Chapter 17: Evolution of Populations

Chapter 17.1 (Pgs 482-486):Genes and Variation

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

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

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

Single-Gene Traits

- Are controlled by only one gene

- Only have two alleles

- May only have two or three distinct phenotypes

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