SCIENCE
ETO
SUCCESS ACADEMY
February 11, 2012
Preparing ___________________________ to be a Sensational Scientist.
(Name)
Big Idea 17: Interdependence
Benchmark:
SC.7.L.17.2: Compare and contrast the relationships among organisms such as
mutualism, predation, parasitism, competition, and commensalism.
____
Pre-assessment
1 Cleaner fish feed on parasites in a shark's mouth and gills. Which of the following
best describes the relationship between the cleaner fish and the shark?
A
B
C
D
competitive.
mutualistic.
neutral.
parasitic.
Explain how you decided on your answer: ___________________________________
______________________________________________________________________
______________________________________________________________________
____
2 Wildcats, such as the lynx, are predators of rabbits. Which will MOST likely occur
if a new, aggressive species of wolf is introduced into the ecosystem that is a
predator of the lynx?
F
G
H
J
The new species population will consume the food that the rabbits eat.
The population of the rabbits in the ecosystem will increase.
The new species population will be consumed by the lynx.
The population of the lynx in the ecosystem will increase.
Explain how you decided on your answer: ___________________________________
______________________________________________________________________
______________________________________________________________________
2
Student Exploration: Food Chain
Vocabulary: consumer, ecosystem, equilibrium, food chain, population, predator, prey,
producer
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
The Food Chain Gizmo™ shows a food chain with hawks, snakes, rabbits, and grass. In this
simulation, the hawks eat snakes, the snakes eat rabbits, and the rabbits eat grass.
1. Producers are organisms that do not need to eat other organisms to obtain energy.
a. Which organism is a producer in this food chain? ____________________________
b. Where does the producer get its energy? __________________________________
2. Consumers must eat other organisms for energy. Which organisms are consumers in this
food chain? _______________________________________________________________
Gizmo Warm-up
The SIMULATION pane of the Gizmo shows the current population,
or number, of each organism in the food chain.
1. What are the current populations of each organism?
Hawks: _____ Snakes: _____ Rabbits: _____ Grass: _____
2. Select the BAR CHART tab, and click Play (
). What do you
notice about each population as time goes by?
_________________________________________________________________________
If populations don’t change very much over time, the ecosystem is in equilibrium.
3. Compare the equilibrium populations of the four organisms. Why do you think populations
decrease at higher levels of the food chain? ______________________________________
_________________________________________________________________________
_________________________________________________________________________
3
Activity A:
Get the Gizmo ready:
 Click Reset (
).
 Check that the BAR CHART tab is selected.
Predator-prey
relationships
Question: Predators are animals that hunt other animals, called prey. How do predator
and prey populations affect one another?
1. Observe: Run the Gizmo with several different starting conditions. You can use the + or –
buttons to add or remove organisms, or you can choose Diseased from the dropdown lists.
2. Form hypothesis: How do you think predator and prey populations affect one another?
_________________________________________________________________________
_________________________________________________________________________
3. Predict: Based on your hypothesis, predict how changing the rabbit population will affect the
other organisms at first. Write “Increase” or “Decrease” next to each “Prediction” in the table.
Change
Grass
Snakes
Hawks
Doubling
rabbit
population
Prediction:
Prediction:
Prediction:
Result:
Result:
Result:
Halving
rabbit
population
Prediction:
Prediction:
Prediction:
Result:
Result:
Result:
4. Test: Add rabbits until the population is about twice as large as it was (200% of balance).
Click Play, and then Pause (
) after approximately ONE month. Next to each “Result”
line in the table, write “Increase” or “Decrease.” Click Reset and then halve the rabbit
population (50% of balance). Record the results for this experiment in the table as well.
A. How did doubling the rabbit population affect the grass, snakes, and hawks at first?
___________________________________________________________________
___________________________________________________________________
B. How did halving the rabbit population affect the grass, snakes, and hawks at first?
___________________________________________________________________
___________________________________________________________________
4
5. Predict: Predict how changing the snake and hawk populations will affect the other
organisms within the first month. In the tables below, write your predictions.
