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27 Cards in this Set
- Front
- Back
What two claims are put forth by the theory of evolution?
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(1) species have changed over time
(2) new forms have arisen from common ancestors |
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Provide evidence that species have changed through time (direct observation, there are 6)
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- peppered moths evolved in response to pollution (validated by experimental evidence)
- evolution of pesticide resistance (increase in # species resistant to pesticide) - decrease in weight and horn length of bighorn rams due to hunting - HIV evolved to be resistant to AZT - Finches evolved deeper beaks following drought - size of cod fish decreased due to fishing and then increased due to moratorium on fishing |
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Provide evidence that species have changed through time (fossil records, there are 2)
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- transitional/intermediate forms of species
- lineage splitting in diatom Rhizosolenia |
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Provide evidence that new forms have arisen from common ancestors
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Fossil record (intermediate forms between two species)
Direct observation (ring species of salamander)Homology (vestigial structures, embryological similarities, genetic homologies) |
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What is the difference between homology and analogy?
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Homology: similarity due to shared ancestor, not necessarily functional (e.g. early embryonic development)
Analogy: similarity due to shared way of life (not due to common ancestor, e.g. panda's thumb) |
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What are Darwin's four postulates of evolution by natural selection?
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1. TURNOVER: There needs to be multiple units that undergo death and reproduction
2. VARIABILITY: There must be variability among the units 3. HERITABILITY: Variation must be passed down from parents to offspring 4. DIFFERENTIAL REPRODUCTIVE SUCCESS: Some variants must be more likely to survive than others. |
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What is the role of genetic drift?
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Neutral evolution and non-adaptive evolution, but also may act as a creative force to explore "rugged fitness landscapes". For example, the evolution of HIV from SIV had a relatively high fitness valley and adapted to humans easily.
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What are the three potential hypothesis for the evolutionary basis of disease symptoms?
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(1) adaptation of the host
(2) adaptation of the pathogen (3) side effect of their interaction |
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Describe the arms race between prey and predator
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If prey evolve traits to avoid detection from predator, predators evolve traits to better detect/hunt prey. This continues back and forth.
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What advantage do parasites and pathogens have over animals, and how have animals overcome this disadvantage? |
Pathogens and parasites have short life spans, huge population sizes, and high mutation rates. Animals have overcome this by evolving adaptive immunity. |
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How do parasites/pathogens escape the attack from an adaptive immune system?
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e.g. african sleeping sickness - continual switching of surface antigens (variable surface glycoprotein, VSG)
e.g. influenza - antigenic drift: "changes to the flu virus that happen slowly over time". antigenic shift: when two strains recombine in the same cell. |
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What is the problem of antibiotic resistance?
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Bacteria evolve very quickly, and the horizontal transfer of resistance factors, and compensatory mutations make up for cost of resistance
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How do fitness landscapes influence antibiotic resistance? |
In the absense of antibiotic, you'd expect pathogens to revert to wild (sensitive) type, but other mutations compensate for the cost of antibiotic resistance, creating a fitness valley that prevents that revertion. |
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What does Ro represent, and what does it mean if it is above or below 1?
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Basic reproductive number. Mean # of secondary infections arising from one infected individual in a totally susceptible population.
If Ro > 1, then the disease is spreading. The larger it is, the harder it is to control. |
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Define virulence, give example.
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reduction in lifetime reproductive success of host due to harm done by pathogen. e.g. over time, Myxoma virus became less virulent to rabbit population.
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How does mode of transmission affect virulence?
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1) vertical vs horizontal - opportunities for horizontal transmission increase virulence (e.g. fig wasps and parasitic nematodes)
2) direct vs vector tranmission - vector-based confers greater virulence |
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How does opportunity for transmisison affect virulence?
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Behaviour of host and vector affect the likelihood that the parasite/pathogen infects an individual and spreads to others. As does the population structure and density.
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Factors affecting disease emergence
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1) opportunity for transmission between animal resevoir and humans (determined by animal/human contact, animal-animal contact)
2) opportunity for spread of new disease (human population structure/density) |
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Factors affecting drug resistance
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1) Frequency/intensity/variety of drug use (overprescription, non-med use)
2) opportunity for transmission of antibiotic resistance factors + pathogens (in bodies, hospitals, public places) |
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What are the 5 assumptions of the Hardy-Weinberg equilibrium?
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- no selection
- no mutation - no migration - random mating - infinite population size |
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In a HW equilirbium, given the frequency of both alleles, what is the frequency of each diploid combination of P and Q?
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PP = P^2
PQ or QP = 2PQ QQ = Q^2 |
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How do you calculate expected equilibrium frequency of a recessive allele under mutation-selection balance?
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qˆ= sqrt(µ/s)
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Give two examples of heterozygote advantage
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1) Cystic fibrosis heterozygote might provide carriers resistance to typhoid, cholera, others.
2) Sickle-cell anemia: in normal regions, w (fitness) of ++ > w of S+. in malaria regions, Ws+>W++! |
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Why hasn't natural selection eliminated genetic disease? (there are 5!)
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- Heterozygote advantage (e.g. CF, sickle-cell anemia) - Genetic drift/founder effect (e.g. Tay-Sachs, hereditary tyrosinemia) - Recurrent mutation with, perhaps, mutational bias (e.g. Huntington's) - Late onset (e.g. Huntington's) - Fitness tradeoff (equal or greater fitness prior to onset)
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How does the mutational bias affect the likelihood of a child being born with a Huntington's gene?
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number of repeats more likely to increase than decrease, and male sperm mutations increases with father's age
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Be able to calculate the expected frequency of an allele in a population given their fitnesses
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Ok :)
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Heritability?
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Go over the slides and write out the notes, it's not flashcard friendly!
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