5 Steps to a 5 AP Biology, 2014-2015 Edition

238 ❯ STEP 4. Review the Knowledge You Need to Score High

straightforward portions of these labs, including a summary of what the key ideas are from

each investigation.

Investigation 1: Artificial Selection

This lab focuses on the role of differential reproductionin natural selection, meaning some

organisms in a population reproduce more than others and leave more offspring. But

instead of it being “natural” selection, it’s “artificial” because youget to choose which organ-

isms are allowed to reproduce!

Basic Setup

For natural selection to occur, first there needs to be variation in a population, right? Well,

look closely at the Wisconsin Fast Plants that you’ll be working with. Do you see any trait

that you could easily measure (e.g., leaf color, hairiness, height)? Are there any variations in

this particular trait? It should not be something that is a clear-cut yes or no, but rather

a trait that exhibits a range. Now you get to make selection decisions! You will choose the

top (or bottom) 10 percent of your plants with this trait, and those lucky few are the ones

allowed to reproduce. You will transfer pollen between this pool of “winners” and, once the

seeds develop, plant and grow your second generation of plants. Once again, you will mea-

sure your chosen trait in this second population.

Results

In this experiment you are essentially choosing which genes are passed to the next genera-

tion. By artificially selecting, say, only the purplest of the plants, you are ensuring that the

next generation will have inherited those “purpley” genes. You will hopefully observe an

increase (or decrease, depending on your investigation) of your chosen trait in the second

population of plants. This is called directional selection. Considering that one of the require-

ments of this class is your ability to graph and analyze data, it would probably be an excel-

lent idea for you to create a bar graph to compare the quantity of your trait between these

two generations. Are the means significantly different?

Don’t forget to keep this a controlled experiment! Did you measure the trait of your

first-generation plants when they were nine days old? Remember to measure the second

generationat the same age, using the same method.

Key Skills

• Graph your data.


• Explain how natural selection acts on phenotypes.


• Use data to show how a measurable trait is changing in your plant population.

Investigation 2: Mathematical Modeling: Hardy-Weinberg

This investigation lets you build upon what you learned from Investigation 1: the idea of

natural selection and how it changes a population. If you truly wanted to see if a popula-

tion was evolving, you would track the frequency of alleles and how they change from gen-

eration to generation. To do so, you first need to determine what your population’s alleles

look likeright now, before any funky evolutionary stuff happens. This information can then

be used as a point of comparison to see if the allelic frequencies are indeed changing in your

population. The Hardy-Weinberg equilibrium is used to describe a population that is in

BIG IDEA 1

Evolution

BIG IDEA 1

Evolution