Biology I Chapter 23

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Yasham
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84418
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Biology I Chapter 23
Updated:
2011-10-06 18:20:13
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Biology Campbell Evolution Populations
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Chapter 23 of Campbell's Biology Textbook 8th - The Evolution of Populations
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  1. (T/F) The evolutionary impact of natural selection is only apparent in changes in individual an organism.
    The evolutionary impact of natural selection is only apparent in changes in populations of organisms over time.

    The populations evolve, not the individuals members.

    One common misconception about evolution is that individual organisms evolve. It is true that natural selection acts on individuals: Each organism's combination of traits affects its survival and reproductive success compared to other individuals.
  2. What is microevolution?
    The evolutionary change in populations on the smallest scale as changes in allele frequencies occur in a population over generations.
  3. What are the main mechanisms for allele frequency changes (essentially microevolution)?
    • Natural selection - individuals in a population exhibit variations in their heritable traits, and those with traits that are better suited to their environment tend to produce more offspring than those with traits that are less suited.
    • Genetic drift - chance events that alter allele frequencies
    • Gene flow - the transfer of alleles between populations
  4. What did Mendel do?
    Mendel published a paper on inheritance in pea plants. He proposed a particulate model of inheritance, which stated that organisms transmit discrete heritable units (now called genes) to their offspring.
  5. (T/F) Phenotypes are a product of an inherited genotype and many environmental influences. The entire phenotype may be passed down to the next generation.
    False

    While phynotypes are a product of an inherited genotype and environmental factors, only the genetic part of the variation may be passed down.

    For example, a body builder does not pass down his large muscles.
  6. Describe a phenotype.
    The physical and physiological traits of an organism, which are determined by its genetic makeup.


    • For example, we distinguish between an organism's appearance or
    • observable traits as the phenotype and the genetic makeup as the
    • genotype.

    In the case of flower color in pea plants, PP and Pp have the same phenotype (appearance of the purple color) but 3 different genotypes (PP - purple, Pp - purple, and pp - white). P represents the dominate allele and p represents the recessive allele.

  7. Describe a genotype.
    The genetic makeup, or set of alleles, of an organism.

    For example, we distinguish between an organism's appearance or observable traits as the phenotype and the genetic makeup as the genotype.

    In the case of flower color in pea plants, PP and Pp have the same phenotype (appearance of the purple color) but 3 different genotypes (PP - purple, Pp - purple, and pp - white). P represents the dominate allele and p represents the recessive allele.

  8. What is a discrete character within a population?
    An either-or basis in which the character is determined by a single gene locus with different alleles that produce distinct phenotypes.
  9. What is a quantitative character within a population?
    A variation within the population that usually results from the influence of two or more genes on a single phenotypic character.

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