Answer:
When calcium concentration increases during depolarization, it shifts the conformation of troponin and tropomyosin, and actin is able to associate with myosin. As calcium is taken up again by the sarcoplasmic reticulum the muscle cell relaxes.
Divergent evolution is when two different species share the same ancestral origins but have evolved differently whereas convergent evolution is when species with different ancestral origins have developed similar features.
In convergent evolution, two species that are not necessarily closely related develop similar features often as a result of adaptation to similar conditions.
homeostasis, that is what i think at least