Question

what are two hypotheses about the source of organic molecules on earth

Answer 1

The combination of gases like methane, ammonia, hydrogen, and water in the atmosphere with lightning most likely contributed the most organic molecules early in the Earth's history. Such conditions were recreated in the Miller-Urey experiment in the 50's and they were able to produce a huge variety of organic molecules, including more amino acids than are used in your body, some sugars, and lipids.

I think it has also been proposed that early organic molecules were introduced to the Earth through meteorites. Although I've always wondered where the organic molecules on such meteorites came from.