Biology 101 Unit 3 GRQs PDF

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Biology 101 Unit 3 GRQs...

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Unit 3: Ecology and Evolution Guided Reading Questions Biology 101: Introduction to Biology How Populations Evolve Reading Objectives: Explain why evolution is considered a theory Explain the conditions that must be met for evolution to NOT occur Explain microevolution and how it’s measured and how allele frequencies in a population are affected by microevolutionary forces Guided Reading Qs (Reading Chapter 13) 1. Prior to Darwin’s trip around the world, what did religious scholars believe about Earth and the living species on it? 1. Aristotle: species are fixed, permanent forms that do not evolve 2. Religious scholars used biblical accounts to estimate the age of Earth at 6,000 years a. The idea that all living species came into being relatively recently and are unchanging in the form dominated the intellectual climate of the western world at the time 2. Did Darwin find as he traveled the world that species resembled each other more closely if they were geographically located near each other or of the two species lived in similar environments (possibly very far apart)? What is an example of this? 1. Geographic proximity is a better predictor of relationships among organisms than similarity of environment 2. The plants and animals living in temperate regions of South America more closely resembled species living in tropical regions of the continent than species living in temperate regions of Europe 3. What did Darwin learn about geology? 1. Earth sculpted over millions of years by gradual geological processes that continue today 2. Natural forces gradually changed Earth’s surface and these forces still operate a. The growth of mountains as a result of earthquakes could account for the presence of marine snail fossils he collected on mountaintops in the Andes 4. Darwin called evolution, “descent with __________” and unlike others who had thought of ideas similar to this, he proposed a scientific mechanism for this worked. What did he propose? 1. Descent with modification 2. Natural selection: hypothesized that descendants of a remote ancestor spread into various habitats over millions and millions of years, they accumulated diverse modifications, or adaptations, that fit them to specific ways of life in their environment 5. Darwin suggested that whales evolved from terrestrial (land-living) mammals but he did not have evidence. What kind of evidence do we have today that could answer this question? 1. Observations of fossil teeth led paleontologists to hypothesize that whales were the descendants of primitive hoofed, wolflike carnivores. 2. Found fossil of a carnivorous four-legged mammal that had cetacean (a group of animals that includes whales) ear structures 3. Found another fossil of a perfect intermediate between modern whales and their land-dwelling ancestors 4. Molecular biologists tested an alternative hypothesis using DNA analysis to infer relationships among living animals a. Close relationship between whales and hippos i. Researchers hypothesized that whales and hippos were both descendants of a cloven-hoofed ancestor Was he right? Yes.

