Ch. 17 The evolution of populations Objectives Identify the main sources of genetic variation in a population Determine allele frequencies given population data Describe the different mechanisms of speciation (a new species arising) Ch. 17 The evolution of populations

Populations and Gene Pools All the genes of a population, including the different alleles for each gene Q: What is allele frequency and how do I calculate it? The number of times an allele appears in a population divided by the total number of alleles for that gene.

Lets Practice!

Allele Frequency Calculation Genotypes: BB – Dark Brown Bb – tan bb – light What is the allele frequency for b? Out of 40 total alleles for color (2 alleles/bug) 22/40 = .55 or 55%

17.1 – 17.2 Genes and Population Change FQ’s: How do we get diversity in a species? What are the types of natural selection? What causes reproductive isolation In evolution, what does a “cause and effect” relationship look like?

Sources of Genetic Variation Mutations Sexual Reproduction (combinations of alleles) Lateral Gene Transfer (bacterial conjunction)

Natural Selection on Polygenic Traits

Isolating Mechanisms that cause Reproductive Isolation Behavioral – Songs or rituals Geographical Temporal – time of day or seasons

Survival of the weak and scrawny 5 min. SSR Working on questions with your group Group discussion Survival of the weak and scrawny

17.3 – The Process of a New Species Arising = Speciation FQ: How do new species arise? ET: Considering your butterfly graph, do you think our butterflies will evolve into separate species?