ECOSYSTEM

PRIMARY GROUPS OF ECOSYSTEM FUNCTIONS 

REGULATORY FUNCTIONS

This group of functions relates to the capacity of natural and semi-natural ecosystems to regulate essential ecological processes and life support systems through bio-geochemical cycles and other biospheric processes. In addition to maintaining the ecosystem (and biosphere health), these regulatory functions provide many services that have direct and indirect benefits to humans (i.e., clean air, water and soil, and biological control services).

HABITAT FUNCTIONS

Natural ecosystems provide refuge and a reproduction habitat to wild plants and animals and thereby contribute to the (in situ) conservation of biological and genetic diversity and the evolutionary process. 

PRODUCTION FUNCTIONS

Photosynthesis and nutrient uptake by autotrophs converts energy, CO₂, water and nutrients into a
wide variety of carbohydrate structures which are then used by secondary producers to create an even larger variety of living biomass. This broad diversity in carbohydrate structures provides many ecosystem goods for human consumption, ranging from food and raw materials to energy resources and genetic material. 

INFORMATION FUNCTIONS

Since most of human evolution took place within the context of an undomesticated habitat, natural ecosystems provide an essential 'reference function' and contribute to the maintenance of human health by providing opportunities for reflection, spiritual enrichment, cognitive development, recreation and aesthetic experience.

ENERGY FLOW IN ECOSYSTEM

Energy is the capacity to do work. Solar energy is transformed into chemical energy by the process of photosynthesis, and is stored in plant tissue and then transformed into mechanical and heat forms during metabolic activities. The energy, in the biological world, flows from the sun to plants and then to all heterotrophic organisms such as microorganisms, animals and man.

'THE STUDY OF ENERGY TRANSFER AT DIFFERENT TROPHIC LEVEL IS KNOWN AS 'BIOENERGETICS'.

FLOW OF MATERIALS IN ECOSYSTEM IS CYCLIC BUT THE FLOW OF ENERGY IS UNIDIRECTIONAL

The materials like water, carbon (as carbon dioxide) and nitrogen (as minerals) are taken up by the plants from soil, air and water bodies, etc., and made into food. This food is then passed on to the animals like herbivores and carnivores in a food chain. After the death and decay of plants and animals, the materials like water, carbon and nitrogen present in their bodies are returned to soil, air and water, from where they were taken originally. These materials can then be reused for the growth of new plants. In this way, the same materials are used again and again, the materials are not lost from the environment. So, the flow of materials like water, carbon and nitrogen, etc., in the ecosystem is said to be cyclic. This is not so in the case of energy. The flow of energy in the ecosystem is unidirectional (or one-directional). The energy enters the plants (from the sun) through photosynthesis during the making of food. This energy is then passed on from one organism to another in a food chain. Energy given out by the organisms as heat is lost to the environment, it does not return to be used by the plants again. This makes the flow of energy in ecosystem 'unidirectional'. Thus, the flow of energy in the ecosystem is said to be unidirectional because the energy lost as heat from the living organisms of a food chain cannot be reused by plants in photosynthesis.

The Ten Per Cent (10%) Law 
During the transfer of energy through successive trophic levels in an ecosystem, there is a loss of energy all along the path. No transfer of energy is 100 per cent. The studies of transfer of energy in different food chains in a large number of ecosystems have revealed a uniform pattern of transfer of energy, which is given by 10 per cent law.
The 10 per cent law which was given by Lindeman in the year 1942 is one of the most useful generalizations about the magnitude of loss of energy in food chains. According to ten per cent law, only 10 per cent of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
All the energy transfers in food chains follow the 10% law which in simple terms means that the energy available at each successive trophic level is 10 per cent of the previous level. Thus, there is a progressive decline (gradual reduction) in the amount of energy available as we go from producer level to the higher trophic levels of organisms. Let us take one example to understand the 10 per cent law more clearly.
Suppose 1000 joules of light energy emitted by the sun falls on the plants (called producers). We know that the plants convert only one per cent (1%) of the light energy falling on them into chemical energy of food. So, the energy which will be available in plant matter as food will be only 1% of 1000 joules, which comes to 10 joules.
The remaining 1000 - 10 = 990 joules of light energy or solar energy which is not utilized by the plants is reflected back into the environment. Please note that the ten per cent law will not apply at this stage. It will apply only in the transfer of energy in the food chain.
We will now apply the 10 per cent law to the food chain: Plants------ > Herbivores ------> Carnivores. The plants or first trophic level has 10 joules of energy in it. Now, according to ten per cent law, only 10% of 10 joules of energy (which is 1 joule) will be available for transfer at the next trophic level, so that the herbivore (deer) will have only 1 joule of energy stored as food at the second trophic level.
Applying the ten per cent law again we find that 10% of the remaining 1 joule (which is 0.1 joule) will be transferred to third trophic level of carnivore (lion). So, the energy available in the lion as food will be only 0.1 joule. We will now solve some problems based on ten per cent law.
For example 
Plants -------- > Deer -------- > Lion

