Thursday, May 11, 2017

4-H STEM: Wiggly, Squiggly, Slimy Worms

Our latest 4-H STEM activity was all about worms.  This was a big reach for me because I am borderline phobic about worms.  Seriously.  I walk around them on the sidewalk, I shudder when I see them.  But, it my endless attempts to not infect the kids with my squeamishness (about various things), I pushed through it.  Mainly because I thought the kids would get a real kick out of these activities.   They definitely did.  I was actually surprised that all the kids (except Squidy) were really into it.  Only a few of them even felt the need to wear gloves.

First thing we did was talk about why worms were so important for your garden and lawn.  They help aerate the soil, their tunnels help prevent soil erosion by allowing water to seep into the ground easier, they are decomposers that eat dead leaves and other organic materials, their waste is high in nutrients, and they eat some garden pests.

We then discussed interesting facts about worms.  Like the largest one ever found was 22 feet long!  (EEEK!), and that they come in all colors including blue and purple.

We went ahead and made our worm jars first, so that they would be all ready for their inhabitants once we finished our observations.  We put some aquarium gravel in the bottom, then layered sand and soil to fill the jar to about 3 inches from the top.

We put aside our jars, and got out our worms.  First the kids observed the external anatomy of the worms using magnifying glasses.  We noted how the worms had ridges all the way around them. This is why they are called segmented worms, or annelids.   We also noted the wide, smooth section toward the "head" end of the worms - the clitellum, which is responsible for mucus production during reproduction; worms are hermaphrodites – both male and female but two are needed for reproduction.

We talked a little bit about internal anatomy and how it was not possible to cut a worm in half and wind up with two living organisms.  If cut in the certain places, one part of a worm may still survive, as long as the major organs were avoided.

We then took a close look at the "head" end of our worms to see if we could identify any sensory organs.  After we decided we didn't see any, we did some tests to see if worms would react to various stimuli.

We started with testing if worms showed a preference for wet versus dry.  We placed a wet paper towel next to a dry paper towel, then placed our worms half on each.  We observed to see if they crawled to one side or the other. We then repeated our experiment with them turned the opposite direction.  We also tried starting them entirely on the dry side and entirely on the wet side.  Just about everyone's worms showed a clear preference for the wet side.

We then tested their reactions to light.  We had white lights, our UV lights, and I brought along clear red plastic to see if they reacted differently to the red lights.   We used a black piece of paper to shade a small section of the area we were working in to see if the worms would go toward the shade.  We tried shining the lights on various parts of the worm ("head" end versus "tail" end) to see how they would react.  In general, the worms crawled very quickly away from the white and UV lights, but did not react to the red lights.  We discussed a little bit of why that would be true.

Our final test was to place a small amount of acetone on a Q-tip and wave it near the worms.  We were very careful NOT to touch our worms with the acetone since it would be toxic to them.   Our worms did not like the smell of acetone and wiggled away from the q-tip.

After we finished observing our worms, we placed them in the prepared jars.

We moistened the soil slightly using a spray bottle, placed grass and cut carrots on top of the soil, wrapped the jars in black paper (so the worms would dig tunnels close to the sides) and covered it with a piece of cheesecloth.

The kids took their worm jars home for a week, then removed the paper to observe any changes in the layers, and to release their worms back into the wild.

The layers were slightly mixed up. More time might have been good there.
The worms really seemed to like carrots since multiple people noticed there were a lot of carrots missing.
One of the kids had a small extra worm more coming out then went into the jar, and two of the worms were tangled together when released.  So, we may have had some reproduction going on.

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