Please enable JavaScript.

Coggle requires JavaScript to display documents.

Chapter 22 - Coggle Diagram

- - - - The main source in genetic variation among human individuals is the reshuffling of alleles in sexual reproduction
        
        Gene flow
        
        the transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
        
        relative fitness- the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.
  - - - cause extreme variants in a population
    - - Disruptive selection-favors individuals at both ends of the phenotype selection
        
        Occurs when conditions favor individuals at both extremes of phenotypic range over intermediate phenotypes
      - Directional selection- acts against individuals at one of the phenotypic extremes
        
        balance selection- maintains stable frequencies of two or more phenotypic forms in a population
        
        In intrasexual selection- selection within the same sex, individuals of one sex compete directly for mates of the opposite sex.
        
        intersexual selection(mate choice)- individuals of one sex (usually the females) are choosy in selecting their mates from the other sex.
        
        frequency-dependent selection- the fitness of a phenotype depends on how common it is in the population.
      - heterozygote advantage- Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
  - - - gene duplication-is an important source of new genetic material
        
        point mutation in noncoding regions of DNA result in neutral variation, differences in DNA sequence that do not confer a selective advantage or disadvantage
        
        although mutations most often do not result in favorable adaptations, they are the primary way that new alleles come about
      - Characteristics of genetic drift
        
        -it can lead to loss of genetic variation in a population
        
        -can cause harmful alleles to become fixed in a population
        
        -can cause allele frequencies to change at random
        
        genetic drift- Chance events cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations
        
        Founder effect- When individuals isolated from larger population; smaller group may establish a new population whose gene pool differs from source population
        
        Bottleneck effect-Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions
      - evolution is a change in a populations allele frequencies over generation
- - - - evolution
      - Descent=shared ancestry resulting in shared characteristics
      - Modification=accumulation of differences
        
        has given rise to the diversity of life
- - - - related species can have characteristics that have underlying similarity resulting from common ancestry
        
        Homology
        
        skeletons of arms, forelegs, flippers, wings of different mammals are homologous structures that represent variations on structural theme that was present in their common ancestor
- - - - 1830-Lyrell w/principles of geology
        
        1858-Malay Archipelago Wallace and Charles Darwin- Create hypotheses of natural selection
        
        1859-Charles Darwin publishes the book Origin of Species
        
        orchid mantis-illustrates unity of life highlighting shared characteristics
        
        Darwin saw a connection between natural selection and the capacity of organisms to over produce