Life of an Earthworm
What's it like to be a worm? How would the world look, sound, and feel
if you lived at ground level or below, if you couldn't control your body
temperature or even shiver when you were cold, and if you had no arms or
legs and could only wiggle to move about?
Compare how your body does each of these things with how a worm does. Then do
the journaling project at the end.
- Seeing: Earthworms have no eyes, but they do have light receptors
and can tell when they are in the dark, or in the light. Why is being able
to detect light so important to a worm?
- Hearing: Earthworms have no ears, but their bodies can sense the
vibrations of animals moving nearby.
- Thinking and feeling: Worms have a brain that connects with nerves
from their skin and muscles. Their nerves can detect light, vibrations, and
even some tastes, and the muscles of their bodies make movements in response.
- Breathing: Worms breathe air in and carbon dioxide out, just like
us, but they don't have lungs. They can't breathe through their mouth, and
certainly can't breathe through their nose because they don't even have one!
They breathe through their skin. Air dissolves on the mucus of their skin,
so they MUST stay moist to breathe. If worms dry out, they suffocate. As
fresh air is taken in through the skin, oxygen is drawn into the worm's circulatory
system, and the worm's hearts pump the oxygenated blood to the head area.
The movements of the worm's body make the blood flow back to the back end
of the body, and the hearts pump the blood forward again. Carbon dioxide
dissolves out of the blood back to the skin.
- Eating: Worms do not have teeth, but their mouths are muscular and
strong. Nightcrawlers can even pull leaves into their burrows using their
strong mouths. The front end of the worm, its prostomium, is pointed
and firm, making it easy for worms to push their way into crevices as they
eat their way through their burrows. (The mouth of the worm is just behind
the prostomium.) Worms swallow pieces of dirt and decaying leaves, and the
food passes through the pharynx, (located in body segments 1-6), the esophagus (segments
6-13), and into the crop, which stores food temporarily. The worm's stomach
is very muscular, so is called a gizzard. Like a bird's gizzard, it
grinds up the food, which then moves into the intestine. The intestine
extends over two-thirds of the worm's body length. In the intestine, food
is broken down into usable chemicals which are absorbed into the bloodstream.
Leftover soil particles and undigested organic matter pass out of the worm
through the rectum and anus in the form of castings, or worm poop.
Worm poop is dark, moist, soil-colored, and very rich in nutrients. That's
why farmers and gardeners like to have lots of worms in their soil.
- Cleaning out the blood: Worms don't have kidneys, but they have
something serving the same purpose. Worms have nephridia to filter
out the dead cells and other wastes that are sloughed into the blood. Wastes
from the nephridia are eliminated through the same opening as the digestive
wastes. Worm urine is more dilute than ours, but has ammonia as well as urea.
- Heartbeats: Worms don't have just one heart. They have FIVE! But
their hearts and circulatory system aren't as complicated as ours -- maybe
because their blood doesn't have to go to so many body parts.
- Moving around: Worms have two kinds of muscles beneath their skin.
The outer layer of muscles are circular muscles, which decrease the diameter
but stretch the length of the earthworm's body when contracted. The inner
layer of muscles are longitudinal, which shorten but widen the body when
contracted. Every segment of a worm's body (except the first and last) has
four pairs of tiny, stiff hair-like projections called setae. To move
forward, this is what a worm does:
- First it grips the soil with some of its back setae
so its back part can't move.
- Then it squeezes its circular muscles, which makes
its body get longer. Since the back of the body is gripping
the soil, the front part of the body moves forward.
- Then the front setae grip the soil and the back setae
- Then the worm squeezes its longitudinal muscles, which
makes its body shorter. The back part moves forward.
Try This! Activities
- Journaling Project Imagine you are
the first worm on earth with the ability to write in a diary. Based on your
understanding of how worms live, write some diary entries. Try to pick days
when you won't get gobbled up by a robin! Choose three days from the following:
- a nice, sunny day after an overnight rainstorm in spring
- a day when it's pouring rain in spring
- a cool, moist summer day
- a hot, dry day in the middle of summer
- a warm, misty day in autumn
- a cold, windy day in autumn
- Valentines. Imagine you're a worm.
Use art materials to create a Valentine for your best friend.
- Heart Sounds. Imagine what a worm's
five hearts would sound like if you were listening through a stethoscope.
Practice making the sounds you think you would hear. Use your mouth or any
objects to create the heart sounds. Take turns with your friends to hear
each other's versions of worm heart sounds.