Abstract
Charles Darwin wrote in his diary, "hath in space and time, we seem to he hrought somewhat near to that great fact - that mystery of mysteries - the first appearance of new heings on this Earth." The beginning of species is at the focal point of evolutionary theory, for it is in new species that biological diversity arises.
Diversity is a hallmark of life.
Biological diversity is something to relish and preserve, hut it can also be a bit overwhelming. SELECTIVE REPRODUCTION is what Charles Darwin called NATURAL SELECTION and he envisioned it as the cause for evolution. Life comes from life, an axiom known as "BIOSYNTHESIS."
In some ways, hiology is the most demanding of all sciences, partly hecause living systems are so complex. Modern hiology is the decathlon of science. Biologists have identified and named about 1.7 million species, including 400,000 plants, almost 40,000 vertebrates (animals with a backbone) and more than 750,000 insects; thousands of newly identified species are added to the list each year.
As nature progresses, it does so in one of two ways; either by inspiration or desperation. Nature can move forward, which is known as NATURAL SELECTION, or nature can stand still, known as ARTIFICIAL SELECTION and extinction will eventually occur. The hiochemical hasis and understanding for each of these diametrically opposed phenomena is the subject of a great deal of confusion, misrepresentation and wonder. The results of each of these natural occurrences differ dramatically.
Hybridization, or ARTIFICIAL SELECTION, does occur in nature under adverse conditions. Birds spend 85% of their waking hours in pursuit of food or in pursuit of a suitahle mate.
When a hird wanders out of its range in pursuit of either of these two life sustaining items, hyhrids can occur. When a population is geographically separated, it is known as "ALLOPATRIC." When their ranges overlap, it is known as "SYMPATRIC."
Even if two distinct species mate and produce hyhrid youngsters that are vigorous, the hyhrids are very likely sterile hecause genes cannot flow from one species' gene pool to the other. One cause of this harrier is a failure of meiosis (a special kind of emhryonic cell division) to produce normal gametes (sex cells) in the hyhrid if the chromosomes of the two parent species differ in numher or structure. In some cases when species cross-mate and the first generation would he viahle and fertile, in the succeeding generation when the hyhrids mate or they are paired with either of their parents, the next generation of hyhrids will he feehle or sterile or can he hoth. This is the pathway that eventually leads to extinction.
It is estimated that once a viahle hybrid parrot has been created, the attempts to purify the original biochemical structure of the species will take at least seven generations to return the chromosomal structure to it's near original, viable state.
A case in point of possible hybridization caused by artificial selection is that of the single Spix's Macaw which is the only known memher of his species in the wild. Out of desparation he has mated with a female Iliger's Macaw and they seem to have produced a clutch of eggs. The eggs were old when the field biologists found them, one contained an embryo that died at about 10-11 days, and the other two were clear. As I write this article, DNA work is being done to determine if the egg was fertilized by the Spix's Macaw or whether the hen slipped off
and mated with a local Iliger's male.
Another phenomenon within the realm of BIOSYNTHESIS is NATURAL SELECTION, ALSO KNOWN AS MICROEVOLUTION. There are five potential agents of microevolution: genetic drift, gene flow, mutation pressure, assortive mating and natural selection. MUTATIONS ARE THE EXCLUSIVE SOURCE OF NEW GENES and experts estimate that a mutation appears spontaneously about I/10th of 1 %, thus evolutionary genetic recombination.
As mutations occur in nature, they are the programmed product of genes that are transmitted by orderly mechanisms and subject to modification. The aspect of genes and their capacity for change is an important link between genetics and evolution.
The most cited and extensively documented example of natural selection/mutations involves the English Peppered Moth (Biston vetularia). It is found throughout the English countryside. It occurs in two varieties of different colors. The color for which the peppered moth is named is light, with splotches of color pigment. The other color is pretty uniformly dark. Peppered moths feed at night and rest during the day on trees and rocks encrusted with lichens. Lichens often resemble mosses or other simple plants growing on rocks, tree trunks, the sides of buildings and other surfaces. Light colored moths can easily camouflage themselves, leaving the dark moths looking very conspicuous and easy prey for birds.
Prior to the Industrial Revolution, dark Peppered Moths were very rare, probably because they were bird food before they could pass their genes on to the next generation.
As the industrial pollution in England darkened the foliage in the 1800s, light moths stood out against the dark background of soot covered trees and rocks and dark moths were then concealed. The frequency of dark moths began to increase.
By the turn of the century the population in the Manchester, England region consisted almost entirely of dark moths. This phenomenon occurred in hundreds of other species of moths in polluted areas.