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Unit I Evolution

Unit I Evolution. Learning Goal 1 Natural Selection is a major mechanism of evolution. Natural Selection is a major mechanism of evolution.

myles-barrett
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Unit I Evolution

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  1. Unit IEvolution Learning Goal 1 Natural Selection is a major mechanism of evolution

  2. Natural Selection is a major mechanism of evolution Natural Selection – in a population, organisms with a genetic trait that increases the chance of having offspring will pass on their genes to the next generation more than those without. Reproductive Fitness – relative ability to survive and leave offspring

  3. Requirements • More offspring born than can survive to adulthood • Competition for resources • Genetic variation/diversity within the population • Some varieties have an increased chance to survive long enough to reproduce.

  4. Genetic variation and mutation play roles in natural selection. A diverse gene pool is important for the survival of a species in a changing environment.

  5. Environments can be more or less stable or fluctuating, and this affects evolutionary rate and direction; different genetic variations can be selected in each generation.

  6. An adaptation is a genetic variation that is favored by selection and is manifested as a trait that provides an advantage to an organism in a particular environment.

  7. In addition to natural selection, chance and random events can influence the evolutionary process, especially for small populations.

  8. Mathematical approaches are used to calculate changes in allele frequency, providing evidence for the occurrence of evolution in a population. This can be done using the Hardy-Weinberg Principle

  9. The Hardy-Weinberg Principle The Hardy-Weinberg law is an algebraic formula to estimate the frequency of a dominant or recessive gene in a population based on the frequency with which the trait or condition is found in a population.

  10. A population with: • A large number of individuals • No migration • No mutations • Random mating • No natural selection Is said to be in Hardy-Weinberg equilibrium and no evolution can occur.

  11. The equation is p2 + 2pq + q2 = 1 where: p = the frequency of the dominant allele q = the frequency of the recessive allele p2 = the frequency of the homozygous dominant genotype 2pq = the frequency of the heterozygous genotype. p2 = the frequency of the homozygous recessive genotype.

  12. Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years. If 4 in 10,000 newborn babies have the disease, what are the expected frequencies of the three genotypes in newborns, assuming the population is at Hardy- Weinberg equilibrium? Why is this assumption not strictly correct?

  13. The allele y occurs with a frequency of 0.8 in a population of clams. Give the frequency of genotypes YY, Yy, and yy. Show your work!

  14. In the year 2374, humans finally developed the technology necessary for time travels. You are a scientist interested in the population genetics of extinct animals. Taking advantage of this technological advance, you decide to go to the past 8 million years to conduct a field work in Venezuela to study a population of Phoberomys pattersoni*, the world’s largest extinct rodent weighing approximately 700 kg (1500 lb) and looking vaguely like a giant guinea pig. The coat color of this rodent varies between tan (dominant) and brown (recessive). Assume the population is in Hardy-Weinberg equilibrium. You observed 336 tan Phoberomys and 64 brown Phoberomys during your study.

  15. What is the frequency of the homozygous recessive genotype? b) What is the allelic frequency of the dominant (tan) allele in the population? c) Of the animals you observed, how many were heterozygous?

  16. You make another trip to Venezuela and this time you observe 650 animals. d) How many of the 650 animals would you expect to be tan, assuming the population is still in Hardy-Weinberg equilibrium? e) How many of these tan animals are homozygous for the dominant allele? f) How many of these 650 animals would you expect to be brown, assuming the population is still in Hardy-Weinberg equilibrium?

  17. Key Vocabulary • Biological Evolution • Natural Selection • Reproductive Fitness • Competition 5. Variation 6. Adaptation 7. Hardy-Weinberg Principle 8. Genetic equilibrium 9. Hardy-Weinberg Conditions 10. Hardy-Weinberg Equation

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