Edit: Why do **some** mushrooms…
In: Biology
You would need some mechanism to push the spores up and out into the world. Gills on the bottom allow gravity to do the work. So on top might not be better.
However, the real answer is simply, evolution is not intelligent. The mutation or mutations that led to gills being what they are “worked” enough that they propagated. Maybe one day there will be a mushroom with a mutation that causes the gills to grow upside down, and maybe it will work and be successful or maybe it will die out. Maybe this has already happened.
I’m no expert, but I’ve seen spores pool at the top of fruiting bodies before, so I don’t think they struggle with passing on the seed. Maybe they’re on the underside as some defense mechanism.
I know at least one mushroom that spreads its spores topside. A puffball. We used to step on them for fun, to see spores spread like dust.
The gills wouldn’t be protected from the water and would be damper longer, Dry conditions are optimal.
There is nothing to carry the spores out, and they would get drenched/flooded by the rain as they developed. This would end up breaking the mushroom itself due to the weight of the water pooling in the gills.
Instead mushrooms rely on gravity. Most spores are not sticky, and the simply fall out of the gills.
As someone else pointed out, evolution does not have a goal. It’s random, and this is the solution that ended up being most successful (so far).
Since mushrooms have been around for millions of years and have flourished, they probably have the design that’s most compatible with life now.
I just want to add that everyone’s saying that gravity is the force that pulls the spores out of a mushroom are not technically correct.
There’s a process called Ballistospory the mushroom uses to eject the spores out of it’s gills. Because the spores are literally microscopic, they have very little mass, therefore they need an incredible amount of force to ‘throw” them.
Long story short, the spores experience over 5000 G’s of force to be shot out of the mushrooms.
Don’t morel spores spread from everywhere on the cap?
Mushrooms generally grow them on the bottom because either mutations that caused them to grow on top were not evolutionarily advantageous enough to dominate (‘it’s not better to grow on top’) or such mutations never happened (‘it may be better, but it hasn’t been tested’).
You’re not wrong, but you’re wrong.
First, not all mushrooms are gilled. One of the first things we learn in my country when wanting to learn to forage mushrooms is the main categories of undersides:
– Gills
– Pores
– Spikes
– Swamp
– Ridges
– Others (like puffballs)
In my country, all the horrendous poisonous ones are gilled. The 4 other categories are easier to learn and easier to be safe with. However. There are some really, really good gilled mushrooms, and it’s important to learn them.
However; I’m going on a complete tangent to what you’re asking. I’m not going to try to answer that. I just wanted to point out that gilled mushrooms is only one of many.
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