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Evolution (Chapter 23 (Genetic Variation (Genetic variation- differences…
Evolution
Chapter 23
Genetic Variation
Genetic variation- differences among individuals in the composition of their genes or other DNA sequences
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Depends on mutations, gene duplication, or other processes produce new genes and alleles
Neutral variation- differences in DNA sequence that do not confer a selective advantage or disadvantage
Altering gene number or position- duplication of genes due to errors in meiosis (such as crossing over, DNA replication, and transportable elements)
Rapid reproduction- mutation in every 100,000 genes per generation in plant and animals, prokaryotes are much more prone to mutations
Sexual reproduction- genetic variation in a population results from the unique combination of alleles have originated from past mutations
Hardy-Weinberg
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Gene pool- consist of all copies of every type of allele exists for a particular locus in a population
Hardy-weinberg equation- one way to assess whether natural selection or other factors are causing evolution at a particular evolution
Hardy-weinberg equilibrium- in a population that is not evolving, allele and genotype frequencies will remain constant from generation to generations to provided that only Mendelian segregation and recombination of alleles at work
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Conditions: 1. No mutations 2. Random mating 3. No natural selection 4. Extremely large population size 5. No gene flow
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Adaptive Evolution
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Sexual Selection
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sexual dimorphism- a difference in secondary sexual characteristics between males and females of the same species
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Intersexual selection- individuals of one sex are choosy, in selecting their mates from the opposite sex
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Frequency-dependant selection- the fitness of a phenotype depends on how common it is in the population
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Chapter 22
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Evolution is Supported
The evolution of drug resistant bacteria- Bacteria and viruses can produce new generations in a short period
Homology
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Homologies
Homologous structures- represent variations on a structural theme that was present in their common ancestor
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Fossil record- documents the pattern of evolution showing the past organisms differ from the present or extinct organisms
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Chapter 24
Reproductive Isolation
Biological species concept- a group of populations whose members have the potential to interbreed in nature and reproduce viable, fertile offspring
Reproductive isolation- the existence of biological factors that impede members of two species from interbreeding and produce viable fertile offspring
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Ecological species concept- defines a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of the environment
Speciation Occurs
Allopatric speciation- gene flow is interrupted when a population is divided into geographically isolated subpopulations
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Polyploidy- a species may originate from an accident during cell division that results in a extra set of chromosomes
Autopolyploidy- is an individual that has more than two chromosome sets that are derived from a single species
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