Download Hardy-weinberg equilibrium

Science Starter #4 – 2/27/17

Draw a graph that shows a normal distributed
population being disruptively selected for.
What might happen to this population?

TURN IN YOUR:

 1)
Histogram Lab
 2) Evidence Packet

TAKE OUT A SHEET OF PAPER FOR NOTES 9.3
A quick recap of types of selection

Three types of selection:
1.
2.
3.
Directional
Stabilizing
Disruptive
Type 1: Directional Selection
average
population average
New population
New
Individuals with ONE extreme form of trait has higher
fitness
Phenotype
Type 2: Stabilizing Selection
New population average
Average form of trait has highest fitness
Phenotype
Type 3: Disruptive Selection
Individuals with EITHER extreme trait has a higher
fitness and most likely results in two new species
Phenotype
NOTES 9.3:
HARDY-WEINBERG
EQUILIBRIUM
Ch. 16-1 pp. 317-320
The Gene Pool


Gene Pool- total genetic information stored in a population
 Ex. Alleles for green and brown skin in a frog population
Gene Frequency: Each allele exists at a certain percentage
 6 frogs = total of 12 alleles (skin color gene = two alleles)
 7 G (green) alleles and 5 g (brown) alleles
Normal Distribution

Normal distribution = Population is IN equilibrium
Hardy-Weinberg Genetic Equilibrium
G. H. Hardy and Wilhelm Weinberg
 Hardy-Weinberg equilibrium describes
populations that are NOT evolving

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Hardy-Weinberg Equilibrium (HWE)

Genotype frequencies stay the same over
time as long as FIVE conditions are met:
Conditions for HWE:
#1 Large Population


Population: group of the same species that live in a
specific area
Ideally an infinitely large population
Conditions for HWE:
#2 No Gene Flow

Gene flow: process of genes moving from one
population to another
 Ex:
Movement of individuals into and exit of the
populations (Immigration and emigration)
Conditions for HWE:
#3 No Mutations
Mutation: change in the sequence of DNA
 Alleles in the population stay the same

Conditions for HWE:
#4 Random Mating

The selection of choosing a mate between
individuals is random
Conditions for HWE:
#5 No Selection Occurs


All phenotypes of the population have equal
chances of surviving and reproducing
Natural selection does not happen