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.
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
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.
