Pick the odd pair out.

Options

A. Cellular level: Porifera
B. Tissue level : Aschelminthes
C. Organ level : Phatyhelminthes
D. Organ system level : Annelida

Answer

To solve the question of picking the odd pair out, we will analyze each option based on the level of organization associated with the respective phyla mentioned.

### Step-by-Step Solution:

1. **Analyze Option A: Cellular Level - Porifera**
- Porifera (sponges) exhibit a cellular level of organization. This is correct as they are the simplest animals and do not have true tissues or organs.

2. **Analyze Option B: Tissue Level - Echinoderms**
- Echinoderms (like starfish) actually exhibit an organ system level of organization, not a tissue level. The tissue level of organization is typically seen in Cnidarians (like jellyfish) and Ctenophores (like comb jellies). Therefore, this pair is mismatched.

3. **Analyze Option C: Organ Level - Platyhelminthes**
- Platyhelminthes (flatworms) do show an organ level of organization. This is correct as they have developed organs but not organ systems.

4. **Analyze Option D: Organ System Level - Annelida**
- Annelida (segmented worms) do exhibit an organ system level of organization, which is correct. They have complex organ systems that allow for more advanced functions.

### Conclusion:
The odd pair out is **Option B: Tissue Level - Echinoderms**, as Echinoderms do not have a tissue level of organization; they have an organ system level.

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