ECOLOGY

 Ecology is a sub-discipline of biology, the study of life. The word "ecology" ("Ökologie") was coined in 1866 by the German scientist Ernst Haeckel (1834–1919). Ancient philosophers of Greece, including Hippocrates and Aristotle, were among the earliest to record notes and observations on the natural history of plants and animals. Modern ecology branched out of natural history and matured into a more rigorous science in the late 19th century. Charles Darwin's evolutionary treatise including the concept of adaptation, as it was introduced in 1859, is a pivotal cornerstone in modern ecological theory. Ecology is not synonymous with environment, environmentalism, natural history or environmental science. It is closely related to physiology, evolutionary biology, genetics and ethology

Ecology is the study of environmental systems, or as it is sometimes called, the economy of nature. "Environmental" usually means relating to the natural, versus human-made world; the "systems" means that ecology is, by its very nature, not interested in just the components of nature individually but especially in how the parts interact. Ecology is technically an academic discipline, such as mathematics or physics, although in public or media use, it is often used to connote some sort of normative or evaluative issue as in something is “ecologically bad” or is or is not “good for the ecology”. More properly ecology is used only in the sense that it is an academic discipline, no more evaluative than mathematics or physics. When a normative or evaluative term is needed then it is more proper to use the term “environmental”, i.e., environmental quality or “environmentally degrading”. Most professional ecologists are not terribly unhappy when ecology is used in the normative sense, preferring the wider public awareness of environmental issues today compared to the widespread ignorance of three decades ago.

 

 The scope of ecology covers a wide array of interacting levels of organization spanning micro-level (e.g., cells) to planetary scale (e.g., ecosphere) phenomena. Ecosystems, for example, contain populations of individuals that aggregate into distinct ecological communities. It can take thousands of years for ecological processes to mature through and until the final successional stages of a forest. The area of an ecosystem can vary greatly from tiny to vast. A single tree is of little consequence to the classification of a forest ecosystem, but critically relevant to the smaller organisms living in and on it.Several generations of an aphid population can exist over the lifespan of a single leaf. Each of those aphids, in turn, support diverse bacterial communities.The nature of connections in ecological communities cannot be explained by knowing the details of each species in isolation, because the emergent pattern is neither revealed nor predicted until the ecosystem is studied as an integrated whole. Some ecological principles, however, do exhibit collective properties where the sum of the components explain the properties of the whole, such as birth rates of a population being equal to the sum of individual births over a designated time frame
Biodiversity is the variety of life and its processes. It includes the variety of living organisms, the genetic differences among them, the communities and ecosystems in which they occur, and the ecological and evolutionary processes that keep them functioning, yet ever changing and adapting

Community ecology examines how interactions among species and their environment affect the abundance, distribution and diversity of species within communities

Links in food-webs primarily connect feeding relations or trophism among species. Biodiversity within ecosystems can be organized into vertical and horizontal dimensions. The vertical dimension represents feeding relations that become further removed from the base of the food chain up toward top predators. A trophic level is defined as "a group of organisms acquiring a considerable majority of its energy from the adjacent level nearer the abiotic source." The horizontal dimension represents the abundance or biomass at each level.When the relative abundance or biomass of each functional feeding group is stacked into their respective trophic levels they naturally sort into a 'pyramid of numbers'. Functional groups are broadly categorized as autotrophs (or primary producers), heterotrophs (or consumers), and detrivores (or decomposers). Autotrophs are organisms that can produce their own food (production is greater than respiration) and are usually plants or cyanobacteria that are capable of photosynthesis but can also be other organisms such as bacteria near ocean vents that are capable of chemosynthesis. Heterotrophs are organisms that must feed on others for nourishment and energy (respiration exceeds production).Heterotrophs can be further sub-divided into different functional groups, including: primary consumers (strict herbivores), secondary consumers (carnivorous predators that feed exclusively on herbivores) and tertiary consumers (predators that feed on a mix of herbivores and predators). Omnivores do not fit neatly into a functional category because they eat both plant and animal tissues. It has been suggested that omnivores have a greater functional influence as predators because relative to herbivores they are comparatively inefficient at grazing.
Trophic levels are part of the holistic or complex systems view of ecosystems.Each trophic level contains unrelated species that grouped together because they share common ecological functions. Grouping functionally similar species into a trophic system gives a macroscopic image of the larger functional design While the notion of trophic levels provides insight into energy flow and top-down control within food webs, it is troubled by the prevalence of omnivory in real ecosystems. This has lead some ecologists to "reiterate that the notion that species clearly aggregate into discrete, homogeneous trophic levels is fiction."Nonetheless, recent studies have shown that real trophic levels do exist, but "above the herbivore trophic level, food webs are better characterized as a tangled web of omnivores."