How does the circulatory system interact with the digestive system

Rank the three variables in terms of how strongly they affect the "species" composition of the bacterial communities. place the variable with the weakest effect on the left and the variable with the strongest effect on the right.

How does a lytic infection differ from a lysogenic infection?

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important