BIO_SC 3400: FINAL EXAM
87 Cards in this Set
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What is evolution?
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a change in allele frequencies in a population over time
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What are the mechanisms of evolution?
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things that can cause allele frequencies to change; artificial; natural; sexual
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What is heritability and how is it measured?
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the slope of the regression line between parent and offspring values for a trait; measured using graphs and then determining the slope
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How do the different forms of selection differ from each other?
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in what/who will choose which individuals reproduce most and this what traits are passed on
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How are the different forms of selection the same?
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posses heritable variation (genetic differences); differences among individuals in the # surviving offspring exist
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What is genetic drift?
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any change in allele frequency due to chance
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What is the bottleneck effect?
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catastrophic event reduces the population to a small # of individuals (those individuals are unlikely to carry all the alleles from a population)
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What is the founders effect?
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a few individuals start a new population (carrying only a subset of the former population)
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Why are males usually the competitive sex, and females the choosey sex?
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females are choosy because the invest more time/energy into the offspring and thus males compete for the choosy females
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What is fitness?
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# copies of an individuals genes that get passed on to the future generation
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What are adaptations?
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a characteristic of an organism that helps it to survive and reproduce in a particular environment
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What are the modes of selection?
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selection can cause a trait to change or to stay the same; directional (favors one extreme); stabilizing (favors intermediate); disruptive (favors both extremes, but not middle)
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What is the evidence that evolution is responsible for the diversity of life on Earth?
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Artificial Selection; Fossils; Vestigial structures; Homology; Genetic Analysis; Biogeography; Natural selection in action
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How does artificial selection show evidence that evolution is responsible for the diversity of life on Earth?
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demonstrates that organisms can change, there not fixed in form
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How do fossils show evidence that evolution is responsible for the diversity of life on Earth?
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organisms are found in a historical sequence (simplest organisms at bottom of cliffs, most complex at top); demonstrate a gradual transition among forms
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How do vestigial structures show evidence that evolution is responsible for the diversity of life on Earth?
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are structures that have no apparent purpose, but that are carry-overs from ancestral species
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How does homology show evidence that evolution is responsible for the diversity of life on Earth?
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the skeletons of different animals are similar in structure (even if they vary in function) which is to be expected if they arose from the same structures in a common ancestor
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How does genetic analysis show evidence that evolution is responsible for the diversity of life on Earth?
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the more closely related two species are according to fossil record, the more similar their DNA is; we know that the genetic code is nearly the same among all organisms
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How does biogeography show evidence that evolution is responsible for the diversity of life on Earth?
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we observe that many island species are endemic (found nowhere else) and that those endemic species are similar to species on the nearest mainland and to species on island near them; be can best conclude that the island species evolved from populations that were begun by individuals from …
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How does natural selection in action show evidence that evolution is responsible for the diversity of life on Earth? (examples)
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evolution of body size in finches (average size increased as a result of better survival/reproductive success); evolution of drug resistance in bacteria/viruses
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How is the age of a rock determined?
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Carbon dating (half life)
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What is a species, and what steps are necessary for speciation to occur?
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divergence of 1 species into 2; requires that 2 populations become reproductively isolated from each other and that genetic differences arise between the 2 isolated populations
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Under what circumstances does stasis occur?
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lack of genetic variation; stabilizing selection; constant environment; fluctuating selection that will give the appearance of stasis
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Under what circumstances does adaptive radiation occur?
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ecological opportunity ( new habitat w/ few predators); morphological innovations (develop of 1st shell)
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What is the difference between punctualism and gradualism?
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punctualism is long periods of stasis followed by rapid diversification; gradualism is slow, continuous change
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What is the endosymbiont hypothesis?
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eukaryotes evolved from prokaryotes that engulfed other cells but did not digest them
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How do we interpret evolutionary trees?
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Every split is a divergence in species. A split does not imply that an existing species was the ancestor at the split but had common ancestor. (i.e. Humans and monkeys share common ancestor but humans did not evolve from monkeys, or vice versa)
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How do we determine which possible evolutionary tree is the most parsimonious?
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a simpler explanation is more likely than a complex one (least amount of steps to reach current organism)
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How are fish, birds, reptiles, and mammals related to each other?
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1 Amphibians evolved from fish
2 Reptiles evolved from amphibians
3 Both birds and mammals evolved from reptiles
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What were the important trends in human evolution?
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evolution photosynthesis; evolution eukaryotes; multicellularity; internal skeleton; invasion land (plants then invertebrates); reptiles evolved from amphibians; asteroid impact/environment change (dinosaurs extinct, small mammals lived); mammals diversified; human evolution
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Where and when did modern humans evolve?
