APB - Unit 7.3 - Evolution

APB - Unit 7.3 - Evolution

Hardy-Weinberg Equilibrium

Chapter 23

How do you know?

How do you know if you are looking at a new species?

First, you need to have a population - group of individuals of the same species living in the same area that are interbreeding with each other.

You assume that the population has a gene pool

or its genetic makeup that can be studied.

A means of gathering genetic data.

Hardy-Weinberg Equilibrium

p² + 2 pq + q² = 1

Where

p = frequency of the dominant allele

and

q = frequency of the recessive allele

How and Why did they come up with this idea? What was the mathematical logic?

https://www.genetics.org/content/179/3/1143

https://historyofinformation.com/detail.php?id=3834

https://www2.palomar.edu/anthro/synthetic/ synth_2.htm

Hardy-Weinberg Equilibrium has some conditions:

• There can be no mutations.

• There has to be random mating.

• There can be no natural selection.

• There has to be an extremely large population size.

• There can be no gene flow.

Some terminology

• Gene flow - immigration into or emigration out of the population

• Adaptive evolution - the environment may cause one set of characteristics to be more beneficial

• Genetic drift - impacts small populations more and caused by fluctuations in the environment such as droughts or floods that yield big fluctuations in allele frequencies

More terminology

• Founder effect - at least one mating pair of a species arrives in a new location

• Bottleneck effect - genetic drift after the population is reduced due to a possible "catastrophe" so that the population that exists is no longer representative of the original population.

Natural Selection & Relative Fitness (best adapted adding to the gene pool wins)

• Directional selection - one side wins

• Disruptive selection - either side wins

• Stabilizing selection - middle wins

Time to do some math.

There are practice HWE problems posted on Google Classroom.

You will be asked about the conditions necessary for HWE to occur on your test.

Just for fun.

Why not?

We will be having a Pandemic Version of April Animal Madness.

Review

• Hardy-Weinberg equilibrium - What is it, What are the conditions, and how to use it.

• We discussed gene flow, adaptive evolution, genetic drift, founder effect, and bottleneck effect.

• We discussed directional vs. disruptive vs. stabilizing selection.