Which organisms fix nitrogen into forms like ammonia?

The majority of nitrogen is fixed by bacteria most which are symbiotic with plants recently fixed ammonia is then converted to biologically useful forms by specialized bacteria.

The rate that would change would be the  searching efficiency/attack rate. there are only two other rates in this model: the  growth rate of prey, and the  predator or consumer mortality rate.the  searching efficiency/attack rate is what indicates how effectively can a predator capture its prey whether in the searching process or actual capturing/attacking process.