4) digestive and circulatory, because the bladder is part of the digestive system. The circulatory system carries blood around the body using blood vessels.
This can be identified as a population. In a population, the organisms are the same species and they have to live in the same area. For example, the population of cities are the head count of the species of human in that one area.
Answer:
the zygote, because it is formed by the sperm and egg cells of both sex
