Fish Ways Activities
SUMMARY
Students will try to design the most efficient
fish for moving in flowing water by testing models in a stream
of air. In meeting this challenge, students will investigate
how the shape of a fish and the size and placement of its
fins are related to drag and stability.
OBJECTIVES
Students will be able to:
- identify the relative efficiency of various fish shapes
in moving through water; and
- determine the most stable arrangement, and function,
of fish fins.
LESSON INFORMATION
Curriculum Link: (7SSM), (8SMM), (8SLS)
Setting: science lab classroom
Duration: minimum of two hours
Key Terms: drag, fins (caudal, dorsal, pectoral, pelvic, ventral),
friction, streamlining, turbulence
TEACHER BACKGROUND
Friction is the force that resists the motion
of one surface relative to another with which it is in contact.
Turbulence arises when particles of a fluid move in irregular
paths. However smooth a surface looks to the eye, it has many
microscopic irregularities - humps and crests - that restrict
the easy flow of water over it and increase turbulence. Drag
is the combined effect of friction and turbulence acting on
an object. The greater the drag, the slower the shape will
be able to move through a fluid.
Fins are the locomotory appendages of aquatic
vertebrates. A fish's complement of fins typically includes:
one or more dorsal and ventral fins whose function are balance;
a caudal fin, or tail, the main propulsive organ; a pair of
pectoral fins attached to the pectoral (shoulder) girdle and
pelvic fins attached to the pelvic (hip) girdle, both of which
are used in steering.
Many fishes have adapted to a non-flowing situation,
so that their shapes are most efficient for hovering or feeding
on the lake bottom. This lesson tests only for efficiency
in flowing water and hence seeks to identify the best shape
for fishes living in moving water or needing speed to feed
or travel.
For this lesson, the most efficient shape will
be identified as one that can be pushed along a ruler the
least distance by a stream of air. From this observation,
students should be able to infer that the most efficient fish
for flowing water is the most streamlined - i.e., the one
with the least drag.
Using a Plasticine sphere of the same mass as
that given to the students, try out the activity a few times
to determine the best distance for the vacuum outflow or hair
dryer to be positioned from the Plasticine shape (this will
depend upon the strength of the stream of air the vacuum cleaner
produces). Use this standardized distance for all the students'
tests. Allow students the opportunity for a good deal of trial
and error as they will need to check the efficiency of a variety
of shapes and fin placements.
MATERIALS
Plasticine (pieces of about 100 g); string;
rulers; blocks of wood (2"x4" or 2"x 6"); vacuum cleaners
or hair dryers; cardboard (shoebox type); scissors; retort
stands; clamps
PROCEDURE
- Help students focus on the relationship between body
shape and adaptation of a species by discussing the following
questions.
- How might the shape of a fish help it survive in a shallow,
vegetated habitat?
- How might the shape of a fish help it survive as a bottom
feeder?
- How might the shape of a fish help it survive in a large,
deep lake where it is both a predator of smaller fishes
and prey to larger fishes?
- How might the shape of a fish help it move easily through
the strong current of a swiftly- flowing stream?
- Have each student or group make three Plasticine shapes
with the least amount of drag possible.
- Have students test each of their shapes in the stream
of air generated by a vacuum cleaner or hair dryer, as follows:
- Suspend the shape to be tested on a string from a
clamp on a retort stand between the wooden block and
the ruler. Make sure that the front edge of the shape
is just alongside the 0 mm mark of the ruler.
- Position the vacuum outflow or hair dryer at the
predetermined distance from the edge of the ruler.
- Turn on the vacuum and measure the maxi- mum distance
(in mm) travelled by the anterior (front) tip of the
Plasticine shape along the ruler; record this distance.
- Note the stability of the shape in the stream of
air and record it. You might use a scale from 0 to 5,
where 0 represents a shape that spins uncontrollably
and 5 a shape that is completely steady and unwavering.
- Have students cut cardboard fins of various sizes and
shapes and insert up to five of these into the Plasticine
shapes they found to have the least drag.
- Have students repeat the vacuum hose test with various
types and placements of fins and record the results.
- When all the students or groups have found arrangements
that they consider to be as stable as possible, have all
the fishes in the class compete in the vacuum test to see
which is the most efficient model.
EVALUATION
Have students examine the "Fish of Ontario" information cards
and make a Plasticine body shaped like one of its fish, such
as pumpkinseed, yellow perch, northern pike or white sucker,
with appropriate fins. After they have tested such a fish
for drag, ask students the following questions.
- How did your results compare with results of previous
shapes you made?
- How do your results compare with results from other
class members using the same shape?
- Is this fish suited for slow or fast moving water?
EXTENSIONS
- A trip to a local stream could follow the classroom lesson
to test the efficiency of the Plasticine fish in slow-moving
water. Have students suspend their fishes from a metre stick
placed above the water and observe the behaviour of the
various models.
- Have students study fishing lures and note how the design
features of the lure affect its movement through the water.
Different kinds of lures, such as plugs and spoons, could
be compared. Ask students how the lures' movement is similar
to that of fishes. Many lures are designed to resemble injured
fishes by moving in an erratic or unstable fashion. Students
might make lures from old spoons or wood.
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