What is mimicry?

Sunday, August 24, 2014

   Mimicry is the resemblance of an animal to another animal or plant or to its surroundings. This resemblance, which often helps to protect the animal, is usually based on a similarity of color or structure.
   Many examples of mimicry may be found among insects. The dead leaf butterfly of India, when resting, has the color and shape of a dead leaf and is therefore not disturbed by its enemies. People are often afraid of the harmless hover fly because it looks like a stinging wasp. The viceroy butterfly is rarely eaten by birds because it resembles the bad-tasting monarch butterfly. The walking stick looks just like a small twig. Spider mites that live among moss look just like part of the moss plant.
   Many other animals also have protective coloring or structure. Young deer and some baby birds blend with their environment. The stripes of the tiger blend with the tall grass. Many nocturnal spiders are black and therefore difficult to see at night. Tree frogs are green. Arctic animals are often white. Protective coloring not only protects these animals from their enemies, but it also makes it possible for them to prey on other animals more easily. For example, the white fur of the polar bear, who has few enemies, enables it to approach its prey, the seal, unseen.
   Animals do not plan a color or shape for themselves. Their protective coloring and structure is the result of selective evolution. Through the ages the animals with the most effective protective coloring and structure have survived the longest and therefore have been able to reproduce more of their kind.
   After many generations of breeding, more and more members of their species were born with the coloring and structure necessary for their survival.

Electron microscope

   The electron microscope is an instrument which permits scientists to see and photograph objects too small to be seen with an optical MICROSCOPE. The electron microscope uses beams of electrons in place of beams of light. Its magnifying power is about 200 times that of the very best optical microscope.
   The human eye is a very fine OPTICAL INSTRUMENT. However, the eye cannot distinguish objects smaller than about four one-thousandths of an inch.
   The power of an instrument to enlarge and form a distinct image of small details is its resolving power. The limit of resolution of an optical instrument is the smallest distance between two objects for which the instrument can form two distinct images of these objects.
   The magnifying power of an optical microscope is thus limited by the fact that objects cannot be distinguished unless they are somewhat larger than the waves of light reflected from them.
   In 1932 Ruska, a German, constructed an electron microscope. He allowed a beam of electrons to be reflected from an object. (Since electrons are charged they can be controlled by electric and magnetic fields.) The reflected electrons were directed through a magnetic field and then focused on a screen (as electrons are focused on a television screen to make a visible image) or on a photographic plate so that the image would be recorded.
   The superiority of the electron microscope over the optical microscope depends on the fact that fast-moving electrons have a wave length a thousand times smaller than the wave length of visible light.
   In most cases an electron microscope must be used with objects which are very thin. Thus, stray electrons will pass through them rather easily. Only recently has it been possible to investigate living matter with an electron microscope.
   The electron microscope can be used to investigate a wide variety of materials. Many applications have been made in chemistry, biology, metallurgy and other fields. Many new structures have been discovered in insects. Details which occur in chemical changes have been seen.

Peony flowers

Wednesday, August 20, 2014

   The peony is one of the showiest of modern garden flowers. The kind most popular is a hybrid of the common peony of southern Europe and the Chinese peony.
   Peonies belong to the crowfoot, or butter-cup, family. There are over 300 varieties of the bush peony. It is a herbaceous PERENNIAL that reaches a height of about three feet. The flowers usually appear during June. They have single or double blooms ranging in color from white to red to purple. The petals are waxy. The large leaves possess deep grooves or divisions. The roots are fleshy and store food material for new growth each year. The stem has a red to green color. When peony bushes are separated and transplanted to a new location, flowers will not appear for a year or two while the plant rests.
   Some peonies have woody stems and are called tree peonies. They grow about five feet tall with many branches and a great number of blossoms. The woody tree peonies are native to Pacific coastal areas of Asia and North America.

What is a depressant?

A depressant is a drug that reduces the activity of various body functions. Some depressants such as anesthetics, sedatives, antiepileptics, narcotics analgesics, and some muscle relaxants, slow nervous and muscular activity by acting on the central nervous system. Tranquilizers are depressants that affect only part of the nervous system. They induce relaxation without causing total depression.

Facts about birthstones

Facts about birthstones
Did you know? The current assignation of stones to months was established in 1912