Question

the heart is an example of which level of organization within an organism?
o cell
o organ
o tissue
o organ system

Explanation:

In the biological hierarchy of organization, a cell is the basic unit. Tissues are groups of similar cells. An organ is a structure made up of different tissues working together. An organ system is a group of organs working together. The heart is made of multiple tissues (like cardiac muscle tissue, connective tissue etc.) that work together to pump blood, so it fits the definition of an organ.

Answer:

organ