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.
Monday, May 30, 2011
Wednesday, May 4, 2011
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.
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.
Wednesday, March 30, 2011
Seasonal Essay for April
April showers give us a chance once again to ponder the cycle of water as it moves from sky to earth and back to sky again, but through such a tortuous route! Surplus rain, collected in numerous streams, Kayaderosseras, Bog Meadow, Spring Run, pours into lakes Lonely and Saratoga. From here Fish Creek takes water to the Hudson which wends its way to the sea. Evaporation from the sea returns water to the sky once again, a cycle repeated over and over through many millions of years. Particles, eroded from the land and transported in our rivers have a different fate. Some, reaching the mouth of the Hudson, may be carried out to sea, slowly falling to the bottom as the current slows and over the course of many centuries a thick carpet of sediments piles up on the ocean floor reaching as far as 200 miles from shore. Dissolved solids carried in streams don't settle out directly, each kind having a different fate. Silica, upon reaching the sea, may be taken up by minute photosynthetic cells called diatoms and used to build glassy shells within which they live. When these cells die, their houses rain down upon the ocean floor and over great spans of time some deposits of these may be raised above sea level where we can mine them. The resulting fine abrasive is used in silver polish and even toothpaste. When we watch raindrops falling, we can think of their different fates. Some will soak into the earth and be taken up into the tallest trees where they will participate in the making of leaves. Others will evaporate back into the air to fall somewhere else. Still others will be embarking on that long journey to the sea.
Monday, February 28, 2011
Seasonal Essay for March
Some years ago I descended Spuce Mountain with windblown sleet splattering my back. The trail was wide and open making movement easy, freeing my mind and senses for other occupations. At a turn, a valley extended to one side and through it came wind which, added to that already blowing, set the trees into violent swaying, even the larger trunks moving almost to ground level. And the noise! The big trunks creaked and groaned. On top of them the smaller branches, hitting against each other cracked and rattled, and above it all the rushing sound of the wind provided the continuo.
It was too compellintg a scene to leave, so I pulled my square of insulated pad from my shoulder bag and sitting on it, leaned my back against a tree. Dark branches against a uniformly grey sky had their own fast beat, but in addition, each tree crown swayed as an entity, each tree size having its own resonant frequency. The effect was that of rows of dancers, arms upraised, each row bending first right andf then left, but in a direction opposite to that of the rows in front of and behind it, each tree-dancer having not two arms but many. I watched until a lull in the wind signaled intermission and as darkness fell I plodded homeward to offer a review of the performance.
It was too compellintg a scene to leave, so I pulled my square of insulated pad from my shoulder bag and sitting on it, leaned my back against a tree. Dark branches against a uniformly grey sky had their own fast beat, but in addition, each tree crown swayed as an entity, each tree size having its own resonant frequency. The effect was that of rows of dancers, arms upraised, each row bending first right andf then left, but in a direction opposite to that of the rows in front of and behind it, each tree-dancer having not two arms but many. I watched until a lull in the wind signaled intermission and as darkness fell I plodded homeward to offer a review of the performance.
Saturday, January 29, 2011
February Seasonal Essay
Winter offers us a chance to note again that among living organisms, each act of creation has its destructive counterpart. each great tree, rising out of the forest floor, finds many of its building materials among the ruins of former plants and animals. In addition, each forest creature throughout its life, sheds its used and worn-out parts onto the ground to be broken into its chemical constituents and recycled once again. We are fully aware of this in the fall when the great mass of leaves, generated through spring and early summer, having fulfilled their task of food manufacture, are cast free. But we are not so aware that this process of shedding continues in some degree throughout the year. In winter we see this especially clearly.
However pure the white new-fallen snows of February may be, in the woods they quickly lose their virginity. Soon they become littered with myriad dark fragments, some formless, others with clear and recognizable form repeated again and again. The last-remaining portions of birch catkins litter the snow and open cones of hemlocks and pines, shaken by the wind, shed the last of their more tenacious seeds. Strong wind loosens some of the last remaining leaves of oaks and beeches. A pile of wood chips at the base of a tree is readily explained by looking upward at the squared hole made by a Pileated Woodpecker. Masses of tiny black specks in snow hollows are jumping! They are insect-like springtails. And everywhere are fragments of bark, loosened by growth in girth of trees. The whiteness of snow gives the perfect background on which to display the products of the never-ending process of shedding, of life and death.
However pure the white new-fallen snows of February may be, in the woods they quickly lose their virginity. Soon they become littered with myriad dark fragments, some formless, others with clear and recognizable form repeated again and again. The last-remaining portions of birch catkins litter the snow and open cones of hemlocks and pines, shaken by the wind, shed the last of their more tenacious seeds. Strong wind loosens some of the last remaining leaves of oaks and beeches. A pile of wood chips at the base of a tree is readily explained by looking upward at the squared hole made by a Pileated Woodpecker. Masses of tiny black specks in snow hollows are jumping! They are insect-like springtails. And everywhere are fragments of bark, loosened by growth in girth of trees. The whiteness of snow gives the perfect background on which to display the products of the never-ending process of shedding, of life and death.
Subscribe to:
Posts (Atom)