Science Assessment ~ Items ~ AP042006

Prior to winter, black bears eat large quantities of food and gain up to 30 pounds of additional body weight. The food that the bears eat is made up of carbon-containing molecules such as glucose, carbohydrates, fats, and proteins. When winter begins, the bears go into dens or caves to hibernate. After several months of hibernation, they wake up and leave their dens. Scientists who study hibernating bears have found that bears lose a quarter of their body weight during hibernation.

Black bear den, NPS Photo / Harlan Kredit

Observations of hibernating bears show that they breathe in and out during hibernation, but they do not eat, drink, or "go to the bathroom."

How is it possible for bears to stay alive during hibernation if they don’t eat anything?

Below is a model showing one of the chemical reactions taking place inside a bear that will help you to understand how bears can stay alive during hibernation.

Using the model, answer the following questions about the processes happening inside the bear during hibernation.

1. How was the oxygen that the bear breathed in used by the bear to get energy?

2. Where did the carbon atoms that are in the carbon dioxide molecules that the bear breathed out come from?

3. Use the model to explain how the bear got the energy that it needed to stay alive during hibernation. Be sure to describe the role that molecules and chemical reactions play.

A. Drauglis / flickr

4. Now think about the fact that the bear lost weight during hibernation. Use the model to write an explanation for what caused a bear to decrease in mass during hibernation. Think about the difference in masses of the molecules the bear breathes in and breathes out during hibernation. Be sure to refer to the model in your explanation.

Details
Performance
NGSS

Topic: 3D Energy Tasks
Scoring Rubric: Q1; Student states or uses a general science idea

Cellular respiration in plants and animals involve chemical reactions with oxygen that release stored energy (i.e., oxygen is involved in a chemical reaction inside the bear or oxygen reacts with molecules of food). [Oxygen is a reactant]; Q2; Student uses a general science idea

Complex molecules containing carbon react with oxygen to produce carbon dioxide (i.e., the carbon atoms that make up the carbon dioxide molecules come from carbon-containing molecules form the bear's food). [linking CO₂ and food]

Note: Just saying "from inside the bear" does not count. The student must be explicit about the atoms coming from the molecules from food.; Q3; 1. Student makes a claim that answers the question

The bear got energy from a chemical reaction, by reacting food with oxygen, or by burning food.

Note: "The bear got energy from/by" part of the claim can be implied.

2. Student uses a general science idea

Complex molecules containing carbon react with oxygen (i.e., the reaction between carbon-containing molecules and oxygen releases energy for the bear). [cellular respiration]; Q4; 1. Student makes a claim that answers the question

The bear decreased in mass/lost weight because

Matter/atoms that was/were once part of hte bear's body left/is no longer part of the bear's body.

The bear exhaled more mass than it took in.

Note: Students who explicitly state that matter is destroyed or not conserved should not receive the claim point.

2. Student uses the crosscutting concept about the flow of matter into and out of a system to provide evidence

The bear breathes in oxygen molecules.

The bear breathes out carbon dioxide molecules.

The bear breathes out water molecules. (optional)

3. Student states or uses science ideas

Carbon dioxide has more mass than oxygen. [mass]

Complex molecules containing carbon react with oxygen to produce carbon dioxide (i.e., Carbon-based food molecules already inside the bear are involved in a reaction that produces carbon dioxide). [cellular respiration]

4. Student uses reasoning to link crosscutting concepts to the claim

There is a net loss of mass (weight, atoms, or matter) from the bear during hibernation because oxygen is entering the bear and carbon dioxide is leabing the bear, and carbon dioxide is heavier than oxygen.

OR

The carbon atoms that leave the body as part of carbon dioxide came from carbon-based molecules that were part of the bear's body, therefore, there is a net loss of mass (weight or atoms) from the bear during hibernation.

Percent of Points Earned

Chart showing distrubtion of responses for Item AP042006

Points Earned

	Avg. Earned	Possible	Percent
Q1	0.16	1	16%
Q2	0.32	1	32%
Q3	0.25	2	13%
Q4	0.26	4	7%

Overall Task Difficulty

	Total Points Earned	Total Points Possible	Total Percent
	0.99	8	12%

n = 219

Note: The total percent is a weighted average based on the total number of points earned divided by the total number of points possible.

Science and Engineering Practices: SEP6 Construct an explanation using models or representations.
Crosscutting Concepts: CC4 Models can be used to represent systems and their interactions--such as inputs, processes and outputs--and energy, matter, and information flows within systems.
CC5 Matter flows and cycles can be tracked in terms of the weight of the substances before and after a process occurs. The total weight of the substances does not change. This is what is meant by conservation of matter. Matter is transported into, out of, and within systems.
Disciplinary Core Ideas: PS3.A A system of objects may also contain stored (potential) energy, depending on their relative positions.

Science Assessment

Item AP042006: Use a model to explain how matter that flows into and out of a hibernating bear leads to the bear losing mass. (CR version)