Ascaris is characterized by

Options

A. Presence of true coelom but absence of metamerism
B. Presence of neither true coelom nor metamerism
C. Presence of true coelom and metamerism
D. Absence of true coelom but presence of metamerism

Answer

To solve the question regarding the characteristics of Ascaris, we can follow these steps:

### Step 1: Understand the classification of Ascaris
Ascaris is a type of roundworm that belongs to the phylum Aschelminthes (or Nemathelminthes). It is important to know the basic classification to understand its characteristics.

**Hint:** Remember the phylum classification and the general traits of organisms within that phylum.

### Step 2: Identify the habitat and lifestyle of Ascaris
Ascaris is commonly found as a parasite in the large intestine of humans. It can be found worldwide, and a single host can harbor a large number of these worms.

**Hint:** Consider the ecological role of Ascaris and its impact on human health.

### Step 3: Analyze the body structure of Ascaris
Ascaris is characterized by the presence of a pseudocoelom. Unlike true coelomates, which have a body cavity fully lined with mesoderm, Ascaris has a body cavity that is not completely lined.

**Hint:** Distinguish between true coelom and pseudocoelom when considering body structures.

### Step 4: Determine the segmentation of Ascaris
Ascaris does not exhibit metamerism, meaning its body is not segmented into repeated units. This is a key characteristic that differentiates it from segmented worms (like annelids).

**Hint:** Recall the definition of metamerism and how it applies to different groups of organisms.

### Step 5: Summarize the characteristics of Ascaris
Based on the information gathered:
- Ascaris has a pseudocoelom (not a true coelom).
- Ascaris does not exhibit metamerism (not segmented).

Thus, the correct characterization of Ascaris is the presence of neither true coelom nor metamerism.

**Final Answer:** The correct option is "presence of neither true coelom nor metamerism."