Question

If you were to count the number of insects feeding on a big tree. What kind of pyramid would you get? Now add an estimate of the number of small birds depending on the insects and also the number of larger birds eating the smaller. Draw the shape you would get.

Answer 1

Part 1: Ecological pyramid
Ecological pyramids are a visual representation of the numbers/ biomass/ energy present in different trophic levels in the food chain. The basic types are:-

• Upright pyramid: Formed when the base of the pyramid (consisting of producers) is wider compared to successive layers in terms of number, biomass or energy.
• Inverted pyramid: The lowest level (producers) forms a narrow base while the successive levels are wider.
• Spindle-shaped pyramid: The lowest level contains very few producers, the primary consumers are more in number, secondary and tertiary consumers successively are lesser in number.

Part 2: Forest ecosystem
In a tree within a forest ecosystem, the trophic levels are as follows:-

• Producer: One tree
• Primary consumers: Insects (more in number)
• Secondary consumers: Birds (less in number than the previous level)
• Tertiary consumers: Larger birds (less in number than the previous level)

This gives a spindle-shaped pyramid.