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Biology

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Biology is the science of living systems. It is inherently interdisciplinary, requiring knowledge of the physical sciences and mathematics, although specialities may be oriented toward a group of
organisms or a level of organization. BOTANY is
concerned with plant life, ZOOLOGY with animal
life, algology with ALGAE, MYCOLOGY with
fungi, MICROBIOLOGY with microorganisms
such as protozoa and bacteria, CYTOLOGY with
CELLS, and so on. All biological specialties,
however, are concerned with life and its
characteristics. These characteristics include
cellular organization, METABOLISM, response
to stimuli, development and growth, and
reproduction. Furthermore, the information
needed to control the expression of such
characteristics is contained within each organism.
FUNDAMENTAL DISCIPLINES Life is divided
into many levels of organization--atoms,
molecules, cells, tissues, organs, organ systems,
organisms, and populations. The basic disciplines
of biology may study life at one or more of these
levels. Taxonomy attempts to arrange organisms in
natural groups based on common features. It is
concerned with the identification, naming, and
classification of organisms. The seven major
taxonomic categories, or taxa, used in
classification are kingdom, phylum, class, order,
family, genus, and species. Early systems used
only two kingdoms, plant and animal, whereas
most modern systems use five: MONERA
(BACTERIA and BLUE-GREEN ALGAE),
PROTISTA (PROTOZOA and the other
ALGAE), FUNGI, PLANT, and ANIMAL. The
discipline of ECOLOGY is concerned with the
interrelationships of organisms, both among
themselves and between them and their
environment. Studies of the energy flow through
communities of organisms and of the environment
(the ecosystem approach) are especially valuable
in assessing the effects of human activities. An
ecologist must be knowledgeable in other
disciplines of biology. Organisms respond to
stimuli from other organisms and from the
environment; behaviorists are concerned with
these responses. Most of them study animals--as
individuals, groups, or entire species--in describing
ANIMAL BEHAVIOR patterns. These patterns
include ANIMAL MIGRATION, courtship and
mating, social organization, TERRITORIALITY,
INSTINCT, and learning. When humans are
included, biology overlaps with psychology and
sociology. Growth and orientation responses of
plants can also be studied in the discipline of
behavior, although they are traditionally
considered as belonging under development and
PHYSIOLOGY, respectively. Descriptive and
comparative EMBRYOLOGY are the classic
areas of DEVELOPMENT studies, although
postembryological development, particularly the
aging process, is also examined. The biochemical
and biophysical mechanisms that control normal
development are of particular interest when they
are related to birth defects, cancer, and other
abnormalities. Inheritance of physical and
biochemical characteristics, and the variations that
appear from generation to generation, are the
general subjects of GENETICS. The emphasis
may be on improving domestic plants and animals
through controlled breeding, or it may be on the
more fundamental questions of molecular and
cellular mechanisms of HEREDITY. A branch of
biology growing in importance since the 1940s,
molecular biology essentially developed out of
genetics and biochemistry. It seeks to explain
biological events by studying the molecules within
cells, with a special emphasis on the molecular
basis of genetics--nucleic acids in particular--and
its relationship to energy cycling and replication.
