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

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

at the head of the gel will migrate to the other side, with the smaller pieces moving the

fastest. The more voltage there is running through the gel, the fasterthe DNA will

migrate. The longer the voltage is run through the gel, the fartherthe DNA will migrate.

The more DNA cut by the same restriction enzymes you put into each well, the thicker

the bands will be on the gel. If you reverse the flow of the current on the gel, the DNA

will migrate in the opposite direction. The DNA just wants to go toward the positive

charge... optimists, we suppose.

Important Facts About Electrophoresis

1.DNA migrates from negative to positive charges.

2.Smaller DNA travels faster than larger DNA.

3.The DNA migrates only when the current is running.

4.The more voltage that runs through the gel, the faster the DNA migrates.

5.The more time the current runs through the gel, the farther the DNA goes.

Key Concepts

• Understand how to use restriction enzymes and gel electrophoresis to create genetic
  profiles.


• The pattern made by RFLP using gel electrophoresis will look different for each
  individual.

Investigation 10: Energy Dynamics

You will create a simple model of an ecosystem, with a single producer (plant) and a

single consumer (caterpillars). Producers are so important because they capture the sun’s

energy and convert it into a form that can be used by us nonphotosynthetic organisms

(consumers). The term gross productivityrefers to the total amount of energy captured

by producers. The net productivityis the amount of that energy that is actually stored

by the plant (and thus is available for consumers to munch on).

As you may recall, the second law of thermodynamics says that energy transfer is never

100 percent efficient. This lab demonstrates that fact by tracking energy as it travels

through a food chain. Specifically, how much of a plant’s energy is actually used by the

caterpillars who eat it? How much is applied to the caterpillar’s growth, and how much is

burned up in cellular respiration? Also, be aware that this lab has the best procedure direc-

tion of the entire year: you get to mass the frass (more on that in a bit).

Basic Setup

You will determine the total weight of all your caterpillars at the beginning of the investi-

gation and then, after they feed for three days, weigh them again. Their change in mass was

fueled by the plants they ate. The question is what percentage of that plant’s energy was

actually turned into caterpillar mass? If you determine the plant energy consumed by each

larva, and also take into consideration the amount of their food that wasn’t actually used

(caterpillar poop, also called “frass”), then you’re left with the amount of the producer’s

energy that was used for the caterpillar’s metabolism. Furthermore, if you knew the amount

of plant energy consumed by the larva, and subtracted from that both the energy lost in the

poop and energy used for the caterpillar’s increase in mass, what you’re left with is the

energy used in respiration.

TIP

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