6. Fossils provide evidence for evolution, but so do homologies. Explain what homologies are and how they provide more evidence for shared ancestry? 1. Homology: similarity resulting from common ancestry. a. Ex: the same skeletal elements make up the forelimbs of humans, cats, whales, and bats. The functions of these forelimbs differ, so if these structures had been uniquely engineered, then we would expect that their basic designs would be very different. The logical explanation is that the arms, forelegs, flippers, and wings of these different mammals are variations on an anatomical structure of an ancestral organism that over millions of years has become adapted to different functions. 2. Homologous structures: features that often have different functions but are structurally similar because of common ancestry. 7. How does homology in molecular biology support Darwin’s idea that “all life forms are related”? 1. The evolutionary history of each species is documented in the DNA inherited from its ancestral species. If two species have homologous genes with sequences that match closely, biologists conclude that these sequences must have been inherited from a relatively recent common ancestor. Conversely, the greater the number of sequence differences between species, the more distant is their last common ancestor. 2. Molecular biology provides evidence for claim that all life-forms are related: a. All forms of life use the same genetic language of DNA and RNA, and the genetic code - how RNA triplets are translated into amino acids - is essentially universal. 8. What are vestigial structures and vestigial genes? 1. Vestigial structures: remnants of features that served important functions in the organism’s ancestors. a. Ex: the small pelvis and hind-leg bones of ancient whales are vestiges (traces) of their walking ancestors 2. Vestigial genes: organisms may also retain genes that have lost their function, even though homologous genes in related species are fully functional. 3. Researchers have identified many of these inactive “pseudogenes” in humans a. Ex: one such gene encodes an enzyme known as GLO that is used in making vitamin C. Almost all mammals have a metabolic pathway to synthesize this essential vitamin from glucose. Although humans and other primates have functional genes for the first three steps in the pathway, the inactive GLO gene prevents vitamin C from being made - we must get sufficient amounts in our diet to maintain health. 9. Look at Figure 13.5, which animal groups all have the shared characteristic of the amnion? Mammals, lizard/snakes, crocodiles What is the most common ancestor for hawks and lizards? Crocs 10. What are the 3 KEY points emphasized about evolution by natural selection? 1. Although natural selection occurs through interactions between individual organisms and the environment, individuals do not evolve. Rather, it is the population - the group of organisms - that evolves over time as adaptive traits become more common in the group and other traits change or disappear. 2. Natural selection can amplify or diminish only heritable traits. An organism may become modified through its own interactions with the environment during its lifetime, and those acquired characteristics may help the organism survive. But unless coded for in the genes of an organism’s gametes, such acquired characteristics cannot be passed onto offspring. 3. Evolution is not goal directed; it does not lead to perfectly adapted organisms. Whereas artificial selection is a deliberate attempt by humans to produce individuals with specific traits, natural selection is the result of environmental factors that vary from place to place and over time. A trait that is favorable in one situation may be useless - or even detrimental - in different circumstances.

11. What happens to a population of insects (maybe cockroaches in a large apartment building) over time if the same pesticide is repeatedly applied for years and years? Explain your answer. A relatively small amount of poison initially kills most of the insects, but subsequent applications are less and less effective. The few survivors of the first pesticide wave are individuals that are genetically resistant, carrying an allele (alternative form of a gene) that somehow enables them to survive the chemical attack. So the poison kills most members of the population, leaving the resistant survivors to reproduce and pass the alleles for pesticide resistance to their offspring. The proportion of pesticide-resistant individuals thus increases in each generation. 12. TRUE or FALSE, justify your answer: ___Pesticide sprayed over and over causes some bugs to acquire a mutation in a gene that makes them resistant to the chemical. False - the bugs with the mutation have that mutation whether the pesticide is spread or not. ___Some bugs in the population may be resistant to pesticide even if there is no pesticide being sprayed. True 13. Give an example of an inherited phenotype or. an acquired phenotype. Which is relevant to natural selection? 1. Inherited - Size of facial features 2. Acquired - large muscles a. Inherited is relevant to natural selection, because only inherited traits can be passed onto offspring. 14. What creates new alleles in a population? 1. New alleles originate by mutation, a change in the nucleotide sequence of DNA. 2. In multicellular organisms, only mutations in cells that produce gametes can be passed to offspring and affect a population’s genetic variability. What shuffles alleles already existing in a population? Sexual reproduction 15. TRUE or FALSE Justify your answer): ___Resistance to the pesticide DDT is always a good thing for the mosquito carrying it. False, because the gene for resistance to DDT also reduces growth rate. Therefore, if DDT is not present, it’s better for the organism to not have the gene. 16. Can an individual organism evolve? ____Can a population evolve?_____ The evolutionary impact of natural selection is only apparent in the changes in a population of organisms over time. 17. We know microevolution is occurring if we see what changing over many generations? The relative frequencies of alleles in a population. 18. If a population is NOT evolving it would satisfy five conditions of genetic equilibrium (Hardy Weinberg non-evolution): 1. Very large population. The smaller the population, the more likely that allele frequencies will fluctuate by chance from one generation to the next. 2. No gene flow between populations. When individuals move into or out of populations, they add or remove alleles, altering the gene flow. 3. No mutations. By changing alleles or deleting or duplicating genes, mutations modify the gene pool. 4. Random mating. If individuals mate preferentially, such as with close relatives (inbreeding), random mixing of gametes does not occur, and genotype frequencies change. 5. No natural selection. The unequal reproduction of certain traits

