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Midterm 2 Learning Objectives Biol 1001

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BIOL 1001
Tamara Kelly

D9. Differentiate between the different types of evolutionary mechanisms; the conditions under which they occur; their effects on a population’s genetic structure (e.g., variation, and mean character value); their relative effects on evolution; and factors that can impact their effects. Given a scenario, determine the type(s) of mechanism(s) acting, and predict the effects on the population, justifying your choices. • Gene Flow- important source of genetic variation and can change frequency of alleles • Mutation- Sources of new alleles: mutations- cannot account for big changes in allele frequencies in one generation b. Describe the impact of gene flow between two populations • Any movement of genes from one population to another. Gene flow includes lots of different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries. If genes are carried to a population where those genes previously did not exist, gene flow can be a very important source of genetic variation • Reduces genetic variation as populations become more alike • Original Population: where people came from • Founder Population: people that are stranded and starting new population • New Population: descendants of founders c. Relate and explain the effects of drift as a function of population size; relate these effects to conservation biology. • Greater effects in smaller populations sizes due to sampling error d. Compare founder and population bottleneck events (causes and outcomes). • 1) Founder Effect: few individuals begin new population • 2) The Bottleneck effect: Populations reduce in size because due to a random event where surviving individuals do not represent random genetic sample of original population. e. Compare genetic drift and natural selection in terms of: how they work; their potential outcomes with respect to fitness, adaptation, and genetic variation; and random vs. non- random processes. • Genetic drift: causes random changes in allele frequency and for a small isolated population elimination of alleles by chance. It happens toALL populations—there’s no avoiding chance. • Pseudogenes have reached to fixation and some codons that code for a particular amino acid have reached fixation even though we can’t see the changes: genetic drift can effect large populations given enough time • Comparison between Genetic Drift and Gene Flow: gene flow also allows some populations to remain reasonably identical in the frequency of alleles and tends not to cause speciation, gene flow requires populations to be in contact with each other and to be able to move between these populations. D10. Compare inbreeding and sexual selection, and their potential effects on a population; given a scenario, determine which is acting. • Inbreeding: reproduction from the mating of pairs who are closely related genetically, meaning that they have a common ancestor therefore they share similar alleles • 1) Increasing homozygosity, which can increase the chances of offspring being affected by recessive deleterious traits 2) Does not cause evolution as it does not change a population as a whole and does not change allele frequencies • Sexual Selection: acts on an organism's ability to obtain or successfully copulate with a mate • Often powerful enough to produce features that are harmful to the individual’s survival. a. Describe the impact of inbreeding on a population’s genetic variation, phenotypes, and heterozygosity; explain how non-random mating may not result in evolution. • Decreases heterozygosity b. Explain how sexual selection has resulted in showy structures in males, commenting on what this indicates about the males (relating to fitness tradeoff, handicap hypothesis, honest signals etc.); provide examples of male traits/behaviours to explain it. • Handicap Hypothesis: reliable signaling between animals which have an obvious motivation to bluff or deceive each other • Honest signals: reliable signals must be costly to the signaler, costing the signaler as a fitness trade-off. Receivers know that the signal indicates quality because inferior quality signalers cannot afford to produce such wastefully extravagant signals • Deceitful communication: get fooled by other males c. Differentiate between inter- and intra-sexual selection; given a scenario, identify which is acting, which sex will show the greater variation in reproductive success, the extent of sexual dimorphism, justifying your answer. • Reproductive success: number of offspring • Variation in reproductive success: some individuals have more offspring then others • Intersexual selection: male attract females- female choice driving evolution of male traits • Intrasexual selection: male-male competition and forming territories Greater variation in reproductive success: males, comparing reproductive success of males to other males vs females with other females • Greater Variation: females • Sexual Dimorphism: in humans: breasts, muscle mass, and height d. Compare founder and population bottleneck events (causes and outcomes) • Outcome: same • Cause: F: move to new population B: original population wiped out e. Compare genetic drift and natural selection in terms of: how they work; their potential outcomes with respect to fitness, adaptation, and