Final answer:
Sponges are truly unique organisms because they lack true tissues and have specialized cells that perform specific functions.
Step-by-step explanation:
Sponges are truly unique organisms because they lack true tissues and have specialized cells that perform specific functions. While other animals have tissues with specific functions, sponges have cell-level organization.
For example, sponges have pinacocytes, which are epithelial-like cells that form the outermost protective layer of the sponge.
They also have porocytes, tube-shaped cells that act as valves to regulate water flow, and amoebocytes, which are the stem cells of sponges. These different cell types work together for the common goal of the sponge.