Ecology (from Greek: οἶκος, “house“, or “environment“; -λογία, “study of“) is a branch of biology that study the distribution and abundance of living organisms and how the distribution and abundance are affected by interactions between the organisms and their environment. The environment of an organism includes both physical properties, which can be described as the sum of local abiotic factors such as solar insolation, climate, and geology, as well as the other organisms that share its habitat. Also called ecological science.

Word ecology was first introduced in the field of biology by Ernst Haeckel in 1866. Haeckel’s definition was: investigating the total relationship of the animal (living beings) both to its organic and inorganic environment. In 1927 Charles Elton stated that the natural history related to science is called ecology, further study brought another statement that study of the function and structure of nature said to be ecology (E.P. Odum and de la Cruz, A.A., 1963). After studying the factor involved another definition makes a scientific impact on ecology by stating that; scientific study of interaction that determines the distribution and abundance of an organism (Muhsin, T. and Al-Qadir, A., 1995).

Ecology is the branch of biology concerning co-operations among living beings and their biophysical condition, which incorporates both biotic and abiotic segments. Types of ecology are:

  • Organismal Ecology: the study of physiology and behavior interacting with environmental challenges.
  • Population Ecology: the study of the factor that impacts the number of individuals of species in an era.
  • Community Ecology: the study about interacting with organisms with each other and also with the environment.
  • Ecosystem Ecology: Study of energy flow and chemical cycling in a specific region.

Studies of ecological character were undertaken by S. A. Forbes, Ch. Darwin, K. Möbius and others, but an organic character to this discipline was given by E. Haeckel to whom we owe the introduction of the term (1866) and the definition of ecology as “the science of the whole relationship of organisms with the external world”.

In the first decades of the twentieth century, the results of ecology were used by agronomy and agrobiology of experimental centers, mainly in the USSR and the USA. Ecology deals mainly with the biology of groups of organisms and functional processes in the land, sea and fresh water; it can be defined as the study of the structure and functions of nature, bearing in mind that man is part of it. The best way to identify the spaces that ecology occupies is to consider it, from the point of view of levels of organization, viewable as a biological spectrum ranging from gene to community in a hierarchical progression, from small to large.

The interaction with the physical environment that takes place with exchange of energy and matter produces, at each level, characteristic functional systems. Ecology is concerned with systems above the organismal level and has identified the principle of functional integration whereby as the complexity of the structure increases, additional features occur. In addition, as some features grow in complexity as they move from simple to more complex systems, others become less complex and less variable, achieving forms of integration and balance. This indicates the importance that ecology has even independently of the stage of development of the biological sciences related to the less complex hierarchical levels ranging from the gene to the individual organism. In this way ecology has achieved within itself a strong interdisciplinary integration with the acquisition of knowledge of physics, chemistry, geology, lithology, pedology, hydrology, meteorology, biology, becoming an autonomous science, analytical and experimental, with wide possibilities of practical applications.

New problems, more and more urgent and dramatic (such as demographic growth and growing food needs, the protection of the environment now in danger, the responsible exploitation of natural resources, the fight against atmospheric, water and land pollution) require a necessary development of ecological studies in all directions, aimed at protecting the very survival of man and nature that surrounds him. In this regard, however, it should be noted that the term ecology, contrary to incorrect current usage, is not synonymous with “defense of nature”, and that ecology does not deal exclusively with pollution and environmental pathology. The groups of organisms studied by ecology are divided into three levels of organization, populations, communities, and ecosystems. In the ecological sense, a population consists of of individuals belonging to a single species.

A biotic community includes all populations that occupy a well-defined physical area. The various communities, together with the physical and biotic components of the environment, form an ecosystem. Its first task is in fact to investigate the relationships between organisms and the environment, to clarify how the fundamental units (ecosystems) function and what the related problems are; later, making use of the collaboration of technicians and specialists in other fields, it will study the methods for the care, conservation and defense of the environment. The latter is the more specific competence of a discipline that has appeared in Italian universities since the end of the Seventies: environmental policy.

The preservation of the natural environment is fundamental because it is the “medium” that surrounds animal and plant organisms and influences every biological process through abiotic and biotic factors. Abiotic factors include temperature, light, gravity, pressure, water, fire, oxygen, carbon dioxide, pH, salinity, etc.; biotic factors include intra- and interspecific competition (for food, territory, conservation of the species, etc.), predation, symbiosis, commensalism, parasitism, mutualism, numerous aspects of the life cycle, movement and migration, behavior, etc.. These factors are considered the fundamental constituents of ecosystems because they act both on individual populations and on biocenosis and condition, in whole or in part, the relationships between individuals and groups with the environment, the interchanges between individuals or groups among them, the interactions and integrations between ecosystems themselves.

