Which of the following statements is TRUE regarding the earliest photosynthetic organisms on Earth? A)These organisms likely possessed two photosystems. B)Given the abundance of H₂O on early Earth, these organisms used H₂O as an electron donor. C)The organisms likely used molecules other than water (i.e., H₂S)as electron donors. D)The organisms likely produced oxygen as a waste product, resulting in Earth's current atmosphere. E)These organisms likely used both inorganic molecules and water as electron donors.

Question

Quizplus · Accepted Answer

The earliest photosynthetic organisms likely used molecules other than water as electron donors, since the oxygen produced by photosynthesis would have reacted with the abundant iron and other minerals in the oceans at that time. H₂S is a commonly proposed electron donor for these organisms. There is no evidence that they possessed two photosystems, used H₂O as an electron donor, or produced oxygen as a waste product. While some later photosynthetic organisms may have used both inorganic molecules and water as electron donors, this is not believed to be the case for the earliest photosynthetic organisms.

Which of the Following Statements Is TRUE Regarding the Earliest