Green plants and trees that synthesize their own food are called as Autotrophs.
Others who depend on them are called as Heterotrophs.
There are many other categories too like Parasites, Saprophytes, and Insectivorous etc.
Parasites are those who depend of other living organisms.
Saprophytes are those who depend on dead and decaying matter.
Insectivorous plants take away nitrogen of small animals like insects through different mechanisms.
There is a dynamic relation among all the components of an ecosystem.
Green plants absorb solar energy from the sun. This energy is passed ahead into consumers of different order through the cycle of food.
When the top consumer dies this energy escapes away into the atmosphere. Thus the pathway of energy in the environment is acyclic.
The dead body of the top consumer is decomposed by decomposers. Thus complex substances are turned into simple substances to get mixed into the soil and be absorbed by plants.
All this proves that there is a dynamic relation among all the components of an ecosystem. All the mass retained inside the body of an organism is called as its Biomass.
It is the biomass which makes the mass of weight of an organism.
Functions of Ecosystem
An ecosystem has following functions –
1. Flow of Nutrients
2. Flow of Energy
3. Bio-geo-chemical cycles
Flow of Nutrients in Ecosystem- The flow of nutrients in ecosystem takes place in cyclic pathways through food chains, food webs and bio-geo-chemical cycles.
A. Food Chain: Flow of materials in an ecosystem in a cyclic pathway is called as food-chain. In fact the food synthesized by green plants passes through different trophic levels to the top consumer after the death of which it is decomposed in simpler form to get mixed with the soil. From there plant roots again absorb them through water solution. Thus the cycle goes on.
Food Chains are of diverse types.
It depends on the structure of ecosystem. For example food-chains of a pond, a desert, and grassland remain highly diverse. There exists great diversity in terms of trophic levels in food chains of different places.
In grassland or a crop field plants are the only producers.
Numerous insects get their food from these plants.
Insects are Primary Consumers. Frogs eat away insects and so they are Secondary Consumers. There may be snakes in the grassland or crop field as they live in the holes dug out by rats. Snakes eat away frogs. So snakes are Tertiary consumers.
Since snakes too are eaten by some animals say Peacock or Vulchers, these snake eaters may be called as Top Consumers.
When top consumer dies, its body is decomposed by numerous decomposers. The decomposed simple organic substances get mixed into soil and absorbed by plan roots. Thus the cycle completes. Thus we can trace out food-chains of other places as well.
In an aquatic food chain, aquatic plants like lemna, sagitaria, vallisneria, eichornia etc. are producers.
Small aquatic insects eat aquatic plants and in turn are eaten up by fish. Fish is eaten up by water bird. Thus the aquatic food chain is completed after the death and decomposition of the top consumer. We may trace many other food chains too that run in a water body.
If we take the example of a forest we can very easily guess that the lion or a tiger may be the top consumer.
Producers like grasses or plants that grow on the forest floor are eaten by deer and deer is eaten by the lion. Many other food chains may be traced out from a forest ecosystem.
B. Food- Web
It is food –chain which transfers nutrients and energy through trough different trophic levels in the ecosystem.
But a single food-chain is not sufficient to transfer food and energy in the whole ecosystem. As producers are of many types so are consumers.
Different consumers have different food preferences due to which a single consumer often eats many different types of food.
Rabbit, rat and insects can eat grass in an ecosystem. In the same way a Vulcher can eat both rat and rabbit. Again a snake can eat many types of animals like frogs, eggs of birds and rats and many more.
A Vulcher can eat rabbit and snake. Thus many food-chains can run at the same time in an ecosystem. This is called as Food-Web. The network of food-chains is called as food-web.
C. Food- Pyramid
It so happens sometimes in an ecosystem that the number of organisms in trophic levels becomes too much as compared to the other trophic level.
Let us consider it through an example- There are numerous insects in a forest but the number of birds that feed upon these insects is very less. The number of predator birds is very less than insectivorous birds.
If we demonstrate the number of individuals of different trophic levels on a vertical line, we get a Pyramid which is called as Food-Pyramid. The concept of food pyramid was presented for the first time in 1972 by Charles Elton.
The Food-pyramid may be drawn on the basis of number and their biomass. The first one is called as Pyramid of Number and the second one is called as Pyramid of Biomass.