Research has shown that the ecological balance tends to be stable, however, considering long periods of time, the fundamental constituents of the various ecosystems undergo slow changes that lead to radical transformations. The main causes of this are the geological evolution of the planet (known are the successions of different ecosystems during the Quaternary period, following the alternation of glaciations) and the action of animals. In this regard, the study of the evolution of ancient ecosystems (paleoecology) has allowed a better understanding of current ecological mechanisms: for example, it is established the determining action on the environment (and then the work of transformation of previous ecosystems) due to the undisturbed spread of Unguligrade (typical action of bison in the formation of the North American prairie). Since protohistory, the work of man has been profoundly determinant in altering ecological balances.

Pure and applied ecology

In order to reach its conclusions, ecology makes use above all of statistical methods (for example, for population dynamics) and of the comparison between theoretical models and experimental data obtained in the field. The result is a multiplicity of aspects both in the elements considered and in the specialized fields of investigation; in principle a distinction is made between pure ecology and applied ecology: the former highlights the basic biological problems, the latter deals with these problems for direct application to practical purposes (for example, methods of cultivation, reforestation, animal husbandry, the formation of nature reserves, environmental engineering works, sewage treatment plants, etc.).

Fundamental subdivisions of pure ecology, though arbitrary, are autoecology, synecology, and mesology. Autoecology deals with individual species or individuals in their environment, analyzing their relationships with various ecological factors and using methods and techniques of several experimental sciences (physiology, climatology, biochemistry, genetics, ethology, etc.).

Synecology, on the other hand, deals with the ecology of groups of organisms, biocenosis, belonging to the same or different species; it can be descriptive (if it deals with the qualitative and quantitative distribution of populations of organisms of a given environment) or functional, when the groups of living beings are examined in their dynamic succession in a given environment.

The mesology, finally, can be considered a completion and a further aspect of autoecology: it studies in a more direct way the environment, analyzes the physical structure, composition and chemical structure and all that complex of phenomena that have determined its formation.

Given the vastness of the field of action, ecological research is divided according to the major ecosystems classified, so we have a terrestrial ecology, ecology of aerial environments, hydrobiology, divided into marine ecology and ecology of fresh water, agricultural ecology, as well as special areas such as the study of relationships between parasitic organisms and “environment” provided by the internal host organisms; the study of the relationships between animals and plants living together (biocenology); the study of the relationships between plant species (phytosociology) and animals (zoosociology); the study of underground environments (speleobiology) and finally the study of the influence that the environment has on animal behavior (ethological ecology). Moreover, just for pure didactic convenience, we consider an animal ecology and a plant ecology, addressed respectively to problems of zoology and botany, although problems and methods of one are closely related to those of the other and vice versa.

Recently developed is human ecology, which studies the relationships of interdependence between man and environment. The action of the environment on man is manifested both genetically and ethologically. In the first case it is expressed in a whole series of selective pressures that end up translating, with greater or lesser intensity, in the appearance of a particular character. Typical are the variations in pigmentation, body size, the degree of hairiness in relation to the Arctic, temperate or equatorial environment, up to the different development of twins grown in different environments. In the second case, we have seen how the environment influences human behavior to the point of involving the formation of cultures.

Think of the diversity of cultural products between agricultural and pastoral people and, within related cultures, between forest farmers and open land farmers, between shepherds and cattle breeders, between hunters and fishermen, between technologically advanced societies and societies backward in the technological sense up to the differences between the inhabitants of the North and South within the same nation. The importance of precise research in this sense has opened, among other things, a new field of investigation, human ethology, which studies human behavior in relation especially to the environment.

The action of man on the environment is, perhaps, the most macroscopic aspect; in fact, man has passed from the dependence on nature of hunter-gatherer societies to the hegemony on nature at the time of semi-nomadic farmers. To these, above all, we owe the destruction of vast wooded areas to obtain agricultural land with the consequent radical transformation of the ecological balance of entire regions. In particular, it has been estimated that before the development of human activities (end of Paleolithic) forests covered at least 70% of the emerged lands while today they cover no more than 10%. With the advent of metallurgy first and then with the constant spread of technology, man ended up adapting the environment to his ever changing needs: this initially led to the disappearance of many of the original habitats and, in recent times, to the transformation of almost all ecosystems with the dangerous consequence of having altered the ecological balance on a planetary scale.

The environmental problems associated with the use of chemicals

The use of new chemicals in all sectors of the economy (industry, agriculture, services) contributes to raising the quality of life, to a greater extent in industrialized countries, but also in developing countries. At the same time, however, it is causing increasing alterations to the natural environment and its cycles at local and global levels. Until now, partial and inadequate, or even misleading and unsocial, responses have been given to these problems (for example, transfer of the most polluting production to Third World countries).

As with other human activities, the industrial applications of chemistry have been developed according to a production and consumption model that does not use resources in a rational manner, resulting in a strong effect of alteration of the natural environmental cycle. In order to maintain and increase the benefits derived from the chemical industry, it is necessary to bring all its applications within a technological cycle that is as closed as possible. This objective can be achieved by exploiting current knowledge more rationally in order to direct developments in chemistry and its industrial applications towards production processes and products that allow the recovery and reuse of substances that are currently discarded during processing and after use by consumers, or to transform them into non-polluting products. Some developments in chemistry in this direction are already giving rise to new “clean” technologies and new “ecological” products.

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