Ecology and Ecosystem

Definition of Ecology

Ecology is defined as the science of interactions among individuals, populations and communities and it involves the interrelationship between the living components (biotic) with their non-living components (abiotic components) and their environment.

• The study of organisms in relation to their environment.
• The study of structure and function of nature.
• The study of an ecosystem.
• The study of community.

Rightly we can say that ecology is the study of interactions between the organisms with their environment.

The different definition of ecology from different aspects are given below:

1. Ecosystem paradigm:

   The study of the structure and function of nature (Odum 1971).

2. Population paradigm:

   The study of interactions that determine the distribution and abundance of organisms (Kerbs 1978).

3. Toward Integration:

   The scientific study of the process influencing the distribution and abundance of organisms and the transformation of the flux of energy and matter ( International Ecological Society 1992).

Key Concepts in Ecology

• Organisms are adapted to their environment.
• Ecological systems function according to the laws of physics, particularly thermodynamics.
• The physical environment controls and influences the development of the biological community and its population dynamics.
• The functioning of the community is dependent on the number of inter-species interactions.
• Human alters ecological processes.

Organisms are adapted to their Environments:

1. The crucial determines of an organism’s habitat are water, soil,O₂and CO₂, osmotic potential, temperature, inorganic nutrients, light and the size of the organisms.
2. Salt balance, water balance, nitrogen excretion, gas exchange and temperature regulation are interlinked for all the organisms.
3. Individual organisms try to maintain internal homeostasis in a variety of parameters.

Ecological system function according to the law of physics, particularly thermodynamics.

• All ecosystems rely on the sun for energy.
• Because energy use is not 100% efficient, energy is lost from ecosystems in the form of heat.
• Unlike energy, nutrients can be cycled through an ecosystem.
• Biomass is controlled by climatic factors, habitats by local irregularities of topography. Therefore, distribution of organisms is also determined by these factors.

The physical environment controls and influences the development of the biological community and its population dynamics.

• Organisms can respond to environmental change or patchiness with varied behavior or life cycle.
• Reproduction in organisms is also influenced by the environment.
• Groups of organisms of a single species (populations) are not usually distributed in an even manner no matter what the scale.
• Community structure is determined by both biotic and abiotic factor.
• Under ideal conditions, most organisms undergo exponential growth.
• 2 types of factors may limit population growth, density independent and density dependent factor.
• Individual differences between members of a population affect their survival and birth rates are ultimately reflected by a change in the genetic makeup of the populations.

The functioning of a community is dependent on a number of interspecies interactions.

• Community succession occurs as species change the environment in ways that favor other species.
• Patterns of biodiversity are based on underlying physical characteristics of the environment.
• Predator-prey interactions result in co-evolution of species.
• Competition for resources is one of the strongest ecological factors & is strongest between conspecifics.

Concept of Ecosystem

The term ecosystem was first proposed by British Ecologist A.G Tansley in 1935. He defined it as a system resulting from the integration of all living and non-living factors of the environment. The system includes both living (biotic) and non-living (abiotic) environment & influences other for the maintenance of life. It can be illustrated by the fact that the holozoic animals can synthesize their food and hence depends upon plants either directly or indirectly. But even plants which are capable of synthesizing their own food depends on their biotic environment from which they receive raw materials and other organic substances which are the absolute necessity for the synthesis of food.

The organic substances & some of the organic compounds are accumulated in the soil by decomposition of dead bodies & the excreta of living individuals. Thus, a delicate dynamic balance exists between the biotic and abiotic (living and non-living) environment.

Odum 1991, defines an ecosystem as any unit that includes all the organisms in the given area interacting with physical environment so that flow of energy leads to clearly defined biotic (living) structures & Cycling of materials between living (biotic) & non-living (abiotic) components.

An ecosystem is a functional unit of ecology. The system may be as small as ponds ecosystem, a cropland ecosystem very large as ocean system, a forest ecosystem or desert ecosystem. In entire earth ecosystem together makes up the ecosphere. The collection of living ecosystem & dead organisms interacting with one another & their non-living environment throughout the world is called ecosystem because they are functionally operating system, consideration of both input environment & the output environment an important part of an ecosystem.

The ecosystem is a very broad term and it incorporates following aspects;

• The major ecological unit contains both living and non-living (biotic & abiotic) components through which nutrient cycle & energy flows.
• To accomplish those cycles and flows, ecosystem possesses a number of structural relationship with soil water, nutrients, producers, consumers & decomposers.
• The function of an ecosystem is related to the flow of energy & cycling of materials through the structural components.
• The amount of energy that flows through a natural system depends on the amount of energy fixed by plants or autotrophs. As energy is transferred from one feeding level to another, a considerable loss is seen which limits the number & mass of the organisms that can be maintained at each feeding level.
• Ecosystem tends toward maturity, in doing so they pass from a less complex to more complex state. This directional change is called succession. Early stages of succession are characterized by an excess of potential energy & relatively high energy flow per unit biomass. In a mature ecosystem, there is less waste & less accumulation of energy because the energy flows through more diverse channels.
• Major functional unit of the ecosystem is the population. It occupies a certain functional niche that is related to the population role in the energy flow of cycling of nutrients & nutrients cycling.
• Both environment & amount of energy fixation in any given ecosystems are limited. When a population reaches the limits imposed by the ecosystems, its number must be stabilized or this will decline from starvation, low reproduction & so on.
• Distribution of ecosystem in the earth is remarkably small in geographic extent when compared with the total volume of the earth. Biosphere includes only the surface layer of solid ground or sediments beneath water bodies like oceans, lakes & that portion of atmosphere inhibited by flying & floating organisms. E.g. birds, bacteria, insects, bats etc.

References:

E.p., Odum. Fundamentals of Ecology. USA: W.B Saunters Company, n.d.

Jr., Miller G.T. Living in the Environment. Belmont, California, USA: Wadsworth Publishing Company, 2003.