•  Plants can trap only 1% of the sun's energy falling on them. Now, 1% of 20000 J is 200 J, so the plants have actually 200 J of energy available in them as food (The 10 per cent law does not apply at this stage).

•  The plants are eaten up by deer. Now, according to 10 per cent law, 10% of 200 j, that is, 20 J  of energy will be available in deer as flesh food.

• The deer will transfer 10% of its 20 J energy to the lion. Thus, the food energy available to the lion will be 10% of 20 J which comes to 2 J.

STUDY OF ECO SYSTEM

ECO SYSTEM

An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. There are many examples of ecosystems

•   a pond,
•   a forest,
•   an estuary
•  a grassland

The boundaries are not fixed in any objective way, although sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for practical reasons having to do with the goals of the particular study.

The study of ecosystems mainly consists of the study of certain processes that link-

•  The living, or biotic, components to

•  The non-living, or abiotic, components. 

Energy transformations and biogeochemical cycling are the main processes that comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur. We can study ecology at the level of the individual, the population, the community, and the ecosystem.

• Studies of individuals are concerned mostly about physiology, reproduction, development or behavior
•  Studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction.
• Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.

In ecosystem ecology we put all of this together and, insofar as we can, we try to understand how the system operates as a whole. This means that, rather than worrying mainly about particular species, we try to focus on major functional aspects of the system. These functional aspects include such things as-

• The amount of energy that is produced by photosynthesis
•  How energy or materials flow along the many steps in a   , or
• What controls the rate of decomposition of materials or rate at which nutrients are recycled in the system

STRUCTURE OF AN ECOSYSTEM

You are already familiar with the parts of an ecosystem. From this course and from general knowledge, you have a basic understanding of the diversity of plants and animals, and how plants and animals and microbes obtain water, nutrients, and food. We can clarify the parts of an ecosystem by listing them under the headings "abiotic" and "biotic". 

Usually, biological communities include the "functional groupings" shown above. A functional group is a biological category composed of organisms that perform mostly the same kind of function in the system; for example, all the photosynthetic plants or primary producers form a functional group. Membership in the functional group does not depend very much on who the actual players (species) happen to be, only on what function they perform in the ecosystem.

FUNCTION OF AN ECOSYSTEM

Ecosystem function is the capacity of natural processes and components to provide goods and services that satisfy human needs, either directly or indirectly (de Groot et al 2002). By following this definition, ecosystem functions are conceived as a subset of ecological processes and ecosystem structures. Each function is the result of the natural processes of the total ecological sub-system of which it is a part. Natural processes, in turn, are the result of complex interactions between biotic (living organisms) and abiotic (chemical and physical) components of ecosystems through the universal driving forces of matter and energy. 

PRODUCERS, CONSUMERS AND DECOMPOSERS

Producers or autotrophs are organisms that make their own organic material from simple inorganic substances. For most of the biosphere the main producers are photosynthetic plants and algae that synthesis glucose from carbon dioxide and water. The glucose produced is used both as an energy source and combines with other molecules from the soil to build biomass. It is this biomass that provides the total theoretical energy available to all non- photosynthesizing organisms in the ecosystem.

Consumers or heterotrophs are organisms that obtain organic molecules by eating or digesting other organisms. These are the herbivores and carnivores of the ecosystem. By eating other organisms they gain both food as an energy supply and nutrient molecules from within the biomass ingested. For instance to build new protein consumers have to eat protein contain amino acids.

Decomposers are the waste managers of any ecosystem. They are the final link in a food web breaking down Dead Organic Matter (DOM) from producers and consumers and ultimately returning energy to the atmosphere in respiration and inorganic molecules bake to the soil during decomposition. Decomposers can be divided into two groups based on their mode of nutrition. DETRITIVORES are organisms that ingest non-living organic matter.These can include earthworms, beetles and many other invertebrates. SAPROTROPHS are organism that lives on or in non- living organic matter, secreting digestive enzymes into it and absorbing the products of digestion. These include Fungi and bacteria.