Ecological Pyramids : The pyramid of numbers, biomass, energy

Ecological Pyramids

The number, biomass and energy of organisms gradually decrease from the producer to the consumer level. This can be represented by a pyramid called ecological pyramid. It is the graphic representation of the number, biomass and energy of the successive trophic level of an ecosystem. The use of ecological pyramid was first described by Charles Elton in 1927.

There are three types of ecological pyramids namely,

1. The pyramid of numbers,

2. The pyramid of biomass,

3. The pyramid of energy.

1.The Pyramid of Number

The number of individuals at the trophic level decrease from the producer to the consumer level. In croplands the crops are more in numbers. The grasshoppers feeding on crop plants are lesser in number, The frogs feeding on grasshopper are still lesser in number. The snakes feeding on frogs are fewer in number.

In a grassland the grasses are large in numbers. The consumers decrease in the following order.

Crops  - > Grasshopper  - > Frogs  - > Snakes  - > Hawks.

2. The pyramid of biomass

Biomass refers to the total weight of living matter per unit area. In an ecosystem the biomass decreases from the producer level to the consumer level.

In a grassland the biomass of grasses is the maximum and it gradually decreases towards the consumer level.

Grass                               -> Grasshopper  -> Garden Lizard  -> Hawk.

Grass                               -> Mouse  ->      Snake  -> Hawk.

In a forest, the biomass of trees is the maximum and the top consumer is the minimum. The decrease in weight occurs in the following order.

Plants                              ->    Deer   ->     Fox   -> Tiger.

Plants                              ->    Rabbit  ->   Fox   -> Lion.

3. Pyramid of energy

In an ecosystem, the energy flow from the producer to the consumer level will be decreasing. In a grassland, grass plants trap the maximum sun light energy. The energy gradually decreases towards the top consumer level. The chemical energy is transformed into kinetic energy.

Grass                               -> Rabbit  -> Fox         -> Lion.

Grass                               -> Grasshopper  -> Garden Lizard  -> Hawk.

Grass                               -> Mouse  -> Snake     -> Hawk.