How does genetic drift affect the diversity of a population? MT: Evolution

DNA frequency in a population changes simply by CHANCE not fitness Genetic Drift DNA frequency in a population changes simply by CHANCE not fitness Survivors are lucky, not more fit Deceased are unlucky, not less fit

Causes of Genetic Drift Random events: 1. natural disasters – hurricane, volcano, tsunami, earthquake, fire, etc 2. stepped on, ran over, picked up, put on a boat, stuck in a car, stuck to fur or clothing 3. at the wrong place at the wrong time

some individuals of a population colonize a new habitat Types of Genetic Drift 1. Founder’s Effect some individuals of a population colonize a new habitat 2. Bottleneck Effect few survivors are left to reproduce

Founder's Effect: some individuals of a population colonize a new habitat ex: Columbus bringing organisms to USA S. America: DNA Frequency 25% pink 75% red Spain: DNA Frequency 66% pink 33% red

After Katrina: DNA Frequency Bottleneck Effect: few survivors are left to reproduce ex Hurricane Katrina survivors! Before Katrina: DNA Frequency 66% pink 33% red After Katrina: DNA Frequency 40% pink 60% red

How does genetic drift affect the diversity of a population over time?

Genetic drift decreases diversity Genetic drift decreases diversity. In this case yellow and pink DNA are gone, and red DNA is now the majority. Genetic drift = decrease in DNA diversity

Let's Do This Together: Did this population of Rivasitus undergo genetic drift after a tornado killed all except one X and one O? Allele frequency of Original Population: 13/26 X's = 50% 13/26 O's = 50% Allele frequency of New Population: 1/2 X's = 50% 1/2 O's = 50% X O X O O X X X O O O O X X X X X X X X X O O O O O O O survivors!

NO DNA frequency the SAME before and after! Let's Do This Together: Did this population of Rivasitus undergo genetic drift? Original Population: 13/26 X's = 50% 13/26 O's = 50% New Population: 1/2 X's = 50% 1/2 O's = 50% NO DNA frequency the SAME before and after! X O O X X X O O O O X X X X X X X X X O O O O O O O X O

You Try: Allele Frequency of Original Population: Did this population of Rivasitus undergo genetic drift? Allele Frequency of Original Population: __/__ X's = ___% __/__ O's =___% Allele Frequency of New Population: __/__ X's = __% __/__ O's = __% X O O X X X O O X X X X O O O O XOXX O

different before and after! YES! DNA frequency different before and after! You Try: Did this population of Rivasitus undergo genetic drift? Original Population: 8/16 X's = 50% 8/16 O's =50% New Population: 3/5 X's = 60% 2/5 O's = 40% XOXX O X O O X X X O O X X X X O O O O

What does genetic drift do to the diversity of a population? If genetic drift occurred on a population, and then there was a large change in their environment, how would the population be affected? Critical Questions