Which of the following is a feature of the digestive tube in most animal phyla?

• A. A complete digestive tract with a separate mouth and anus
• B. Digestion occurring entirely outside the body
• C. A single opening serving as both mouth and anus
• D. Absence of specialized regions for digestion

Answer: (A)

Verified step by step guidance

1. Understand the structure of a complete digestive tract: It typically consists of a continuous tube with two separate openings, a mouth for intake and an anus for waste elimination.
2. Recognize that a complete digestive tract allows for a more efficient digestion process, as food moves in one direction and can be processed in specialized regions.
3. Consider the alternative options: Digestion occurring entirely outside the body is not typical for most animal phyla, as internal digestion allows for better nutrient absorption.
4. Evaluate the option of a single opening serving as both mouth and anus: This is characteristic of a gastrovascular cavity, found in simpler organisms like cnidarians, not most animal phyla.
5. Identify the absence of specialized regions for digestion: This is less efficient and not a feature of a complete digestive tract, which typically has specialized regions for different digestive processes.