Coral Cam Web Site

Sexy Coral Reef and I Want My Own Space     Gail Swenson

OBJECTIVE:  To learn how coral polyps increase the chances of egg and sperm
                              meeting after being released into the vast ocean waters

AGE GROUP:   Suitable for ages 10 and up 


Like many organisms, corals reproduce sexually using egg and sperm cells.  Their romantic life is a bit different, in some ways, from what we humans are used to.  For one example, reproduction seems to be partly controlled by water temperature.

Once an egg cell is fertilized by a sperm cell, the resulting zygote becomes a planula larva, which needs to find a place to settle and grow into a coral polyp.  In these activities you will learn about some of the adaptations that have helped insure the success of the next generation of coral.

Before starting the activities, you should view the video on this web site: .  Here you will see exciting video of coral polyps releasing their eggs and sperm into ocean water.



Bottles of the soft drink called ORBIT
A transparent plastic jar, like a peanut butter jar
Plastic beads of two different colors (use any small object that will float and comes in different colors)


1.Tip and turn the bottle of ORBIT to try to cause collisions between the DIFFERENT colored spheres floating in the soft drink liquid.  Let your lab partner try his or her skill at achieving collisions.

2.Now fill the plastic jar about full of water and add the different colored beads.  Remember that the beads must float.  Put the cover on the jar and try to cause collisions between the DIFFERENT beads.

Processing the Results:

1.How many different directions could the ORBIT spheres move?
2.How many different directions could the beads move?
3.Which set up was the easier to use to cause collisions?
4.If you were a coral polyp, would you design egg and sperm cells with a density like the ORBIT spheres or like the colored beads?  Remember that egg and sperm cells must join for fertilization to occur.
5.Write a summary of what you have learned about collisions in 2 and 3 dimensions.


PURPOSE:  To learn about density of liquids and relate to egg and sperm cells of coral polyps.


Metric Balance                                                Two liter empty soda bottle

Graduated cylinder (100 ml)                            Small plastic pail

Calculator                                                       Small funnel with stem that will fit into tubing

Water                                                             Cooking oil

Tubing (rubber hose or any other small diameter tubing)


1.Mass 100 ml of water.           Record mass:_________
2.Mass 100 ml of cooking oil.  Record mass:_________
3.Fill the two liter bottle full of water.
4.Fill the pail to full of water.
5.Place you hand over the mouth of the bottle to keep the water inside and invert the bottle.
6.Set the inverted bottle into the pail of water and remove your hand.  The water should stay in the bottle.
7.Carefully insert one end of the tubing into the mouth of the bottle.  The other end should be outside of the bucket.
8.Have your lab partner hold the funnel so that you can pour a small amount of oil into the tubing through the funnel.  Watch what happens.

Processing the Results
1.Calculate the density of the water by dividing the mass of the water by the volume.  Density is reported in grams/milliliter.
2.Calculate the density of the cooking oil in the same way as you did in # 1. 
3.Which liquid has the greater density? 
4.Explain why the cooking oil behaved as it did when you added it to the soda bottle.
5.I f you were a coral polyp, and you wanted your egg and sperm cells to float, what would you do?


PURPOSE:  To learn about the survival challenges faced by the planula larvae when they
                      receive the signal to settle (sink) onto a solid submerged surface (substrate).  The
                      planula larvae must settle before they expire (die)..


Plastic bingo tokens or lots of pennies
Poster paper


1.Students should design a sea floor that has different sites.  Each sea floor will be different but be sure that each poster has EXACTLY the following:

    Two strong current areas (planula  cannot attach)
    Two dark areas (planula will not stay there)
    Two areas full of mature coral (planula will be eaten by coral)
    Two areas with thick sediment (planula cannot attach)
    Two areas that are empty and full of light (planula can attach and grow here)

2.Standing a challenging distance above the poster board, each student should drop 50 tokens or pennies    onto the poster board sea floor .

3.The 50 tokens must be dropped in 10 seconds.  Any tokens not dropped WILL DIE.

4.Your lab partner will record how many planula larvae successfully attached.

5.Repeat using your lab partner's sea floor.

Processing the Results:

1.What percentage of the planula larvae survived the settling and successfully attached?
2.What are some of the environmental factors that contribute to the successful settling of the planula larvae?
3.Suggest an adaptation that might increase the percentage of planula larvae that successfully settle and attach.

BBSR and TCOE Coral Web Site Team 1999
Funded by a grant from the Goldman Foundation