Survival of the Fittest— Battling Bacteria
Setting the Scene
Bacteria have cell walls made of peptidoglycan, which is made of carbohydrates and proteins. Some bacteria have more proteins in their cell walls and some have more carbohydrates. The combination of protein and carbohydrates allows bacteria to survive in various environments.
The research team studying the bacteria hypothesized that the color of the bacteria’s cell wall and the strength of the cell wall are related. To test the color and cell wall strength hypothesis, your team will conduct an experiment in which a brown bacteria and an orange bacteria are crushed together.
You have 10 brown and 10 orange candies in your evolution materials so that you can perform the experiment below. Watch the video to see the procedure for red vs blue bacteria.
Questions - Answer in your notebook.
- Evolution is a change in the allele frequency of a population over time. (Remember, and allele is just a version of a gene.) We started with equal numbers of brown and orange bacteria. Based on the definition of evolution, did our population of bacteria evolve during the course of this experiment?
- Explain why it is important to use class results and not just the results obtained by an individual team.
- Based on class results, are color and cell wall strength related? Support your answer using data.
- Many antibiotics work by limiting the bacteria's ability to build a strong cell wall. Based on class data, which color bacteria are most likely to survive a treatment of antibiotic so that they can go on to reproduce? Explain.
- Assuming the trait for color and cell wall strength are genetic (meaning they can be passed from one generation to the next through reproduction), describe what you think will happen to the population of bacteria after 20 generations?