1.) How do organ systems work independently and together?
Each organ/body system has specific task to do, like the digestive system. Its job is to break down food into small molecules for the body to use, mainly for energy.
Many organ systems work together to maintain homeostasis in the body. For example, the respiratory system and the circulatory system work together to deliver oxygenated blood to the body and to get rid of CO2 (carbon dioxide) the cells make.
2.) What is homeostasis and how is it maintained?
Homeostasis is the body's ability to maintain a safe and secure internal environment (regulating pH levels, water balance, body temperature, and etc...).
Homeostasis is maintained by negative response within the organism. Like the nervous system and urinary system work together to balance out the fluids in your body (mainly water and electrolytes) if there is any imbalance, to maintain homeostasis.
Hope this helped :D