chapter 17: evolution of populations. chapter 17.1 (pgs 482- 486): genes and variation
TRANSCRIPT
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Chapter 17: Evolution of Populations
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Chapter 17.1 (Pgs 482-486):Genes and Variation
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Phenotypic Variation
- Most organisms contain two sets of genes- One allele from each parent
- Different combinations of alleles and environment produce variation in phenotypes
- Natural selection acts directly on phenotypes, not the alleles
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Populations and Gene Pools
- A group of individuals of the same species that mate and produce offspring is called a population
- These individuals share a gene pool, all the genes and alleles for each gene in a population
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Allele Frequency
- The # of times an allele occurs in a gene pool, compared to the total # of alleles for that gene
- Evolution occurs when allele frequency in a population changes over time
- Populations, not individuals, evolve
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Single-Gene Traits
- Are controlled by only one gene
- Only have two alleles
- May only have two or three distinct phenotypes
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Polygenic Traits
- Are controlled by two or more genes- Each gene has two or more alleles
- Has many possible genotypes and even more different phenotypes