Dave Mundy, North Kitsap High School Science - DAVE …



CHAPTER 1 INTRODUCTION: EVOLUTION AND THE FOUNDATIONS OF BIOLOGY8. Scientific Inquiry/Science Practice 4Many legitimate hypotheses could be proposed to extend the investigation. Here is one example. If the camouflage color has arisen through the processes of natural selection due to visual predators, then you might wonder what would happen if a population of beach mice lived in an area where predators were absent. It might be possible to do a long-term study in an area where you excluded predators. Mice have fairly short generation times, so if predation is “naturally selecting” lighter colored mice, then in the absence of predation you might predict the fur color would not remain predominantly light in such an experimental population.9. Focus on Big Idea 1Sample key points:Darwin used reasoning based on observations to develop his theory of natural selection as a mechanism for evolution.His observations included:Heritable variations exist in each population.A population has more individuals than can be supported by the environment.Each species seems suited for its particular environment.He proposed that the best-adapted individuals in a population would outcompete others for resources and disproportionately survive and produce more offspring, leading to an increase in the adaptations seen in the population.Sample top-scoring answer:Based on many observations of different species, Darwin proposed his theory that evolution by means of natural selection accounts for both the unity and diversity of life on Earth. He noticed that variations existed among the individuals in a population and that these variations seemed to be heritable. He also saw that populations could grow larger than could be supported by the resources around them. Finally, he observed that species (like the different species of finches) seemed to suit their environment. He proposed that the best-suited individuals in a population would survive and reproduce more successfully that those less adapted to their environment, and he called this “natural selection.” In Darwin’s view, this mechanism could account for both the unity and diversity of features among species. The descent of organisms from a common ancestor explains similar features, while the force of natural selection in different environments accounts for differences between organisms. 10. Focus on Big Idea 3Common ancestry explains this observation. The thousand-some-odd genes shared by humans and prokaryotes originated in early prokaryotes. They have been retained, with some modification, over the billions of years of eukaryotic evolution. These genes no doubt code for proteins and RNAs whose functions are essential for survival—for example, the genes that code for ribosomal RNA, which is important for protein synthesis in both prokaryotes and eukaryotes.CHAPTER 19 DESCENT WITH MODIFICATION7. Focus on Big Idea 1 Organisms share many characteristics from their common descent, and more closely related organisms share more characteristics than distantly related organisms. This reasoning applies to all of an organism’s characteristics; hence, anatomical and molecular features often fit a similar nested pattern because of common descent. Convergent evolution can break this nested pattern for characteristics that evolved as distantly related organisms adapted to similar environments in similar ways.8. Focus on Big Idea 4Sample key points:All organisms interact with the living and nonliving components of their environment.An organism whose inherited traits cause it to be particularly successful in its environmental interactions will tend to leave more offspring than other organisms.However, traits that are successful in one environment may be less successful or even detrimental in another environment.Hence, if a feature of the environment changes, that change may result in evolutionary change in one or more of the species affected by the change in environmental conditions.Sample top-scoring answer: All organisms interact with the living and nonliving components of their environment. Furthermore, as a result of descent with modification by natural selection, an organism whose inherited traits cause it to be particularly successful in its environment will tend to leave more offspring than other organisms. However, natural selection often favors different traits in different environments. In fact, a trait that is favorable in one environment can be less successful or even harmful in another environment. Thus, if a feature of the environment changes, selective pressures may change as well. For example, an increase in temperature may select against cold-adapted genotypes, or the introduction of a new species of predator may cause the evolution of new defenses in some prey species. Overall, it is likely that a change in environmental conditions will result in evolutionary change in some of the species affected by the environmental change.CHAPTER 20 PHYLOGENY 8. Scientific Inquiry/Science Practice 7 (c) The tree in (a) requires seven evolutionary changes, while the tree in (b) requires nine evolutionary changes. Thus, the tree in (a) is the most parsimonious, since it requires fewer evolutionary changes.9. Focus on Big Idea 1 Darwin’s suggestion directly anticipates phylogenetic bracketing, a method that uses shared characteristics of organisms in a clade to make predictions about the common ancestor of the clade and all of its descendants. His suggestion is also similar to how outgroups are used to help differentiate between ancestral characters (present in the outgroup) and derived characters (new features that originated with the ingroup).10. Focus on Big Idea 1Sample key points:DNA is the hereditary material.By