Mother?

[Twizeguy]

I had this thought one day; Every living thing on earth besides plants needs plants to survive. So would it not be safe to say plants are critical to the evolution of all living things that are not photosynthetic?

[lemur]

I just posted the question in another thread whether there are any non-living processes that create hydrocarbons (or carbohydrates or any other fuel). If not, I would say that plants are the mothers from which all life and even non-living machines "nurse." Actually, I am forgetting about those deep-sea organisms that utilize geothermal heat, though I don't know how that works. Many animals and plants use water and wind power to assist them in various ways but I don't think there's such a thing as a living organism that can convert these forms of energy into consumable sugars the way photosynthesis does with sunlight. This all seems very simple in my mind, so maybe I am forgetting about something.

[Arete]

As with almost all good scientific questions, the answer is yes, and no... generally, organisms can be divided into autotrophs - those which can fix inorganic carbon into complex organic compounds and heterotrophs - those which can't.

 

Autotrophs can be further divided into photoautotrophs - those which use photosynthesis (plants, algae, phytoplankton, cyanobacteria etc) and chemolithoautotrophs - those which are able to synthesize organic carbon compounds using chemical reactions - these are exclusively microbial and support communities like the deep sea vent systems. In addition to these, "radiotrophic" fungi was found surviving inside the Chernobyl nuclear reactor and is theorized to have been harnessing energy from radiation.

 

Heterotrophs can be divided into organotrophs - animals, bacteria, fungi etc which get their resources from complex organic compunds produced by other organisms. Photoheterotrophs, such as purple and green bacteria can sythesize ATP using light but build require organic compounds to create structures.

 

Then there's mixotrophs - some sulfur bacteria which can do both.

 

So in the typical macro scale ecosystems we tend to observe and think of, the basis of energy production is photosynthesis of organic compounds by photoautotrophs, which are then used by all the organotrophs which eat them, but a variety of other systems demonstrate that photosynthesis is not a requirement for the evolution of life.

 

edit - spelling fail

Edited June 3, 2011 by Arete

[CharonY]

Well, radiotrophy is probably overstated. But simply put, many bacteria are able to fix carbon (the mentioned autotrophs). As such the premise is inaccurate that plants are needed for every organism. Of course, the first photosynthetic organisms were bacteria, not plants.

 

The first organisms used anaerobic respiration (iron is a good candidate) to generate the energy for carbon fixation. Bacterial photosynthesis came way later.