19. Make sure for now, to lost what type of individual does each of these variables represent in the population? 1. P2 frequency of homozygous dominant 2. 2pq frequency of heterozygous 3. Q2 frequency of homozygous recessive 20. Aside from mutation and non-random mating (which have smaller effects) what are the three major mechanisms leading to microevolution? 1. Natural selection: individuals with adaptations are more suited to their environments → those allele frequencies are increased in the gene pool from one generation to the next → genetic equilibrium is disturbed. 2. Genetic drift: chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next. a. The smaller the population, the more impact genetic drift is likely to have. 3. Gene  flow: a population may gain or lose alleles when fertile individuals move into or out of a population or when gametes are transferred between populations. Tends to reduce differences between populations. 21. When a population goes from large to small genetic drift is more pronounced in the small population. What are two major reasons that populations go from large to small? 1. Bottleneck effect: certain alleles may be present at higher frequency, and some may not be present at all. After a population is drastically reduced (usually by some kind of catastrophe like a fire), genetic drift may continue for many generations until the population is again large enough for fluctuations due to chance to have less of an impact. a. Even if a population that has passed through a bottleneck ultimately recovers its size, it may have low levels of genetic variation because of the genetic drift that occurred when the population was small. 2. Founder effect: genetic drift is also likely when a few individuals colonize an island or other new habitat. The smaller the group, the less likely that the genetic makeup of the colonists will represent the gene pool of the larger population they left. 22. Describe gene flow and give at least one example of it that you understand. 1. Gene flow: a population may gain or lose alleles when fertile individuals move into or out of a population or when gametes are transferred between populations. Tends to reduce differences between populations a. Ex: humans today move more freely about the world than in the past, and gene flow has become an important agent of evolutionary change in previously isolated human populations. 23. Natural selection is the only mechanism that consistently leads to a daptive evolution.For each of the FIVE types of natural selection, a) define it, b) give at least one example of it that will help you understand and remember it c) draw a graph if appropriate 1. Directional selection: shifts the overall makeup of the population by acting against individuals at one of the phenotypic extremes. a. Ex: there might be a trend toward darker fur color in a mouse population if a fire darkened the landscape so that darker fur would more readily camouflage the animal. b. Most common during periods of environmental change or when members of a species migrate to some new habitat with different environmental conditions. 2. b. Stabilizing selection: immediate phenotypes are more fit than extreme ones (bell curve tends to narrow) 3. Disruptive selection: typically occurs when environmental conditions vary in a way that favors individuals at both ends of a phenotypic range over individuals with intermediate phenotypes. a. Ex: for mice, individuals with light and dark fur have increased numbers. Perhaps the mice colonized a patchy habitat where a background of light soil was studded with areas of dark rocks. b. Can lead to two or more contrasting phenotypes in the population. 4. Sexual selection: a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates. a. Sexual dimorphism: distinction in appearance - can include forms of adornment, such as manes on lions or colorful plumage on birds.