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Africa about 2 mya
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What is the relationship between humans and chimpanzees?
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Diverged about 6 mya and share a common ancestor
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What is a 'group selectionist' argument, and why are some biologists skeptical of them?
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A population in which individuals sacrifice their own reproductive success for the good of the species is vulnerable to invasion by "selfish" alleles (alleles that favor the individual over the species; skeptical because individuals typically reproduce faster that groups, once selfish beh…
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Under what situations do we expect animals to behave altruistically toward relatives and toward non-relatives?
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helping to raise younger siblings; emitting alarm calls
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What is kin selection?
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favors behaviors that enhance the survival of reproduction of relatives
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How do animals optimize offspring size and number?
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produce offspring of size that will yield the greatest # of survivors but the trade off is that the larger the offspring, the fewer that can be produced
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How are population sizes estimated in the field?
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Mark and recapture studies:
a Capture sample of animals and mark them
b Release marked animals
c Later date: capture new sample of animals
d Use the proportion of marked animals that were re-caught to estimate total population size
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What is an age structure diagram and how is it used?
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Diagram that shows the number of people alive at each age level; Use the population of reproductive age and those under to predict population growth
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What is a survivorship curve and what does it tell you about a population?
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Represents probability of survival relative of stage of life
Type 1: High survivorship rate for majority of population (low # of offspring per birth, i.e. humans)
Type 2: Survivorship rate and age do not affect the other (straight line, i.e. mice)
Type 3: Lower survivorship for o…
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How do we use a life table to determine life expectancies and survivorship curves?
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We determine how many years a person/creature has left to live on average for a give age range. We plot these on an exponential graph to determine type of survivorship
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What is intrinsic rate of increase (r)?
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max rate at which a population can increase
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What is carrying capacity (k)?
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max sustainable population size for a given environment, based on resources
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How do r and K influence the shape of population growth curves?
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the larger the r value, the steeper the population growth curve; population growth curve will stabilize around K
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What is environment resistance?
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factors that limit population growth
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What is the difference between density-dependent and density-independent effects on population growth?
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density-dependent factors limit population growth as density increases; density-independent factors affect population size regardless of the population density
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What are the trends in human population growth?
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human populations are increasing at a faster rate in developing countries versus developed countries and it is predicted that the world human population will stabilize over the next few decades
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What is the competitive exclusion principle?
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no two species can have exactly the same niche because one species will out compete the other
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What is resource partitioning?
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the use of slightly different niches to minimize competition
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How do we interpret the zero-growth isoclines for competing populations?
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draw an arrow along the graph point in the direction of growth; if the arrows point to each other it is a stable equilibrium point; if arrows point away from each other it is unstable equilibrium point
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How do predator-prey cycles work?
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the two populations limit each other's density
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What is coevolution?
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two species evolve together and have specific adaptations for dealing with each other
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What are the different forms of symbiosis?
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parasitism (one species benefits to determine of the other); commensualism (one species benefits, other is unaffected); mutualism (both benefit)
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What is the difference between the movement of energy and the movement of nutrients through an ecosystem?
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the movement of energy is one directional where as the movement of nutrients are recycled through an ecosystem
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Why is there a loss of energy as it moves up the food chain?
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most of the energy an organism consumes is used for its own metabolism and is converted to heat and thus the only energy available to the next trophic levels is the energy stored in the bodies of the organisms they consume
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What are the implications of this loss (energy loss as it moves up the food chain)?
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explains why there is a limit to the # trophic levels possible; explains why # individuals decreases as you move up the trophic levels
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How does biomagnification work?
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chemicals dissolve in the fat of animals and remain there; the next trophic level eats that animal and an accumulation of toxic substances in the higher trophic levels
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What are the causes and consequences of the thinning of the ozone layer?
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caused by an imbalance in the oxygen cycle; consequences are increased UV radiation reaching Earth which leads to health problems, reduction in crop yield, and loss plankton
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How does the greenhouse effect work?
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greenhouse gases allow visible light energy to pass through easily; that light energy is absorbed and converted to heat energy that attempts to leave Earth's atmosphere; greenhouse gases absorb that heat energy/radiate it back down which prevents it from leaving Earth's atmosphere
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What are the causes and consequences of climate change?
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climate increases are caused by addition of CO2 to the atmosphere (greenhouse gas layer); the two major consequences are a rise in sea levels and region climate changes (more severe weather, plant/animal distribution, extinctions, disease)
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How does climate change reflect an imbalance in the carbon cycle?
