Fig. I: It is a single population and all individuals are of the same species i.e. A. Individual interact among themselves and their environment.
Fig. II: It is a community and it contains three populations of species A,B and C. They interact with each other and their environment.
Fig. III: It is a biome. It contains three communities. of which one is in climax and other two are in different stages of development. All three communities are in the same environment and they interact with each other and their environment.
