НАУЧНАЯ БИБЛИОТЕКА - РЕФЕРАТЫ - The evolution
The evolution theories.
By the term of evolution is meant the development of
natural and social occurrence. Some negligible and invisible changes occur
evolutionary. The evolution theory gives us the explanation of historical
development of living things.
In this assay I try to describe the development of the
main evolution conceptions from the ancient times to now days. The beginning
and development of life have always been a matter of people’s concern and
interest. Rather than the theory of evolution, we should speak of several
theories of evolution. On the one hand, this plurality has to do with the
different explanations advanced for the mechanism of evolution, and on the
other, with the various philosophies on which it is based.
Before a theory can be included in the system of science, it must meet all of the following criteria:
ability to explain what has been observed;
ability to predict what has not yet been observed; and
ability to be tested by further experimentation and to be modified as required
by the acquisition of new data.
These definitions mean that a
scientific theory is not used, as people often use the word theory, to mean a
hunch or a guess. A scientific theory
is held with a high degree of confidence and is supported by enough evidence to
make its abandonment unlikely. As new evidence is found,
a theory may be modified but only with compelling evidence, verification and
peer review. The business of science is to build theories that explain
how the natural world works and can predict how it might work in the future.
Let’s take a look at the most
After more than two thousand year
old history of science development in ancient Greece, Rome, China and India the
European countries fall into dark middle ages, a pitch darkness for natural
science. People were burnt on fire not only for telling the ideas of life
development, but also for reading books of ancient natural scientists and
philosophers. Violent implementation of religion makes science a church
appendage. The Renaissance appeared a real breakthrough in the sphere of
The ideas of evolution begin to
appear in the works of some philosophers and natural scientists. In 1646-1716
the gradation principle was declared by Leibnitz who divined the existence of
intermediary forms between plants and animals. Hereafter, the principle of
gradation has been amplified in conception of “the ladder of beings”, which
became a picture of ideal continuity of formation for some and confirmation of
evolution of living things for others.
Fairly, this theory had the right
to exist. But, in my opinion, it is not reliable in now days because of its
By the 18th century,
scientists have gone through a great deal of work collecting and describing
plants and animals throughout the world. But it started to become more and
more difficult to orient oneself in the ocean of information that they’d
cumulated. A Swedish naturalist Karl Linney has colligated and systemized the
data. He laid a foundation of modern systematic.
In order to classify the great
amount of plant and animal descriptions a specific systematic unit was needed.
Linney thought the genus is the unit. Genus was called a group of persons that
shared the same qualities. The genus consists of the variety of kin persons
that gives plentiful offspring. For example, a wild raspberry is a specific
genus, strawberry is another genus and cranberry is a third genus. All the
domestic cats make up an independent genus, tigers do, too and so on.
Therefore, all the organic world consists of different genera of plants and
animals. All the living nature consists of somewhat like the separate elements,
It is hard to agree with this
theory as well because the modern stage of biology evolution makes it clear
that the genus cannot be the only unit of systematic. Because of the religious
influence on science at that time can be concluded that Linney was an idealist.
He insisted that in nature there are plants and animals species just as many
as the God has created at the very beginning of the world. So, I cannot agree
to this point.
A French scientist Lamark is
known as the first biologist who tried to develop a complete theory of life
evolution. He introduced the term of gradation as an internal force of improvement
inherent to all living things. By the act of this factor of evolution defines
the development of living nature and constant improvement of organization of
beings from the simple forms to the most developed ones. According to Lamark,
all animal and plant classes are being constantly changed and improved in their
organization as a result of influence of external environment and some kind of
internal tendency of improvement. All the organisms were allocated by Lamark
to 14 different classes and put in the ladder of beings in specific order:
reptiles, birds and mammals.
This theory is more substantial
than the previous ones. For his time period Lamark has very successfully
developed the question of species change under influence of natural causes and
noted the importance of time and environmental conditions in evolution process,
which was accounted as demonstration of a blanket law of natural development.
The merit of Lamark is that he was the first one to announce the genealogical
classification of animals according to the kinship principle.
Speaking of the Evolution theory it would be wrong to avoid
the great work of Darwin. Charles Darvin lived in the time of rapid society
development when natural science was on the up-grade. There were many
scientific inventions. The epochal work “Origins of species” has been
republished seven times during the author’s life. It became known to many
scientists from other countries and has been translated into the majority of
European languages. The driving forces of evolution, according to Darwin, are
heritable change and natural selection. Evolution theory says that all living
things are related to one another through common ancestry from earlier forms
that differed from the present forms. According to the theory, variability
among individuals in a population of sexually reproducing organisms is produced
by mutation and genetic recombination. The mutation becomes a base of new words
of organisms structures and functions formation, and the heritance anchors
them. The resulting genetic variability is subject to natural selection in the
Despite the popularity of that
theory, I cannot call it the absolutely right, as well. Darwinism is
discredited by the lack of prognoses and unability to forecast new facts.
Darwinism turned out to be very appealing to the materially oriented scientific
society of 19th century because this evolution conception alleged to
eliminate supernatural ideas of ancestry. It seems to me that the appeal of
Darwinism is that it uses pure mechanistic explanations for the evolutionary
process allowing the appeal to the term of contingency.
The account of all the system of
modern evolutionary biology is a compositive evolution theory, the principal
case of which have been established by the works of Chetverikov, Fisher,
Holdane, Dubinin and etc. The elementary cell of a compositive evolution theory
is a population. The elementary particle of heredity is a gene. The
hereditary change of population in a particular way happens under influence of
evolutionary factors, such as the mutation process, population waves, isolation
and natural selection. The first place in the compositive evolution theory
belongs to population, not to ontogenesis. This theory, in my opinion, is the
most perfect. It is more integral in theoretical and terminological views. It
might be related to the ability of this theory to systemize in itself variety
of terms and reflect the full system of evolutionary process.