Which animal phylum is characterized by body asymmetry?

Which animal phylum is characterized by body asymmetry?

• A. Porifera
• B. Cnidaria
• C. Platyhelminthes
• D. Echinodermata

Answer: (A)

Understanding symmetry patterns in animals helps group them. Some groups have a defined axis of symmetry, while others do not. Porifera, the sponges, lack true tissues and do not have a consistent left-right or central axis; their bodies are irregular and built around pores, so they are described as asymmetrical. In contrast, cnidarians exhibit radial symmetry around a central axis, flatworms show bilateral symmetry with a distinct head region, and echinoderms have fivefold (pentaradial) symmetry as adults (though their larvae are bilateral). So the phylum characterized by body asymmetry is Porifera.

Understanding symmetry patterns in animals helps group them. Some groups have a defined axis of symmetry, while others do not. Porifera, the sponges, lack true tissues and do not have a consistent left-right or central axis; their bodies are irregular and built around pores, so they are described as asymmetrical. In contrast, cnidarians exhibit radial symmetry around a central axis, flatworms show bilateral symmetry with a distinct head region, and echinoderms have fivefold (pentaradial) symmetry as adults (though their larvae are bilateral). So the phylum characterized by body asymmetry is Porifera.