Hydra is tissue, not a cell.
Hydra, though simple, is a multicellular organism and has achieved the tissue level of organization. This means its cells are organized into functional tissues but not into complex organs.
Here's a breakdown:
- Cellular Level: The most basic level of organization.
- Tissue Level: A group of similar cells performing a specific function. Hydra fits this level.
- Organ Level: Different tissues combine to form an organ with a more complex function. Hydra lacks organs.
- Organ System Level: Multiple organs working together.
- Organism Level: The complete living being.
Hydra's body consists of two primary epithelial tissue layers:
- Ectoderm: The outer layer, serving as protection and sensory interface.
- Endoderm: The inner layer (also called gastrodermis), specialized for digestion.
These tissue layers work together to allow Hydra to function, but they do not form distinct organs. The simple structure of Hydra, while not possessing organs, is more complex than a single cell and therefore qualifies as tissue-level organization. Hydra's body plan is essentially a tube made of these two tissue layers.
