemical environment different from their surroundings. Laboratory experiments demonstrate protobionts could form spontaneously from abiotically produced organic compounds and with a membrane or membrane-like structure. Protobionts likely had RNA. The simplicity of RNA allowed protbionts to carry limited amount of genetic information. The most successful protobionts would increase in number, because they could effectively exploit their resources and pass their abilities to future generations. The RNA likely gave way to the DNA world and future generation of life on Earth. 2

30 ANSWER KEY- LO 1.32 Which of the following is the likely source of energy for the synthesis of the small organic molecules that presumably predated the first forms of life on Earth? A.) Fermentation by bacteria B.)Photosynthesis by microscopic algae C.) Lightning from constant storms D.) Shifts in ocean currents Some scientists believe that in order for ecosystems to maintain a balanced or steady state, biodiversity must be conserved. Using both classical Darwinian thought and the modern synthesis of evolutionary theory, answer the following question as it relates to biodiversity. Insects are the most diverse group of organisms on Earth. Give some possible explanations for why this diversity exists. The most diverse group of organisms by far is the Class Insecta. Their diversity is explained by a combination of certain morphological advantages and ecological associations. First of all, insects evolved wings that allowed them to escape predation and take advantage of several new ecological niches. Insects are closely associated with flowering plants and their fast radiation is closely linked to the radiation of the angiosperms as they colonized a changing land climate. Insects also have short generations, allowing them to produce many offspring in short periods of time. These factors combined in traits that conferred selective advantages and provided insects with higher fitness. Also, the higher rate of reproduction and gamete production allowed more chances for viable mutations to occur. Since mutations are the ultimate source of genetic variation, the greater the rate of mainting a mutation, the higher the rate of accruing variation.

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