1. Suppose you wanted to learn more about the behaviors of Pacific Tree Frogs in the forest ecosystem, and decided to set up a terrarium as shown below:

Describe two ways the model might be unable to reliably predict the behaviors of frogs in the forest. In your description, be sure to

• Identify two ways the model is different from the forest.• Describe how each way prevents you from making reliable predictions about the

behaviors of the Pacific tree frog in a forest ecosystem.

• Model doesn’t have other animals in it. Frogs probably behave differently with other animals.

• Model doesn’t get same light as forest. Frogs might behave different with sunlight or different amounts of light.

2. Snakes eat frogs. When the population of frogs increases, the population of snakes increases. This in turn causes the frog population to decrease. Is this an example of a positive feedback system or a negative feedback system? Explain your answer.

• Negative.• Populations go up and down instead of just up or just down.• “Consistently” is not the same as “constantly”

Positive feedback loop:• Both populations

only increase, or only decrease.

Negative feedback loop:• Both populations increase and decrease.

Positive feedback loop or negative?

3. Pollution from people’s cars can affect animal and plant life in the forest ecosystem. Describe why adding car exhaust to the forest model you constructed in question #1 may be unable to predict the consequences of car pollution in the surrounding forest ecosystem. In your description, be sure to

• Identify a way that car exhaust could affect the forest ecosystem.• Describe why the forest model may be unable to reliably predict the

consequence.

• Car exhaust could make plants sick. In forest, winds might blow car exhaust away.

• Car exhaust can make animals sick. Model only has frogs. Don’t know how it will affect other forest animals.

4. Population density is a measure of how many individuals animals or plants there are in a particular area. For example, if there were ten worms in a square foot of topsoil, the population density would be 10 worms per square foot. What would be the population density of…. (Show your work!)

2 owls in 5 square miles of forest? _________ owls per square mile.

53 crayfish in 40 square meters of a stream. ___________ crayfish per square meter.

1 mi

1 m

i

2 owls/5 sq. mi = ______

0.4

53 crayfish/40 sq. m = ______

1.3

crayfish

Crayfish eat plants and animals on the bottoms of ponds and streams.

Nitrogen, a chemical element in our atmosphere, is needed by plants and animals to build cells and tissues. Using the Nitrogen Cycle diagram shown below, explain how nitrogen moves from the body of a cow out into the surrounding ecosystem. How is that nitrogen transferred to plants?

• Through its poop, or when it dies and its body goes into the ground.• Plants take it in from the ground through their roots.

Nitrogen Cycle: How does nitrogen from the air get into plants and animals?

Nitrogen from air converted by bacteria into form plants can take up through roots. Animals get nitrogen by eating plants or other animals.

Describe one way introducing Eastern gray squirrels could limit the population of chipmunks .

The squirrels will compete for the same food as chipmunks. There will be less food for chipmunks.

Eastern gray squirrel

Describe a condition in the forest ecosystem that could allow the toad population to increase rapidly.• A lot of food for them (insects, spiders)• Not many predators (snakes, coyotes)

1. Please take out the assignment below.2. Get a computer and start logging on…..

5. Sometimes invasive animal or plant species come to Washington State from elsewhere by hiding in cargo ships, trains, or trucking containers. An example would be the Eastern gray squirrel, which originally came from the east coast and compete for food with Western gray squirrels. Local wildlife biologists want to solve the problem of increased eastern gray squirrels in our area. One criterion for measuring the success of a solution to this problem would be a reduction in the population of Eastern gray squirrels. Describe a different criterion for measuring the success of a solution to the problem.

Eastern gray squirrel Western gray squirrel

Increase in Western gray squirrel population

6. One way to solve the Eastern gray squirrel problem is to trap and move them to another location. Describe one unintended consequence of trapping or moving the Eastern gray squirrels other than the possible death of the squirrels.

Eastern gray squirrel Western gray squirrel

• They’ll compete with squirrels at the new place.• They’ll eat all the food at the new place.

7. Two possible solutions to the squirrel problem are

Solution A: Use a natural predator of the eastern squirrel.Solution B: Educate shipping and trucking companies about how to check more carefully for invasive species.

Describe a way to test whether Solution A or Solution B is more effective at reducing the eastern squirrel population. Be sure your description includes:

• A method for testing each solution.• The data to be collected to determine whether Solution A or Solution B is more effective

at reducing the eastern squirrel population.

• Solution A: Bring in coyotes, wolves, owls, or hawks to one area. Count how many Eastern squirrels there every year for 5 years.

• Solution B: Send people to teach trucking/shipping companies how to check carefully for invasive species in another area. Count how many Eastern squirrels there every year for 5 years.

• Compare number of eastern squirrels, see where numbers went down more.

8. You are trying to get rid of dandelions and other weeds in your front yard and help the grass grow more. You are considering adding herbicide to kill the weeds or fertilizer to help the grass outgrow the weeds. Describe two criteria you could use to evaluate your solutions. Criteria = ways to measure success.

Decrease in dandelions, weeds.Increase in grass.

9. You are trying to get rid of dandelions and other weeds in your front yard and help the grass grow more. You are considering adding herbicide to kill the weeds or fertilizer to help the grass outgrow the weeds. Describe a way to test whether using herbicide or lawn fertilizer would be more effective in solving the weed problem. Be sure your description includes

• A method for testing each solution.• The data to be collected to determine whether using herbicide or fertilizer is more

effective for solving the weed problem.

1. Measure out three 10 ft x 10 ft. patches of yard. Add herbicide to each patch according to directions. Count how many weeds there are in each patch after one month.

2. Measure out three other 10 ft. x 10 ft. patches of yard. Add fertilizer to each patch according to directions. Count how many weeds there are in each patch after one month.

Today’s task: DIY Plant Experiment, question 4