Evolutionists believe that progressive, evolution occurred in small, incremental steps from mutations (genetic, copying mistakes) which were preserved by natural selection because they provided a significant survival or reproductive advantage. In the evolution of the vascular system, blood would be no use without fully, evolved blood vessels and vice versa. Both of these would be of no use without a heart to pump the blood, which itself requires a pumped blood supply, as do the brain, lungs, other organs and muscles etc. So what evolved first?
2006-09-25 05:49:09 · 10 answers · asked by A.M.D.G 6 in Science & Mathematics ➔ Other - Science
Go ask the chicken (or is it the egg?)
2006-09-25 05:51:09 · answer #1 · answered by mistral23 2 · 1⤊ 4⤋
The function of blood is to transport dissolved substances. When tissue fluid is formed, the substances eg glucose, move by diffusion (moving from an area of high concentration to an area of lower concentration). If a body cavity was filled with blood, diffusion would still happen, but it would be a LOT slower and less efficient. Therefore having blood would still be useful, even without blood vessels. Blood vessels without blood on the other hand would be utterly pointless. Obviously the kind of organisms that have blood but no blood vessels are much smaller and simpler than humans, but they do exist.
2006-09-25 10:16:30 · answer #2 · answered by Kate W 2 · 0⤊ 2⤋
You skipped a possibility... there could be movement of soluble oxygen carrying molecules without the existence of blood cells. Easy to imagine such molecules diffusing between cells (interstitial space) or being sloshed about by body movements against a membrane in contact with oxygenated water. Special compartments might develop, that were not yet "vessels" and did not have active circulation, to bring those molecules in contact with the source of oxygen more efficiently. There would be some strict practical limits on how large/complex an organism could be with this approach.
Sorry, I'm speculating like an exobiologist now... or maybe not since we see such things in known organisms.
Aloha
2006-09-25 06:06:37 · answer #3 · answered by Anonymous · 1⤊ 2⤋
There are creatures such as flatworms that have open circulatory systems. These have no blood vessels, but they have fluid that serves the same role as blood.
Some insects possess hearts which maintain blood flow around their body cavities although they do not possess any blood vessels.
Worms have blood vessels and blood but no hearts as such. They move the blood through their bodies via peristalsis.
So your claim that heart, blood and circulatory systems are all essential elements that can only function when all three are present is incorrect.
This is fortunate for developing human embryos, otherwise they would have serious problems, since they initially develop a heart but have no circulatory system. Nonetheless they survive and grow.
So the answer to your question is that it doesn't actually matter which came first.
2006-09-25 06:04:35 · answer #4 · answered by Anonymous · 1⤊ 3⤋
It would be blood. There are a lot of creatures with an open circulation system--no blood vessels, but they have blood. And since they would have been formed first on the evolution scale...
Creatures with a fully developed vascular system are more complex and came later in evolution.
2006-09-25 05:57:36 · answer #5 · answered by willow oak 5 · 0⤊ 3⤋
Blood
2006-09-25 05:51:04 · answer #6 · answered by Sawcutting Shogun 3 · 0⤊ 2⤋
vessels came first. blood is only used as a means of transport and vessels have been used way before then by plants and sea critters. it would transport water minerals oxygen and many other things. vessels came before blood itself
2006-09-25 06:06:04 · answer #7 · answered by magic conor 2 · 0⤊ 2⤋
You are wrong, there are many primative animals that have blood but no vessels, including insects and arthropods. So, the blood started first.
2006-09-25 05:51:59 · answer #8 · answered by QFL 24-7 6 · 5⤊ 2⤋
Fascinating question, illuminating answers
2006-09-25 05:59:55 · answer #9 · answered by Anonymous · 0⤊ 0⤋
Well it would have had to be blood vessels;otherwise the blood would be sloshing about in the legs. It would be like having boots full of water !
Joke ! Duh.
2006-09-25 05:53:11 · answer #10 · answered by Tracker 5 · 1⤊ 2⤋