Darwin Beagles Essay, Research Paper

Biology came of age on November 24, 1859, the day Charles Darwin published On The Origin

of Species by Means of Natural Selection. His book presented the first convincing case for

evolution and led the way in the emergence of biology from a bewildering chaos of facts into a

cohesive science. In biology, evolution refers to all the changes that have transformed life on

Earth from its earliest beginnings to the seeningly infinite diversity that characterizes it today.

Darwin addressed the sweeping issues of biology: the great diversity of organisms, their origins

and relationships, their similarities and differences, their geographical distribution, and their

adaptations to the surrounding environment.

Darwin made two points in The Origin of Species. First, he argued from the evidence that

species were not specifically created in their present forms, but had evolved from ancestral

species. Second, Darwin described a mechanism for evolution, which he termed natural selection.

Evolutionary change is based mainly on the interactions between populations of organisms and

their environments. The Origin of Species was truly radical, for not only did it challenge

prevailing scientific views, but it also shook the deepest roots of Western culture. Darwin?s view

of life contrasted sharply with the conventional paradigm of an Earth only a few thousand years

old, populated by immutable (unchanging) forms of life that had been individually made by the

Creator during the single week in which he formed the entire universe. Darwin?s ideas subverted a

world view that had been taught for centuries.

THE VOYAGE OF THE BEAGLE — Darwin was 22 years old when he sailed from England

with the Beagle in December 1831. The primary mission of the voyage was to chart poorly

known stretches of the South American coastline. While the crew of the ship surveyed the coast,

Darwin spent most of his time on shore, collecting thousands of specimens of the exotic and

exceedingly diverse fauna and flora of South America.

As the ship worked its way around the continent, Darwin was able to observe the various

adaptations of plants and animals that inhabited such diverse environments as the Brazilian

jungles, the expansive grasslands of the Argentine pampas, the desolate lands of Tierra del Fuego

near Antartica, and the towering heights of the Andes Mountains. He realized that the fauna and

flora were very distinct from the life forms of Europe. The plants and animals living in temperate

regions of South America were taxonomically closer to species living in tropical regions of that

continent than to species in temperate regions of Europe. Furthermore, the South American

fossils that Darwin found, though clearly different from modern species, were distinctly South

American in their resemblance to the living plants and animals of that continent. Darwin was

perplexed by the peculiarities of the geographical distribution of species.

A particularly puzzling case of geographical distribution was the fauna of the Galapagos

Islands, which lie on the Equator about 900 km. west of the South American coast. Most of the

animal species on the Galapagos live nowhere else in the world, although they resemble species

living on the South American mainland. Among the birds Darwin collected on the Galapagos

were 14 types of finches that, although quite similar, seemed to be different species. Some were

unique to individual islands, while other species were distributed on two or more islands that were

close to each other. Darwin wondered about the relationships of the island finches to one another

and to the finches on the mainland, which were different.

By the time the Beagle sailed from the Galapagos, Darwin had read Lyell?s Principles of

Geology. Darwin was doubting the church?s position that the Earth was static and had been

created only a few thousand years ago. By acknowledging that the Earth was very old and

constantly changing, Darwin had taken an important step toward recognizing that life on Earth

had also evolved. He would soon realize that evolution was the only rational explanation for the

relationships between the species he had collected, particularly those from the Galapagos Islands.

At the time Darwin collected the Galapagos finches, he was not sure whether they were

actually different species or merely varieties of a single species. Soon after returning to England in

1836, he learned from ornithologists (bird specialists) that the finches were indeed separate

species. He began to reassess all that he had observed during the voyage of the Beagle and in

1837 began the first of several notebooks on the origin of species.

Darwin began to perceive the origin of new species and adaptation as closely related

processes. A new species would arise from an ancestral form by the gradual accumulation of

adaptations to a different environment. For example, if one species became fragmented into

several localized populations isolated in different environment by geographical barriers, the

populations would diverge more and more in appearance as each adapted to local conditions,

gradually, over many generations, becoming dissimilar enough to be designated separate species.

This is apparently what happened to the Galapagos finches. Among the differences between the

birds are their beaks, which are adapted to the specific foods available on their home islands.

Darwin anticipated that explaining how such adaptations arise was essential to understanding

evolution.

Bibliography

1. Biology by Neil A. Campbell C.1986

2. Aol.www.charlesdarwin.com