Evolution, a term that is often controversial in public forums on education, is a term that simply means "change occurs." Looking around at the world, one can quickly assess that very few things remain unchanged from computer design to clothes and hairstyles. When considering BIOLOGICAL EVOLUTION, one is still observing change. However the changes occur in living organisms from one generation to the next. That is, BIOLOGICAL EVOLUTION is based on genetic changes, which range from subtle to drastic changes in an organism's DNA. These genetic changes may result in a new physical trait that may confer some advantage to the organism. That's where the process of Natural Selection comes in. The question that Nature asks each and every organism on this planet is: to survive and reproduce or NOT to survive and reproduce.

Introduction to Learning Module

This teaching/learning module is useful to introduce the concepts surrounding evolution. It is designed to be modular, each section can be used independently. The last two sections deal with the evolution of HIV drug resistance, which serves as an example of how evolution, adaptation, and diversity occur.

 
Overall Objectives:
1) Identify Darwin's principles of evolution and demonstrate knowledge to instructor through successful completion of worksheets and activities

2) Identify these principles in the context of HIV evolution
 

3) Analyze scientific data and draw conclusions about HIV evolution
 

4) Formulate hypotheses about how HIV will respond to different selective pressures
 

5) Predict outcomes of survival of HIV variants based on data
 

6) Apply knowledge about HIV evolution to other contexts

 

Section 1: Introduction to Evolution

Evolution is a process of change that can occur over millions of years (macroevolution) or over a few weeks (microevolution). Click here for a glossary of evolution-related terms.
 
 

Click here for an outline of how evolution works. This worksheet can be used as a study guide, homework assignment in conjunction with reading in a text, or as an in class activity.
 
 

For an example of the process of evolution, click here for slides describing the evolution of two species of peppered moth

To help present evolutionary ideas and concepts, download an evolution powerpoint presentation



Section 2: Active Learning Exercise

Click Natural Selection Simulation for exercise procedure

In this exercise, you will simulate natural selection with beans that represent "beetles" in two environments thus evaluating the effectiveness of natural selection in these habitats.The "beetles" will be easy or hard to find depending on how well they can be concealed by the environment. If they are successful (not eaten by a predator) they will be able to produce more offspring with the same advantageous trait.

Objectives

After completing this exercise, students should be able to:
1. Define: natural selection, random, nonrandom. Possible outcomes of natural selection process. Genetic variation vs Phenotypic variation
2. Explain the basic ideas of the process of natural selection.
3. Determine if a sample set of data represents random or nonrandom results.
4. Determine which variation of an organism is the most successful and the least successful in a species, in a given sample set of data.
5. Determine if an environment allows natural selection to occur for a given variation in a species, in a given sample set of data.
 



Section 3: Basics of HIV

For the past 20 years, AIDS incidences has increased worldwide and is a major health concern for humans. HIV is primarily a sexually transmitted disease but can be transmitted from mother to child and through dirty needles by IV drug users. A cure for AIDS is still a major goal of the scientific community. Some of the reasons why it has been so difficult to find a cure for AIDS is due to the biology of the virus itself. A major obstacle in the race to find a cure for AIDS is that HIV proteins evolve so quickly, escaping immune system defenses.

Section 4: Understanding HIV evolution


 
 

What do we know?
 

1) HIV evolves (changes) over time to evade host immune responses
2) HIV RT has poor editing ability therefore HIV has high mutation rates and these mutations get passed on to the next generation of viruses
3) Selective pressures on HIV evolution include immune cells, anti-HIV drugs, vaccines
4) HIV changes at the DNA level in order to change amino acids in many of its proteins

What do we want to know?

1) What are the specific changes in HIV that increase drug resistance?
2) How specific changes in HIV arise and how these changes alter protein structure?
3) How does HIV evolution fit into Darwin's Theory of Evolution?
4) What happens with multiple changes in HIV during its evolution?
 
 

Step 1: Print out the following handout on the Biology of Protease Inhibitors for background about the enzyme protease

Step 2: Use the following worksheet, Evolution of HIV Protease Resistance as an in-class activity, which includes scientific data for students to analyze the evolution of protease resistance.

This module was created by:

Allison Welch, PhD

Kristen Williams, PhD

Cathy Silver-Key, PhD

Brian Rybarczyk, PhD

Department of Biology, University of North Carolina - Chapel Hill, Chapel Hill, NC 27599