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Introduction To Evolution Essay, Research Paper

Introduction To Evolution

What is Evolution? Evolution is the process by which all living things

have developed from primitive organisms through changes occurring over billions

of years, a process that includes all animals and plants. Exactly how evolution

occurs is still a matter of debate, but there are many different theories and

that it occurs is a scientific fact. Biologists agree that all living things

come through a long history of changes shaped by physical and chemical processes

that are still taking place. It is possible that all organisms can be traced

back to the origin of Life from one celled organims.

The most direct proof of evolution is the science of Paleontology,

or the study of life in the past through fossil remains or impressions, usually

in rock. Changes occur in living organisms that serve to increase their

adaptability, for survival and reproduction, in changing environments. Evolution

apparently has no built-in direction purpose. A given kind of organism may

evolve only when it occurs in a variety of forms differing in hereditary traits,

that are passed from parent to offspring. By chance, some varieties prove to be

ill adapted to their current environment and thus disappear, whereas others

prove to be adaptive, and their numbers increase. The elimination of the unfit,

or the “survival of the fittest,” is known as Natural Selection because it is

nature that discards or favors a particular being. Evolution takes place only

when natural selection operates on apopulation of organisms containing diverse

inheritable forms.

HISTORY

Pierre Louis Moreau de Maupertuis (1698-1759) was the first to

propose a general theory of evolution. He said that hereditary material,

consisting of particles, was transmitted from parents to offspring. His opinion

of the part played by natural selection had little influence on other

naturalists.

Until the mid-19th century, naturalists believed that each species

was created separately, either through a supreme being or through spontaneous

generation the concept that organisms arose fully developed from soil or water.

The work of the Swedish naturalist Carolus Linnaeus in advancing the classifying

of biological organisms focused attention on the close similarity between

certain species. Speculation began as to the existence of a sort of blood

relationship between these species. These questions coupled with the emerging

sciences of geology and paleontology gave rise to hypotheses that the life-forms

of the day evolved from earlier forms through a process of change. Extremely

important was the realization that different layers of rock represented

different time periods and that each layer had a distinctive set of fossils of

life-forms that had lived in the past.

Lamarckism

Jean Baptiste Lamarck was one of several theorists who proposed an

evolutionary theory based on the “use and disuse” of organs. Lamarck stated that

an individual acquires traits during its lifetime and that such traits are in

some way put into the hereditary material and passed to the next generation.

This was an attempt to explain how a species could change gradually over time.

According to Lamarck, giraffes, for example, have long necks because for many

generations individual giraffes stretched to reach the uppermost leaves of trees,

in each generation the giraffes added some length to their necks, and they

passed this on to their offspring. New organs arise from new needs and develop

in the extent that they are used, disuse of organs leads to their disappearance.

Later, the science of Genetics disproved Lamarck’s theory, it was found that

acquired traits cannot be inherited.

Malthus

Thomas Robert Malthus, an English clergyman, through his work An

Essay on the Principle of Population, had a great influence in directing

naturalists toward a theory of natural selection. Malthus proposed that

environmental factors such as famine and disease limited population growth.

Darwin

After more than 20 years of observation and experiment, Charles

Darwin proposed his theory of evolution through natural selection to the

Linnaean Society of London in 1858. He presented his discovery along with

another English naturalist, Alfred Russel Wallace, who independently discovered

natural selection at about the same time. The following year Darwin published

his full theory, supported with enormous evidence, in On the Origin of Species.

Genetics

The contribution of genetics to the understanding of evolution has

been the explanation of the inheritance in individuals of the same species.

Gregor Mendel discovered the basic principles of inheritance in 1865, but his

work was unknown to Darwin. Mendel’s work was “rediscovered” by other scientists

around 1900. From that time to 1925 the science of genetics developed rapidly,

and many of Darwin’s ideas about the inheritance of variations were found to be

incorrect. Only since 1925 has natural selection again been recognized as

essential in evolution. The modern theory of evolution combines the findings of

modern genetics with the basic framework supplied by Darwin and Wallace,

creating the basic principle of Population Genetics. Modern population genetics

was developed largely during the 1930s and ’40s by

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