If we were to draw a graph representing the height of everyone in the room (x axis: height y axis: # of students) what shape would you expect it to take? Line up along the sides and back of the classroom by height. Two (or more) people of the same height should stand in front of each other. Challenge: do it without talking and under five minutes.

What is a normal distribution?

Did your class have a normal distribution? If not, why might that be? Or why might not all classes show a normal distribution?

Did your class have a normal distribution? If not, why might that be? Or why might not all classes show a normal distribution? Small sample size Students still growing

Natural Selection can affect allele frequency in predictable ways Directional selection Stabilizing selection Disruptive selection

Directional selection Finch beaks

Stabilizing Selection Woodpeckers and wasps on gall-fly population

Disruptive Selection Male lazuli birds

Other mechanisms of evolution Gene flow o Movement of alleles from one population to another Genetic drift o Changes in alleles frequency due to chance o Results in loss of diversity Bottleneck effect o Greatly reduces size of population o Ex: natural disasters, over-hunting Founder effect o Small number of individuals colonize a new area

Sexual Selection Occurs when certain traits increase mating success Reproduction is usually more energetically costly for females than males, which means females are often more “picky” about mates Intrasexual selection – males compete to win over females Intersexual selection – males display certain traits to win females (showing off tail feathers, doing a dance, signing a song)

Sexual Selection o Birds of paradise o More birds o

Speciation through Isolation Speciation o Development of new species from one existing— o Discuss dog breeds…..6ft. Irish wolfhound v. chihuahua Reproductive isolation o Physical inability to mate Behavioral isolation o Differences in courtship/mating behavior Geographic isolation o Physical barriers that divide population Temporal isolation o Timing barriers –timing prevents reproduction

11.6 Patterns of Evolution Convergent (come together) evolution: evolution toward similar characteristics in unrelated species due to benefit within environment. Examples- wings on birds/insects, tail fin on dolphin and sharks, shells of turtles and mollusks

Divergent (Divide) Evolution: when closely related species evolve in different directions and become different Examples: red fox and kit fox

Coevolution: when two or more species evolve in response to changes in each other. Examples: ant and acacia plant; bird vision & lizard with tail like a head.