Change
Grass
Rabbits
Hawks
Doubling
snake
population
Prediction:
Prediction:
Prediction:
Result:
Result:
Result:
Halving
snake
population
Prediction:
Prediction:
Prediction:
Result:
Result:
Result:
Change
Grass
Rabbits
Snakes
Doubling
hawk
population
Prediction:
Prediction:
Prediction:
Result:
Result:
Result:
Halving
hawk
population
Prediction:
Prediction:
Prediction:
Result:
Result:
Result:
6. Test: Click Reset. Try each experiment with the Gizmo. Record each result after one month.
A. How did increasing the snakes affect the grass? ____________________________
Explain why: ________________________________________________________
___________________________________________________________________
B. How did increasing the hawks affect the rabbits? ____________________________
Explain why: ________________________________________________________
___________________________________________________________________
7. Draw conclusions: In general, what effect did removing prey have on predators? _________
_________________________________________________________________________
What effect did removing predators have on prey? _________________________________
_________________________________________________________________________
Extend your thinking: In North America, many top predators, such as wolves, have been driven
nearly to extinction. What effect do you think this has on their main prey, deer? Write your
answer on a separate sheet, and/or discuss with your classmates and teacher.
5
Predator and Prey
Overview:
Within every ecological community there lives a variety of species. In stable communities each
of these species tends to maintain a relatively constant population size, particularly when
examined over the long term. This condition is known as equilibrium. However, during times
when environmental conditions change, a new equilibrium must be established. The student
simulates the interactions between a predator population of lynx and a prey population of rabbits
in a meadow. After collecting the data, the student graphs the data and then extends the graph to
predict the populations for several more generations.
The overall goals of this activity are as follows:
 Students will observe how population size can vary from generation to generation as a
consequence of the predation relationship.
 Students will determine how populations of a predator species affect populations of prey
species and vice versa.
 Students will prepare graphs comparing population size and generation for both predator
and prey populations.
Materials:
 One 7.5 cm square representing the lynx
 Two hundred 2.5 cm construction paper squares representing the rabbits
 A 30 cm x 30 cm square section of tabletop representing the meadow
 Graph paper
Procedure:
Part A: Set-Up
1. Using rulers to mark off a ‘meadow’ of 30 cm X 30 cm.
Part B: Rules of Play
General Rules:
1. Each surviving rabbit reproduces.
2. A lynx must capture 3 rabbits to survive.
3. Each surviving lynx reproduces.
4. No more than 200 rabbits can inhabit the meadow at any given time
5. If no lynx survives, one will immigrate into the meadow (i.e., the game doesn’t just end).
6. If no rabbits survive, 3 will immigrate into the meadow.
7. The rabbits should be distributed in the field.
8. Lynx are not allowed to cheat, but they should try to be efficient. Stupid lynx result in an
overabundance of rabbits.
9. As the number of lynx increases throw the lynx square once for each lynx. You don’t
have to make more lynx cards.
10. A lynx card touching any part of a rabbit card allows the lynx to catch the rabbit.
11. A lynx card landing on the meadow border counts as a turn.
6
Specific Rules:
1. Distribute 3 rabbits in the meadow.
2. Toss the lynx square once in an effort to catch a rabbit. (At this point in the activity, there
is no way that the lynx can catch the 3 rabbits that it needs to survive and reproduce.)
3. Complete the data table for generation #1.
4. The lynx will starve and there will be no surviving lynx or new baby lynx.
5. At the beginning of generation #2, double the rabbits left at the end of generation #1.
6. A new lynx immigrates into the meadow. Be sure to disperse the rabbits in the meadow.
7. Continue to complete the data table for each generation that the lynx dies and that rabbits
continue to double their population until eventually the rabbit population increases to a
level that allows the lynx to catch 3 rabbits in a single toss.
8. Remember that the number of rabbits at the beginning of each generation is the number
of rabbits not caught + the number of new baby rabbits.
9. Remember that the number of lynx at the beginning of each generation is the number of
surviving lynx + the number of new baby lynx.
10. If the lynx catches 3 rabbits, it not only survives but it reproduces too! It has one
baby lynx for each 3 rabbits that it catches. Therefore, if it catches 6 rabbits it will
have 2 babies.
11. *Record the number of rabbits caught by each lynx.
