Barnacle's Story of Food, Energy Edition

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Students will examine the origin of a barnacle’s energy by identifying the points of energy transfer leading to the barnacle and tracing them back to the sun.


Students will be able to:

  • Identify the source of matter and energy for different organisms in an ecosystem, in this case, the harbor.
  • Explain how energy flows through an ecosystem and does not cycle as matter does.


  • Tell the story of food for a barnacle

Age group: 4th-6th grade

Venue: Harbor

Materials: Plankton tow net(s), barnacle jar(s) (clear, wide mouthed, plastic, lidded jar), Whiteboard/paper & pens

The Lesson Plan:


“Who has every told a story? Who has ever told a story backwards, where you start at the end and go back to the beginnings? That's what we're going to do! We're going to tell, "The Story of A Barnacle’s Food" (write at the top of your paper) backwards and then we’re going to tell it forwards.”


“Remember when we told The Story of Food for our lunch? Well, now we are going to see if we can tell the story of how a barnacle gets its energy! Just like you, barnacles need to have lunch in order to have enough energy to do their barnacle thing. First we’ll need to find out what the barnacle is eating for lunch, and then we can trace it back to the beginning of the story.”

Hook Activities:

  1. Free explore/scavenger hunt at the harbor
  2. Plankton towing

This lesson works well in conjunction with a classic Story of Food lesson or water investigation at the harbor.


  • Begin by addressing common alternative conceptions about barnacles. Many people mistakenly assume barnacles are a type of plant or possibly abiotic. Assess student’s current knowledge and explain how to identify barnacles that are good candidates for feeding: still alive (not just an empty shell) and on a substrate that will fit in the available jar. Model how to carefully fill the jar with water from the harbor (some space should remain to accommodate the additional volume of captured plankton) and add barnacles while attached to their substrate. Make sure students know not to attempt to scrape the barnacles off!
  • Observe feeding plankton:
    • One way to do this is to divide students into teams of 2-4. Each team readies a barnacle jar and finds good candidates for feeding. Once a team has a barnacle jar prepared they can work with the instructor to capture plankton via plankton towing.
    • Add captured plankton to barnacle jars.
    • Plankton can take some time to begin feeding. You may want to pause for a snack or have another quick activity planned if the barnacles are taking their time.
    • Barnacles will begin opening and grabbing plankton! Check out this video for an idea of what the feeding plankton will look like.
  • Return plankton and barnacles to their habitats.
  • Have students get comfortable with their journals in a circle on sitting pads, on a log, or however else you would like them arranged. Write “How did the barnacle get its energy?” at the top of the page. You can have students following along taking notes in their journals as you wish.
  • Draw the barnacle. Ask, where did the barnacle get its energy?
  • Hopefully, the students will supply an answer of “from the plankton.” You can add detail by explaining that there are two types of plankton, zooplankton and phytoplankton. Zooplanktons get energy from eating phytoplankton, so our backwards story so far goes: Barnacle, zooplankton and phytoplankton.
  • So where did the phytoplankton get their energy? Phytoplankton can photosynthesize, so they primarily got their energy from the sun! Now our backwards story goes barnacle, zooplankton, phytoplankton, sun.
  • Have a student or students read the story forwards, starting with the sun.

Debrief Questions

Now that the energy is in the barnacle, what happens to it?

Possible answers: another animal eats the barnacle and converts it to energy/the barnacle uses it up/etc

Does the energy in the barnacle ever make it back to the sun?

No, the energy may keep flowing through the system, but it will never go back to the sun. This is why we say that energy flows while matter cycles.