The circulatory system of a whale is considered an organ system because it is composed of multiple organs working together to perform a specific function.

Here's a breakdown:

* Organs: The whale's circulatory system includes the heart, blood vessels (arteries, veins, capillaries), and blood itself. Each of these components is a distinct organ with its own specialized structure and function.

* Integrated Function: These organs work together to transport oxygen, nutrients, and hormones throughout the whale's body. They also remove waste products and help regulate body temperature.

* Shared Purpose: The circulatory system is a vital system for the survival of the whale. It's essential for maintaining homeostasis and enabling all the other organ systems to function correctly.

In summary: The circulatory system of a whale is a complex, integrated network of organs that work together to maintain life. This interconnectedness and shared purpose classify it as an organ system.