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Alive & KickingNurse Trees— And Things That Go Around |
Over the decades, life science teachers have employed different memory aids to help their students learn.
I used one such mnemonic device (pronounced “neh-mon-ik”) to help my students remember which elements are most common in the tissues of living things. It went like this: CHOPKINS CaFe Mg NaCl (read as, “See Hopkins Café mighty good salt”).
The letters stand for the major elements found in the tissues of plants, animals, and everything in between (the line between plants and animals is not clear in some cases).
The most common elements found in life forms are Carbon, Hydrogen, Oxygen and Nitrogen. I’m sure many of the element symbols listed in the mnemonic above, including K for potassium and P for phosphorus, are in your memory bank.
In addition, numerous trace elements like copper (Cu) are present in living tissue in very small amounts. But of course, that copper atom didn’t originate in that tissue.
Nature is the great recycler.
Each atom of each element in your tissues has had a unique history through the ages!
Wouldn’t it be interesting to know where a single atom of carbon, for example, has traveled all these centuries past?
Many generalizations can be made. A single hydrogen atom, the most common element on earth, certainly spent a great deal of time in water, bound in ice, trapped in an aquifer deep in the ground, sucked up in plants, captured in fat, carbohydrate, protein and DNA molecules and in many races, animals and places—maybe even molded into a snowman on somebody’s front yard.
I am sure that many of your atoms, for instance, were temporarily located in the tissues of mastodons, dinosaurs, worms, frogs, mud and in things too fierce to mention.
The elements do cycle and cycle and recycle.
Consider for a moment the entrapments and liberation of materials in a common biological example: a large windfall tree in a forest otherwise known as a NURSE TREE.
We have such a fallen tree by our garage on the edge of a copse of trees. The tree spent its life gathering materials (atoms), which enabled growth and repair in much the same way as our bodies do.
To feed the growth spurt of young living things, nutrients must be gathered rapidly. In middle age, growth is slower and finally we and the tree will be recycled as other living things reorganize our elements.
Some of the living forms on the dead and decaying tree use the sunlight energy trapped in its woody tissue. Others need its protective covering for burrows and dens in which to escape the cold of winter and provide protection for their fragile young. Some of the living forms need soft and absorbent rotting wood as a source of moisture during periods of drought.
But to many life forms, especially those that possess photosynthetic capabilities and thus can make their own food, the minerals of the past living tree are a much sought treasure, a repository of fertilizer for building body tissues.
The recycling of our disappearing nurse tree is very complex. During the rot, more heat is given to the earth and atmosphere than if we had burned the whole tree, for the natural decomposition is more complete—thus releasing more energy—than the process of burning. Few atmospheric smog-producing molecules are released. Instead, the end products are carbon dioxide (CO2), water (H2O) and minerals.
My decomposing tree has not finished: 30% or so of the tree remains at present. It is a community of life. Th e nurse tree is nursing all the living forms growing on its remains.
I called the roll today— some species are numerous— and some, like bacteria, cannot be seen by the naked eye but are undisputedly present.
Each is recycling matter atom-by-atom from the atmosphere, rain and the decomposing nurse tree. See the list of those present when I called roll (Page 4).
Guest columnist John Cooke taught high school biology for 30 years and is pleased to share his insights with our readers.