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Anytime Lesson Plan: Coral Polyp Party


In this lesson, students will learn the anatomy of a coral polyp, and review a few of the differences between plants and animals.


In this lesson, students will:

  1. learn the anatomy of a coral polyp.
  2. review a few of the differences between plants and animals.


  • paper towels/rag for clean-up
  • plates (1 per student plus a few extras)
  • marshmallows (1 per student)
  • pretzel sticks (6 per student)
  • toothpicks (1 per student)
  • 1 spray bottle filled with water
  • sugar sprinkles
  • transparency of coral polyp illustration
  • coral polyp drawing worksheets (1 per student)


  • coral polyp: a marine animal with a body shaped like a cylinder and tentacles around a central mouth
  • algae: a general term for microscopic or larger aquatic plants. They differ from trees and bushes because they don’t have true roots, stems, and leaves.
  • zooxanthellae: tiny algae that sometimes live inside other organisms such as coral
  • tentacles: a flexible body part that is used for feeding, grasping, or moving
  • predator: animals that eat other animals



  1. Set out enough plates for each student to have one.
  2. On each plate, place 1 marshmallow, 6 pretzel rods, and 1 tooth pick.
  3. On 4-5 other plates, pour sugar sprinkles.
  4. Prepare the food supply table: sugar sprinkle plates, spray bottles with water, and extras of the other ingredients.



  1. Ask students if they have ever heard of coral. Tell students that corals live in the oceans. Ask students, “How many of you think coral is a plant? How many of you think coral is an animal?”
  2. Corals are animals! Go over some of the main differences between plants and animals. Make a table on the board.



    Plants use the sun’s energy to make food.


    Animals cannot produce their own food from the sun and must eat other organisms in order to get food and energy.

    Only plants have roots, stems and leaves.

    Animals do not have roots, stems and leaves.

    Plants generally do not move from one place to another.

    Animals generally can move to catch food.


  4. Show students the coral polyp illustration overhead transparency and discuss all of the labeled parts: tentacles, mouth, gut, skeleton, and zooxanthellae. Find pertinent information in the background section above. (Note that it is very difficult to draw a typical coral polyp as there is a lot of variation in their forms. This illustration shows the basic components of coral polyps. Although the skeleton sits underneath the polyp in this illustration, the skeleton is actually outside the polyp itself and the polyp can contract and retract inside the calcium carbonate skeleton for protection.)
  5. Ask students, “What makes this coral polyp an animal?” (It eats other organisms by capturing them with its tentacles. It does not have plant parts. It cannot make food from the sun’s energy without the help of zooxanthellae.)
  6. Tell students that deciding whether coral is a plant or an animal can be confusing at first. Even early scientists thought corals were plants until they studied them more closely.
  7. Tell students they are going to do a very cool activity: make an edible coral polyp.
  8. Hand out one plate of materials to each student.


Directions to tell students

  1. Make one big hole with the toothpick in the top of the marshmallow. This will be the mouth of the coral polyp. Make sure it doesn’t go all the way through since coral polyps only have one hole, not two.
  2. Poke six holes with your tooth pick around the mouth of the coral polyp. These holes will be for the tentacles.
  3. In groups of 3 to 4, stand up and approach the supply table.
  4. Take the marshmallow off the plate and spray it with water. Make sure to cover the entire marshmallow.
  5. Roll the marshmallow in the sprinkles, which represent zooxanthellae.
  6. Sit back down.
  7. Add the pretzel sticks, which represent tentacles, to the six holes around the mouth.



  1. Hand out one coral polyp drawing worksheet to each student.
  2. Students draw their coral polyp and label the body parts.
  3. After the drawings are complete, tell students that there are a lot of different animals that live on reefs, from fishes and sharks to shrimps and snails. People sometimes call coral reefs the “rainforests of the ocean” because so many different animals live there, just as in the rainforests.
  4. Tell students they can now pretend to be predatory fish, such as parrotfish, that eat coral. But remind them that fishes don’t have hands, and so they need to eat their coral polyp without using their hands.


Wrap Up

Discuss coral reef threats and conservation with your students.

