Mini-essay for June 2011

In June birds are in full abundance. They are on the ground, in the trees and flying here and there. But why in the air? Why do birds fly at all? One good reason is that they escape ground-dwelling predators. Another is that the air is filled with nutritious insects. Here is a whole new environment available to whomever can enter it. Over time any slight hereditary modification in a bird ancestor, which at first enables soaring from a tree or a brief taleoff while running, when further enhanced leads to flight.

What about insects, most of which fly? What advantages does an aerial capability confer upon them? One great advantage is faster locomotion. It would take a fly a long time to walk from Saratoga Springs to Ballston Spa, but in flight it could be done in 20 minutes. The great advantage of fast flight is the ability to disperse over large areas which in turn means a greater chance of surviving abrupt environmental changes. In the fossil record wings first appear in insects as a double pair and many existing kinds of insects still have four wings (beetles, bees, butterflies). Some insects have lost a pair of wings and now have only two (flies) and a few kinds of insects have lost flying wings altogether (fleas, bedbugs). There is a hitch in flight as a way of escaping predators. Some birds have evolved as predators (hawks) and among their prey are their fellow birds. The same thing occurred among insects. Dragonflies feed upon many kinds of insects.

The only other truly flying animals are bats and they serve us well by eating enormous numbers of night-flying insects, especially mosquitoes. All those other animals described as flying (flying squirrels, flying fish) do not truly fly, they soar and glide. If we sometimes imagine how delightful it might be to fly lke a bird, we should keep in mind to look over our shoulder for the flying predator always lurking nearby.

Miniessay for May 2011

In May with leaves emerging, we think of that vast amount of leaf surface accomplishing photosynthesis, making food for those leaf-producing plants. We also know that the process is valuable in that it helps reduce carbon dioxide in the atmosphere and supplies oxygen. It is much less well known that photosynthesis occurs in the oceans as well, though not so much the shoreside seaweeds or those in the Sargasso Sea. Instead, there are minute photosynthetic bacteria (cyanobacteria) in the oceans that produce as much as 20% of the oxygen we breathe, but this was not known until the late 1980's. The discovery was made by a Skidmore College Biology Department graduate, Sally (Penny) Chisholm, and others, working at the Woods Hole Oceanographic Institute and MIT.

Of such small size that it would take 1000 to line up across the head of a pin, there might be a million of these oxygen-producing bacteria in a thimbleful of seawater. It is hard to believe that such important organisms were unknown for so long, but in fact the whole world of tiny creatures drifting in the oceans (and in lakes and ponds) was not known until 1828 and was not called plankton until 1887. When creatures are large, we easily recognize differences (an elephant is roughly 100 times longer than a mouse), but we tend to think of tiny organisms as pretty much alike and sommetimes group them under the same name, microbe. In this Lilliputian world, however, slowly opened up to us in the 1600's by the microscope, there are great differences in structure, size, chemical composition and function. Some bacteria are 150 times larger than others. Bacteria in our gut synthesize vitamin K, others cause disease, bacteria in the oceans help degrade oil from oil spills and now we know that other ocean bacteria make a sizeable portion of the oxygen we breathe.

How much there is that we would not know except for the instruments of modern day science. Pure science and technology are a productively matched pair.