Comparing Artificial, Natural, and Sexual Selection

Evolution  A change in species over time  But how does this happen? – 3 ways  Artificial Selection  Natural Selection  Sexual Selection

Artificial selection Variation exists naturally in a population Humans select the variations (traits) we found useful “descendants” of wild mustard

Selective Breeding Humans create the change over time “descendants” of the wolf

Natural Selection  Three things needed  A big, diverse population with heritable adaptations (variation of traits)  Variations ultimately caused by mutation  More born than survive: selection pressures that favor some individuals over others  Examples  Predation – may favor those who run faster  Disease – may favor those with better immune systems  Competition for resources (food, water, space, etc) – may favor those who are bigger/stronger/smarter  Time  Many generations needed to pass on traits

Natural Selection

Sexual Selection  Instead of traits that help survival, they are traits to help reproduce  Usually hurts ability to survive  Two types  Male competition  Weapons for combat  Large Size  Female (mostly) choice  Looking fancy  Causes males and females to look very different

Sexual Selection  Male Competition  Female Choice

Sexual vs. Natural Selection

Fitness  The ability to survive AND reproduce  Used to describe Natural and Sexual selection  Survival of the Fittest  Basic idea of evolution by natural selection  The organisms that can survive and reproduce the most successfully pass on their adaptations

Selection gone bad!  Unexpected consequences of:  Pesticide Resistance  Antibiotic Resistance

Resistance  Spray the field, but…  insecticide didn’t kill all individuals  variation  resistant survivors reproduce  resistance is inherited  insecticide becomes less & less effective