Snippets from Science

• Viruses have always been part and parcel of man’s existence. Whether they are alive or not can be debated, but the fact remains that they can replicate only by gaining entry to living cells. Viruses don’t have the machinery to make the molecules required for their assembly. Once inside the cell, the genetic material of the virus typically induces the cell to produce new viruses, which escape by budding through the surface of the host cell or by causing its rupture. Many viruses insert their own DNA sequences into the cell’s DNA without killing their “host cell.” No doubt many cells of your body, including reproductive cells, contain stretches of DNA of viral origin. Over evolutionary time, new kinds of genes, resulting from the integration of viral DNA, were introduced into human offspring, and at least some of these genes allowed our ancestors to better survive changes in their environment. In other words, they provided an adaptive advantage. The other side of the coin is that many viruses were, and are, deleterious to the evolutionary process by causing disease and death. This is one of Nature’s “good news bad news,” stories.

• The average human brain weighs about 3 pounds. The average adult sperm whale has a 16 pound brain.

• There were 600,000 soldiers killed during the Civil War. For every soldier killed in combat, some data suggest that two died from disease. It’s estimated that over 20 percent of these deaths were due to malaria, a disease caused by a parasite carried by mosquitoes. During the war, the Union army alone had 1,315,955 cases of malaria, with over 10,000 deaths. Typhus, carried by lice or fleas, also took its toll on Civil War soldiers, and amoebic dysentery, spread by common house flies, killed 44,500 Union soldiers. In fact, there were instances where entire regiments couldn’t go into battle because of rampant diarrhea. (Clearing course)

• Our sense of smell is probably our most primitive sense, and over evolutionary history it helped ensure the survival of our species. When our ancestors evolved the ability to get around on their two back legs, their noses became less important for survival, since they became far removed from the source of ground level odors. Odor molecules must be airborne and soluble in water for us to recognize them. Our smell cells are called olfactory neurons, and they are plastered against the roof of our nasal cavities. A layer of mucus (= snot) covers the layer of smell cells. Odor molecules breathed into our nasal passages dissolve in the mucus and become attached to the ends of olfactory neurons. The neurons signal the brain, and eureka, we perceive an odor. The sense of smell also works with signals from our taste buds to allow us to taste food flavors. Dogs enjoy a much keener sense of smell than we do, because they have about 40 times more olfactory neurons. In man the layer of olfactory neurons is about the size of a postage stamp, but in dogs the layer is about the size of a handkerchief.

• Giant dragonflies were present about 300 million years ago. Some of these were the largest insects ever known, with a 27-28 inch wing span and a body about a foot long. (Mitchell and Lasswell, A Dazzle of Dragonflies, 2005)