Q.54 On the basis of type of body cavity, platyhelminthes can be categorized as
1. Aceolomate
2. Schizocoelomate
3. Pseudocoelomate
4. Enterocoelomate
Title: Platyhelminthes Body Cavity Type: Acoelomate Classification Explained (MCQ Solved)**
Platyhelminthes (flatworms) lack a true body cavity and are classified as acoelomates.
Correct Answer: 1. Acoelomate
Flatworms fill the space between their outer epidermis and inner digestive mesenchyme with solid parenchyma tissue instead of a fluid-filled cavity. This acoelomate condition distinguishes them from more advanced bilaterians and influences their flattened body shape for diffusion-based gas exchange.
Body Cavity Classification
Acoelomate: No body cavity (Platyhelminthes, Porifera, Cnidaria).
Pseudocoelomate: False cavity not lined by mesoderm (Nematoda).
Coelomate: True cavity fully lined by mesoderm (Annelida, Chordata).
Explanation of All Options
| Option | Definition | Why Correct/Incorrect for Platyhelminthes |
|---|---|---|
| 1. Acoelomate | No body cavity; solid mesenchyme fills space. | Correct: Flatworms lack coelom/pseudocoelom. |
| 2. Schizocoelomate | Coelom forms by mesoderm splitting. | Incorrect: Requires true coelom (e.g., Arthropoda). |
| 3. Pseudocoelomate | Body cavity between mesoderm/endoderm. | Incorrect: Nematodes/rotifers; flatworms solid. |
| 4. Enterocoelomate | Coelom forms from mesoderm pouches. | Incorrect: Echinoderms/chordates; advanced coelomates. |
