The earth, as it appears to be, is made up of four interrelated spheres known as the lithosphere, atmosphere, hydrosphere and biosphere. These components of the earth are the domains in which different natural elements occur.
The lithosphere is the sphere of rocks and minerals, whereas the atmosphere is essentially the sphere of gases and, or air. Also, the hydrosphere is made up of all water bodies and the biosphere is the domain of all living organisms on the earth’s surface. These four spheres interrelate because the naturally occurring non-living and living organisms living in them depend on one another.
This will give us an understanding of the nature and functioning of the natural environment. It will be pertinent to give a description of these interrelated elements and how they vary both in space and time.
The Concept of Ecosystem
As earlier mentioned, the components of an environment exist and interrelate in such a manner similar to the components of a functioning system. F. R. Fosberg defines an ecosystem as ‘a functioning, interacting system composed of one or more living organisms and their effective environment, both physical and biological’. It is the nature of the close relationship and interaction between the components within the environment that is often referred to as an ecosystem. In other words, an ecosystem is an organic community of plants and animals, viewed within its physical environment or habitat. Ecosystem is also used for the physical, chemical and biological relationships which bind plant and animal communities together in their physical environment.
The ecosystem is maintained by the constant flow of energy supply almost entirely from solar radiation as well as recycling of matter by the environment.
Spatial units that may make up a recognised ecosystem include ponds or lakes, parts of forests, grasslands or desert areas, mountain slopes, coastal lagoons and creeks, river flood plains and deltas. The study of the ecosystem is known as ecology.
The Components of an Ecosystem
AII ecosystems are made up of two large components which are the physical (abiotic) environment and the biological (biotic) community. The physical environment consists of the inorganic substances, such as gases, water, soil, rocks and all other inorganic mineral compounds. The environment (abiotic) provides the energy, raw materials and living space for the use of the organisms of the biotic or biological community.
The second component of the ecosystem (biotic community) is composed of three levels of living organisms. These include:
1. The primary producers, usually called autotrophs, are mainly green plants that produce their own food with the use of solar energy in the process of photosynthesis.
2. The consumers, known as heterotrophs are the animals that feed on organic matter provided by plants and other animals.
3. The reducers (i.e. decomposers) which are micro organisms e.g. bacteria and fungi that promote decay of dead organic matter. The substances they release can be used up again by the producer organisms.
1. Four interrelated spheres of the earth (lithosphere, atmosphere, hydrosphere and biosphere) constitute the domains within which the interactions and interdependencies of the elements of the earth’s surface take place.
2. The biotic and abiotic components which include gases, water, rocks, minerals, soils, plants, animals and micro organisms, depend on and interact with one another.
3. The concept of the ecosystem provides a model for a better understanding of the nature of the interaction and interdependencies that exist within the natural environment. There is a constant flow of energy from the solar radiation and a constant cycling of matter among and between the biotic and abiotic components of the ecosystem.
4. There are many types of natural ecosystems. Land ecosystem identifies other ecosystems within it as flood and coastal plains, dissected highland plains and uplands, and mountain and highland ranges.
5. There exist within each ecosystem recognised and significant aspects of interactions and interdependencies between climate, soils, vegetation, animal communities, etc.
6. A high degree of environmental balance exists within each ecosystem. This balance results from the processes involved in the flow of energy and exchange of matter within each system. Conceptual models used to illustrate those processes include hydrological cycle, nitrogen, carbon and mineral nutrient cycles, as well as food chains and webs.
7. Some interventions occur within the environment which result from natural or human factors. The interventions are capable of creating short or long-term changes which can adversely modify the character of the environment.
8. The occurrence of certain natural phenomena, e.g. climatic change and vulcanicity, etc., and of human activities such as forest exploitation, overgrazing and mining, can have adverse significant impact on the environment. Such impacts have created environmental disasters or hazards on different parts of the earth’s surface.
9. Some of the well known environmental hazards include soil and coastal erosion, deforestation, flooding, land subsidence, as well as atmospheric and water pollution.