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15 Cards in this Set
- Front
- Back
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Natural selection is one of the basic __________ of evolution?
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mechanism
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What is fitness?
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How much of a benefit an adaptation gives an organism to survive. The ability of an organism to survive and reproduce. A measure of the relative contribution of an idividual to the genetic makeup of the next generation.
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Why are adaptations environment specific?
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Adaptations can protect against predation, weather, competition with other populations.
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Which is NOT a positive factor that influences a populations fitness?
A) the number of healthy offspring produced B) the length of time individuals survive C) inbreeding D) adaptations such as mimicry |
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Evolution occurs because individuals in a population mustANSWER with each other.
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Compete |
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Why is it not considered an adaptation if an individual moves to a warmer climate because they function better there?
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An adaption is not what an individual does to improve its situation, it is a heritable trait that increases an individuals fitness. Moving to a warmer climate might be advantageous but not an adaption |
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List 3 factors that influence fitness below:
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The length of time an individual survives
The number of offspring the individual produces Likelihood offspring grow to maturity and reproduce |
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Explain Darwin's idea of the "struggle for existence" ?
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Within a population, there is a struggle for existence because of limiting factors and competition. There is a limit to the number of individuals in a given population. The amount of resources to support the population is also limited. Therefore, individuals must compete within the population for resources and to ensure their own survival.
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What is a heritable trait that increases an organism's fitness?
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adaptation
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What did the French author Francois de la Rochefoucauld say and what does his saying epitomize in relation to evolution?
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He said that ' The only thing constant in life is change," and it epitomizes how change is constant in nature.
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The length of time an individual survives, the number of offspring it produces, and the likelihood that those offspring will survive to reproduce are all factors that describe an organism's _______ .
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allele frequency
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Briefly explain the mechanism by which the allele for HgB S, the hemoglobin variant that causes sickle cell anemia in homozygotes, was able to evolve and propagate in certain human populations.
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There are many different alleles coding for the oxygen carrying protein hemoglobin which is found in red blood cells. The majority of the human population carry alleles coding for HgB A, which is normal functioning adult hemoglobin. In areas of Africa in which malaria is endemic a variant allele has evolved through time coding for HgB S. The HgB S gene causes sickle cell anemia, a debilitating disease, in homozygous individuals. The HgB A and HgB S alleles are codominant and as such are both expressed (not equally though) in heterozygous individuals. Malaria, which is caused by species of the genus Plasmodium carried by mosquitoes, is a disease in which a protozoan parasite infects the red blood cells. When the protozoan infects the red cell it utilizes certain cellular processes to evade the body's mechanisms for destruction of senescent and defective red cells so that the parasite can grow and reproduce. Heterozygous individuals (and HgB S homozygous individuals) are able to thwart infection by Plasmodium species because the cellular processes the parasite would use to keep the red cell from being destroyed are not available due to the presence of HgB S. Thus the allele for HgB S confers greater fitness to individuals in this environment than individuals that are homozygous for HgB A. However, whereas the heterozygous individuals are able to thwart infection due to the presence of HgB S and are simultaneously able to have oxygen delivered to tissues easily due to the presence of HgB A, the homozygous HgB S individuals develop sickle cell anemia due to the polymerization of HgB S molecules which distorts the shape of red cells causing blockages in capillaries and hypoxia in tissues. Thus the heterozygous individuals overall have the greatest fitness in comparison to the homozygous HgB A individuals (susceptible to malaria) and the homozygous HgB S individuals (develop sickle cell anemia). Hence, both alleles, including the seemingly maladaptive HgB S allele, have been able to propagate under this selection pressure.PreviousNext
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What are the 4 conditions required for natural selection |
1. organisms reproduce by passing their genes to the next generation 2. genetic variation between individuals in a population leads to trait variation 3. this variation is heritable 4. some factor causes variation in the fitness of organisms |
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Describe the 5 steps of frequency alleles getting higher fitness's as it increases in each generation |
1.Mutation creates variation 2.Unfavorable alleles selected against 3.Successful organisms reproduce 4.Favorable alleles inherited 5.Frequency of favorable alleles increases |
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