Final answer:
Photoautotrophs like plants, algae, and photosynthetic bacteria use the sun's energy to perform photosynthesis, making them the primary energy source for Earth's ecosystems and the food webs within them.
Step-by-step explanation:
The sun's radiant energy is used by photoautotrophs, which are organisms such as plants, algae, and photosynthetic bacteria. These organisms convert the solar energy into chemical energy by the process of photosynthesis, creating substances like ATP (Adenosine Triphosphate) and NADP (Nicotinamide Adenine Dinucleotide Phosphate).
The energy stored in ATP is then used by photoautotrophs to synthesize complex organic molecules, such as glucose, which are essential for life processes. These photoautotrophs form the basis of the world's ecosystems, providing the primary source of energy for food webs, including both grazing and detrital food webs.
Moreover, the gross primary productivity is the measure of the rate at which these producers incorporate energy from the Sun. The energy left after respiration and growth, known as net primary productivity, is what is available to other organisms in the ecosystem, acting as a critical energy source for primary consumers in the food chain.