Given below is an imaginary pyramid of numbers. What could be one of the possibilities about certain organisms at some of the different levels? 
| 1. | Level PC is insects and level SC is small insectivorous birds | 
| 2. | Level PP is phytoplanktons in the sea and Whale on top-level TC | 
| 3. | Level PP is pipal trees and the level SC is sheep | 
| 4. | Level PC is rats and level SC is cats | 
 
The upright pyramid of number is absent in:
1. Pond
2. Forest
3. Lake
4. Grassland