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climate change is caused by excess CO2 that comes from burning fossil fuels and deforestation
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Evolutionary medicine (definition)
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the application of evolutionary theory to our understanding of health/disease
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EvoMed explanation of morning sickness
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most common in 1st trimester; elicited by strong tastes/smells; may protect fetus from toxins/food poisoning; lack of morning sickness is associated with a higher risk of miscarriage
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EvoMed explanation of menstruation
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may protect women from STDs/parasites; modern women experience many more cycles than ancestors; high rates of breast cancer may be associated with increased cycling of estrogen
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EvoMed explanation of back pain/arthritis
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walking upright puts more pressure on our spine; ancestors had pressure spread out because of four legged posture
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EvoMed explanation of cough, fever, vomiting, diarrhea
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may be bodies defenses against pathogens; stopping defenses may prolong the infection
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EvoMed explanation of alcohol consumption
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fermentation helps primates locate trees with ripe fruit; selection may have favored both attraction to/ability to consume small amounts alcohol; may be maladaptive in modern society
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To what group did selection favor reduced tolerance for alcohol? How?
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Asians; when the domestication of rice occurred
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Virulence (definition)
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tendency to cause disease in a host
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What is the old idea about pathogen virulence?
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pathogens should become more benign over time due to costs of virulence
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What is the new idea about pathogen virulence?
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some conditions select for high virulence
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Virulence is a function of what?
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growth rate
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What is illness in regards to growth rate?
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it is a side effect of a high growth rate
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What is the transmission rate hypothesis?
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natural selection favors highly virulent strains of HIV-1
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What are three things characteristic of a more virulent strain of HIV?
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maintains higher concentrations of virus in patients blood; kills patient faster; is more likely to be transmitted during sex
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If a host switches partners more frequently, which strain has an advantage? Why?
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more virulent strain because it can infect many new hosts, even though the original host dies relatively quickly
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If a host switches partners less frequently, which strain has an advantage? Why?
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less virulent strain because host lives long enough to infect multiple new hosts
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Virulent strains of HIV should spread most efficiently when?
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rates of partner change are high
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Benign strains of HIV should spread most efficiently when?
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rates partner change are low
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What has allowed for HIV to become so fatal
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in the 1970/80s there was a large sex industry in African cities and there was a high rate of partner change among homosexual men in the US/Europe
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There is some evidence that infecting patients with parasitic worms is a useful therapy against multiple sclerosis. What is thought to be the physiological mechanism by which worms may inhibit the progression of MS?
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All patients had MS. Those patients not infected with wormshad worsening symptoms of MS in a much shorter time than those patientsinfected with worms.
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One section of the paper is titled 'mismatches to modernity.' What does the author mean by this?
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Mismatches to modernity is the inability of our biology tokeep pace with cultural change
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'Aging and lifespan have thus NOT evolved because they are direct objects of selection; they have evolved as by-products of selection for reproductive success in younger organisms.' Explain.
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This is an example or statement explaining antagonisticpleiotropy. The idea is that any traitthat selects for increased reproduction (even if it has detrimental effectslater in life) will be selected for.
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How do cancer metastases represent a form of natural selection?
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The multiple clones will compete with each other forresources, space, etc. Natural selectionwill favor that benefiting clone. Theclone most favored will be the one that is able to spread/grow and also the onethat has the highest resistance to treatments.
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Why do imperfect vaccines select for greater virulence in pathogens?
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imperfect vaccines would kill say 80% of a pathogen, but leave the most virulent 20% behind because those pathogens that survive are going to be the pathogens that are best able to survive even in the presence of a vaccine
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Why might tolerating pathogens and cancer in the body be preferable to attempting to eradicate them?
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Tolerating a pathogen could be preferable to attempting toeradicate it simply because the cost of defending against it could exceed thatof the benefits.
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Why does the author find it surprising that whales and elephants exist?
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There is a proven correlation between larger body size andan increased risk of cancer. With whales being 1000X larger than humans andelephants 100X larger, it would be predicted that they have a fairly high rateof cancer. However, there is very few cases of cancer seen in these animals.
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What is the connection between cancer metastasis and invasive placentas?
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reproductive cancers (those of the uterus, cervix, ovaries, etc.) are more prevalent in animals with an invasive placenta (a placenta more directly linked with the blood supply of the animal) because those cells have learned to facilitate movement of cells that 'invades' the body
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Exam 5