The student will be able to identify what luminescence is and
some possible reasons for its biological purpose or
The student will be able to define the terms photophore,
luminescent, and counterillumination.
- flashlight (for each individual or one to share in a small
- masking tape graphic organizer for taking notes (optional)
- drawing paper or picture of squid (optional)
- glow in the dark crayons (optional)
- To pique the students' interest, ask questions such as
- How many of you have ever played flashlight tag?
- When during the day do you play this game?
- Could you play this game at noon? Why not?
- What is the object of the game?
- Could you play it without the flashlight at night?
- Lead students to the realization that the flashlight has a
purpose in this game, and the only time they can really
effectively use the flashlight is in the dark.
- Ask if students can think of other ways we use
lights, besides playing games in the dark. Some possible
responses might be for illumination, so we can see; to
decorate, as during holidays or at a carnival to decorate
a Ferris wheel; for warnings, such as a traffic light; for
signaling, as at an airport to signal to planes.
- Ask students if they know of any land animals, including
insects, that have lights on their bodies. Students will
probably mention fireflies. Ask the students if they know
where the light comes from. (The light is produced by the
breakdown of a protein called luciferin in the firefly's
body. This is done by the action of a enzyme called
luciferase.) Tell the students that there are many sea
animals which have lights on their bodies, also generated
by luciferin. A creature or an object that produces light
is said to be luminescent.
- Ask students if they can figure out where
luminescent sea creatures live and why. Refer to the
discussion that was previously held about ways that people
use lights, and ask the students if they can think of
reasons why deep sea creatures would have lights. Tell the
students that even today we do not know all the ways that
these animals use their lights.
- Tell the students that they are going to pretend
that each of them is a luminescent squid. Luminescent
squid have light producing organs called photophores. Ask
the students if they can figure out what the prefix
"photo" means. Give examples of words to help
them figure out the meaning such as photography,
photogenic, photosynthesis, photographer. Be sure
students understand the prefix "photo" before
- Pass out the flashlights. Tell the students that these are
their photophores. Have the students label the flashlight
with the word "photophore," using the masking
tape for the label. (Option: If there are not enough
flashlights for all students or for small groups, choose a
few students to be the demonstrators in front of the class with
the available flashlights.)
- Tell the students that you are going to give them three
situations (see below) where they must decide whether or
not to use their photophores (flashlights) . They must be
able to give reasons why they did or did not turn on their
photophores. Remind students that they are luminescent
squid and that they need to think like a squid. They live in
the deep dark sea.
Turn off the lights and draw the blinds. If not demonstrating
in front of the class, students are to remain in their
seats. Present the following situations:
- You want to capture a fish.
- You want to make yourself attractive so that you can
attract a mate.
- You want to escape from an enemy.
After each example, ask students why they turned their
"photophores" on or off. Some possible
students' responses might be that they turned their
photophores off to trick the fish so that it could not see
them, or they turned them on to lure the fish. To attract
a mate, they would probably turn on their photophores so
that they would be visible. To escape from an enemy, they
might turn their photophores off to flee in the dark, or
they might turn them on to scare their enemy. There are no
correct answers. It is important to explore the reasons
why light would be used. Tell the students that squids
sometimes pulse their lights, rather than just let them
Tell the students that you are going to show them another very
important reason why a squid might have photophores. Open the
classroom door and place a student in front of the door.
The classroom should still be dark, but the hallway is
lit. Say to the students, "See how easy it is to see
this 'squid'? Squid are easy to see from below
because they cast a silhouette. What do you think would
happen if the squid could light up underneath to match the
Lead the students to realize that by matching the light
overhead, the squid would be difficult to see and thus
protected from its enemies. Illuminating the underside of
an animal so that it makes its silhouette disappear is
- Put away the flashlights and turn on the classroom light.
Have students pair with another student and review the
following: photophore, what "photo" means,
luminescent, reasons for luminescence, counterillumination
and the purpose it serves.
Give further notes about luminescence and counterillumination
in squid. (See the Background
Content for Teachers.) Students may use the accompanying graphic
organizer or any other method of the teacher's choice.
Give students pictures of squid or have them draw their own. Have them
use glow in the dark crayons to draw photophores on the squid.