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Who Is in the Elephant Seal's Food Pyramid?

Students will construct a food pyramid to lay a foundation for understanding the elephant seal life cycle and behaviors.

Time required: 90 minutes Location: classroom Suggested group size: entire class, working in teams Subject(s): science, art Concept(s) covered: food pyramid, human ecology Adapted from: MARE: Marine Activities, Resources and Education, Regents of the University of California Written by: Heidi Strickfaden and Kim Linse, National Park Service Last updated: 12/12/00

Student Outcomes
At the end of this activity, the students will be able to:

• Understand the elephant seals' role in a food pyramid.



• Understand human's role in every food pyramid.

California Science Standard Links (grades 6 – 8)
This activity is linked to the California Science Standards in the following areas:

6th grade:

5a - food webs
5b - matter is transferred from one organism to others in the food web
7d - communicate the steps and results from an investigation

7th grade:

7a - appropriate tools and technology to collect and display data
7c - communicate logical connections

National Science Standard Links (grades 5 – 8)
This activity is linked to the National Science Standards in the following areas:

• Content Standard A - Use appropriate tools and techniques to gather, analyze, and interpret data



• Content Standard C - Populations and ecosystems, diversity and adaptations of organisms



• Content Standard F - Populations, resources, and environments

Materials
To be provided by the teacher:

• Art Supplies for drawings
• Research materials: Field Guide to Pacific Coast Fishes (Peterson), Pacific Coast Field Guide (Audubon), Internet access, encyclopedia

To be photocopied from this guide:

• Marine Food Pyramid activity sheet - one per student (40K PDF document)

Vocabulary
diatom, food chain, food pyramid, habitat, krill, niche, primary producer, zooplankton, 1st - 4th order consumer

Procedures

1. Ecology Discussion
   Lay the foundation for your lesson with the following background information:
   Just as we depend on community members such as doctors, police officers, and grocers to help support our daily activities, other living organisms depend on each other and various ecosystem functions for survival. Within natural communities, living organisms have a place to live (habitat) and a job (niche). Some living organisms are producers; others are consumers. Together with their varied niches, these living organisms form a balanced pyramid. This pyramid illustrates the flow of energy from one tier, or trophic level, to the next. As you move up the food pyramid, less biomass (or fewer organisms), is present at each trophic level than at the lower level. Organisms that are higher on the food pyramid generally require more biomass, or energy, from the lower levels for survival. If any one level becomes too large or too small, the pyramid can topple.
   
   Understanding the place that elephant seals hold in their food pyramid lays a foundation for understanding their life cycles and behaviors. In addition, understanding the connection between these various trophic levels allows us to understand the direct and indirect ways in which elephant seals are impacted by the health and abundance of organisms at these different trophic levels.



2. Discussion of Food Pyramids
   Start by discussing food pyramids. What is a food pyramid? What does it mean to be on the top of the food pyramid versus the bottom? Discuss individual organisms and their role as producers and consumers. Discuss differences between 1st Ð 4th order consumers. If students are having difficulty understanding this concept use an example of a food pyramid from another organism (i.e. mountain lion, grizzly bear ). Discuss differences between 1st Ð 4th order consumers. Why is it important for us to understand food pyramids when studying elephant seals?
   
   Next discuss elephant seals and their role in the food pyramid. Who eats elephant seals? Who do elephant seals eat? What type of consumer are they? What is their habitat? What is their niche? Who do they have to compete with for survival? What do they do to avoid competition?



3. Students Research Food Pyramid Organisms
   
   Students work in groups and research organisms from the following list. Students will refer to previously gathered research material and the section of the elephant seal newspaper entitled "What Do Elephant Seals Eat?"

   white shark	orca	elephant seal	harbor seal
   steller sea lion	California sea lion	fish	squid
   octopus	dogfish	Pacific hake	skate
   ray	smaller shark	bottom fish	ratfish
   rockfish	krill	zooplankton	diatom

   
   
   Students' reports should include a picture of their organism and answer the following questions:
   1. What is your organism?
   2. List three characteristics that describe your organism.
   3. Where does it live? what depth? what temperatures?
   4. What does it eat (prey)?
   5. What eats it (predator)?
   6. Where is your organismÕs place in the food pyramid?



4. Students Create a Food Pyramid
   Either on the chalkboard, or on a large piece of poster paper, create a blank food pyramid for the class. Use the Marine Food Pyramid activity sheet as a model. Starting with primary producers, have students assemble their pictures in the appropriate tiers of the pyramid and give a brief description of their organism. As other reports are presented, string or chalk can be used to draw in food chains as they are mentioned. Once the master food pyramid is complete, students should transcribe the information onto their blank individual Marine Food Pyramid activity sheet



5. Discussion of Human Impacts
   When pyramid construction is complete, begin discussion of humans' impact on food pyramids. Where do humans fit into this food chain? Are human populations balanced with their position in the food chain (i.e., higher order consumers usually have lower population numbers because of their large territory sizes)? How could human impacts on the different trophic levels impact elephant seals?

Extension ideas

1. Reconstruct pyramid as a hanging mobile or mural.



2. Draw a food pyramid that includes humans/ human impacts.
3. Write a story about a year in the life of an elephant seal. Write from the perspective of a mature cow, bull, weaner, or newborn pup. Refer to the elephant seal newspaper to review lifecycle information. Include diet, adaptations, successes and challenges.

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