Historically, it was the Sun, which created the plant life and animal life used to make energy, and which formed fossil fuels. Even hydroelectric energy is dependent on solar heating to return water to its sources.
And because we now have nuclear energy, the answer could be "from nuclear reactions" -- fusion on the Sun and fission in nuclear generators.
This, however, neglects the use of tidal energy and geothermal energy. Tidal energy is caused primarily by the gravitation of the Earth and Moon, not the Sun. And geothermal energy is drawn from magma formed by crustal movements, which ultimately are driven by the Earth's hot core. The heat there is a combination of radioactive heat, tidal heat from the Sun's gravity, and energy left from the formation of the planet.
The ultimate source, therefore would have to be "gravity" because it formed the Sun and planets, keeps fusion going, moves the tides, and keeps the Earth's core hot enough to produce tectonics.
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A plant get it's food from it root. It's roots absorbs all the nutrients from the ground. by the roots and stem.
all living things use energy
The s orbital has the lowest energy level.
Kinetic energy
Tap roots