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History of Ecological Ideas Introduction Although the real explosion in ecological studies did not take place until the 1960's, ecological thought goes back to the ancients

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History of Ecological Ideas

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  • Although the real explosion in ecological studies did not take place until the 1960's, ecological thought goes back to the ancients
  • Buffon and Linnaeus also played a role influencing the great explorers of the eighteenth and nineteenth centuries. For these explorers the ultimate goal was no longer just to collect and describe species, but to understand the interaction of organisms with their environment
alexander von humboldt german 1769 1859
Alexander von Humboldt(German, 1769-1859)
  • From a well-to-do family
  • Traveled extensively throughout Europe, America, and Russia
  • Had a holistic view of nature
ernst haeckel german 1834 1919
Ernst Haeckel (German, 1834-1919)
  • He was the leading German disciple of Charles Darwin
  • He coined the term “Ecology”
  • He originally used the Greek spelling Oecologie, and defined it as “the science of the relations of living organisms to the external world, their habitat, customs, energies, parasites, etc.”
Haeckel derived the new label from the same root found in the older word “economy” (“Oekonomie”): the Greek oikos, referring originally to the family household and its daily operations and maintenance
  • The reason was that at that time, people thought that national economic affairs could be understood as an extension of the housekeeper’s budget. Haeckel thought that the Earth constituted a single economic unit
From the beginning there was a strong Darwinian sense in ecology. Haeckel said in 1869 that ecology was “the body of knowledge concerning the economy of nature (...) the study of all those complex interrelations referred to by Darwin as the condition of the struggle for the existence”
  • For many years the term was ignored. The use “the economy of nature” instead as in previous centuries “natural economy,” was used to refer to physiology
The people working on the subject had little contact with each other. Although literally thousands of papers were published in those decades dealing with the number of species and individuals within a certain measured area and hundreds of new terms were proposed, ecology remained a rather static and descriptive science
  • The term was retaken initially as “oecology” and then with its modern spelling “ecology” after the International Botanical Congress of 1893
major revolutions in the ecological thought
Major Revolutions in the Ecological Thought
  • Three major events revitalized the field:

a) The calculations of Lotka-Volterra: cycle of population changes due to the predator-prey relations, as well as growth, decline, and cycle of populations

b) Emphasis on competition: the principle of competitive exclusion and its experimental testing by Gause

c) Attention to energy turnover problems, particularly in freshwater and in the ocean

  • The ancients (Hippocrates, Aristotle, Theophrastus, and others) had written about regional differences in the distribution of animals and plants and ascribed the differences to climatic factors
  • They tried to explain the facts that there were elephants in Africa and Asia but not in between to the facts of former connections
The imposition of the literal interpretation of the Bible in western thought created major problems
  • The idea was that all plants and animals originated in the Garden of Eden, after the Flood they had been “rescued” in Noah’s Ark from which they had dispersed again supposedly from Mount Ararat
  • This interpretation, however, accepted the fact that species were not fixed in space but that they had to disperse and migrate
The discovery of America and the fact that the fauna there was radically different than that of the Old World, created great consternation
  • The creation of a single fauna and flora from a center of creation seemed more and more an impossibility
The botanist Johann G. Gmelin (German, (1748-1804) was the first, in 1747, in proposing multiple “centers of creations”
  • But the one who really pushed forward this concept was Georges Louis Leclerc Comte de Buffon (French, 1707-1788)
He antagonized Linnaeus by saying that faunas (a practical geographical classification) and rather than shared characters had to be the basis for classification
Buffon postulated that when the Earth cooled off, life was created in the far north because the tropical regions were still too hot for sustaining life. “The earth makes the plants; the earth and the plants make the animals”
  • Still, he could not explain why the tropical faunas of Africa and America, for example, were so different
The first researchers interested in ecology were geographers. This was a very prominent discipline in the 19th. century. The world was still being mapped
  • Two schools appeared:

a) biogeographers: distribution of species around the world (the controlling interest was taxonomic rather than ecological)

b) physiognomists (“ecological geographers”): they talked about vegetation rather than flora, for example