descent with modification, newly formed species share many similarities with parent species—including similarities in cell structure and DNA sequence.The parent species, in turn, share many similarities with their parent species, and so on.Thus, all organisms contain evidence of their evolutionary past, making it possible to construct phylogenies.Sample top-scoring answer: All organisms are composed of cells and have their genetic information encoded in DNA. One result of this fact is that by descent with modification (see Chapter 19), the cells and DNA of newly formed daughter species will share many similarities with the cells and DNA of their parent species—which in turn share many such similarities with their parent species, and so on. As a result, all organisms contain both morphological evidence (for instance, cell structure) and genetic evidence (for example, DNA sequence) of their evolutionary history. Untangling evolutionary history from morphological and genetic data requires that homologous characters be sorted from analogous characters and that shared derived characters be distinguished from shared ancestral characters. Although challenging, the existence of well-supported phylogenies that cover hundreds of millions of years of evolution indicates that organisms contain enough evidence of their evolutionary history to accomplish such tasks.CHAPTER 21 THE EVOLUTION OF POPULATIONS7. Scientific Inquiry/Science Practice 5The frequency of the lap94 allele forms a cline, decreasing as one moves from southwest to northeast across Long Island Sound.A hypothesis that explains the cline and accounts for the observations stated in the question is that the cline is maintained by an interaction between selection and gene flow. Under this hypothesis, in the southwest portion of the Sound, salinity is relatively low, and selection against the lap94 allele is strong. Moving toward the northeast and into the open ocean, where salinity is relatively high, selection favors a high frequency of the lap94 allele. However, because mussel larvae disperse long distances, gene flow prevents the lap94 allele from becoming fixed in the open ocean or from declining to zero in the southwestern portion of Long Island Sound.8. Focus on Big Idea 1 Although natural selection can improve the match between organisms and their environments, the evolutionary process can also lead to imperfections in organisms. A central reason for this is that evolution does not design organisms from scratch to match their environments and ways of life but works instead by a process of descent with modification: Organisms inherit a basic form from their ancestors, and that form is modified by natural selection over time. As a result, a flying mammal such as a bat has wings that are not perfectly designed, but rather represent modifications of forelimbs that bat ancestors used for walking. Imperfections in organisms result from a variety of other constraints, such as a lack of genetic variation for the trait in question, and the fact that adaptations often represent compromises (since organisms must do many different things, and a “perfect” design for one activity might impair the performance of another activity). 9. Focus on Big Idea 4Sample key points:In sickle-cell heterozygotes, red blood cells that contain relatively large amounts of sickle-cell hemoglobin are prone to sickling. Sickled cells are rapidly destroyed by the body.When sickling occurs, malaria parasites inside sickled red blood cells tend to be killed rapidly. This reduces the density of the parasites and hence the severity of the disease—an emergent property at the level of the individual. Natural selection can lead to an emergent property at the population level—a rise in the frequency of the sickle-cell allele due to heterozygote advantage in regions where malaria is common.Sample top-scoring answer: In a sickle-cell heterozygote, red blood cells that contain relatively large amounts of sickle-cell hemoglobin are prone to sickling, and sickled cells are rapidly destroyed by the body. Malaria parasites spend part of their life cycle inside red blood cells. If a heterozygote has malaria, parasites that live inside red blood cells that become sickled are killed when the sickled cell is destroyed. These events lead to two emergent properties: At the individual level, heterozygotes receive protection from the most severe effects of malaria (since parasite density is lowered when sickled cells are destroyed); at the population level, partial protection against the effects of malaria can lead to an increase in the frequency of the sickle-cell allele in regions where malaria is common.CHAPTER 22 THE ORIGIN OF SPECIES7. Scientific Inquiry/Science Practice 1Here is one possibility:8. Science, Technology, and Society It is possible to argue both sides of this question based on the underlying biology. For example, if the biological species concept is followed strictly, one could argue that red wolves and coyotes are the same species since they can interbreed. Because coyotes are not rare, this line of argument would suggest that red wolves should not be protected under the Endangered Species Act. On the other hand, because red wolves and coyotes differ in many ways, they can be viewed as distinct species according to alternative species concepts (or to a less strict application of the biological species concept). This approach would suggest that red wolves should be protected because they are rare. 9. Focus on Big Idea 1 All fertile humans alive today can interbreed to produce viable, fertile offspring. Thus, they conform to the biological species concept and are assigned to a single species. For a new human species to originate, a small breeding population would have to