9 upvotes, 2 direct replies (showing 2)
View submission: Ask Anything Wednesday - Engineering, Mathematics, Computer Science
I have two questions, somewhat related to each other:
1. Why don't we see more blue in nature? Specifically, blue flowers, blue fruits and blue vegetables? I'm aware there's blueberries, gentian flowers and blue corn. But why are they rare rather than the norm?
2. What kind of chemical composition, atmosphere, etc. would be needed for beings with blue blood to exist? Is there something unique to Earth that means most animals have red blood?
Comment by [deleted] at 10/03/2022 at 10:51 UTC
3 upvotes, 0 direct replies
this is a complete hypothesis, but....
Blue is pretty damn close to the UV spectrum. If there was a pigment that appeared blue, then that would mean that it absorbs every other color *but* blue.
Such a pigment would also not stop UV light from damaging the host organism's tissues, and probably cause a lot of problems.
As for blue blood, it is caused by presence of a copper-containing molecule instead of iron-containing hemoglobin in the blood. Moreover, said molecule is not bounded to any blood cell, but floats freely inside the plasma.
It's great for when temperature fluctuations might be high, but has poor oxygen carrying capacity when compared with good ol red blood.
Comment by atomfullerene at 10/03/2022 at 19:40 UTC
1 upvotes, 0 direct replies
What kind of chemical composition, atmosphere, etc. would be needed for beings with blue blood to exist? Is there something unique to Earth that means most animals have red blood?
Blue blood animals exist right here on earth, using hemocyanin[1]. The most famous example is horseshoe crabs, you can see a pic here[2] which describes how medically useful horseshoe crab blood is (not necessarily because it's blue).
1: https://en.wikipedia.org/wiki/Hemocyanin
2: https://www.nhm.ac.uk/discover/horseshoe-crab-blood-miracle-vaccine-ingredient.html
As far as I know, hemocyanin and hemoglobin are vaguely comparable and the main reason most animals you know of have red blood is because they are vertebrates, and all have kept the same basic molecule of hemoglobin from the ancestral vertebrates that used it. They don't come by it independently, it comes from a common source. If the earliest vertebrate had happened to use hemocyanin, we'd all be using that.