Which of the following animals have a single opening in their digestive system that serves both as a mouth and an anus?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) – Platyhelminthes
The correct answer is:
Platyhelminthes, commonly known as flatworms, have a digestive system with a single opening called a "gastrovascular cavity." This opening serves both as a mouth for ingesting food and as an anus for expelling waste. This type of digestive system is known as incomplete because it lacks a separate mouth and anus.
On the other hand:
- Arachnids: Arachnids, such as spiders and scorpions, have a complete digestive system with separate mouth and anus.
- Echinoderms: Echinoderms, like starfish and sea urchins, have a complete digestive system with separate openings for the mouth and anus.
- Arthropods: Arthropods, including insects and crustaceans, also have a complete digestive system with separate mouth and anus.