genetic variation; and random vs. non- random processes. • Genetic Variation: NS: maintains GD: neutral, generally decreases • NS: non-random based on fitness • Genetic Drift: random D10. Compare inbreeding and sexual selection, and their potential effects on a population; given a scenario, determine which is acting. • Comparisons between Sexual Selection and inbreeding: both violate assumptions of HW principle, but SS causes alleles to increase and decrease in frequency and results in evolution and inbreeding does not d. Describe the phenomena of assortative mating (positive and negative) and its potential impact on a population. • PositiveAssortative Mating: mate with individuals that share a particular phenotype Impact: greater number of homozygous • NegativeAssortative Mating: mate with individuals that do not share a particular phenotype Impact: greater number of heterozygotes • DO NOT change specific allele frequencies e. Explain the adaptive value of sexual cannibalism and self-sacrifice. • Male Redback spiders: get ready to be eaten as very few find a mate and it is an adaptive trait to constrict organs to save time so that the spider can insert to sperms into the female and produce more kids Genetic marker: specific allele that causes a distinctive phenotype Bateman-Trivers hypothesis: Pattern: sexual selection acts strongly on males Mechanism: Eggs are expensive and sperm is cheap. Females fitness limited by ability to gain resources and produce more eggs, males fitness limited by the number of females he can mate with. Sexual dimorphism: any trait that differs between males and females Monogamy: 1 male + 1 female Polygamy: competition of sperm- 1 male, many females- sometimes there is an fitness advantage for females to mate with different males as they produce more offspring Sexual cannibalism: female cannibalizes her male mate prior to, during, or after copulation E Phylogenetics (this builds on LOs and definitions from History of Evolutionary Thought) E1. Using the Linnean system of classification, list from most inclusive to least inclusive and most similarities to least similarities, the terms: phyla, family, genus, species, and domain. • Inclusivity highest to lowest: domain, phyla, family, genus, species- Dear King Phillip Comes Over For Good Spaghetti E2. Read a phylogenetic tree. That is, given a phylogenetic tree, determine: where speciation events occurred (nodes); common ancestors between specific lineages; orientation of time scale; unique vs.shared histories; identify outgroups. Explain the link between phylogenies and ‘descent with modification’. • Unique Histories: descendant groups traits after speciation are derived from common ancestor • Ataxon should be monophyletic E3. Identify a phylogenetic tree or description of a group of organisms as monophyletic, paraphyletic, or polyphyletic. • Monophyletic= clade composed of ancestor and all and only its descendants • Paraphyletic: most recent common ancestor + some descendants of CA but not all descendants- eg pongidae but not humans, reptiles but not birds • Polyphyletic: share traits that are not homologous, looks at descendants and not the most common ancestor- typically because of convergent evolution- traits that look similar but are not homologous E4. Differentiate between the following terms with respect to the information they provide regarding shared ancestry and their use in constructing phylogenies: homology (homologous), analogy (analogous), and homosplasy (homoplasious) E5. Describe how the principles of parsimony is used in the construction of cladograms and phylogenetic hypotheses phylogenetic trees. Utilize the principle of parsimony to construct a phylogenetic tree. • Parsimonious with respect to a specific trait- meaning that it evolved once • Principle/assumption of parsimony: the most likely explanation or pattern is the one that implies the least amount of change- this is because convergent evolution and homoplasy should be rare compared to similarity from common decent E6. Based on a trait/genetic sequence, determine the degree of relatedness among several individuals/species. Given a table of derived characteristics, construct a simple cladogram. E7. Describe attributes of a reliable molecular clock. • rRNA- has a slow rate of change *encoded in dna • You can use it to measure divergence for long periods of time • MitoDNA- rate of change is rapid- can use it to measure divergence for short period of time • Doenst have to different in every singles species • Non-coding regions are used to calibrate the molecular clock- as they are not subject to natural selection Assumptions: 1) rates of mutations should be constant over time 2) If two taxa diverged from common ancestor a long time ago, then they should have more differences in the sequences compared to two taxa that diverged relatively recently 3) we want the sequences of the DNA where the changes have occurred to be selectively neutral (introns): DNAthat does not code for proteins and natural selection cannot act on them F Speciation F1. Explain how the term ‘species’can vary between groups of organisms. Compare and contrast the four species concepts, addressing their uses and limitations. Given a scenario, determine which species concept would be most appropriate to determine if two organisms were the same spe
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