1. Biology: Life on Earth (Audesirk)
Chapter 22
Biology: Life on Earth (Audesirk)
Evolution
Chapter 15

2. Evidence for evolution
Chapter 15
Direct observation (i.e. antibiotic resistant bacteria)
Homology (similarity resulting from common ancestry-structure, embryonic development, molecular similarity)
Fossil record
Biogeography-endemic species: only found in one place.

3. Population Genetics and Evolution
Evolution: Change in gene frequencies in a population over time
Due to differential reproduction among organisms bearing different alleles
Fitness of the selected allele leads to viable offspring
Not "good” or “purposeful.”

4. Population Genetics and Evolution, cont.
Chapter15
Natural selection=how adaptations arise.
Individuals with phenotypes that increase the chance of survival & reproduction
causes changes in gene frequencies of a population
Mutations: Source of new alleles

5. Rules of natural selection
Chapter 15
Individuals don’t evolve, populations do!
Variation and diversity of phenotypes (and genotypes) is a pre-requisite
Place based: an adaptation for one environment would not necessarily be an adaptations for another environment.

6. Selection - Sickle Cell Anemia
Chapter 15
Genotypes
HH = Normal
Hh = Trait
hh = Sickel Cell Anemia

7. Selection - Malaria
Chapter 15

8. Stabilizing Selection & Balance Polymorphism
Biology: Life on Earth (Audesirk)
Stabilizing Selection & Balance Polymorphism
Chapter 15 HH Hh hh
Homozygous Normal
Homozygous Defective
Heterozygous
Dies of malaria
Lives and reproduces
Dies of sickle-cell anemia
Two or more alleles, each producing a different phenotype, may be maintained in a population by opposing environmental pressures. The alleles for normal (H) and sickle-cell (h) hemoglobin are maintained by selection against both homozygotes. Heterozygotes (Hh) reproduce the most, thereby keeping both alleles in the population. HH Hh hh
Dies of malaria
Lives and reproduces
Dies of sickle-cell anemia HH Hh hh
Chapter 15