True they are in the heart as well as the rest of your body
Photosynthesis gives the plant food/nutrients to be able to survive. They make their own food
The object's mass. Weight would be how gravity affected it, size is how large it is, density is how tightly the molecules are to each other. Mass is how much matter is in the object.
I believe the answer you are looking for is they are all body systems found in the human body, or organ systems.