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The concept of the natural environment can be distinguished as components: Complete ecological units that function as natural systems without massive civilized human intervention, including all vegetation, microorganisms , soil , rocks , plateaus, mountains, the atmosphere and natural phenomena that occur within their boundaries and their nature.
For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside. [ 9 ] : 39 [ 10 ] : 66 Other external factors that play an important role in ecosystem functioning include time and potential biota , the organisms that are present in a region and could ...
Ecosystem services are ecologically mediated functional processes essential to sustaining healthy human societies. [6] Water provision and filtration, production of biomass in forestry, agriculture, and fisheries, and removal of greenhouse gases such as carbon dioxide (CO 2) from the atmosphere are examples of ecosystem services essential to public health and economic opportunity.
Terrestrial ecosystems occupy 55,660,000 mi 2 (144,150,000 km 2), or 28.26% of Earth's surface. [5] Major plant taxa in terrestrial ecosystems are members of the division Magnoliophyta (flowering plants), of which there are about 275,000 species, and the division Pinophyta (conifers), of which there are about 500 species.
The main subdisciplines of ecology, population (or community) ecology and ecosystem ecology, exhibit a difference not only in scale but also in two contrasting paradigms in the field. The former focuses on organisms' distribution and abundance, while the latter focuses on materials and energy fluxes.
Environmental science is an interdisciplinary academic field that integrates physics, biology, meteorology, mathematics and geography (including ecology, chemistry, plant science, zoology, mineralogy, oceanography, limnology, soil science, geology and physical geography, and atmospheric science) to the study of the environment, and the solution of environmental problems.
The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. [1] Freshwater ecosystems may be lentic (slow moving water, including pools , ponds , and lakes ); lotic (faster moving water, for example streams and rivers ); and wetlands (areas where the soil is saturated or inundated for at least part of the time).
These two main biological components are respectively mainly algae and cyanobacteria on one side, and bacteria and fungi on the other. [20] Micro- and meiofauna also inhabit the biofilm, predating on the organisms and organic particles and contributing to its evolution and dispersal. [23]