# How would endo-skeletal systems adapt to the atmospheric pressures given?

Surface gravity:

• 1G

Info regarding of altitude, pressure, and atmospheric density:

altitude    pressure    density
(meters)    (atm)       (kg/m^3)
0           17          10
1000        15.3        9
2000        13.8        8.1
3000        12.5        7.3
4000        11.3        6.6
5000        10.1        6
10000        6          3.6
15000        3.6        2.1
20000        2.2        1.3
30000        0.8        0.5
40000        0.3        0.2
50000        0.1        0.06


What adaptations would endo-skeletal systems have based on higher atmospheric pressure but earth-like gravity. Could the bones be slimmer, could they be pneumatic / hydraulic? Could they be looser? Could they have a special external coating? Would they be supported better by higher pressures thus making bones slimmer? Etc. NOTE: The data for my atmosphere may not be entirely correct, but nonetheless, that's not my focus here, my focus is how this much of an atmospheric pressure AT the surface would have impact on the evolution of endo-skeletal systems.

• Looking at your numbers and applying the ideal gas law suggests that you are keeping temperature almost constant at all altitudes, which seems very unlikely in a realistic scenario. Venus might be a useful model to work from because a one-gee planet with that kind of surface pressure would probably be like Venus' extreme greenhouse one. But Venus would not have such a uniform temperature gradient either. – StephenG Dec 2 '18 at 13:10
• Honestly, I'd like to get the realistic temperatures, thank you for mentioning this. But as of now I don't know how to calculate this, still working on it. I'd need help with that later on, but thank you for your mention! ^^ @StephenG – Neuryte Dec 2 '18 at 19:27
• I get 180C at sea level. Mighht be useful onceinawhale.com/2013/06/03/down-to-the-bone – Giu Piete Dec 7 '18 at 7:15
• @GiuPiete, that depends on the distance from the star, you've probably plopped it near where earth is, mines is further away from the star in the habitable zone. – Neuryte Dec 7 '18 at 20:48

## 1 Answer

One key misconception to avoid is the assumption that you will be much lighter at the higher elevation. At 40,000 feet elevation for example, you've only increased your distance from the CoM of an earth sized planet by 1%, but the difference in buoyancy between 10 and 0.2 kg/m^3 is also about 1% mass displacement since most organisms have a mass of about 1000 kg/m^3.

As far as pressures go your ground level would have an atmospheric pressure equal to a ~560 feet under water. Since bony fish can survive 20x that deap without significantly different bone structures than their shallow water counterparts, I'd assume the skeletons of animals on this planet would be mostly unaffected by these extreme conditions. Instead the biological differences would be much more subtle such as different respiratory systems, or other adaptations designed to take advantage of the high/low density atmospheres or the temperatures and other environmental features these differences create.

• different bone structures/compositions are a large part of what allows, for instance, aquatic mammals to survive pressure. it's not really a 'mostly unaffected' change...still props for being the first person brave enough to answer. – Giu Piete Dec 7 '18 at 20:53
• Metabolism changes a lot because protein folding works differently under pressure, but overall bone structure is mostly unaffected. So, on a celular scale life will be different at different elevations if that is what you mean, but a full range of things like porous bird bones or dense mammal bones would all be fine at higher or lower pressure as long as the pores are filled with equal pressure gases as the environment, or a noncompressive liquid like water. – Nosajimiki - Reinstate Monica Dec 7 '18 at 21:41
• onceinawhale.com/2013/06/03/down-to-the-bone I'll stop trying to push you towards making a more comprehensive answer! =) – Giu Piete Dec 7 '18 at 22:24
• Thats a uniquely whale adaptation and there is no evidence it is related to pressure, whales have high density bones for buoyancy control because they have to have air filled lungs. – John Dec 7 '18 at 22:55
• @john Exactly, and since this hypothetical atmosphere only has density of 10kg/m^3, buoyancy adaptations are not needed. – Nosajimiki - Reinstate Monica Dec 7 '18 at 23:07