Question

What is the ultimate source of energy for organisms?

Answer 1

Hint: The ultimate source of energy for almost all organisms on earth provides energy to organisms through the process of photosynthesis. Autotrophic organisms produce carbohydrates that are passed down through the food chain.

Complete answer:
Sunlight is a part of the electromagnetic radiation emitted by the Sun. It is generally composed of infrared, ultraviolet and visible light. The ultraviolet radiation emitted by the sun has both useful as well as harmful consequences. The UV radiation is a prerequisite for the synthesis of vitamin $D_3$. UV radiation is also a mutagen that causes skin cancer.
Sunlight plays a major role in photosynthesis.
Nearly all life on earth exists because of sunlight. Almost all organisms on earth ultimately receive their energy from the Sun. Autotrophic organisms use the energy of the Sun with the help of carbon dioxide and water to produce simple carbohydrates. This process is known as photosynthesis. The process of photosynthesis allows the growth of autotrophic organisms. Heterotrophic organisms use sunlight as an energy source by consuming autotrophic organisms and/or their products. The sugars and other components present in the autotrophic organisms break down in the heterotrophic organisms. This provides solar energy to the heterotrophic organisms. This energy is necessary for the survival of the organism. The process of using the autotrophic nutrients to derive energy for survival is known as cellular respiration.

Note:
Photosynthetic autotrophs convert the light energy from the sunlight into chemical energy. This chemical energy is used for the synthesis of carbohydrates and energy to fuel the basic activities of an organism.
Prehistoric humans gathered plants to derive energy from them. These skills were passed down to later generations.