Question

Body organisation in Hydra is of
1. Tissue grade
2. Organ grade
3. Cellular grade
4. Organ system grade

Answer 1

Correct Answer - Option 1 : Tissue grade

Concept:

• Though all members of Animalia are multicellular, all of them do not exhibit the same pattern of organization of cells.
• Different groups exhibit different levels of body organization.
• For example, in sponges, the cells are arranged as loose cell aggregates, i.e., they exhibit a cellular level of organization.
• In coelenterates, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues, hence is called tissue level of organization.
• organ level is exhibited by members of Platyhelminthes and other higher phyla where tissues are grouped together to form organs, each specialized for a particular function.
• In animals like Annelids, Arthropods, Molluscs, Echinoderms, and Chordates, organs have associated to form functional systems, each system concerned with a specific physiological function. This pattern is called the organ system level of organization.

Explanation:

• Hydra belongs to the phylum Coelenterata. It exhibits tissue level of body organization.
• Here the cells performing the same function are arranged into tissues
• Hydra shows the polyp body form i.e. it is sessile and cylindrical