Is a heart an organism?

no its a organ

Explanation:

Your heart is actually a muscular organ. An organ is a group of tissues that work together to perform a specific function. In the case of your heart, this function is pumping blood throughout your body. Additionally, the heart is largely made up of a type of muscle tissue called cardiac muscle

the difference bewteen them are group of similar cells together form tissue. And the tissues form organs and different organs together constitute the organ system. ... Whereas in complex organism they are mostly multi cellular and various Functions are done by various kinds of cells.