Biology - 11.4 Hardy-Weinberg Equilibrium

The creators of the Hardy-Weinberg equilibrium

-made by British mathematician Godfrey Hardy and German physician Wilhelm Weinberg -in 1908, Hardy and Weinberg showed that genotype frequencies in a population stay the same over time as long as certain conditions are met. -They also showed that these frequencies can be predicted. -Hardy and Weinberg identified 5 conditions needed for a population to stay in equilibrium.

Name two things that can change in a population/species:

1. Perhaps a flood carries part of a population to a new place. (this population may then go through genetic drift.) 2.A mutation mau create a new allele that allows some individuals to run faster and get away from predators (the frequency of this allele may then increase in the gene pool as it is passed on to future generations.)

what does the 1 in the equation represent?

100% of the population

There are __ factors that can lead to evolution.

5

...Their model shows that there are __ factors that can lead to __.

5 evolution

Genetic drift

Allele frequencies can change due to chance alone.

Natural selection

Certain traits may be an advantage for survival. Alleles for these traits increase in frequency.

Sexual selection

Certain traits may improve mating success. Alleles for these traits increase in frequency.

What are the five factors that can lead to evolution?

Genetic drift Gene flow Mutation Sexual selection Natural selection

Mutation

New alleles can form through mutation. Mutations create the genetic variation needed for evolution.

Hardy-Weinberg equilibrium

Populations that meet these conditions are not evolving. They are said to be in Hardy-Weinberg equilibrium: - Very large population: No genetic drift can occur. -No immigration or immigration: No gene flow can occur. -No mutations: No new alleles can be added to the gene pool. -Random mating: No sexual selection can occur. -No natural selection: All traits must equally aid in survival.

Gene flow

The movement of alleles from one population to another changes the allele frequencies in each population.

Population biologists compare predicted genotype frequencies with __ frequencies.

actual

As environments change, populations either __ or go __.

adapt extinct

In their studies, Hardy and Weinberg concluded that evolution should be expected in populations almost __ of the time.

all

...It can be hard to figure out what is causing a population to __.

change

Biologists often compare their data to a model to study how a population is __.

changing

The conditions needed for Hardy-Weinberg equilibrium are not __ in nature.

common

Evolution is __.

continuous

For traits in simple __-__ systems, biologists can predict genotype frequencies using the Hardy-Weinberg equation.

dominant-recessive.

In nature, populations evolve, or change in response to their __.

environments

values predicted by the equation are those that would be present if the population is in __.

equilibrium

Hardy-Weinberg equilibrium describes populations that are not __.

evolving

Populations that are not in Hardy-Weinberg equilibrium are __.

evolving

The Hardy-Weinberg equation is used to predict genotype __ in a population.

frequencies

Use the Hardy-Weinberg equation to calculate predicted genotype __ for this population.

frequencies

If the __ data do __ match the equation, the population is __ in equilibrium; it is __.

genetic not not evolving

Environment's are always changing, though often very slowly relative to a __ __. Evolution is a __ to these changes.

human's lifetime response

...Therefore, biologists use __ to learn more about how populations change over time.

models

What is the Hardy-Weinberg equation?

p^2 + 2pq + q^2 = 1

When a population goes extinct, a different species takes its __, and the cycle __.

place continues

Many things affect how __ evolve.

populations

...Biologists can compare real data to data __ by this model. They can learn more about how the population is __. The model also gives a __ for testing the factors that can lead to evolution.

predicted evolving framework

Real populations __ meet all five conditions. However, Hardy-Weinberg equilibrium is still a very important __.

rarely concept

...If they are the __, the population is in Hardy-Weinberg equilibrium for that trait.

same

...Some parts of a population's environment may stay the __ over time. However, other things will likely __.

same change

what does p represent?

the frequency of the dominant allele

what does q represent?

the frequency of the recessive allele

what does 2pq represent?

the heterozygous genotype

what does p^2 represent?

the homozygous dominant genotype

what does q^2 represent?

the homozygous recessive genotype

Studying populations in nature can be __.

tricky