  • Explain that coral reefs are in danger of disappearing because of changes that people are making to the oceans.
  • What do you think people are doing to change the reefs? (fishing too much, polluting, physically damaging the reef by taking coral or anchoring on top of coral, breaking off coral while swimming, taking coral for jewelry, developing coastal areas which can cause increased sediment in the water and smother coral, and climate change is making the water too warm and too acidic)
  • What can we do? (Reduce, reuse, and recycle to help stop pollution, don’t get too close to reefs, don’t buy coral jewelry, reduce fossil fuel emissions associated with climate change, and help spread the word to friends and family).


  • Ayres, R. California Academy of Sciences. Coral Polyp Party.
  • California Academy of Sciences' Educator Resource Materials. (2007). Coral Symbiosis: Coral Polyp and Zooxanthellae.

California Content Standards


Life Sciences

  • 2a. Students know how to observe and describe similarities and differences in the appearance and behavior of plants and animals.
  • 2c. Students know how to identify major structures of common plants and animals.

Grade One

Life Sciences

  • 3a. Students know different plants and animals inhabit different kinds of environments and have external features that help them thrive in different kinds of places.
  • 3b. Students know both plants and animals need water, animals need food, and plants need light.
  • 3c. Students know animals eat plants or other animals for food and may also use plants or even other animals for shelter and nesting.

Investigation and Experimentation

  • 4a. Draw pictures that portray some features of the thing being described.




Corals are animals that belong to the phylum Cnidaria, which contains sea anemones, jellyfish, hydra, and corals. The name “Cnidaria” comes from the Greek word “cnidos” which means stinging nettle. Cnidarians are radially symmetrical with an opening at one end that is surrounded by tentacles. The tentacles have specialized stinging structures called nematocysts that are used for protection and to capture prey. The tentacles bring food into the animal’s one opening, which is used both to take in food and to expel waste materials. The coral animal, made up of its tube-shaped body, its tentacles, and its mouth, is called a coral polyp.

There are two main types of corals: hard corals and soft corals. Hard corals are classified within the subclass Hexacorallia because their tentacles are arranged around the mouth in multiples of six (“hexa” = six). They are called hard corals because they extract calcium and carbon from the ocean water and deposit a hard calcium carbonate skeleton that surrounds the lower portion of the body. Coral polyps fuse their skeletons together and form large coral colonies. These fused polyps are the basis for coral reefs. Coral polyps extend their tentacles from their skeleton to feed and withdraw into the skeleton for protection. Thus, the appearance of a coral colony can look very different depending on whether the polyps are extended or not. When hard coral polyps die, the calcium carbonate skeleton remains intact. You can often find pieces of white coral, the remains of former coral colonies, washed up on tropical beaches.

Soft corals are classified within the subclass Octocorallia because their tentacles are arranged around the mouth in multiples of eight (“octo” = eight). Soft corals do not produce a hard external calcium carbonate skeleton and therefore do not contribute significantly to the building of reefs. They do however have small, hard internal structures called spicules, which are uniquely shaped for each species and are used to help identify soft corals. When soft coral polyps die, they decompose and simply disappear, except for their small spicules. Hard corals and some soft corals contain zooxanthellae within their tissue. Zooxanthellae are marine algae, some of which are free living and some of which live inside the translucent, fleshy tissue of many corals and other marine organisms. Zooxanthellae that live in marine animals have a mutually beneficial symbiotic relationship with their host. This means that both the coral and the alga benefit from being in the relationship. The zooxanthellae photosynthesize from within their coral host and produce sugars that provide nutrition to both the zooxanthellae and the coral. In return, the coral provides protection and assists the growth of the zooxanthellae by passing on some of its waste, which the zooxanthellae use as a nutrient source. It is the colorful zooxanthellae that give coral their different colors and because zooxanthellae need sunlight to perform photosynthesis, they are the reason why corals need sunshine to survive.

If coral is affected by an environmental stress such as increased temperature or sedimentation, the zooxanthellae leave the coral and the coral turns white. This is termed coral bleaching. Although zooxanthellae can live freely in the water without coral, corals that normally contain zooxanthellae in their tissue cannot survive for long without their symbiotic algae. They will slowly starve. Thus, coral bleaching can be lethal for the coral if the coral polyps do not reacquire zooxanthellae. The phenomenon of coral bleaching is of particular concern as sea surface temperatures rise with human-induced climate change.


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