The sun.
The original source of most energy on Earth is the sun. Solar energy provides the power for various processes like photosynthesis, which is the basis of the food chain and ultimately sustains all life on the planet.
The sun, or plants
carbon
Yes fats are the most calorific energy source.
The Sun
The original source of almost all energy in an ecosystem is the sun.
In most food webs the Sun is the ultimate source of energy. Some food webs start with chemotrophs and in those cases the source of the energy are chemicals often from underwater volcanoes.
Energy is most food does indeed come from sunlight. Producers are the most abundant food source and producers make their food from sunlight during photosynthesis.
water and electricity
sugars
Fats
Carbohydrates