Title: The Incredible Edible Egg
Correlation v. Causation
Time: 1.5 hours (1 h for introduction, experiment and data analysis; 0.5 h for discussion of results)
Objectives:
Data will be analyzed by students, demonstrating good scientific inferences and logical
conclusions in their discussion
Students will formulate a hypothesis based on observations and scientific information
Biology standards covered in this lesson:
B - 6: The student will demonstrate an understanding of the interrelationships among organisms
and the biotic and abiotic components of their environments.
6.1, Explain how the interrelationships among organisms (including predation, competition,
parasitism, mutualism, and commensalism) generate stability within ecosystems.
6.6, Explain how human activities (including population growth, technology, and
consumption of resources) affect the physical and chemical cycles and processes of Earth.
Materials:
Map of North Inlet, SC with latitude and longitude graticules
Classroom supplies: metric rulers, dry erase markers in two colors
Background:
Diamondback terrapin are aquatic turtles that live in brackish water and lay eggs on land. Raccoons are
prime suspects. Question for students:
Diamondback terrapin are primarily aquatic turtles that inhabit salt marshes of the US east and gulf
coasts. Like all turtles they nest on dry land. The nests are created in dry, open, sandy areas. Females
crawl across sand and mud to dig a nest in dry sand where they lay eggs, they then cover the nest with
sand (and scratch marks) and return to the water. Nests are raided, often at rates exceeding 90% and
usually within the first two nights. Terrapin nests are depredated (i.e. raided) by numerous predators
including raccoons and wild hogs. As terrestrial animals, raccoons and hogs are both associated with
mainland habitats. Raccoons are one of the rare larger animals that tend to thrive near human
developments.
Examples for Correlation v. Causation:
Humans generate a lot of trash and much of that trash is considered edible by other animals. Raccoon populations
are increasing in neighborhoods. Are rising raccoon numbers caused by humans or is it merely a coincidence?
Armadillos are being spotted further north than ever before. They now live in states that used to be too cold for
them. Polar bears are losing ice in their habitats that they formerly utilized to hunt seals from. Are these two
strange occurrences causing one another or are they correlated?
Procedure:
Use the supplied chart of terrapin nests and map of North Inlet to locate and mark nesting habitats.
Remember latitude (lat is flat) gives north-south position and longitude gives east-west position. Place a
dot on the map for each nest using different colors for depredated and intact nests. Use reference grid
(e.g. B2 = 79° 12’ 00” W to 79° 11’ 30” W and 33° 22’ 0” N to 33° 22’ 0” N) to describe nesting areas.
Which areas have the most nests? Which areas have the most depredated nests?
Characterize the areas with high predation pressure:
How would you describe the area? What are the adjacent areas like?
Do diamondback terrapin nest in housing developments or along popular beaches? Why or why
not?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Nest location (latitude, longitude)
33° 22’ 18” N, 79° 9’ 30” W
33° 22’ 20” N, 79° 9’ 20” W
33° 21’ 45” N, 79° 10’ 15” W
33° 22’ 0” N, 79° 10’ 25” W
33° 22’ 0” N, 79° 10’ 15” W
33° 21’ 45” N, 79° 10’ 15” W
33° 20’ 45” N, 79° 9’ 45” W
33° 20’ 40” N, 79° 10’ 0” W
33° 19’ 45” N, 79° 10’ 15” W
33° 19’ 45” N, 79° 10’ 15” W
33° 20’ 15” N, 79° 11’ 15” W
33° 20’ 15” N, 79° 11’ 15” W
33° 20’ 15” N, 79° 11’ 15” W
33° 21’ 0” N, 79° 11’ 45” W
33° 21’ 0” N, 79° 11’ 35” W
Depredated? (color code for yes, no)
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
No
No
Yes
No
Yes
Yes
No
Evaluation:
All students are expected to participate in discussion and evaluation. A summary discussion at the end
of the day’s exercise will reinforce the lesson and our class conclusions regarding factors affecting
terrapin nest success.
Key points to a successful evaluation will include:
o
o
o
o
Brief review of the day’s topic
What was the group hypothesis regarding predation and development and how was it
formulated?
Verbal and visual presentation of the data
Did the results support the class hypotheses?
Raccoons are omnivorous, they’re nocturnal and they make dens in well hidden areas.
What do you think draws raccoons to populated areas? Is there a correlation between human
development and nest depredation? Are populated areas the cause of higher frequency nest
depredation?
Instructor notes:
In North Inlet there is a decrease in nest survivability near development and mainland
Give background about numerous predators as well as human and mainland associations among
predators.
A numbered map showing locations of nests is best for display on screen for students to check against
their finished maps.
Be sure to fully explain the difference between causation and correlation.
Nest location (latitude, longitude)
Depredated?
1
33° 22’ 18” N, 79° 9’ 30” W
Yes
2
33° 22’ 20” N, 79° 9’ 20” W
Yes
3
33° 21’ 45” N, 79° 10’ 15” W
Yes
4
33° 22’ 0” N, 79° 10’ 25” W
Yes
5
33° 22’ 0” N, 79° 10’ 15” W
Yes
6
33° 21’ 45” N, 79° 10’ 15” W
Yes
7
33° 20’ 45” N, 79° 9’ 45” W
No
8
33° 20’ 40” N, 79° 10’ 0” W
Yes
9
33° 19’ 45” N, 79° 10’ 15” W
No
10
33° 19’ 45” N, 79° 10’ 15” W
No
11
33° 20’ 15” N, 79° 11’ 15” W
Yes
12
33° 20’ 15” N, 79° 11’ 15” W
No
13
33° 20’ 15” N, 79° 11’ 15” W
Yes
14
33° 21’ 0” N, 79° 11’ 45” W
Yes
15
33° 21’ 0” N, 79° 11’ 35” W
No
Pre MacModS
All summer you have noticed an interesting pattern…
Your neighbors leave their porch light on at nights and your family
does not. You notice that your neighbors usually have several tree
frogs on their porch and you rarely see them at your house. You
know that tree frogs are active at night and eat small insects.
Draw and label arrows for the pictures below to create a flow chart of the relationship between these
elements (Hint: make sure your arrow shows which item attracts another).
Why did you draw the arrows the way you did?
Could you describe the relationship between frogs, insects and porch lights? If possible use the words
correlation and causation in your explanation.
Post Assessment
Eating a bunch of very spicy foods can burn your mouth and upset your stomach. Birds feel the same
way when they eat the hot peppers that grow on some plants. You hear about a scientist doing research
on some of the hottest peppers in the world. The scientist notices that the birds eating the hottest
peppers do not fly far before their digestive system needs to make a drop. You know that birds eat both
the spicy and the mild peppers and you have a hunch that might explain the difference in dispersal of
the two types of plants. See if you can help the scientist by drawing and labeling arrows to connect the
pictures of peppers to the pictures of the fields:
Mild
Hot
Why did you draw the arrows the way you did?
Could you describe the relationship between birds, the hottest peppers and the dispersal of the plants?
If possible use the words correlation and causation in your explanation.