12. The simulation is more realistic if the number of new baby lynx is based on each lynx’s
catch rather than merely the total number of rabbits caught in a generation.
13. Remember that the number of rabbits in the meadow needs to be correct at all times.
Remove the rabbits caught and add new ones as indicated by your data table.
14. Model about 10 generations.
15. Graph the data for 10 generations. Place both the rabbit and the lynx data (the first two
columns of the data table) on the same graph so that the interrelationship can be easily
observed. Label the vertical axis "Number of Animals" and the horizontal axis
"Generations." Use one kind or color of line for rabbits and another for lynx.
16. Predict 4 more or up to a total of 14 generations. Base the prediction on the pattern
observed during the first 10 generations. Use dotted or dashed line to illustrate your
prediction on your graph paper.
7
Data Table 1: Experimental Results
Generation
#Rabbits
1
3
(Rabbits left x 2)
#Lynx
#Rabbits
Caught
#Lynx
Surviving
#New
Lynx
Baby
Rabbits Left
1
2
3
4
5
6
7
8
9
10
Predictions:
11
12
13
14
Assessment:
1. Why was the rabbit population limited to 200 rabbits?
2. Why is it appropriate to expect the rabbits to be distributed throughout the meadow?
3. Why is it appropriate to expect rabbits and or lynx to immigrate?
4. Describe how you made your prediction of generations 11-14 in step #14 of the specific
procedure.
5. Describe what would happen to the rabbit population if after generation #10, hunters set
out traps to trap and kill all the lynx.
6. Describe what would happen to the rabbit and lynx population if after generation #10,
there was a severe drought that killed all the grass and vegetation.
8
9
ASSESSMENT
NAME: _________________________
____
1 Some animals in the northern latitudes have to migrate south in order to survive.
What abiotic factor causes the animals to annually leave their ecosystems?
F
G
H
J
____
____
decreasing the potential for soil erosion.
increasing the food available for consumers.
decreasing the nutrients available for new plants.
increasing the accumulation of organic materials.
3 Scientists have discovered that there has been a reduction in the butterfly
population in an ecosystem. After much research, they have identified that the
carrying capacity for butterflies has been decreased. If the scientists want to
increase the butterfly population, which action should they recommend?
F removing primary producers
G spraying of insecticides
H increasing runoff
J planting flowers
4 In 1989, an oil spill off the coast of Alaska led to a decline in the population of
many organisms. Which other population was MOST likely affected by the drop in
population of the fish, otters, and seals?
A
B
C
D
____
heavy rains
less oxygen
cold weather
increased sunlight
2 The removal of plant material, such as grass clippings, would MOST likely affect
an ecosystem by
A
B
C
D
____
DATE: ______________
Deer
Eagles
Frogs
Snakes
5 In the geologic past, abiotic factors such as volcanic eruptions have had an
impact on the availability of resources. How can volcanic eruptions impact the
availability of resources?
F
G
H
J
carbon dioxide
minerals
sunlight
water
10
____
6 In any ecosystem, the survival of a species depends on the resources that are
available. Beneath the tree canopy in a tropical rainforest, growth of some plant
species may be limited. The availability of which of these resources most likely
limits the growth of plants on the ground level in this ecosystem?
A
B
C
D
____
7 In a grassland ecosystem, organisms of the same species eat the same food.
When there is a lack of rain, which is MOST likely increased?
A
B
C
D
____
carrying capacity
population density
competition for space
competition for resources
8 Wolves, which are top predators, were eliminated from Yellowstone National Park
in the 1930s. In 1995, wolves were reintroduced into Yellowstone. During the
period in which wolves were absent from Yellowstone, which MOST likely
occurred?
F
G
H
J
____
Less solar radiation would enter the region.
Larger plants and trees would take over the region.
The region would become a habitat for large and small sea organisms.
The primary producers in the region would have less ability to recycle
carbon.
an increase in competition for food resources among small prey
a greater opportunity for primary producers to flourish
an increase in the population of tertiary consumers
a greater balance of predator-prey relationships
9 Which of the following is an example of parasitism?
A.
B.
C.
D.
bees and flowers
a tick on a dog
barnacles attached to a whale
a wolf and a rabbit
11