Evolution, including the appearance of new
species, the modification of existing species, and
the characteristics of extinct ones, is based on
genetic principles. Information about the structure
and distribution of fossils that is provided by
paleontologists is essential to understanding these
changes. Morphology (from the Greek, meaning
"form study") traditionally has examined the
ANATOMY of all organisms. The middle levels
of biological organization--cells, tissues, and
organs, are the usual topics--with comparisons
drawn among organisms to help establish
taxonomic and evolutionary relationships. As
important as the form of an organism are its
functions. Physiology is concerned with the life
processes of entire organisms as well as those of
cells, tissues, and organs. Metabolism and
hormonal controls are some of the special interests
of this discipline. HISTORY OF BIOLOGY
Origin and Early Development. The oldest
surviving archaeological records that indicate some
rudimentary human knowledge of biological
principles date from the Mesolithic Period. During
the NEOLITHIC PERIOD, which began almost
10,000 years ago, various human groups
developed agriculture and the medicinal use of
plants. In ancient Egypt, for example, a number of
herbs were being used medicinally and for
embalming. Early Development As a science,
however, biology did not develop until the last few
centuries BC. Although HIPPOCRATES, known
as the father of medicine, influenced the
development of medicine apart from its role in
religion, it was ARISTOTLE, a student of Plato,
who established observation and analysis as the
basic tools of biology. Of particular importance
were Aristotle's observations of reproduction and
his concepts for a classification system. As the
center of learning shifted from Greece to Rome
and then to Alexandria, so did the study of
biology. From the 3d century BC to the 2d
century AD, studies primarily focused on
agriculture and medicine. The Arabs dominated
the study of biology during the Middle Ages and
applied their knowledge of the Greeks' discoveries
to medicine. The Renaissance was a period of
rapid advances, especially in Italy, France, and
Spain, where Greek culture was being
rediscovered. In the 15th and 16th centuries,
Leonardo da Vinci and Michelangelo became
skilled anatomists through their search for
perfection in art. Andreas VESALIUS initiated the
use of dissection as a teaching aid. His books,
Fabrica (1543) and Fabrica, 2d ed. (1550),
contained detailed anatomical illustrations that
became standards. In the 17th century, William
HARVEY introduced the use of experimentation
in his studies of the human circulatory system. His
work marked the beginning of mammalian
physiology. Scientific Societies and Journals. Lack
of communication was a problem for early
biologists. To overcome this, scientific societies
were organized. The first were in Europe,
beginning with the Academy of the Lynx (Rome,
1603). The Boston Philosophical Society, founded
in 1683, was probably the first such society to be
organized in colonial America. Later, specialized
groups, principally of physicians, organized
themselves, among them the American Association
for the Advancement of Science (AAAS),
founded in 1848. Much later, in 1951, the
American Institute of Biological Science (AIBS)
was formed as an alliance of the major biological
societies in the United States. The first journals to
present scientific discoveries were published in
Europe starting in 1665; they were the Journal des
Savants, in France, and Philosophical Transactions
of the Royal Society, in London. Over the years,
numerous other journals have been established, so
that today nearly all societies record their
transactions and discoveries. Development and
Early Use of the Microscope. Before 1300 optical
lenses were unknown. At that time, except for
crude spectacles used for reading. Modern optics
began with the invention of the MICROSCOPE
by Galileo Galilei about 1610. Microscopy
originated in 1625 when the Italian Francesco
Stelluti published his drawings of a honeybee
magnified 10 times. The 17th century produced
five microscopists whose works are considered
classics: Marcello MALPIGHI (Italy), Antoni van
LEEUWENHOEK and Jan SWAMMERDAM
(Holland), and Robert HOOKE and Nehemiah
GREW (England). Notable among their
achievements were Malpighi's description of lung
capillaries and kidney corpuscles and Hooke's
Micrographia, in which the term cell was first
used. Basis for Modern Systematics. Consistent
terminology and nomenclature were unknown in
early biological studies, although Aristotle regularly
described organisms by genos and eidoes (genus
and species). Sir Isaac NEWTON's Principia
(1687) describes a rigid universe with an equally
rigid classification system. This was a typical
approach of the period. The leading botanical
classification was that used in describing the
medicinal values of plants. Modern nomenclature
based on a practical binomial system originated
with Karl von Linne (Latinized to Carolus
LINNAEUS). In addition to arranging plants and
animals into genus and species based on structure,
he introduced the categories of class and order.
Jean Baptiste LAMARCK based his system on
function, since this accommodated his view of the
inheritance of acquired characteristics. In 1817,
Georges, Baron CUVIER became the first to
divide the entire animal kingdom into subgroups,
for example, Vertebrata, Mollusca, Articulata, and
Radiata. Explorations and Explorers. During the
18th and 19th centuries numerous important
biological expeditions were organized. Three of
these, all British, made outstanding contributions to
biology. Sir Joseph BANKS, on Captain Cook's
ship Endeavor, explored (1768-71) the South
Seas, collecting plants and animals of Australia.
