BIO 105 Science of Biology w/Lab

ekatdubr19

Experiment4.pdf

Home >Biology homework help >BIO 105 Science of Biology w/Lab

Experiment 4Natural Selection Experiment Inventory

Materials Blue Beads

Red Beads

*Access to a Color Printer

Labware 100 mL Beaker

Note: You must provide the materials listed in *red.

EXPERIMENT 4: NATURAL SELECTION

Natural selection is a selection pressure that affects phenotypes in one of three ways:

1. A phenotype may have an adaptive advantage.

2. A phenotype may have an adaptive disadvantage.

3. A phenotype may remain entirely neutral.

A classic example to illustrate natural selection comes from England. Prior to the Industrial Revolution, the majority of the native moths were a light color though a rare, darker phenotype of the species existed. The lighter color blended with the light bark of the local trees. The darker moths experienced a higher predation rate as they were easier for birds to spot, and few survived to re produce. As England entered the Industrial Revolution, the burning of fossil fuels increased pollution. As a result, the trunks of the trees became coated with soot, and their color darkened. The lighter moths became more conspicuous, and the darker moths were better camouflaged. As more dark moths than light moths survived to reproduce, the ratio of light vs dark moths changed in favor of the darker phenotype.

PROCEDURE

Make a color copy of the Red Habitat (Figure 7) and the Blue Habitat (Figure 8), found on the next two pages.

1. Place 50 red and 50 blue beads into a 100 mL beaker.

2. Mix them well, and pour them onto the Red Habitat sheet.

3. Return to the beaker the beads that fall onto the habitat areas that match their color.

4. For each bead you keep (and return to the beaker), add another bead of the same color to the beaker.

5. Repeat this three times.

6. Record the resulting distribution of colors on your data sheet.

7. Repeat Steps 2-6 using the Blue Habitat with the remaining beads.

8. Answer the post-lab questions.

Figure 7: Red habitat.

Figure 8: Blue habitat.