L22 GRQs How Populations Evolve I PDF

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GRQs for How Populations Evolve I 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? Many people believed species were fixed groups which do not evolve. Religion especially fortified this idea with literal interpretations of the book which tells stories of each species being created in its present-day form.

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? Darwin found that geographical proximity is a better predictor of relationships among organisms that the similarity of their environments. (EX: the species in temperate locations of South America were more closely related to species in tropical regions of the same continent, than they were related to the species in the temperate regions of Europe). 3. What did Darwin learn about geology? Natural forces gradually changed Earth’s surface and that these forces still operate. 4. Darwin called evolution, “descent with _modification___” and unlike others who had thought of ideas similar to this, he proposed a scientific mechanism for this worked. What did he propose? Descent with modification (Darwin’s phrase for evolution): The differences that gradually accumulate through present day species being the descendants of ancient ancestors that they still resemble in some ways. -Other people have previously explored the concept of organisms changing over time (evolution), but the difference with Darwin’s was that he proposed the scientific mechanism for how life evolves: Natural Selection. 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? Darwin did not have access to fossil evidence like we do today. Fossils can show how different species have evolved into others. Was he right? Yes! The evolution of whales having a terrestrial ancestor is one of the best-documented evolutionary transitions to date.

6. Fossils provide evidence for evolution, but so do homologies. Explain what homologies are and how they provide more evidence for shared ancestry? A homology = a similarity resulting from common ancestry. For example, species that have an underlying similarity yet function differently are examples of homologies. It shows how things are structurally similar due to common ancestry.

7. How does homology in molecular biology support Darwin’s idea that “all life forms are related”? Molecular biology = the study of the molecular basis of genes and gene expression. -the evolutionary history of each species is documented in the DNA inherited from its ancestral species -2 species with homologous genes with sequences that match closely is concluded as these sequences must have been inherited from a common ancestor -molecular biology supports Darwin’s claim that all life-forms are related, because all life forms use the same genetic language of DNA and RNA – the genetic code -It is universal that all life-forms have the same amino acids in their DNA 8. What are vestigial structures and vestigial genes? -Vestigial structures: structures that are of marginal or perhaps no importance to the organism. They are remnants of features that served important functions in the organism’s ancestors. -Ex: eye remnants that are buried under scales in blind species of cave fishes -Vestigial genes: genes that have lost their function, even though homologous genes in related species are fully functional (aka “pseudogenes”) -Ex: a pseudogene in humans that encodes GLO is used in making vitamin C, but is inactive in humans, so we must get sufficient amounts of vitamin C in our diets 9. Look at Figure 13.5, which animal groups all have the shared characteristic of the amnion? The species which all have the shared characteristic of the amnion are those that come after the purple “slash” labeled amnion. Those are mammals, lizards and snakes, crocodiles, ostriches, and hawks and other birds. What is the most common ancestor for hawks and lizards? The most common ancestor shared between hawks and lizards is ancestor “4” on the tree 10. What are the 3 KEY points emphasized about evolution by natural selection? a. individuals do not evolve; the population evolves over time as adaptive traits become more common b. natural selection can only amplify or diminish heritable traits. Traits that are coded for in the genes of an organism’s gametes (ex: a championship female bodybuilder will not give birth to a muscle-bound baby c. evolution is not goal-oriented; 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) 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.

The majority of pests are killed off by the pesticide; the few survivors happen to be genetically resistant, carrying a specific allele allows them to survive; that allele makes those who have it reproduce and increase their genetic offspring. Soon there is a population of insects who all have an allele that makes them resistant to the pesticide.

12. TRUE or FALSE, justify your answer: _F__Pesticide sprayed over and over causes some bugs to acquire a mutation in a gene that makes them resistant to the chemical. The mutation is not caused by the pesticide. The bugs who are resistant already carried that allele before the spraying, but just happened to be the most fit to survive. _T__Some bugs in the population may be resistant to pesticide even if there is no pesticide being sprayed.

13. Give an example of an inherited phenotype vs. an acquired phenotype. Which is relevant to natural selection? Interited phenotype: inherited through genes (related to natural selection) -Ex: blue eyes vs brown eyes Acquired phenotype: acquired through behavior / environment -Ex: working out a lot and getting a ripped 6 pack 14. What creates new alleles in a population? Mutations What shuffles alleles already exiting in a population? Genetic variation in sexual reproduction (independent assortment, crossing over, and random fertilization) 15. TRUE or FALSE Justify your answer): _F__Resistance to the pesticide DDT is always a good thing for the mosquito carrying it. -It is good for an environment with pesticide DDT, but in other environments could be a handicap to flies 16. Can an individual organism evolve? _no___Can a population evolve?__yes___ Explain your answers. Evolution occurs through many generations and the emergent traits are traits that are shown in populations not individuals. One individual does not evolve.

17. What is a common misconception about individuals and evolution? That an individual can evolve

18. We know microevolution is occurring if we see what changing over many generations? Relative frequencies of alleles in a population’s gene pool change over a number of generations

19. True or False? __T__The shuffling of alleles through sexual reproduction leads to changes in the frequencies of alleles in the gene pool.

20. In class, we’ll work with the Hardy Weinberg equations a bit more, for now, let’s examine two equations: Hardy-Weinberg equilibrium: condition where the frequency of each allele in a gene pool remains constant, given that other factors are under certain conditions. p + q = 1 (the frequency of the dominant allele + the frequency of the recessive allele = 1) Which variable is the frequency of the dominant allele in the population? _p___ Which variable is the frequency of the recessive allele in the population? _q____ p2 + 2pq +q2 = 1 (the frequencies of the genotypes in the next generation also add up to 1) (also, the frequencies of the alleles in this next generation also adds up to 1 and has the same frequencies as the parent generation)

Make sure for now, to lost what type of individual/genotype does each of these variables represent in the population? p2 = frequency of homozygous dominant in the next generation 2pq = frequency of heterozygous in the next generation q2 = frequency of homozygous recessive in the next generation

21. If a population is NOT evolving it would satisfy five conditions of genetic equilibrium (Hardy Weinberg non-evolution): a. very large population (smaller populations are more susceptible to random fluctuations between generations, such as genetic drift) b. no gene flow between populations (no individuals leaving or entering the population that is being studied) c. no mutations (mutations modify the gene pool) d. random mating (if individuals mate preferentially, then mating is not random, and some individuals might have preferences to phenotypes that correspond to specific alleles) e. no natural selection (unequal survival and reproductive success of individuals can alter allele frequencies)

22. What can the Hardy-Weinberg equations tell us that is important to public health?

That populations must evolve to survive. The Hardy-Weinberg equation can help scientists estimate how many people in a population are carriers for a certain allele if they know how many people have this allele and then can apply p and q given what they know....