Symmetry in Animals

Animals exhibit various types of symmetry, such as radial symmetry, bilateral symmetry, and asymmetry. Radial symmetry is characterized by body parts arranged around a central axis, while bilateral symmetry involves a division of the body into two equal halves. Asymmetrical animals lack any specific symmetry. In this context, let's analyze the four animals mentioned and determine which one has different symmetry compared to the others.

1) Pila
- Pila is a type of freshwater snail that belongs to the class Gastropoda.
- It exhibits bilateral symmetry, which means its body can be divided into two mirror-image halves along a sagittal plane.
- The anterior and posterior ends of Pila are distinct, and it has a coiled shell that shows a spiral pattern.
- Therefore, Pila does not have different symmetry compared to the other three animals.

2) Sycon
- Sycon is a genus of marine sponge that belongs to the phylum Porifera.
- Sponges typically lack any specific symmetry and are considered asymmetrical.
- The body of Sycon is cylindrical, with numerous small pores called ostia on its outer surface.
- It also possesses radial canals and a central cavity where water circulates.
- Hence, Sycon does not have different symmetry compared to the other three animals.

3) Pleurobachia
- Pleurobachia is a type of comb jelly that belongs to the phylum Ctenophora.
- Comb jellies exhibit biradial symmetry, which is a combination of radial and bilateral symmetry.
- The body of Pleurobachia is elongated and possesses eight comb rows, which are ciliated structures used for locomotion.
- It also has two tentacles and a mouth opening associated with the comb rows.
- Therefore, Pleurobachia has different symmetry compared to the other three animals.

4) Asterias
- Asterias is a genus of sea stars, commonly known as starfish, belonging to the class Asteroidea.
- Starfish exhibit radial symmetry, with their body divided into multiple arms radiating from a central disk.
- The arms of Asterias are typically five in number, but some species may have more.
- Each arm contains numerous tube feet used for locomotion and feeding.
- Thus, Asterias does not have different symmetry compared to the other three animals.

Conclusion
Among the given animals, Pleurobachia shows different symmetry compared to the others. While Pila and Asterias exhibit bilateral and radial symmetry, respectively, Sycon is asymmetrical. Pleurobachia, on the other hand, demonstrates biradial symmetry, which is a unique combination of radial and bilateral symmetry.

Pila is bilaterally symmetrical and others are radially symmetrical