be geographically isolated from all other populations for a long enough time that genetic drift, mutation, or natural selection (or all of them together) would change the gene pool of this isolated population. If so much genetic change occurred that the population became reproductively isolated from all other populations, even when reunited with them in the same range, it would constitute a new human species. This is unlikely given the increasing size and mobility of the human population.10. Focus on Big Idea 3Sample key points:Overall, 50% of the DNA in F1 hybrids comes from each parent species. However, on a per-chromosome basis, 100% of the DNA in one member of each homologous pair is from one parent species, while 100% of the DNA in the other homolog is from the other parent species.In later-generation hybrid offspring, genetic recombination will produce chromosomes that contain a mixture of DNA from each parent species.At one genetic locus, natural selection may favor DNA from one parent species, while at another locus, selection may favor DNA from the other parent species. Sample top-scoring answer: When parent species with homologous chromosomes produce hybrid offspring, overall 50% of the DNA in the F1 hybrids comes from each parent species. On a per-chromosome basis, however, 100% of the DNA in one homolog is from one parent species, while 100% of the DNA in the other homolog is from the other parent species. In later-generation hybrid offspring, genetic recombination will produce chromosomes that contain a mixture of DNA from each parent species. This mixing is similar to what happens when members of a single species have offspring, where recombination produces chromosomes that contain a mixture of maternal and paternal DNA. In addition, at one genetic locus natural selection may favor DNA from one parent species, while at another locus selection may favor DNA from the other parent species. Selection can therefore cause chromosomes to consist primarily of DNA from one parent species or the other.CHAPTER 23 BROAD PATTERNS OF EVOLUTION 7. Scientific Inquiry/Science Practice 3The information presented in this problem suggests that the evolution of herbivory in moths and butterflies may have contributed to their adaptive radiation. To test this hypothesis, other comparisons could be made between a group of insects in which herbivory evolved and their sister group in which it did not. If groups of herbivorous insects consistently have more species than their nonherbivorous sister groups, we could conclude that the evolution of herbivory promotes adaptive radiation in insects. [This hypothesis has been tested; see C. Mitter et al., The phylogenetic study of adaptive zones: has phytophagy promoted insect diversification? The American Naturalist 132:107–128 (1988).]8. Science, Technology, and Society If present trends continue and humans cause a sixth mass extinction, it will be the only one in the history of life caused by a single species. Mass extinctions can reduce complex ecological communities to much simpler ones. It can take millions of years for communities to recover from a mass extinction, and when they do, the kinds of organisms found in those communities can change. As we will discuss in Unit 7, human societies depend on ecological communities for food, goods (such as lumber), clean air, and clean water. By disrupting ecological communities throughout the world, a sixth mass extinction would have enormous consequences for all species alive today—including humans. 9. Focus on Big Idea 1 A factor (such as the separation of continents by continental drift) that reduces gene flow in many groups of organisms promotes speciation on a grand scale, thereby influencing the diversity of life seen in the fossil record. As discussed in Chapters 21 and 22, genetic drift can lead to the fixation of alleles, causing reproductive isolation and again promoting speciation and influencing patterns of diversity seen in the history of life. Adaptive evolution by natural selection at a wide range of loci—including those that influence development—is a major cause of the evolution of new morphological forms as well as the high rates of speciation that occur during adaptive radiations.9. Focus on Big Idea 4 Sample key points:There is generally a good match between form and function.However, structures are not designed to perform their function in the best possible way. If they were, bird wings might have arisen from scratch, leaving the forelimbs free to perform other tasks.Instead, new structures evolve by “tinkering,” a process in which new forms arise by the modification of existing forms.Sample top-scoring answer:The structure of a feature often gives clues as to its function—there is, in general, a good match between form and function. However, this match does not indicate that the structure has been designed to perform its function in the best possible way. For example, although it might have been advantageous to do so, bird ancestors did not sprout wings de novo from the middle of their backs, leaving the forelimbs free to perform other tasks. Evolution does not work in that way. Instead, new structures often arise as modifications (exaptations) of existing structures by a “tinkering” process. Assuming that the necessary genetic variation exists, natural selection can favor some structural variants over others, leading to improvements in function. Thus, wings in birds originated as the forelimbs of bird ancestors were modified over time. In principle, wings might have originated in some other way, but they could not have arisen completely from scratch. Some existing structure would have to have been modified over time. ................
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