What molecule acts as an electron donor in the light reactions of photosynthesis?

Compare and contrast the adaptations of free-living flatworms and parasitic flatworms

Pl as time goes by and water goes through the water cycle again and again, the amount of water on earth: increases decreases ostays the same goes up and down

The earth formed roughly 4.5 billion years ago, yet evidence of life dates back to about 3.5 billion years ago. which one is not a possible hypothesis of how life on earth arose?