Ecology (from Greek: οἶκος, "house"; -λογία, "study
of"[A]) is the scientific study of the relationships
that living organisms have with each other and
with their natural environment.
Topics of interest to ecologists include the composition, distribution, amount
(biomass), number, and changing states of organisms within and
among ecosystems. Ecosystems are composed of dynamically interacting
parts including organisms, thecommunities they make up, and the
non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis,nutrient cycling, and various niche construction activities, regulate the
flux of energy and matter through an environment. These processes are sustained
by the biodiversity within them. Biodiversity
refers to the varieties of species in ecosystems, the genetic variations they
contain, and the processes that are functionally enriched by the diversity of
ecological interactions.
Ecology is an interdisciplinary field that includes biology and Earth science. The word
"ecology" ("Ökologie") was coined in 1866 by the German
scientist Ernst Haeckel (1834–1919). Ancient Greek philosophers such as Hippocrates and Aristotle laid the foundations of
ecology in their studies on natural history. Modern ecology
transformed into a more rigorous science in the late 19th century. Evolutionary concepts on adaptation and
natural selection became cornerstones of modern ecological theory.
Ecology is not synonymous with environment, environmentalism, natural history, or environmental
science. It is closely related to evolutionary biology, genetics, and ethology. An understanding of how
biodiversity affects ecological function is an important focus area in
ecological studies.
Early
beginnings
Ecology has a complex origin, due
in large part to its interdisciplinary nature. Ancient Greek philosophers such as Hippocrates and Aristotle were
among the first to record observations on natural history. However, they viewed
life in terms of essentialism, where species were
conceptualized as static unchanging things while varieties were seen as
aberrations of an idealized type. This contrasts against the
modern understanding of ecological theory where varieties are viewed as the real
phenomena of interest and having a role in the origins of adaptations by means
ofnatural selection.
Early conceptions of ecology, such as a balance and regulation in nature can be
traced to Herodotus (died c. 425 BC), who described one
of the earliest accounts ofmutualism in his observation of "natural
dentistry". Basking Nile crocodiles, he noted, would open their
mouths to give sandpipers safe
access to pluck leeches out, giving nutrition to the sandpiper
and oral hygiene for the crocodile. Aristotle
was an early influence on the philosophical development of ecology. He and his
student Theophrastus made
extensive observations on plant and animal migrations, biogeography,
physiology, and on their behaviour, giving an early analogue to the modern
concept of an ecological niche.
Ecological concepts such as food
chains, population regulation, and productivity were first developed in the
1700s, through the published works of microscopist Antoni van
Leeuwenhoek (1632–1723)
and botanist Richard Bradley (1688?–1732).Biogeographer Alexander von Humbolt (1769–1859) was an early pioneer in
ecological thinking and was among the first to recognize ecological gradients,
where species are replaced or altered in form along environmental
gradients, such as a cline forming
along a rise in elevation. Humbolt drew inspiration from Isaac Newton as
he developed a form of "terrestrial physics." In Newtonian fashion,
he brought a scientific exactitude for measurement into natural history and
even alluded to concepts that are the foundation of a modern ecological law on
species-to-area relationships. Natural historians, such as Humbolt, James Hutton and Jean-Baptiste Lamarck (among others) laid the foundations of
the modern ecological sciences. The term "ecology" (German: Oekologie) is of a more recent origin and
was first coined by the German biologist Ernst Haeckel in his book Generelle Morphologie der
Organismen (1866). Haeckel
was a zoologist, artist, writer, and later in life a professor of comparative
anatomy.
Since
1900
Modern ecology is a young science
that first attracted substantial scientific attention toward the end of the
19th century (around the same time that evolutionary studies were gaining
scientific interest). In the early 20th century, ecology transitioned from a
moredescriptive form of natural history to a more analytical form of scientific
natural history. Frederic Clements published the first American ecology
book in 1905, presenting the idea of plant communities as a superorganism. This publication launched a
debate between ecological holism and individualism that lasted until the 1970s.
Clements' superorganism concept proposed that ecosystems progress through
regular and determined stages of seral development that are analogous to the
developmental stages of an organism. The Clementsian paradigm was challenged by Henry Gleason, who stated that ecological
communities develop from the unique and coincidental association of individual
organisms. This perceptual shift placed the focus back onto the life histories
of individual organisms and how this relates to the development of community
associations.
