2009년 5월 15일 금요일

Ethology

자료: Wikipedia, http://en.wikipedia.org/wiki/Ethology



Ethology (from Greek: ἦθος, ethos, "character"; and -λογία-logia) is the scientific study of animal behavior, and a branch of zoology (not to be confused with ethnology).

Although many naturalists have studied aspects of animal behavior through the centuries, the modern discipline of ethology is usually considered to have arisen with the work in the 1930s of Dutch biologist Nikolaas Tinbergen and Austrian biologist Konrad Lorenz, joint winners of the 1973 Nobel Prize in medicine. Ethology is a combination of laboratory and field science, with strong ties to certain other disciplines — e.g., neuroanatomyecologyevolution. Ethologists are typically interested in a behavioral process rather than in a particular animal group and often study one type of behavior (e.g. aggression) in a number of unrelated animals.

The desire to understand the animal world has made ethology a rapidly growing field, and since the turn of the 21st century, many prior understandings related to diverse fields such as animal communication, personal symbolic name use, animal emotions, animal culture and learning, and even sexual conduct, long thought to be well understood, have been revolutionized, as have new fields such as neuroethology.

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[edit]Etymology

The term "ethology" is derived from the Greek word "èthos" (ήθος), meaning "character". Other words derived from the Greek word "ethos" include "ethics" and "ethical". The term was first popularized in English by the American myrmecologist William Morton Wheeler in 1902. (An earlier, slightly different sense of the term was proposed by John Stuart Mill in his 1843 System of Logic. He recommended the development of a new science, "ethology," whose purpose would be the explanation of individual and national differences in character, on the basis of associationistic psychology. This use of the word was never adopted.)

[edit]Differences and similarities with comparative psychology

Comparative psychology also studies animal behaviour, but, as opposed to ethology, construes its study as a branch of psychology rather than as one of biology. Historically, where comparative psychology sees the study of animal behaviour in the context of what is known about human psychology, ethology sees the study of animal behaviour in the context of what is known about animal anatomyphysiologyneurobiology, and phylogenetic history. This distinction is not representative of the current state of the field. Furthermore, early comparative psychologists concentrated on the study of learning and tended to look at behaviour in artificial situations, whereas early ethologists concentrated on behaviour in natural situations, tending to describe it as instinctive. The two approaches are complementary rather than competitive, but they do lead to different perspectives and sometimes to conflicts of opinion about matters of substance. In addition, for most of the twentieth century, comparative psychology developed most strongly in North America, while ethology was stronger in Europe, and this led to different emphases as well as somewhat differing philosophical underpinnings in the two disciplines. A practical difference is that early comparative psychologists concentrated on gaining extensive knowledge of the behaviour of very few species, while ethologists were more interested in gaining knowledge of behaviour in a wide range of species in order to be able to make principled comparisons across taxonomic groups. Ethologists have made much more use of a truly comparative method than comparative psychologists have. Despite the historical divergence, most ethologists (as opposed to behavioural ecologists), at least in North America, teach in psychology departments. It is a strong belief among scientists that the mechanisms on which behavioural processes are based are the same that rule the evolution of the living species: there is therefore a strong connection between these two fields.

[edit]Scala Naturae and Lamarck's theories

Until the 18th century, the most common theory among scientists was still the Scala Naturae proposed by Aristotle: according to this theory, the living beings were classified on an ideal pyramid in which the simplest animals were occupying the lower floors, and then complexity would raise progressively until the top, which was occupied by the human beings. There was also an avant-garde group of biologists who were refusing the Aristotelian theory for a more anthropocentric one, according to which all living beings were created by God to serve mankind, and would behave accordingly. A well-radicated opinion in the common sense of the time in the Western world was that animal species were eternal and immutable, created with a specific purpose, as this seemed the only possible explanation for the incredible variety of the living beings and their surprising adaptation to their habitat.

The first biologist elaborating a complex evolution theory was Jean-Baptiste Lamarck (1744-1829). His theory was substantially made of two statements: the first is that animal organs and behaviour can change according to the way they are being used, and that those characteristics are capable of being transmitted from one generation to the next (well-known is the example of the giraffewhose neck becomes longer while trying to reach the upper leaves of a tree). The second affirmation is that each and every living organism, human beings included, tends to reach a greater level of perfection. At the time of his journey for the Galapagos Islands,Charles Darwin was well aware of Lamarck's theories and was deeply influenced by them.

[edit]Theory of evolution by natural selection and the beginnings of ethology

Charles Darwin (1809–1882)

Because ethology is understood as a branch of biology, ethologists have been particularly concerned with the evolution of behaviour and the understanding of behaviour in terms of the theory of natural selection. In one sense, the first modern ethologist was Charles Darwin, whose book, The Expression of the Emotions in Man and Animals, has influenced many ethologists. He pursued his interest in behaviour by encouraging his protégé George Romanes, who investigated animal learning and intelligence using an anthropomorphic method, anecdotal cognitivism, that did not gain scientific support.

Other early ethologists, such as Oskar Heinroth and Julian Huxley, instead concentrated on behaviours that can be called instinctive, or natural, in that they occur in all members of a species under specified circumstances. Their first step in studying the behaviour of a new species was to construct an ethogram (a description of the main types of natural behaviour with their frequencies of occurrence). This approach provided an objective, cumulative base of data about behaviour, which subsequent researchers could check and build upon.

[edit]Fixed action patterns and animal communication

An important step, associated with the name of Konrad Lorenz though probably due more to his teacher, Oskar Heinroth, was the identification of fixed action patterns (FAPs). Lorenz popularized FAPs as instinctive responses that would occur reliably in the presence of identifiable stimuli (called sign stimuli or releasing stimuli). These FAPs could then be compared across species, and the similarities and differences between behaviour could be easily compared with the similarities and differences inmorphology. An important and much quoted study of the Anatidae (ducks and geese) by Heinroth used this technique. The ethologists noted that the stimuli that released FAPs were commonly features of the appearance or behaviour of other members of their own species, and they were able to show how important forms of animal communication could be mediated by a few simple FAPs. The most sophisticated investigation of this kind was the study by Karl von Frisch of the so-called "dance language" underlying bee communication. Lorenz developed an interesting theory of the evolution of animal communication based on his observations of the nature of fixed action patterns and the circumstances in which animals emit them.

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