STRUCTURE OF THE ENVIRONMENT

Environment, Ecology and Ecosystem are three different terms. But they are interrelated. The natural surroundings of an organism, both living and physical is its environment. The physical component consists of air, water, light, land etc. The biotic component consists off all the living organisms surrounding us. Scientists believe that natural environment is a better word to use given the common use of the word environment. Ecology is a branch of study of the interrelationships with the organism and its environment. It is a basic fact that the Earth includes a large variety of living things which depend in some way on other living and non-living things. This study of how the existence and activity of organism influences its environment and the vice versa is ecology. Ecology involves collecting information about organisms and their environment, looking for patterns, and seeking to explain these patterns. The ecology that takes place in a defined area is called ecosystem. Ecosystem is a functional unit of dynamic system of organisms interacting with each other (biotic) and the inanimate environment (abiotic).

The structure of the environment can be depicted as follows:
 

All components of environment are closely related and interact with each other.

Though air, water and land are the components of environment, the Britishand American scientists put in two different manners.

1.Components of Environment as per British literature

Here the components are classified in terms of biotic and abiotic based uponlife. The biotic components are further listed as producers, consumers anddecomposers and the abiotic components are classified as climatic(water, air)and edaphic(land). It is from this component system that the study of structureof ecosystem was evolved.
The biotic components of an ecosystem are the living organisms that exist in the system. These organisms can be classified as producers, consumers or decomposers. Green plants prepare complex organic food using abiotic factors like carbon dioxide and water in the presence of sunlight by a process vital to survival of life on earth – Photosynthesis. Green plants are used by herbivores and the herbivores are in turn consumed by carnivores (secondary consumers) which are then consumed by tertiary consumers which constitutes what is known as food chain. Thus all living beings obtain food from plants directly or indirectly. After the death of all these organisms, decomposers decompose complex organic substances of their body into simple inorganic forms. These are again absorbed by the green plants and this forms a cycle.
The abiotic components of an ecosystem are the non-living features of the ecosystem that the living organisms depend on. Each abiotic component influences the number and variety of plants that grow in an ecosystem, which in turn has an influence on the variety of animals that live there. The way in which plants and animals grow and carry out their different activities is a result of several abiotic factors. These factors are light, temperature, water, atmospheric gases, wind as well as soil (edaphic) and physiographic (nature of land surface) factors. Light energy (sunlight) is the primary source of energy in nearly all ecosystems. It is the energy that is used by green plants (which contain chlorophyll) during the process of photosynthesis The distribution of plants and animals is also greatly influenced by extremes in temperature for instance the warm season. The occurrence or non-occurrence of frost is a particularly important determinant of plant distribution since many plants cannot prevent their tissues from freezing or survive the freezing and thawing processes. In animals, a distinction is made between ectothermic ("cold-blooded" or poikilothermic) animals and endothermic ("warm-blooded" or homothermic) animals. Plant and animal habitats vary from entirely aquatic environments to very dry deserts. Water, which forms the hydrosphere, is essential for life and all organisms depend on it to survive especially in desert areas. The atmosphere also plays a critical role in sustaining life on earth. The most important gases used by plants and animals are oxygen, which is used by all living organisms during respiration, carbon dioxide, which is used by green plants during photosynthesis and nitrogen, made available to plants by certain bacteria and through the action of lightning. Winds or air currents arise on a world-wide scale as a result of a complex interaction between hot air expanding and rising (convection) in the mid-latitudes. This has various effects on the rotation of the earth and results in a centrifugal force which tends to lift the air at the equator. This force is known as the Coriolis force and tends to deflect winds to their left of the southern hemisphere and to the right in the northern hemisphere. Winds carry water vapour which may condense and fall in the form of rain, snow or hail. Wind plays a role in pollination and seed dispersal of some plants, as well as the dispersal of some animals, such as insects. Soil (edaphic factors) factors include soil texture, soil air, soil temperature, soil water, soil solution and pH, together with soil organisms and decaying matter which plays a major role in helping plant growth as well as in providing an environment for sub-terrestrial animals. Lastly, physiographic factors refer to the factors that are those associated with the physical nature of the area, such as altitude, slope of land and the position of the area in relation to the sun or rain-bearing winds. Altitude plays a role in vegetations zones. Slopes are important when considering the temperature of the soil surface on land with a northern slope, on level and on land with south facing slopes.

