Background
Seahorses are among the most unusual-looking animals in the world.
Unlike most fishes, they lack the caudal, or tail, fin. Most fish
species use the caudal fin to propel themselves through the water.
Lacking that, the seahorse uses its dorsal and pectoral fins to
propel itself.
The
seahorse has a unique tail in that it is prehensile or grasping.
Just as monkeys are able to use their prehensile tails to grasp
and swing from trees, seahorses are able to use their tails
to grasp seagrasses, algae, and other stationary objects.
Humans
have thumbs which similarly allow them to grasp objects. This
is one adaptation that has contributed to our ability to use
tools and manipulate objects easily.
Procedure
- Gather
a collection of at least ten tools and objects (screwdriver,
hammer, coins, etc.).
- Divide
a sheet of paper into three long columns. List the tools and
objects down the page in the first column. Label the second
column "with thumb" and the third column "without
thumb."
- Manipulate
each tool and lift each object. Rate the effort required to
perform each task on a scale of one to ten, with ten being
very easy and one being very difficult. Write your rating
in the second column.
- Fold
your thumb across your palm. Using the masking tape, tape
your thumb in place.
- Re-do
each of the tasks that you performed earlier. Rate the difficulty
of each task on the one to ten scale.
- Compare
your ratings with and without the use of your thumb. List
other tasks that would be affected by the presence or absence
of thumbs
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