 
Darwin theory
Charles Darwin was interested in studying all the living organisms
in the world around him. In the 1800s, typically most men who went
to college and were not studying to become a doctor or lawyer studied
the theology
, including anyone who wanted to learn more about any of the
sciences or mathematics. Thus, Charles went back to school to study
theology to be a naturalist, studying under a clergyman who was
a botanist so that he could become a naturalist. At age 22, he got
a job as ship's naturalist on the HMS Beagle and joined the crew
as they sailed around the world. While the sailors were busy keeping
the ship headed in the right direction, he was responsible for doing
a survey of the flora (plants) and fauna (animals) living in the
areas they visited. From England, the ship sailed across the Atlantic,
down the east coast of South America and backs up the west coast,
then across the Pacific, past Australia, around Africa, and back
to England. Darwin is especially noted for his work on the Galapagos
Islands (located in the Pacific Ocean). On these islands, he found
14 species of finches, related to our goldfinches and house finches.
He theorized that these 14 species were all derived from one species
that had somehow gotten there from the mainland, then diversified.
Whereas most finches eat seeds, now, some of Darwin's Finches eat
large seeds, some eat small seeds, some eat insects, and some even
use cactus spines and twigs as tools to pry insects out of crevices.
Many more scientists have subsequently studied Darwin's Finches,
and this has led to a whole specialized branch of biology called
Island Biogeography. After this trip Darwin spent years pouring
over all the data he had collected, and forming his famous theory,
but put off publishing any of his results or ideas for over 20 years.
Only in 1859, The Origin of Species by Means of Natural Selection
or the Preservation of Favoured Races in the Struggle for Life,
better-know as The Origin of Species, was finally published. In
this landmark book, Charles Darwin made four main points:
- individuals, even siblings, in a population vary (there is variation),
- these variations can be passed to offspring (are inherited),
- (from Malthus) more offspring are produced than the environment
can support, so there is competition for resources, and
- those individuals whose characteristics make them best suited
to the environment live and reproduce and have more offspring
(survival of the fittest).
- Thus in any population, there is descent with modification (changes
occur over the generations) due to natural selection (the "pressure"
the environment puts on the various genetic varieties in terms
of their ability to cope and/or survive). Note that he does not
believe in the idea of an innate tendency toward greater perfection,
nor do organisms willfully "decided" to change, nor does the environment
cause any change to occur within an organism. What he does say
is that the environment does "select" various changes that have
occurred in that these (spontaneous) changes make the organism
more or less able to cope with various factors in the environment.
Besides his notes from his trip and his other studies, Darwin
also used artificial selection as justification/evidence for his
theory: if we, by breeding domesticated plants or animals for
a number of generations, can influence their genetics, then Darwin
felt that this could also happen in nature. Actually, Darwin never
used the word "evolution".
He used "descent with modification." Darwin's thinking was influenced
by the work of geologists and paleontologists like Hutton, Smith,
and Lyell, and by the work of Malthus. In the 1930s and 40s, later
people combined Darwin's work, Mendel's work on genetics, and
other new information to form what is called The Modern Synthetic
Theory of Evolution (synthetic in that it is made up of or based
on many smaller parts). Evolution refers to change, or more specifically,
the series of changes that have transformed life on Earth from
its beginnings until now. Besides Darwin's and Mendel's works,
this theory is also based on things like:
- biogeography
, the study of the geographical (locations/regions) distribution
of various organisms. An especially important subcategory is island
biogeography, the study of island populations.
- paleontology,
the study of fossils in rock strata-
- - taxonomy,
the grouping of related species based on
- comparative
anatomy, especially focusing on homologous
structures. Frequently, organisms with similar structures
have common lineage, and
- comparative embryology: the study of stages in embryonic
development in various organisms. This is summed up by the
phrase "ontogeny
recapitulates phylogeny", which roughly means that
the embryonic development of a species goes through stages
analogous to all the steps in the evolutionary history of
that species
-
- - molecular biology is based on similarities and/or differences
in the "big" molecules like proteins or DNA. The more
closely-related any two species are, the more macromolecules that
are shared in their DNA. Environmental pressure or natural selection
"allows" organisms with some genes/alleles to survive
while others die. Eventually, if enough genetic change accumulates,
it can be said that a given population of organisms is a different
species than that from which it arose. In other words, speciation
has occurred. This adds up to the process of evolution.
This article is partial quotation from article
which is at http://129.137.117.61/BIOLOGY/BIO106/darwin.htm
It's part of Clermont College Byology cource Copyright © 1997 by
J. Stein Carter. All rights reserved
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