Besides Annelida and Arthropoda, true metamerism is found in

Options

A. Ctenophora
B. Mollusca
C. Chordata
D. Porifera

Answer

To solve the question "Besides Annelida and Arthropoda, true metamerism is found in?", we will analyze the options provided and determine which of them exhibit true metamerism.

### Step 1: Understand the Concept of Metamerism
Metamerism refers to the division of the body into segments, both internally and externally. True metamerism means that this segmentation is consistent throughout the organism and is reflected in both the external morphology and internal organization.

**Hint:** Remember that true metamerism involves both external and internal segmentation.

### Step 2: Analyze the Options
We have four options to consider: Ctenophora, Mollusca, Chordata, and Porifera.

1. **Ctenophora**: While Ctenophora may show some form of segmentation, it is not considered true metamerism. This is because their body structure does not reflect consistent segmentation throughout.

**Hint:** Look for organisms that have a clear and consistent segmentation pattern.

2. **Mollusca**: Mollusks do not exhibit metamerism. Their body structure is not segmented in the way that true metamerism requires.

**Hint:** Recall that not all animal phyla exhibit segmentation.

3. **Chordata**: Chordates, which include vertebrates and some invertebrates, do exhibit true metamerism. This is evident in their segmented body plan, which includes structures like the vertebral column and segmented muscles.

**Hint:** Consider the complexity of the organism when determining if it has true metamerism.

4. **Porifera**: Sponges (Porifera) do not show any form of metamerism. They are simple organisms without a segmented body structure.

**Hint:** Think about the evolutionary complexity of the organism when assessing metamerism.

### Step 3: Conclusion
After analyzing all the options, we find that the only group that exhibits true metamerism, besides Annelida and Arthropoda, is **Chordata**.

**Final Answer:** Option C - Chordata.