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Underwater Hide and Seek

By Betsy Berg



Type of activity:

  • Hands on activity
  • Simulation

Target audience:

  • Life Science
  • Biology
  • Marine Science (Integrated Science)

What question does this activity help students answer?

  • Students will be able to explain why color patterns that are easy to see above water may be difficult to detect under water.
  • Students will experience the problems predators face when searching for camouflaged prey.

Background information:

This activity requires one class period of approximately 30-40 minutes and a second class of about 20-30 minutes. Preparation time needed should not exceed 30 minutes.


Activity:

Summary:

This learning experience involves an integrated approach to explore the marine environment. It involves fish anatomy, adaptive and disruptive coloration, ecological principles, and the physics of light as it passes through water. The object is to illustrate that a fish that appears very colorful to us (red) may, in fact, be well camouflaged from predators.

Materials:

Each student will need a pencil, piece of red construction paper (8 X 11"), scissors, and a piece of blue cellophane (from art supply store) double thickness 4 X 11".

Procedure:

Begin the activity by having each student draw a fish on red construction paper. They then attempt to add distinctive features including various types of disruptive coloration such as stripes, bars, spots, etc.. Encourage the students to give their fish unusual characteristics so that they will be able to recognize their own fish the next day. The fish are cut out using scissors and the students label (in small print) the names of various structures, i.e. types of fins, eyes, lateral line, gills, etc.. These are collected and the accuracy of the identified anatomical features is graded. After class tape the fish around the classroom, placing some on dark and some on light surfaces, as well as on patterned and plain backgrounds.

The next day meet the students in the hall as they are entering the classroom and give each a 4" X 11" piece of blue cellophane (double thickness). The students are told to enter the classroom with the cellophane over their eyes so they are looking through it. Most of the room lights should be turned off and instruct the students to enter the darkened room and find their fish but not to remove it from the wall. This is a surprisingly difficult task and lots of fun! Do not allow students to wear the blue goggles for more than five minutes. To do so may bleach (temporarily) some of their visual pigments.

Ask them to sit in their seats and switch on the lights. From their seats (without the cellophane) have them look around the room and see how many fish they can now find. They quickly realize that this is much easier when all the lights are on and they are not looking though the cellophane. Class discussion reveals that they have simulated a depth in the ocean greater than 10 meters. Further, some wavelengths (colors) of light are absorbed faster than others when passing through water, particularly red and yellow. This has interesting consequences for color and color patterns and their distribution among animals that live in water

This activity is successful because ecological principles including predator/prey relationships, courtship and finding suitable mates can be more clearly understood if the student has been exposed first hand to some of the dilemmas facing these oganisms in their natural environment. The students have experienced what the world looks like to fish that live far enough below the surface that the world looks blue, the only color that effectively penetrates very deep. We then (hopefully) conclude that we cannot always make judgments about animals based on human perceptions.

Students with varying backgrounds - those who have: fishing/snorkelling/SCUBA experiences, better vision, or those who are artistically gifted and creative have an opportunity to excel. Students tend to be more motivated when they can "do" rather than "be taught". As I noted earlier, this activity is lots of fun and even high school seniors delight in finding their fish.

Extensions:

Have the students view underwater photographs cut from magazines that show bright colors and others that are of wide views that are predominantly blue (SCUBA magazines and National Geographic are good sources). Any colorful photograph was shot with a flash which provided all the wavelengths of light. Any photo in which the predominant color is blue shows what it really looks like under water.

Another extension would be to include discussions about the other senses involved in assessing ones environment. This exercise allows the students to gain some valuable insights about their natural world.

Note: This activity has been adapted from Living in Water, 1987, an aquatic science curriculum which was published by the National Aquarium in Baltimore. I've made a few changes to meet the needs of my students.


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