AP Biology Day 9

Opener Read the “Calculations and Creating a Histogram” section of your Modeling Natural Selection Handout. Answer these questions, in your notebook. What is a histogram? What can a histogram tell us about a population of organisms?

Homework Turn in Hardy Weinberg Practice Finish for Homework, the Hardy Weinberg Packet Assessments are graded, we will go over them on Friday. If you have a zero on one exam. Need to come see me before Friday

Plant Hairs You need to count the number of trichomes on each plant and record down the number How are we going to do that? All the hairs? Hairs on a certain part of the plant? Keep careful record of what plant has what “hairyness”

Histogram Set up axes: Create a histogram—one bar for each range X-ranges from data table Y-number of plants in range Create a histogram—one bar for each range Helps predict how things will shift in a population: this is evolution!

Culling We need to “weed” out the plants that don’t fit in the spectrum Cut at the base carefully

Mating Rated R

Agenda Other causes of evolution Hardy Weinberg Practice

LT #4 I can identify and describe processes that change the genetic structure of a population, resulting in evolution

Genetic Drift Fluctuations in allele frequencies in small populations Result of random chance No guaranteed adaptive benefit Genetic drift affects the genetic makeup of the population but, unlike natural selection, through an entirely random process. So although genetic drift is a mechanism of evolution, it doesn’t work to produce adaptations.

Causes of Genetic Drift. . . Bottleneck effect: An event reduces the population size Founder effect: A new population is established by a small number of individuals In both cases: the NEW gene pool can differ significantly from the old

Gene Flow Adding genes or alleles to a population through the movement of individual organisms No guaranteed adaptive benefit

Mutations Mutation Can effect phenotype No guaranteed adaptive benefit Random changes in the nucleotide sequence of genes Can effect phenotype No guaranteed adaptive benefit

Non-random Mating Non-random mating No guaranteed adaptive benefit Selecting mates No guaranteed adaptive benefit

Natural Selection! We already know about this. . .

The Five Fingers of Evolution Mutations Non-random mating Gene Flow Natural Selection Genetic Drift

Hardy-Weinberg Practice Get out the two packets from last class to work on