Modern Evolutionary Theory Genetics + Natural Selection = Modern Evolutionary Theory

Weaknesses in Darwin’s Theory Did not explain the genetic basis for variations He said variations occurred, but he couldn’t explain WHY. Did not consider the origin of life itself

Mutations  Variations Mutations = random changes in the DNA Mutations in DNA CAUSE variations explained in Darwin’s theory of Natural Selection.

Likelihood of Evolution More Likely to Evolve Less Likely to Evolve Sexual Reproduction Asexual Reproduction Genetic Variation No Variation (Identical to parent) More Mutations Less – No Mutations

Human Impact on Natural Selection Resistance to Pesticides insects naturally resistant to pesticides survive and reproduce Result: increase in resistant insect population Resistance to Antibiotics bacteria naturally resistant to antibiotics survive and reproduce Result: increase in resistant bacteria population Overuse of these substances can result in unintentional consequences!