5. Balancing selection: occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population. a. Heterozygote advantage: heterozygous individuals have greater reproductive success than either type of homozygote, with the result that two or more alleles for a gene are maintained in the population. i. the protection from malaria conferred by sickle hemoglobin. The frequency of the sickle-cell allele is generally highest in areas where malaria is a major cause of death, such as West Africa. Heterozygotes are protected from the most severe effects of malaria. Individuals who are homozygous for the normal hemoglobin allele are selected against by malaria. Individuals homozygous for the sickle-cell allele are selected against by sickle-cell disease. Thus, sickle hemoglobin is an evolutionary response to a fatal disease. It is not an ideal solution - even heterozygotes may have health problems - but adaptations are often compromises. b. Frequency-dependent selection: maintains two different phenotypic forms in a population. Selection either acts against either phenotypic form if it becomes too common in the population. i. a scale-eating fish in a lake in Africa, which attacks other fish from behind, darting in to remove a few scales from the side of its prey. These fish are either “left-mouthed” or “right-mouthed,” a heritable character. Because its mouth twists to the left, a left-mouthed fish always attacks its prey’s right side. Similarly, a right-mouthed fish attacks from the left. Prey fish guard more effectively against attack from whichever phenotype is most common. As a result, scale-eating fish with the less common phenotype have a feeding advantage that enhances survival and reproductive success. ii. Frequency-dependent selection keeps each phenotype close to 50%. 19. True or False? New alleles arise as organisms need them. False - Selection can act only on existing variations. Natural selection favors only the fittest variants from the phenotypes that are available, which may not be the ideal traits. New, advantageous alleles do not arise on demand. Evolution leads to organisms perfectly adapted to their environments. False - natural selection operates on a “better than” basis. Evidence for evolution is seen in the imperfections of the organisms it produces as well as in adaptations. Evolution builds upon and modifies ancestral forms. True

GRQs: The Origin of Species (Chapter 14 .1- 14.6 and 15.1-15.4) Reading Objectives: Explain the biological species concept and its limitations Define conditions that lead to speciation. Compare and contrast the reproductive barriers that keep species separate 1. What is speciation? 1. Speciation: the process by which one species splits into two or more species. a. Each time speciation occurs, the diversity of life increases. What are four ways (i.e. concepts) to define a species? 1. Biological species concept: defines a species as a group of populations whose members have the potential to interbreed in nature and produce fertile offspring (offspring that themselves can reproduce). a. Limitations: i. Reproductive isolation: prevents genetic exchange (gene flow) and maintains a boundary between species. ii. There are some pairs of clearly distinct species that do occasionally interbreed. The resulting offspring are called hybrids. iii. There is no way to determine whether organisms that are now known only through fossils were once able to interbreed. iv. This criterion is useless for organisms such as prokaryotes that reproduce asexually. 2. Morphological species concept: classification based mainly on physical traits such as shape, size, and other features of morphology (form). a. Advantages: i. Can be applied to asexual organisms and fossils and does not require information on possible interbreeding. b. Disadvantages: i. Relies on subjective criteria - researchers may disagree on which features distinguish a species. 3. Ecological species concept: identifies species in terms of their ecological niches, focusing on unique adaptations to particular roles in a biological community 4. Phylogenetic species concept: defines a species as the smallest group of individuals that share a common ancestor and thus form one branch on the tree of life. a. Biologists trace the phylogenetic history of such a species by comparing its characteristics, such as morphology, DNA sequences, or biochemical pathways, with those of other organisms. b. Disadvantages: i. Agreeing on the amount of difference required to establish separate species remains a challenge. 5. Prezygotic barriers: prevent mating or fertilization between species before the zygotes (fertilized eggs) form. 6. Postzygotic barriers: operate after hybrid zygotes have formed.

2. The Visual in 14.3, is an excellent summary of the isolating mechanisms leading to reproductive isolation. List and define each type give and give an example that makes sense to you.

3. What does a geographical barrier do to gene flow? 1. A key even in the origin of a new species is the speciation of a population from other populations of the same species. Changes in allele frequencies caused by natural selection, genetic drift, and mutation will not be diluted by alleles entering from other populations (gene flow). a. Allopatric speciation: the initial block to gene flow may come from a geographic barrier that isolates a population. 4. Diane Dodd’s experiments with fruit flies demonstrated what principle of evolution? 1. Reproductive barriers can evolve as a by-product of changes in populations as they adapt to different environments. How did she create different environments for the fruit flies and what did she find when she mixed the two different fruit fly groups together for mating? 1. Raised fruit flies on different food sources.

a. Some populations were fed starch; others were fed maltose. After about 40 generations, populations raised on starch digested starch more efficiently, and those raised on maltose digested maltose more efficiently. b. When flies from “starch populations” were mixed with flies from “maltose populations,” the flies mated more frequently with partners raised on t...