Which of the following are correct ?
(i) Sponges : Cellular level of organisation
(ii) Cnidaria : Tissue level of organisation
(iii) Platyheminthes : Organ level of organisation
(iv) Annelids, Arthropods, Molluscs, Echinoderms and Chordates : Organ system level of organisation

Options

A. (i) and (ii) only
B. (ii) and (iv) only
C. (ii) and (iii) only
D. (i), (ii), (iii) and (iv)

Answer

To determine which of the statements regarding the levels of organization in different animal phyla are correct, we can analyze each statement one by one.

### Step-by-Step Solution:

1. **Sponges: Cellular level of organization**
- Sponges (Phylum Porifera) are indeed characterized by a cellular level of organization. They are multicellular organisms but lack true tissues and organs. Their body is composed of a loose aggregation of cells, which perform various functions. Therefore, this statement is **correct**.

2. **Cnidaria: Tissue level of organization**
- Cnidarians (such as jellyfish, corals, and sea anemones) exhibit a tissue level of organization. They have two distinct tissue layers: the outer epidermis and the inner gastrodermis, with a jelly-like substance (mesoglea) in between. They do not have true organs but have specialized cells for functions such as digestion and stinging. Thus, this statement is also **correct**.

3. **Platyhelminthes: Organ level of organization**
- Flatworms (Phylum Platyhelminthes) possess an organ level of organization. They have a more complex structure than sponges and cnidarians, with various organs formed from tissues. Although they lack a true coelom and have a solid body plan, they do have organs that perform specific functions. Hence, this statement is **correct**.

4. **Annelids, Arthropods, Molluscs, Echinoderms, and Chordates: Organ system level of organization**
- All these phyla exhibit an organ system level of organization. They have complex structures with multiple organs that work together to perform specific functions. For example, annelids have a segmented body with specialized organs, arthropods have exoskeletons and jointed appendages, molluscs have a muscular foot and visceral mass, echinoderms have a water vascular system, and chordates have a notochord and a central nervous system. Therefore, this statement is also **correct**.

### Conclusion:
All four statements are correct regarding the levels of organization in the respective animal phyla.

### Final Answer:
**All of the statements (i, ii, iii, iv) are correct.**

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