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I am to give a presentation on fun, hands-on soils demonstrations
to primary and secondary school teachers. What suggestions
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for either elementary or secondary students?
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Mother Earth
I
am in eighth grade and doing an experiment for my school science
fair on the effect of temperature on annelids. I wanted to
place earthworms into 3 1-quart glass jars with lids, filled
with soil and watered, with apple peelings on the surface
of each jar and newspaper wrapped around the outside of each
jar. I would also place breathing holds in each jar lid.
Here's
my question: I wanted to place one jar under a heat lamp,
one jar in the refrigerator, and one jar at room temperature.
How do I determine safe temperatures for the earthworms
so that they don't die?
Thanks
so much for your taking time to consider my questionl
K.
Monick
Mother
Earth's reply:
K.
Monick:
Thank
you for your question! Since I didn't have your e-mail address,
I thought I would post your answer here!
Earthworms
are very sensitive to changes in their environment. Two
of the most important environmental factors include moisture
and temperature.
Since
I don't know exactly which earthworm species you are using,
I am going to assume you will be conducting your experiment
with Lumbricus terrestris, also known as nightcrawlers
or dew worms, depending upon where you live.
Nightcrawlers
prefer moist, but not wet soils. They typically thrive when
soil moisture contents are around 30 percent (this recommendation
is for medium textured soils). If you have too little moisture
in the soil, the worms won't be able to produce their protective
slime coat and will not be able to move through the soil
or breathe well. In fact, if the soil gets too dry, the
nightcrawlers dry up and die. However, if you have too much
moisture, the worms will have trouble breathing because
of a lack of oxygen in the soil pores. That is why you see
worms come to the surface after a big rain...to get air!
Therefore during your experiment, make sure to keep the
soil nice and moist, but be very careful about adding too
much water. Your biology teacher can help you determine
how much water to add to your soil to reach the right moisture
content.
As
for temperature, nightcrawlers are more sensitive to warm
temperatures than cool ones. Studies have found that nightcrawlers
thrive when soils are approximately 68 degrees Fahrenheit
(20 degrees Celcius). They can survive for short periods
in warmer soils, but prolonged temperatures close to 86
degrees Fahrenheit (30 degrees Celcius) are likely to prove
fatal. Researchers determined nightcrawlers can survive
for approximately 6 months in soils around 77 degrees Fahrenheit
(25 degrees Celcius), so you might use this as the upper
temperature limit in your experiment. As for their lower
temperature limit, it seems as long as they don't freeze,
nightcrawlers will survive in cool/cold soils. Therefore,
putting the worms in the refridgerator seems pretty safe.
In fact, many fishermen store their worms right next to
their milk and eggs!
Overall,
it sounds like you are well on your way to a fun and interesting
science experiment! My only other recommendation is to use
a neutral (pH 7 or above) soil that has a lot of little
aggregates (a lot of pore space). Worms don't like soils
that are too acidic and they have trouble moving about and
feeding in soils that are too compact. Also, keep the jars
as dark as you can!
Good
luck and have fun! I would love to hear what the results
of your study when you are done!
Yours
in Nature,
Mother
Earth
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