Question: Are there are any serious biological or evolutionary plausibility issues with separating the energy storage/production function from the production of structural/regulatory biomass?
Background: In terrestrial life biomass is initially produced by plants which produce carbohydrates and related molecules (like lipids) from photsythesis. The carbs (and related sugars, lipids etc) fulfil structural and energetic functions.
My alien life on the other hand takes the same carb-based approach for biomass which is not related to energetics, but uses alternative molecule species for energy storage/generation.
Why? My alien lives on a planet with 70% H2 atmosphere on a super earth large enough to have retained such an atmosphere. My plants generate standard carb based biomass using photosynthesis which imports methane and sunlight and exports hydrogen. See my previous question here for details. Creation of this biomass is very efficient (4-5x) in the H2 atmosphere compared to terrestrial photosynthesis for reasons I won't go into here (but see the link if interested) but the downside is that 'burning' this biomass in the H2 atmosphere produces 4-5x less than oxidising it in an O2 based atmosphere.
So my alien animals don't use carbs for energy, they use an alternative molecular species (which for now I'll call a 'pharb') which unlike carbs, produce a good amount of energy when reduced with hydrogen (e.g. the reverse of oxidation).
The 'pharb' is still carbon-based. We are not talking about non carbon metabolism here.
I have two classes of plants:
- primary plants which are the least complex type of autotrophic life which use carbs for energy storage/generation. They grow prolifically.
- secondary plants (call them 'phlants') which either unilaterally or in symbiosis with something else( e.g. fungi) can produce the more energy rich (in the reducing H2 atmosphere) pharbs. These secondary phlants are not all pharb, they use carbs for structure since this is efficient. Parts of their anatomy may be where the pharbs are stored (think of pharb based fruits, nuts, saps etc). Phlant biomass is approx 10 times rarer, or more, than plant based biomass.
- primary heterotrophs (animals) which feed on the primary plants. These must be very simple creatures with slow metabolisms since they have access to only 20% of the energy terrestrial oxidising life has access to.
- secondary heterotrophs (phanimals) which feed on the secondary 'phlants'. Thanks to their diet being pharb based, they have access to similar energy as terrestrial animals. They can digest primary plant carb based biomass, but cannot use this biomass for access to energy. The structural elements of their bodies are carb based but the muscle and energy storage/generation pathways are pharb based. Phanimal biomass is approx 100 times rarer than animal biomass.
- my sapient aliens are phanimals.
Surface gravity and temperatures are earth-like. Surface area is much higher because its a super earth.
Insolation levels at wavelengths suitable for the described photosynthesis process are earth-like.
There is plenty of open water, seas etc. All my lifeforms need water same as terrestrial life.
The methane which is required as the primary input into the primary plant photosynthesis cycle (analogous to CO2 on earth) is regenerated reliably within the ecosphere.
All in all, its a great place for life; as long as the heterotroph energy source problem is solved by use of pharbs.
Assuming such 'pharb' molecules exist*, are there any scientific problems with constructing a rich setting for a sapient civilisation at tech levels similar to 1000-2000AD on this plant?
What are the most obvious differences with the earths ecosystem going to be?