2.Components of Environment as per American literature
As per American literature, the components of environment are listed as:
1.Hydrosphere(Water)
2.Atmosphere(Air)
3.Lithosphere(Land)
4.Biosphere(Flora/Fauna/Microbes)
5.Anthrosphere (man made things)

Hydrosphere:

The hydrosphere contains all the solid, liquid, and gaseous water of the planet. It ranges from 10 to 20 kilometers in thickness. The hydrosphere extends from Earth's surface downward several kilometers into the lithosphere and upward about 12 kilometers into the atmosphere. A small portion of the water in the hydrosphere is fresh (non-salty). This water flows as precipitation from the atmosphere down to Earth's surface, as rivers and streams along Earth's surface, and as groundwater beneath Earth's surface. Most of Earth's fresh water, however, is frozen. Ninety-seven percent of Earth's water is salty. The salty water collects in deep valleys along Earth's surface. These large collections of salty water are referred to as oceans. The image above depicts the different temperatures one would find on oceans' surfaces. Water near the poles is very cold, while water near the equator is very warm. The differences in temperature cause water to change physical states. Extremely low temperatures like those found at the poles cause water to freeze into a solid such as a polar icecap, a glacier, or an iceberg. Extremely high temperatures like those found at the equator cause water to evaporate into a gas. Some scientists place frozen water--glaciers, icecaps, and icebergs--in its own sphere called the "cryosphere." For the purpose of this module, however, frozen water will be included as part of the hydrosphere. The word "hydrosphere" will be used in reference to all water in Earth's system. 

Atmosphere:

 

The atmosphere contains all the air in Earth's system. It extends from less than 1 m below the planet's surface to more than 10,000 km above the planet's surface. The upper portion of the atmosphere protects the organisms of the biosphere from the sun's ultraviolet radiation. It also absorbs and emits heat. When air temperature in the lower portion of this sphere changes, weather occurs. As air in the lower atmosphere is heated or cooled, it moves around the planet. The result can be as simple as a breeze or as complex as a tornado. The atmosphere is made up of many layers namely the toposphere, stratosphere, mesosphere, thermosphere and exosphere.

Lithosphere:

The lithosphere contains all of the cold, hard solid land of the planet's crust (surface), the semi-solid land underneath the crust, and the liquid land near the center of the planet. The surface of the lithosphere is very uneven. There are high mountain ranges like the Rockies and Andes, huge plains or flat areas like those in Texas, Iowa, and Brazil, and deep valleys along the ocean floor. The solid, semi-solid, and liquid land of the lithosphere form layers that are physically and chemically different. The outermost layer of the lithosphere consists of loose soil rich in nutrients, oxygen, and silicon. Beneath that layer lies a very thin, solid crust of oxygen and silicon. Next is a thick, semi-solid mantle of oxygen, silicon, iron, and magnesium. Below that is a liquid outer core of nickel and iron. At the center of Earth is a solid inner core of nickel and iron. The word "lithosphere" can take on different meanings depending on the speaker and the audience. For example, many geologists--scientists who study the geologic formations of Earth--reserve the word "lithosphere" to mean only the cold, hard surface of Earth, not the entire inside of the planet.

Biosphere:

The biosphere contains all the planet's living things. This sphere includes al\l of the microorganisms, plants, and animals of Earth. Within the biosphere, living things form ecological communities based on the physical surroundings of an area. These communities are referred to as biomes. Deserts, grasslands, and tropical rainforests are three of the many types of biomes that exist within the biosphere. It is impossible to detect from space each individual organism within the biosphere. However, biomes can be seen from space. For example, the image above distinguishes between lands covered with plants and those that are not. Some scientists place humans in their own sphere called the "anthrosphere."

All these physical and biological factors working in tandem with cultural, social, economic and other man-made elements provide a suitable environment for sustenance of all life-forms. The manner in which they interact with each other plays a crucial role in maintaining an ecological balance.

Sources:

http://www.cotf.edu/ete/ESS/ESSspheres.html

http://www.bcb.uwc.ac.za/Sci_Ed/grade10/ecology/abiotic/abiot.htm