ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Thursday, January 18, 1996 TAG: 9601180015
SECTION: EXTRA PAGE: 3 EDITION: METRO
COLUMN: WHY THINGS ARE COLUMN
SOURCE: JOEL ACHENBACH
This is what we'll miss about the Why column: The other day, as we were driving through the countryside, we suddenly began to wonder why trees don't walk. Think about it! Why don't plants move? Shouldn't some plant have evolved the ability to walk, run, fly? Why isn't there a big, fast plant that can photosynthesize by day and, by night, stalk cattle?
Most people who think of stupid questions are forced, within a matter of minutes, to forget about them. But the Why staff gets to follow up. We can find the answers, publish them, and pass this whole activity off as a credible professional endeavor.
We can report that plants don't develop animal-like skills because, for one thing, they are full of cellulose.
This is the hard stuff that surrounds the cells of plants. (Plants have ``cell walls,'' you may recall learning in school; animals don't.) The cellulose gives a plant rigidity, allowing a tree to stand tall, for example, rather than just puddling up on the ground in a big blob o' magnolia. The trade-off is that plants are pretty much immobilized.
``If you've got a lot of cellulose in you, you're basically stuck in one place, because of the structural rigidity,'' says Ron Martin, a paleontologist at the University of Delaware.
Another factor in plant immobility: They are autotrophic. They make their own food, through photosynthesis. It would be a waste of time and energy to chase field mice or snag salmon out of mountain streams. If you're autotrophic, you need to be mellow. You find your place in the sun and put down roots.
There are some freakish plants and animals that skirt the rules a little. The Venus' flytrap snags animals but doesn't really eat them - the flies dissolve in those little cages. Corals are animals that, like plants, don't move. In fact corals have plants in them - photosynthetic algae that literally live in the tissues of the animal. The overall coral biomass is more plant than animal.
One thing you might want to remember when you have forgotten the rest of this item: Plants did not come before animals. Animals appeared in the ocean about 540 million years ago. The first plants appeared on land about 400 million years ago.
So it's not like animals are somehow an outgrowth, or evolutionary upgrade, from plants. Biologically speaking, plants have a more modern way of living than animals. You'll probably notice this the next time you're in the woods: Trees are hip.
The Mailbag:
Pam and Bob V. of Honolulu write, ``Why are rainbows so hard to photograph?''
Dear Pam and Bob: You got several problems here. First, a photograph is just an ``interpretation'' of an image. In real life you see lots of hues, but your photograph uses just three dyes (cyan blue, magenta, and yellow) to render that image.
Moreover, you probably take pictures with a 35-millimeter camera, which has a short, wide lens. This means the rainbow is going to be a small part of your image. It just won't be very impressive. You'll have better luck if you use a telephoto lens so the rainbow looms larger on the print.
If the sky is dark behind the rainbow, that's best of all. Normally a rainbow has a bright sky behind it, and so the colors have little contrast with the background.
Now, you may ask why, when we're staring at a rainbow, the lack of contrast with the background sky doesn't bother us as much as it does when we see the lack of contrast in a photograph. Explanation: A photograph is an objective depiction of the world. By contrast, our brains are highly selective, capable of editing out the bright background as we marvel at the rainbow. The photograph shows the real world; what we see is a fantasy.
- Washington Post Writers Group
LENGTH: Medium: 75 linesby CNB