Answer:
Bottom -up models of community:
The bottom up models of the community represents the unidirectional influence of the community. The model shows from the lower to the higher tropic levels in the community. This model determines the nutrient minerals and the primary producer abundance.
Top - down models of community :
The top down model of the community represents the one tropic level to the other tropic levels. This model is also known as cascade model. This model determines how the one tropic level controls the other tropic level. For example: the control of herbivores by the predators.