Functions of the Ecosystem

It depicts the ways of interaction of the abiotic and biotic components. The main components of the function are: 

a. Physical (Energy Flow)

The energy which follows in the ecosystem is always fixed in one direction or unidirectional. 

• It always flows from producers to consumers (herbivores to carnivores) and cannot be vice-versa.
• The energy at each stage of transfer is lost in some amount. So if the energy produced received by plants from sunlight is 100%, then they receive only a few amounts of it. After consuming plants, the animals will receive maybe only 10% of the total energy, not exactly all energy. 
• The energy is lost during respiration, growth, movement, and other activities. 
• This is why trophic levels can be up to four or five as the energy becomes minimal at lower trophic levels, and the organism cannot survive with that amount.
• Different energy flow models depict the transfer of energy, such as the universal energy flow model, single channel energy flow model, and double channel energy flow model.

b. Biological (Food, chain, Food web, and Ecological Pyramids)

Food Chain

It is a sequence or order in which one organism feeds on another. Every organism on this earth is interconnected through the food chain i.e. each organism depends on others for its food requirements. The main definition of the food chain is “it is the sequence of eating and being eaten with the transfer of energy in every stage.” It represents the diet or feeding behavior of organisms along with the flow of energy in the ecosystem. An example of a food chain is the grass that depends on sunlight and oxygen for food which is consumed by grasshopper feeding on grass, which gets eaten by frogs and the frogs are taken as a diet by snakes which are eaten by an eagle and as eagles die they are buried in the soil and decomposed by decomposers which become minerals for plants to grow again.

Grass    →   Grasshopper   →    Frogs    →   Eagle    →   Dies and gets decomposed by decomposers   →    Decomposed matters utilized by grass (Cycle continues).

The food chain can also be ordered at the trophic level. The energy moves from one trophic level to another.

1. First Trophic Level: It includes producers which form the energy, such as green leafy plants.

2. Second Trophic Level: The one which feeds directly on producers for energy comes in this level. Such as the grasshopper in the above example.

3. Third Trophic Level: The one which feeds on organisms of the second trophic level comes under this. For e.g. Frogs and Eagles.

The food chain is of two types:

• Grazing Food Chain: It is the one that starts from sunlight. The energy from sunlight is transferred to the producers and then to the consumers, to the decomposers, and again to the producers.
• Detritus Food Chain: It is the one that begins from dead organic matter. For instance, dead leaves are eaten by insects which are further consumed by birds and so on.

Food Web

It is actually the interconnection or network between different food chains. It is an intricate representation of different food chains that are interrelated. For e.g. grass can be eaten by grasshoppers and goats; grasshoppers can be eaten by frogs, and frogs as well goats can be eaten by one or more carnivores which can be interrelated on the basis of feeding.

Importance of the food chain and food web:

• Ecological Balance: It helps to predict the reason for the imbalance or ecological disturbance in the ecosystem.
• Biomagnification: It is the process by which chemicals increase in concentration at different trophic levels. It takes place through the food chain and can be predicted by it. For, eg., the reason for the decrease in the number of vultures was predicted to be the consumption of dead bodies of cattle which were injected with efficient chemicals to boost their working stamina which then entered vultures and they started to die.

Ecological Pyramids

They are the representations of the number, biomass, and amount of energy at various trophic levels of the food chain in the form of graphs or pyramids. The producers are kept at the bottom of pyramids, and the consumers above, respectively, are based on their food chain. They can be of different types and can be inverted or upright based on the type of ecosystem. 

• Pyramid of Numbers: It depicts the number of organisms at different trophic levels. E.g., In an aquatic ecosystem, the number of plankton is numerous, and they are kept at the bottom of the pyramid with broad bottoms, and the insects consuming that plankton are lesser in number; the small fishes eating insects are lesser than insects, and the large fishes are minimal in number that consume on those fishes, so they are kept at the top with a narrow top. So the pyramid of the number of aquatic ecosystems is upright.
• Pyramid of Biomass: It represents the dry weight of different organisms involved in a food chain. For e.g. In an aquatic ecosystem, the dry mass of phytoplanktons is lesser than those of small fishes, and the large fishes have a large dry mass. Hence the pyramid formed is inverted.
• Pyramid of Energy: It represents the amount of energy at different levels of the food chain. As energy flow is unidirectional and decreases at each step from producer to consumer, so the pyramid of energy is always upright.

c. Biogeochemical cycle (Nutrient cycling)

The biogeochemical cycle is the phenomenon by which nutrients like carbon, nitrogen, phosphorus, etc., are available from the atmosphere or surrounding to the plants and then to the consumers in different forms such as carbohydrates, proteins, phosphates, etc., and get back to the atmosphere in their original form. It is the transfer of nutrients from abiotic to biotic components and vice-versa. The biogeochemical cycle is multi-directional in contrast to the energy flow, which is uni-directional. It includes the water cycle, carbon cycle, nitrogen cycle, etc.