Which of the following is/are the characteristics of the ecological pyramid?
1. A species is accounted only at any one trophic level.
2. It accommodates a food web.
3. Saprophytes occupy a key place in the ecological pyramid.
Select the correct answer using the codes given below.1
1 only
2
2 and 3 only
3
1 and 3 only
4
1, 2 and 3