Robert BROWN, a student of Banks, visited
Australia from 1801 to 1805 on the Investigator
and returned with more than 4,000 plant
specimens. On perhaps the most famous voyage,
Charles DARWIN circumnavigated (1831-36)
the globe on the Beagle. His observations of birds,
reptiles, and flowering plants in the Galapagos
Islands in 1835 laid the foundation for his theories
on evolution, later published in On the Origin of
Species (1859). The Discovery of
Microorganisms. Arguments about the
spontaneous generation of organisms had been
going on since the time of Aristotle, and various
inconclusive experiments had been conducted.
Louis PASTEUR clearly demonstrated in 1864
that no organisms emerged from his heat-sterilized
growth medium as long as the medium remained in
sealed flasks, thereby disproving spontaneous
generation. Based on Edward JENNER's studies
of smallpox, Pasteur later developed a vaccine for
anthrax and in 1885 became the first to
successfully treat a human bitten by a rabid dog.
Beginning in 1876, Robert KOCH developed
pure-culture techniques for microorganisms. His
work verified the germ theory of disease. One of
his students, Paul EHRLICH, developed
chemotherapy and in 1909 devised a chemical
cure for syphilis. The value of ANTIBIOTICS
became evident when Sir Alexander FLEMING
discovered penicillin in 1928. An intensive search,
between 1940 and 1960, for other antibiotics
resulted in the development of several dozen that
were used extensively. Although antibiotics have
not been the panacea once anticipated, their use
has resulted in a decreased incidence of most
infectious diseases. The Role of the Cell.
Following Hooke's use of the term cell, biologists
gradually came to recognize this unit as common
throughout living systems. The cell theory was
published in 1839 by Matthias Schleiden a plant
anatomist. Schleiden saw cells as the basic unit of
organization and perceived each as having a
double life, one "pertaining to its own
development" and the other "as an integral part of
a plant." Schwann, an animal histologist, noticed
that not all parts of an organism are comprised of
cells. He added to the theory in 1840 by
establishing that these parts are at least "cell
products." Between 1868 and 1898 the cell
theory was enlarged as substructures of the
cell--for example, plastids and
mitochondria--were observed and described.
Basic Life Functions. Until the 17th century it was
believed that plants took in food, preformed, from
the soil. Jan Baptista van HELMONT, the first
experimental physiologist, around 1640 concluded
that water is the only soil component required for
plant growth. Stephen HALES showed (1727)
that air held the additional ingredient for food
synthesis. In 1779, Ingenhousz identified this as
carbon dioxide. The study of
PHOTOSYNTHESIS began with a
demonstration by Sachs and Pringsheim in the
mid-19th century that light is the energy source of
green plants. Blackman showed (1905) that not all
parts of this process require sunlight. Results of
work done during the 1920s and '30s proved that
chloroplasts produce oxygen. Subsequently, it was
shown that the light-dependent reactions cause
two types of high-energy molecules to be formed
that use the energy from light. The route of carbon
dioxide in photosynthesis was worked out by
Melvin CALVIN in the early 1950s, using the
radioisotope carbon-14. His results proved
Blackman correct: there exist two distinct but
closely coordinated sets of chloroplast reactions,
one light-dependent and the other
light-independent. High-energy products of the
light-dependent reactions are required for
incorporation of carbon dioxide into sugars in the
light-independent reactions. The earliest
demonstration of ferments (the word ENZYME
was not coined until 1878) in pancreatic juice was
made by Claude BERNARD in France. Bernard
also experimentally determined numerous functions
of the liver as well as the influence of vasomotor
nerves on blood pressure. In the 1930s, Otto
WARBURG discovered a series of cellular
enzymes that start the process of glucose
breakdown to produce energy for biological
activity. When Hans KREBS demonstrated
(1950s) an additional series of enzyme reactions
(the citric acid cycle) that completes the oxidation
process, the general respiration scheme of cells
became known. Chemical synchronization of body
functions without direct control by the nervous
system was discovered in 1905 by Sir William M.
BAYLISS and Ernest Henry STARLING (the
first to use the term hormone). Steroids were
discovered in 1935. Continuity in Living Systems.
