It is necessary for complex organisms to have multiple body systems because we have to know how our bodies work. We have to know how our bodies work so we can know how to cured ourselves of we get sick. Like if we have an infection in our stomach, we will know how to cured ourselves. We need these body systems so our bodies can work properly. Each body system will have their own responsibility. What i learned from this experienced was that frogs body systems are similar to our body systems.