Question

Which of the following food chains shows a spindle shaped pyramid of numbers?
A. Grass – Insects – Frog
B. Phytoplankton – Zooplankton – Small fish
C. Tree – birds – Hawks
D. Tree – birds – Insects – Bacteria

Answer 1

Hint Ecological pyramid is the relation between the producers and consumers in an ecosystem that can be graphically represented in the form of a pyramid.
The base of the pyramid always represents the producers, and on the top represents the top level consumer. The trophic level states that all the organisms in an ecosystem occupy a specific place in the food chain.

Complete Answer-
Pyramid of number represents the relationship between producers and consumers in an ecosystem in the form of a pyramid in terms of number.
1. In the grassland ecosystem the pyramid will be upright or straight because there is a producer in a large number as compared to the consumer community and the size decreases from producer to top carnivore.
2. In ponds, rivers, etc. the phytoplankton are the plants that take carbon dioxide and release oxygen and zooplanktons are the animals that eat up the phytoplankton and become the food for the small fish and other creatures. So, the pyramid will be upright or straight.
3. In a forest ecosystem the pyramid will be the spindle in shape because the large sized tree is attacked by various birds and the top level of organisms in a food chain.
4. In a parasitic ecosystem the shape is inverted because the tree is small in size as compared to larger populations of birds, insects and bacteria.

So, the correct answer is option (3) Tree – birds – Hawks because it belongs to the forest ecosystem.

Note- Ecological pyramid was developed by Charles Elton and named as Eltonian pyramids. Ecological pyramids may be upright or straight means tapering towards the tips and spindle shape means broader in the middle and narrow from the above and below portion. Inverted means widen towards the tips and narrow towards below. They are divided into three types- pyramid of number, biomass and energy.