Final answer:
A complete digestive system is advantageous over an incomplete system as it allows for unidirectional flow and specialization within the digestive tract, leading to improved digestion, absorption, and waste elimination.
Step-by-step explanation:
A complete digestive system is characterized by having two separate openings; a mouth at the beginning and an anus at the end. This arrangement allows for a unidirectional flow of food through the digestive tract, optimizing the digestive process. The advantages of a complete system over an incomplete system, which has a single opening serving as both mouth and anus, include continuous feeding, the opportunity for different parts of the digestive tract to become specialized for various functions, and more efficient digestion and waste elimination.
For example, the complete digestive system allows an organism to ingest new food while simultaneously processing and absorbing nutrients from food already in the system and expelling waste, thus preventing any delay in the digestive process and facilitating continuous nutrient uptake. The segmented organization enables different regions of the gastrointestinal tract to specialize in certain tasks, such as the stomach for storage and initial digestion, the small intestine for nutrient absorption, and the large intestine for water absorption and feces formation.
Such specialization and a one-way flow increase the efficiency of the digestive process, making the complete digestive system an evolutionary advantage for many animals, including humans. This system is an integral part of the body for breaking down food, absorbing nutrients, and eliminating solid wastes.