Assignment 11*
The What, Why, and How of  Change in Populations
   

Goals:

  1. 1. To discuss the significance of the Hardy-Weinberg Theorem as it relates to evolution.
  2. 2. To use the Hardy-Weinberg Theorem to solve problems involving populations.
  3. 3. To understand that most populations evolve due to a combination of factors.

Objectives: Students will be able to

  1. - calculate allele and genotype frequencies of a population,
  2. - apply the Hardy-Weinberg theorem and equation to determine whether a population is evolving or not,
  3. - state the assumptions required for Hardy-Weinberg equilibrium,
  4. - explain how violation of each of the assumptions of Hardy-Weinberg equilibrium can lead to evolution,
  5. - define the following agents of evolutionary change and how they can affect the genetic makeup of populations:
    1. gene flow
    2. genetic drift
    3. founder effects/bottlenecks
    4. non-random mating
    5. natural selection
    6. gene flow
    7. mutation

hardy_weinberg You hear about evolution frequently in the media today.  Recent court cases about teaching of evolution and intelligent design keep the topic in the spotlight.  Through your coursework and discussions, you are beginning to understand the basic components of the process of evolution.  Most students, when asked about evidence for evolution, are aware of fossils and genetic studies on mutations.  Yet, have you ever wondered if there is a scientific way to determine whether or not a particular trait is evolving?  The answer is yes. 

Evolution can be defined as the change in allele frequencies (i.e., genotypes) over time.  In the early 1900s,  G. Hardy and W. Weinberg developed a mathematical model that predicts genotype frequencies when a population is not being affected by evolutionary forces.  The model is known as the Hardy Weinberg Equilibrium Model.  The Hardy-Weinberg equilibrium is a baseline against which the evolution of populations can be measured and is the foundation for the genetic theory of evolution.  When a population is in Hardy-Weinberg equilibrium, there is no change in gene frequencies and, therefor, no evolution of the population.   The conditions required for Hardy-Weinberg equilibrium are almost never met in nature, however.  As a result, gene frequencies change and evolution occurs.  If a population is not at Hardy-Weinberg equilibrium, then we know that one or more of the conditions required for the equilibrium are not being met.mating

For the next two weeks, you will study how various factors affect gene frequencies of populations using a computer simulation.   The simulations involve many of the concepts and terms that you already worked with and read about.  You will see how genotypes change as a result of environmental pressures, population characteristics such as size, and chance effects.  While the activity will demonstrate the process of changing organisms over time in a few minutes, it accurately models the actual process of evolution that occurs over decades to millions of years.

Your Instructor will provide you with directions for using the computer simulations and for completing any written work that you need to turn in.