Question

organ system level of organisation is absent in which phylum​

Answer 1

Answer:

Phylum Platyhelminthes and Aschelminthes have an organ level of organization. Nor-chordates such as Annelids, Arthropods, Molluscs, Echinoderms, and Chordates have a specialised organ system for their physiological activities. They have the organ-system level of organisation.

Explanation:

Answer 2

Poriferra

Explanation:

• Phylum poriferra have cellular- level organization.
• Their cells are specialized so that different cells perform different functions.
• Cells are not organized into tissues, body is in form of loose aggregation  of different kinds of cells.
• Tissue level of organization consists of a group of cells that work together to accomplish one or more specific functions.
• Organ level of organization is when two or more tissues work together for a specific function.