Question

mid-term review
the sun holds a pivotal role in ecosystems due to its function as the primary energy source. through the process of photosynthesis, plants harness the suns energy as primary producers. herbivores rely on these plants for sustenance, and this energy transfer continues up the food chain. the sun provides 99% of the energy that living things use. other sources include underground volcanoes.
where does the energy for over 99% of the living things on earth come from?
the sun
plants
thermal vents

Explanation:

The text explicitly states that the sun provides 99% of the energy that living things use, serving as the primary energy source for ecosystems via photosynthesis and food chain transfer.

Answer:

the sun