Discuss test grade. Define and discuss the steps involved in the heterotrophic hypothesis which deals with the origin of life on Earth. Introduce the steps from the formation of the planet and the original atmosphere through the formation of the hot sea. Discuss how the original atmosphere formed amino acids and then basic proteins. Discuss why heterotrophs would have appeared before autotrophs. Define and discuss heterotrophs and autotrophs. Discuss why and how heterotrophs would lead to aerobic autotrophs.