The Clementsian superorganism
theory was an overextended application of an idealistic form of holism. The term "holism"
was coined in 1926 by Jan Christian Smuts,
a South African general and polarizing historical figure who was inspired by
Clements' superorganism concept. Around the same time, Charles Elton pioneered the concept of food chains
in his classical book Animal
Ecology. Eltondefined
ecological relations using concepts of food chains, food cycles, and food size,
and described numerical relations among different functional groups and their
relative abundance. Elton's 'food cycle' was replaced by 'food web' in a
subsequent ecological text Alfred J. Lotka brought in many theoretical concepts
applying thermodynamic principles to ecology. In 1942, Raymond Lindeman wrote a landmark paper on the trophic dynamics of ecology, which was published
posthumously after initially being rejected for its theoretical emphasis.
Trophic dynamics became the foundation for much of the work to follow on energy
and material flow through ecosystems. Robert E. MacArthur advanced mathematical theory,
predictions and tests in ecology in the 1950s, which inspired a resurgent
school of theoretical mathematical ecologists.[10][32][33] Ecology
also has developed through contributions from other nations, including Russia's Vladimir Vernadsky and his founding of the biosphere
concept in the 1920sand Japan's Kinji Imanishi and his concepts of harmony in nature
and habitat segregation in the 1950s. The scientific recognition of contributions
to ecology from non-English-speaking cultures is hampered by language and
translation barriers.
Ecology surged in popular and
scientific interest during the 1960–1970s environmental
movement. There are strong historical and scientific ties between
ecology, environmental management, and protection. The historic emphasis and
poetic naturalist writings for protection was on wild places, from notable
ecologists in the history of conservation biology,
such as Aldo Leopold and Arthur Tansley, were far removed from urban
centres where the concentration of pollution and environmental degradation is
located. Palamar (2008) notes an overshadowing by mainstream environmentalism
of pioneering women in the early 1900s who fought for urban health ecology and
brought about changes in environmental legislation. These women were precursors
to the more popularized environmental movements after the 1950s. In 1962,
marine biologist and ecologist Rachel Carson's book Silent Springhelped to mobilize the
environmental movement by alerting the public to toxic pesticides, such as DDT, bioaccumulating in the environment. Carson used
ecological science to link the release of environmental toxins to human and
ecosystem health. Since then, ecologists have worked to bridge their
understanding of the degradation of the planet's ecosystems with environmental
politics, law, restoration, and natural resources management.
Hierarchical ecology
The scale of ecological dynamics
can operate like a closed system, such as aphids migrating on a single tree,
while at the same time remain open with regard to broader scale influences,
such as atmosphere or climate. Hence, ecologists classify ecosystems hierarchically
by analyzing data collected from finer scale units, such as vegetation
associations, climate, and soil types, and integrate this information to
identify emergent patterns of uniform organization and processes that operate
on local to regional, landscape, and chronological scales.
To structure the study of ecology
into a conceptually manageable framework, the biological world is organized
into a nested hierarchy,
ranging in scale from genes,
to cells, to tissues, to organs, to organisms, to species, and up to the level of the biosphere. This
framework forms a panarchyand exhibits non-linear behaviours;
this means that "effect and cause are disproportionate, so that small
changes in critical variables, such as the numbers of nitrogen fixers, can lead to disproportionate,
perhaps irreversible, changes in the system propertie
Biodiversity
Biodiversity (an abbreviation of
"biological diversity") describes the diversity of life from genes to
ecosystems and spans every level of biological organization. The term has
several interpretations, and there are many ways to index, measure,
characterize, and represent its complex organization. Biodiversity includes species diversity, ecosystem diversity, genetic diversity and the complex processes operating at
and among these respective levels. Biodiversity plays an important role in ecological health as much as it does for human health. Preventing species extinctions is one way to preserve biodiversity,
but factors such as genetic diversity and migration routes are equally
important and are threatened on global scales. Conservation priorities and
management techniques require different approaches and considerations to
address the full ecological scope of biodiversity. Populations and species
migration, for example, are sensitive indicators of ecosystem services that sustain and contribute natural capital toward the well-being of humanity. An
understanding of biodiversity has practical application for ecosystem-based
conservation planners as they make ecologically responsible decisions in
management recommendations to consultant firms, governments, and industry. The
protected areas have been established under the protected area network across
the world for conservation of biodiversity
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