ECOLOGICAL PYRAMIDS

 Ecological pyramids are graphical representations of the trophic structure in an ecosystem. The major trophic levels in an ecosystem are the following;

1. Producers

2. Primary consumers

3. Secondary consumers

4. Tertiary consumers

5. Decomposers

Producers are green plants and algae which have the potential to fix atmospheric carbon dioxide and make glucose through a process called photosynthesis. 

Primary consumers are the animals which eat the green plants and algae. They are called herbivores, for example cow, rabbit, goat, deer.

Secondary consumers are the animals which prey upon herbivores. For example, Fox, dog, cat

Tertiary consumers are those animals which prey upon all animals irrespective of trophic levels, such as lion, tiger and hawk.

Decomposers are organisms which decay the dead organic matter formed by the death of organism, leaf fall etc. For example, fungi and microbes.

The energy trapped by green plants is transferred to primary consumers, then to secondary consumers and then to tertiary consumers. There is an energy loss at each level, which means only 10% of energy from one trophic level is transferred to the next. This is called 10% Rule. 

For example, if a producer has 1000 calories of energy, then the herbivore will get only 100 calories. When the herbivore is eaten by primary carnivores, they get only 10 calories. Finally the top carnivores will get only 1 calorie. At each trophic level, 90% of energy is lost for activities such as respiration, movement etc.

The following diagram explains the concept.

Ecological pyramids are of different types as given below.

1. Pyramid of Number: Graphical representation of number of organisms at each trophic level is called pyramid of number.

2. Pyramid of Energy: When the energy level of each trophic level is represented in an ecological pyramid, it is called pyramid of energy.

3. Pyramid of Biomass: When the biomass of organisms at each trophic level is represented in an ecological pyramid, it is called pyramid of biomass.

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