Marine biology is the study of marine organisms, their behaviors and interactions with the environment. Marine biologists study biological oceanography and the associated fields of chemical, physical, and geological oceanography to understand marine organisms.
Marine biology, the science that deals with animals and plants that live in the sea. It also deals with airborne and terrestrial organisms that depend directly upon bodies of salt water for food and other necessities of life. In the broadest sense it attempts to describe all vital phenomena pertaining to the myriads of living things that dwell in the vast oceans of the world. Some of its specialized branches concern natural history, taxonomy, embryology, morphology, physiology, ecology, and geographical distribution. Marine biology is closely related to the science of oceanography because of the relationship of the physical features of the oceans to the living organisms that dwell in them. It aids in the understanding of marine geology through the study of those organisms that contribute their skeletal remains to the floors of the oceans or that elaborate the vast coral reefs of the tropic seas.
A principal aim of marine biology is to discover how ocean phenomena control the distribution of organisms. Marine biologists study the way in which particular organisms are adapted to the various chemical and physical properties of the seawater, to the movements and currents of the ocean, to the availability of light at various depths, and to the solid surfaces that make up the seafloor. Special attention is given to determining the dynamics of marine ecosystems, particularly to the understanding of food chains and predator-prey relationships. Marine biological information on the distribution of fish and crustacean populations is of great importance to fisheries. Marine biology is also concerned with the effects of certain forms of pollution on the fish and plant life of the oceans, particularly the effects of pesticide and fertilizer runoff from land sources, accidental spills from oil tankers, and silting from coastline construction activities.
During the second half of the 19th century, when the emphasis was on the collection, description, and cataloging of marine organisms, methods evolved for the capture and preservation of specimens for study. Marine biologists adapted traditional dredges and trawls to collect specimens from the ocean floor; and hoop nets were used to secure free-swimming animals. New instruments for collecting water samples and obtaining temperature information at any desired depth were developed.
Late in the 19th century, the focus began to shift from collecting and cataloging to the systematic analysis of marine ecosystems and the ecological roles and behaviour of marine life. By the early 20th century, oceanographers had begun to intensively study fishing grounds and other localities of economic importance. This research combined studies of marine flora and fauna, ocean currents, water temperature, salinity, and oxygen levels, and other factors in an effort to understand the relationship between marine animals and their environment.
Since World War II, direct observation of marine organisms in their natural habitats has been made possible by underwater cameras, television, improved diving equipment, and submersible craft, or submarines, that can descend to great depths. Underwater television provides the observer with a continuous picture of events that occur within the field of the submerged camera. The development of self-contained diving equipment made it possible for the investigator to inspect marine organisms in their natural habitat.
Morphological and taxonomic studies of marine organisms are generally performed on preserved materials in connection with the work in museums and universities. Physiological and embryological investigations requiring the use of living material are generally pursued at biological stations. These are situated on the seacoast, thus facilitating the rapid transfer of specimens to the laboratory where they may be maintained in seawater provided by special circulating systems.
Teratology
Teratology, branch of the biological sciences dealing with the causes, development, description, and classification of congenital malformations in plants and animals and with the experimental production, in some instances, of these malformations. Congenital malformations arise from interruption in the early development of the organism. Malformations in human infants, for example, may occur because the infant’s genotype contains mutant genes or includes an abnormal number of chromosomes; they also may occur if early in pregnancy the mother has had German measles (rubella), has taken some injurious drug, or has been exposed to an injurious dosage of radiation. Experimental studies suggest similar types of factors can cause malformations in animals and plants.
Anatomy
Anatomy, a field in the biological sciences concerned with the identification and description of the body structures of living things. Gross anatomy involves the study of major body structures by dissection and observation and in its narrowest sense is concerned only with the human body. “Gross anatomy” customarily refers to the study of those body structures large enough to be examined without the help of magnifying devices, while microscopic anatomy is concerned with the study of structural units small enough to be seen only with a light microscope. Dissection is basic to all anatomical research. The earliest record of its use was made by the Greeks, and Theophrastus called dissection “anatomy,” from ana temnein, meaning “to cut up.”
Comparative anatomy, the other major subdivision of the field, compares similar body structures in different species of animals in order to understand the adaptive changes they have undergone in the course of evolution.
Gross anatomy
This ancient discipline reached its culmination between 1500 and 1850, by which time its subject matter was firmly established. None of the world’s oldest civilizations dissected a human body, which most people regarded with superstitious awe and associated with the spirit of the departed soul. Beliefs in life after death and a disquieting uncertainty concerning the possibility of bodily resurrection further inhibited systematic study. Nevertheless, knowledge of the body was acquired by treating wounds, aiding in childbirth, and setting broken limbs. The field remained speculative rather than descriptive, though, until the achievements of the Alexandrian medical school and its foremost figure, Herophilus (flourished 300 BCE), who dissected human cadavers and thus gave anatomy a considerable factual basis for the first time. Herophilus made many important discoveries and was followed by his younger contemporary Erasistratus, who is sometimes regarded as the founder of physiology. In the 2nd century CE, Greek physician Galen assembled and arranged all the discoveries of the Greek anatomists, including with them his own concepts of physiology and his discoveries in experimental medicine. The many books Galen wrote became the unquestioned authority for anatomy and medicine in Europe because they were the only ancient Greek anatomical texts that survived the Dark Ages in the form of Arabic (and then Latin) translations.
Owing to church prohibitions against dissection, European medicine in the Middle Ages relied upon Galen’s mixture of fact and fancy rather than on direct observation for its anatomical knowledge, though some dissections were authorized for teaching purposes. In the early 16th century, the artist Leonardo da Vinci undertook his own dissections, and his beautiful and accurate anatomical drawings cleared the way for Flemish physician Andreas Vesalius to “restore” the science of anatomy with his monumental De humani corporis fabrica libri septem (1543; “The Seven Books on the Structure of the Human Body”), which was the first comprehensive and illustrated textbook of anatomy. As a professor at the University of Padua, Vesalius encouraged younger scientists to accept traditional anatomy only after verifying it themselves, and this more critical and questioning attitude broke Galen’s authority and placed anatomy on a firm foundation of observed fact and demonstration.
From Vesalius’s exact descriptions of the skeleton, muscles, blood vessels, nervous system, and digestive tract, his successors in Padua progressed to studies of the digestive glands and the urinary and reproductive systems. Hieronymus Fabricius, Gabriello Fallopius, and Bartolomeo Eustachio were among the most important Italian anatomists, and their detailed studies led to fundamental progress in the related field of physiology. William Harvey’s discovery of the circulation of the blood, for instance, was based partly on Fabricius’s detailed descriptions of the venous valves.
