Question

One example of animals having a single opening to the outside that serves both as a mouth as well as the anus is?

• A. Fasciola
• B. Octopus
• C. Asterias
• D. Ascidia

Answer 1

The correct option is A

Fasciola

The correct option is A:

Explanation for Correct option:

1. The body of a Fasciola (flatworm) has only one cavity with one opening to the outside.
2. The single orifice serves as both a mouth for ingestion (food intake) and anus for egestion (undigested food is passed out).
3. It's known as the blind sac plan.
4. Coelenterates are another example.

Explanation for Incorrect option:

Option B:

1. Octopus has a complete alimentary canal in a tube inside a tube organization, with two separate entrances in the body that operates as mouth and anus, respectively.

Option C:

1. Asterias is a rubric of ocean stars belonging to the Asteraceae family.
2. In Asterias, the alimentary canal is tubular, straight, short and extends vertically along the oral-aboral axis in the central disc.
3. It starts with the mouth and terminates in the anus.

Option D:

1. The incurrent oral (branchial) siphon and the out current atrial siphon are both present in each ascidian.

Final answer: One example of animals having a single opening to the outside that serves both as a mouth as well as the anus is Fasciola.