Question

why do humans and animals rely on photosynthesis to survive?

Explanation:

Photosynthesis by plants produces oxygen for respiration and forms the base of the food - chain providing energy - rich organic compounds.

Answer:

Humans and animals rely on photosynthesis because plants produce oxygen during photosynthesis which is essential for their respiration, and plants also form the primary source of food providing energy - rich organic substances for herbivores, which in turn are consumed by carnivores and omnivores.