What organ system is monetly responsible for generating behavior in multicellular animals?

Nervous system is the organ system that is mostly responsible for generating behavior in multicellular animals. The nervous system coordinates multicellular animal’s behavior and transmits signals within the body.  Specific excitatory and inhibitory substances are produced by the nerve cells for them to interact with each other and certain chemicals, sound and light is detected by the sense organs such as ear and nose which control the behavior and movement of multi cellular animals in their environment.

"do a testcross with a homozygous recessive plant."