What is the primary source of energy for all ecosystems on Earth, except for the deep-sea hydrothermal ecosystem?

Solar radiation

The correct answer is Option (1)-  Solar radiation.

Solar radiation is the primary source of energy for all ecosystems on Earth, except for the deep-sea hydrothermal ecosystem. Sunlight provides the energy required for photosynthesis, the process by which plants and some other organisms convert solar energy into chemical energy stored in organic compounds.

In most ecosystems, plants, algae, and some bacteria, collectively known as autotrophs or producers, utilize sunlight through photosynthesis to produce organic molecules. This process involves capturing solar energy and using it to make food from simple inorganic materials.

The organic molecules produced by autotrophs serve as a source of energy and nutrients for all other organisms in the ecosystem. Through consumption, energy flows from producers to consumers, such as herbivores (primary consumers), carnivores (secondary consumers), and so on, forming food chains and food webs.