For the latter, three principles dominated the new science:

a) classification of plants by their adaptive forms or structure rather than by their taxonomy

b) emphasis on plants as social beings forming integrated societies

c) identification of climate as the crucial determinant of both individual life forms and the communal pattern

This is in accordance with the teaching of Buffon and, particularly, Alexander von Humboldt
  • The latter had given the notion of isotherms (e.g., in the Andes)
In the U.S., the first to apply this system was C. Hart Merriam, an ornithologist
  • He developed the concept of life zones.
In Europe it was Oscar Drude, Andreas Schimper, and Eugenius Warming
  • The latter introduced the concept of plant communities and a great deal of the biogeographical terminology still employed today
  • He tried to define the borderland where ecology meets physiology and morphology
The latter part of the 19th. century produces terms such as “mutualism”, “comensalism”, “symbiosis”, “succession”, “climax” as well as a system of classification for plants communities such as “hydrophytes”, “xerophytes”, “mesophytes”, etc.
  • The beginning of the 20th. century begins with the development of “autoecology”: the environmental physiology of an individual organism and also the first look by zoologists to this new science
  • For many years, until the 60's there was still talk of “plant ecology” and “animal ecology” as separate entities
the darwinian revolution
The Darwinian Revolution
  • On Darwin’s diary of the voyage of the Beagle, as well as in his Origin and autobiography, he mentioned again and again the importance of the knowledge of the distribution of species to understand their origin
  • He was particularly struck by two facts:

a) The species of the temperate zones of South America were closely related to the ones in the tropical areas of that continent rather to the ones of the temperate zones of North America

b) That fauna of islands were closely related to those of their closest continent

For him, thus, distribution was not random. The question was what factors influence the introduction of species in a particular area?
  • He is considered to be the father of zoogeography although Wallace also made important contributions
  • A radical departure from Linnaeus who believed that all plants derived from a mountainous tropical island (Eden?) from which all spread all over the world
Darwin opposed these ideas and so did Wallace. For them continents were static and animals did have a great ability to disperse
Alphonse de Candolle proposed (1855) 20 botanical regions (“centers of creations”)
  • Louis Agassiz (1857) was a creationist for whom “every unsolved biological mystery was the product of the hand of God.” However, his “Ice Age Theory” laid the bases for explanations related to the changing earth
  • Darwin’s writings would break the non natural explanations for the origin and distribution of animals and plants. For him dispersal was due to two factors: the ability to get to a new locations and the ability to colonize it
the land bridge idea
The Land Bridge Idea
  • Darwin’s ideas, however, did not seem able to explain the discontinuities in distribution patterns in particular. To solve this problem numerous scientists proposed the idea of connections by “land bridges.” These researchers had two things in common: low opinion of the dispersal abilities of animals (particularly mammals) and total disregard of the geological evidence
The real questions came from astonishing facts: beavers in Eurasia and America, same plants in the Pyrenees and in the Alps, mountains of Scandinavia and islands of the Arctic lowlands without anything in between and European plants in Tierra de Fuego, the strangeness of Australian biota (“disjunct distributions”)
  • This became one of the major issues of biogeography during the first half of the 19th. century
E. A. W. Zimmermann (1778-1783) proposed that the distribution of mammals can not be sufficiently explained by climate and rather it had to be explained by the history of earth. He proposed the land bridges theory to explain why continents and islands share the same fauna is because of former connections between then (“land bridges”). He is considered the father of historical biogeography.
In 1922 E. R. Dunn proposed a causal analysis of faunas. The main tool of this school was the idea of land bridges
  • These ideas were championed by the American mammalogist G. G. Simpson by saying that there are different kinds of bridges connecting land masses
The third school came from Alfred Wegener’s publication in 1915 of the continental drift theory
  • Original discounted because of the lack of a mechanical explanation for it
  • This did not see a revival until the 1960's when the mechanisms of plate tectonics became apparent. This changed everything