Biology

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