Tuesday, December 4, 2012

Why Are There Cages of Meat in the Outdoor Classroom?

Note to lower-school teachers: please read this all the way through before you decide to share it with your students!  It was tough to figure out how many details to share for your audience.

Something is rotten in the State of Tennessee, and it just so happens to be right here in our outdoor classroom!  Unfortunately (or fortunately, depending on your perspective), the chance to see this first class example of rot will only be available for another few days.

Scientists will study anything.  And when I say anything, I mean ANYTHING!  Scientists know that even the strangest research topics can lead to useful discoveries.  For example, the discovery of new rainforest organisms can help lead to the development of new medicines, a protein discovered in jellyfish helps to grow better crop plants, and learning about the internal structures of spinach can help us build better solar panels.  The strangest details in nature can help humans change the world, so scientists study nature.  All of it.  Even when studying nature involves looking at dead organisms.  And that is why high school science students have left pieces of rotting meat in our outdoor classroom.
High school students studying rotting meat.
Decomposition (AKA rotting) is nature's way of recycling nutrients.  With no decomposition, we would have no new growth.  Decomposition is a familiar process, especially this time of year when leaves are piling up and rotting (if they are not raked up and removed).  Leaves decompose and break down where they fall, and if you don't rake them up, they will be mostly broken down into soil by spring.  Decomposed leaves return their nutrients into the soil, providing the nutrients for next year's growth.  In Middle Tennessee, we tend to have great soil because leaves from our trees decompose and add to the soil every fall.
High school student documenting the decomposition process.
Animals that die also decompose, just like plants.  Their nutrients are recycled into the soil and into organisms that use dead animals for food.  We are probably not as comfortable with the thought of animals decomposing because the sight of dead plants is so much more common than the sight of dead animals.  Also, the decomposition of animals can be a little smelly at times, since animals contain substances called nitrogen and sulfur, which are not present as much in plants.  Nitrogen and sulfur can turn into odorous compounds during decomposition (also noticed in the odor of urine (for nitrogen) and rotten eggs (for sulfur)).  But never fear - the smell isn't that bad, and it won't hurt you!  Go take a look to see what organisms are nature's recyclers of dead animals.
Animal-proof cage for decomposing meat, allowing decomposition to occur.
The high school science students have built two wire mesh test chambers for studying the organisms that decompose pork meat.  The wire mesh keeps out rats and vultures that might eat the meat before it can decompose.  The students placed the meat in the outdoor classroom last week, and they are now checking the meat daily and documenting what organisms they see on the meat (and you thought your homework was difficult!).  The teacher for their class tells me that the meat will be totally gone in a few days or up to a week and a half, depending on how warm the weather is.  The warmer the weather, the faster nature's recycling organisms will break down the meat.
Two tiny black ants summitted this mountain of meat, and beige-colored blowfly eggs coat the cut bone.
According to the high school teacher, there will be an enormous variety of organisms present on the meat over the next few days.  Mostly, there will be bacteria, which are microscopic organisms that live in and on the meat and break it down.  Bacteria will look like a white, beige or grey slime on the meat.  There will also be immature blowflies soon.  Blowflies look like metallic house flies, and they primarily lay their eggs in rotting meat.  The immature forms are called maggots, which look like fat, short, white worms.  In a day or two, you will be able to see maggots feeding on the meat (should you be so lucky).  Currently, there are a few ants on the meat.  The high school teacher tells me that ants usually show up later in the decomposition process, but I saw two ants that seem to have climbed to the top of the meat.  I thought they appeared to be very satisfied with themselves, standing on what must have been a mountain of food from their perspective!

If you wanted to investigate nature's recycling system for yourself, you could collect leaves or dead insects and monitor their decomposition in paper cups over a few weeks.  See what conditions are good for decomposition.  Is moist or dry better for rotting?  Will a dead insect decompose faster if it is sitting on moist soil or if it is alone in a dry cup?  Will dead leaves break down faster if they are open to the air or sealed into a cup with plastic wrap?  What about a leaf left whole versus a leaf torn into bits?  What leaves have decomposed more in our outdoor classroom - the ones in the pond or the ones laying around on the ground?  (See the leaf skeleton post for more on leaf decomposition.)

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