The early biologists known as preformationists
believed that animals exist preformed, either in
sperm (the animalculist's view) or in the egg (the
ovist's belief). Embryology actually began when
Karl Ernst von BAER, using the microscope,
observed that no preformed embryos exist.
Modern interpretations of developmental control
in embryogenesis can be traced to Hans
SPEMANN's discovery in 1915 of an "organizer"
area in frog embryos. More recent research has
shown the importance of other factors, such as
chemical gradients. Genetics, the study of heredity,
began with the work of Gregor Johann MENDEL,
who published his findings in 1866. Mendel's
extensive experiments with garden peas led him to
conclude that the inheritance of each characteristic
is controlled by a pair of physical units, or genes.
These units, one from each parent (the law of
segregation), were passed on to offspring,
apparently independent of the distribution of any
other pairs (the law of independent assortment).
The gene concept was amplified by the
rediscovery and confirmation of Mendel's work in
1900 by Hugo DE VRIES in Holland, Karl Erich
Correns in Germany, and Gustav Tschermak von
Seysenegg in Austria. De Vries's mutation theory
became the foundation of modern genetics. The
chromosome theory is based on the speculations
of Pierre Paul ROUX in 1883 that cell nuclei
contain linear arrangements of beadlike
components which replicate (produce exact
copies) during cell division. Many important
contributions were made early in the 20th century
by the American Thomas Hunt MORGAN. These
included sex-linked inheritance and the association
with gene theory of the crossing over of
chromosomes. The discovery by Geoffrey Hardy
and William Weinberg of the equilibrium
relationship that exists between frequency of
alleles (a term originated by William Bateson in
1909 for alternate forms of a gene) in a population
led to formulation of the law bearing their names.
The role of genetics in evolution was publicized in
1937 by Theodosius DOBZHANSKY's Genetics
and the Origin of Species. Molecular biology, the
most recent branch of biology, began early in the
20th century with Archibald Garrod's work on the
biochemical genetics of various diseases. The
concept of one gene producing one enzyme was
established in 1941 by George W. BEADLE and
Edward L. TATUM. The work on protein
synthesis by Jacques MONOD and Francois
JACOB and others in 1961 has modified the one
gene-one enzyme concept to one gene-one
protein. Essential to the understanding of protein
synthesis were the advances made in the 1940s
and '50s in understanding the role and structure of
nucleic acids. The structural model proposed in
1953 by James D. WATSON and F. H. C.
CRICK is a landmark in biology. It has given
biologists a feasible way to explain the storage and
precise transmission of genetic information from
one generation to the next. Knowledge of
biological processes at the molecular level has also
enabled scientists to develop techniques for the
direct manipulation of genetic information, a field
now called GENETIC ENGINEERING. UNITY
OF LIVING SYSTEMS Despite the astounding
diversity of organisms that have been discovered,
an equally astounding degree of unity of structure
and function has been discerned. The structure of
flagella is essentially the same in all cells having
nuclei. The molecules involved in growth and
metabolism are remarkably similar, and often they
are constructed of identical subunits. Furthermore,
enzymes, the catalysts of biological chemistry, are
now known to act similarly in all organisms.
Phenomena such as cell division and the
transmission of the genetic code also appear to be
universal. Larry A. Giesmann

Bibliography:
Angros, Robert, and Stanciu, George, The New
Biology (1987); Antebi, Elizabeth, and Fishlock,
David, Biotechnology (1987); Asimov, Isaac, A
Short History of Biology (1964; repr. 1980), and
The Intelligent Man's Guide to the Biological
Sciences (1968); Borek, Ernest, The Sculpture of
Life (1973); Darnell, James, et al., Molecular Cell
Biology (1986); Ebert, J. D., et al., Biology
(1973); Ehrlich, Paul, The Machinery of Nature
(1987); Ehrlich, Paul R., et al., Introductory
Biology (1973); Gardner, Eldon J., History of
Biology, 3d ed. (1972); Hanawalt, P. C., and
Haynes, R. H., eds., The Chemical Basis of Life
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Biology of the Gene, 2 vols., 4th ed. (1987).

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