Which group of Kingdom Animalia has unsegmented, bilaterally symmetrical, soft bodies, with a triploblastic construction (comprising three layers of cells) and a lacking coelom, skeleton and anus?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. Platyhelminthes.
The group of Kingdom Animalia that fits this description is the Phylum Platyhelminthes, commonly known as flatworms.
Explanation:
- Unsegmented Bodies: Flatworms have bodies that are not divided into segments, unlike annelids (segmented worms).
- Bilateral Symmetry: Their bodies are bilaterally symmetrical, meaning they have a left and a right side that are mirror images of each other.
- Soft Bodies: Platyhelminthes have soft, flexible bodies without any hard skeletal structure.
- Triploblastic Construction: They are triploblastic, which means their bodies are derived from three primary germ layers during embryonic development: the ectoderm, mesoderm, and endoderm.
- Lack of Coelom (Acoelomate): Flatworms do not possess a coelom, which is a body cavity lined by mesoderm. Instead, they are acoelomate, meaning their body cavity is filled with mesenchyme, a type of connective tissue.
- Absence of a Skeleton: They lack any form of internal or external skeleton, relying instead on their soft body for movement and structure.
- Absence of an Anus: Unlike more complex animals, flatworms lack an anus. They possess a single orifice that functions as both the mouth and the excretory aperture, necessitating the expulsion of undigested waste through the same opening where ingestion occurs.
These characteristics make Platyhelminthes unique among the invertebrates and distinguish them from other groups in the animal kingdom.