What is the ultimate source of energy in a food web?

Question

ecology

Answer 1

Energy itself.

It used to be thought life could not exist without solar radiation, which was the source of all energy in ecosystems. Plants use solar energy to manufacture sugars from CO2 and H2O. The plant is turning one form of energy into another form. Sugar is solar energy which has been converted to chemical energy. Both plants and animals then use the sugars as an energy source. When the sugars are broken back down into CO2 and H2O, the energy is released. This differs from ordinary combustion, because the energy in combustion takes the form of heat and light. Ordinarily, animals don't produce heat or light when they metabolize sugars.

About 30 years ago, a community of deep sea creatres was discovered living around geothermal geisers at the bottom of the sea. The geisers ocurred where continental plates were being pulled apart. Ocen water seeped deep inside the earth, was heated and erupted as dense black clouds of superheated seawater water rich in minerals, hydrogen sulfide and CO2. Bacteria were using heat energy to turn hydrogen sulfide and CO2 into sugars in a process similar to the photosynthesis of plants.

Photosynthesis strips hydrogen atoms from water using solar energy. The hydrogen is combined with CO2 to form a simple carbohydrate, which is gradually built up into molecules of glucose. Thermosynthesis uses heat energy to strip hydrogen from hydrogen sulfide. Past this point, the process is the same as photosynthesis. Sugars are built up by combining hydrogen and carbon dioxide.

Thermosynthesis takes place without any solar energy, and is responcible for entire communities of deep sea organisms which benefit from thermosynthetic organisms turning heat energy into chemical energy in the form of sugars. Thermosynthesis was probably the original form of metabolism on the earth because it took millions of years for plants to evolve. It might be possible that thermosynthetic organisms exist on other places in the solar system. Jupiter's moon Europa is covered in ice, but there may be geothermal geisers forming pools of liquid water deep under the ice.

Answer 2

Before the sun, the big bang.

Answer 3

On this planet, it's the Sun.

Doug