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Activity: Corals
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
NGSS Disciplinary Core Ideas
Table of Contents


  • Table 3.3
  • Fig. 3.31
  • Fig. 3.32
  • Fig. 3.33
  • Fig. 3.34
  • Reef-building coral skeletons (five or more of different species)
  • Dissecting microscope or hand lens
  • Calipers or ruler
  • Coral identification key (optional)


Fig. 3.31. Examples of solitary coral calyces (A) Tubastraea tube coral with side walls (B) Fungia mushroom coral without side walls

Image by Byron Inouye

Fig. 3.32. Arrangement of calyces (cups) in some colonial corals

Image by Byron Inouye


Fig. 3.33. Arrangement of septa in some colonial corals

Image by Byron Inouye

Fig. 3.34. Septa variations in colonial corals (shown with part of side walls removed)

Image by Byron Inouye


  1. Closely examine each coral skeleton
    1. Place each coral skeleton specimen on the stage of the dissecting microscope
    2. Adjust the lighting to maximize contrast and shadows to best view fine skeleton details
  2. Describe the features of the coral cuplike structures, known as calyces in Table 3.3. Refer to Figs. 3.31, 3.32, 3.33, and 3.34 as needed.
    1. Use the ruler to measure the cup, or calyx, diameter and record it in Table 3.3.
    2. Use the dissecting microscope or hand lens to closely examine the calyx features.
    3. Count the number of divisions, known as septa, per calyx and the features of the septa walls.
    4. Record the coral colony shape in Table 3.3. “Massive” coral colonies take solid, stone-like forms while “branching” colonies appear bush-like.
  3. Sketch the coral colony
    1. without magnification in Table 3.3. Indicate the appropriate scale in your sketch by using a ruler.
    2. under magnification from the dissection scope or hand lens in Table 3.3. Indicate the appropriate scale in your sketch by using a ruler.
  4. Repeat steps 1 through 3 for each coral specimen.
  5. (Optional) Use a dichotomous key to identify the coral skeletons.


Activity Questions
  1. Define the following terms:
    1. polyp
    2. colonial coral
    3. elevated cup
    4. septa
  2. How do the calyx features of the colonial coral specimens differ? How are the specimens similar?
  3. How are the individual calyces in a coral colony made? How does a colonial coral seem to grow? Explain by making sketches.
  4. Which coral calyx features are missing in a solitary coral like Fungia? See Fig. 3.31 B.
  5. Some coral polyps are as small as the lower-case letter o in this text (approximately three millimeters in diameter). How can these tiny animals build massive coral heads and entire coral reefs?
  6. Some coral species have sprawling branches while others adopt more solid, massive shapes.
    1. What are the advantages and disadvantages of these two coral forms? Recall that corals acquire energy both from photosynthesis and from capturing plankton.
    2. For what habitat would a massive-form coral species be well adapted?
    3. For what habitat would a branching-form coral species be well adapted?
  7. Storm disturbance on reef-building corals
    1. Which of the species you observed would probably break during a hurricane or heavy storm?
    2. What skeletal features make one coral more fragile than another?
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.