Human Intestines: Comparing Worms & Humans

[Pranav Jha]

Nourishment is obtained from food through the inner surface area of the intestines. Why is it that a small organism, such as a worm, has a simple and relatively straight intestinal tract, while a large organism, such as a human being, has a complex and extensively folded intestinal tract?

i think this has to with greater surface area to volume ration of earthworm and thus a higher metabolic rate but i am not sure.
Please give a coherent answer

 

[madcat8000]

I think you are right.

 

[spacester]

Nourishment is obtained from food through the inner surface area of the intestines. Why is it that a small organism, such as a worm, has a simple and relatively straight intestinal tract, while a large organism, such as a human being, has a complex and extensively folded intestinal tract?

i think this has to with greater surface area to volume ration of earthworm and thus a higher metabolic rate but i am not sure.
Please give a coherent answer

Earthworms (order Haplotaxida, suborder Lumbricina) have a crop, gizzard and intestine. Food is stored in the crop, passed to the gizzard where it is ground up and enzymes are added, and the intestine actually extracts the nutrition. The intestine runs most of the length of the body, it has thousands of projections that are filled with blood vessels.

The main thing to understand is that earthworms have a special relationship with bacteria. Yes, humans have lots of flora and fauna in our guts too, but worms basically swim in a sea of bacteria. They are at the top of their food chain and the enzymes secreted in the intestine work with the bacteria so that the earthworm gets its nutrition but many beneficial bacteria will pass through unharmed. Most pathogenic bacteria are destroyed.

I'm not a biologist and I am trying to give you a coherent answer. My understanding is that the specifics of this bacterial/enzymatic system are poorly understood on a detailed level.

My best answer is that it's not a matter of metabolic rate per se but a matter of efficiency and simplicity.

The worm's digestive system is highly evolved and efficient and there are normally no microorganisms it cannot deal with. On the other hand, we are omnivores with much less efficient systems. Our feces stink because there is so much organic matter that we could not extract nutrition from. Earthworm castings are essentially "perfect" feces in that they consist of "completely broken down" organic material, where the minerals are highly available to plant rootlets. The castings are also coated with a mucus consisting of (IINM) live bacteria that do great things for the soil.