Structure of Ecosystem processes

• According to Odum, all ecosystems have two basic living components:

1. autotrophic component, and
2. heterotrophic component.

• The autotrophic component fixes the radiant energy of sun and manufactures food from simple inorganic substances.
• The heterotrophic component takes food from autotrophic, rearranges it and finally decomposes the complete organic materials into simple inorganic forms.
• According to Odum, ecosystems generally include four categories of basic structural components:

1. Abiotic components
2. Producers, mainly green plants
3. Consumers, almost exclusively animals
4. Decomposer, mainly bacteria and fungi

A. Abiotic components:

• Abiotic component of ecosystem includes basic inorganic elements and compounds, such as soil, water, calcium, oxygen, carbonates, phosphates and a variety of organic compounds (by-product of organic activity or death).
• It also includes such physical factors and gradients as moisture, wind currents and solar radiation.
• The amount of non-living components, such as phosphorus, nitrogen etc. that are present at any given time, is known as standing state or standing quantity.

B. Biotic components:

a. Producers (autotrophic elements): The producers are the autotrophic elements-chiefly green plants. They use radiant energy of the sun in photosynthesis process whereby carbon dioxide is assimilated and light energy is converted into chemical energy. Oxygen is evolved as by-product in the photosynthesis.

b. Consumers: Those living members of ecosystem which consume the food synthesized by producers are called consumers. Under this category are included all different kinds of animals that are found in an ecosystem. There are different classes or categories of consumers, such as,

I) Primary consumers, consumers of the first order: These are purely herbivorous animals that are dependent for their food on producers or green plants. Insects, rodents, rabbit, deer, cow, buffalo, and goat are some of the common herbivores in the terrestrial ecosystem, and small crustaceans, molluscs etc. in the aquatic habitat.

ii) Secondary consumers, consumers of the first order: These are carnivores and omnivores. Carnivores are flesh-eating animals whereas the omnivores are the animals that are adapted to consume herbivores as well as plants as plants as their food. Examples of secondary consumers are sparrow, cow, fox, wolves, dogs, cats, snakes, etc.

iii) Tertiary consumers, consumers of the second order: These are the top carnivores, which prey upon other carnivores, omnivores and herbivores. Lions, tigers, hawk, vulture, etc. are considered as tertiary or top consumers.

iv) Parasites, scavengers and saprobes: The parasitic plants and animals utilize the living tissues of different plants and animals. The scavengers and saprobes utilize dead remains of animals and plants as their food.

v) Decomposer and transformers: Decomposer and transformers are the living components of the ecosystem and they are fungi and bacteria. Decomposer attack the remains of producers and consumers and degrade the complex organic substances into simpler compounds.