What is the advantage to having a tubelike digestive system verse a saclike digestive system?

Answer 1

Seems like a tubelike digestive system would be more streamlined and function smoother. Get a saclike system and you end up chewing your cud like a cow.

Answer 2

Tubelike might also be longer, and therefore have more surface area than a saclike digestive system would, which means that the organism would be able to absorb more nutrients, and waste less.

Answer 3

sac GI system is in the Cnidarians (jellyfish, hydra, coral, etc) and some Platyhelminthes (some flat worms) and is called INCOMPLETE. It is one-way and food and wastes go in and out the same opening. Simple enzymes, but not as complex as below. Also less surface area involved.

Longer tube GI system is in Nematodes on up the evolutionary ladder in zoology, thus MOST animals are included here. It is called COMPLETE GI tract since it goes from mouth to anus, and there is a lot more surface area for absorption of nutrients. Also the mouth and anus are USUALLY far enough apart so that there is a long tube for more complex digestion,enzymes, accessory structures and more GI tract organs which can specialize their actions (mechanical and digestive processes of diverse food) so food and wastes don't don't have to be mixed like in inc "sac" digestion.