Praxis II: Biology Content Knowledge Exam Prep

Answer: D, According to the heterotroph hypothesis, the false statement is that the dominant species on Earth today descended directly from the anaerobic autotrophs and heterotrophs. Those species in fact descended from the aerobic autotrophs and heterotrophs.

Key Takeaway: According to the heterotroph hypothesis, the first organisms to arise were the unicellular heterotrophs which were incapable of creating their own food but instead fed on the primordial soup that covered the planet. These organisms released carbon dioxide into the atmosphere, which gave rise to the photosynthetic autotrophs that could create their own food with carbon dioxide and sunlight. These organisms released oxygen into the atmosphere, which was toxic to the anaerobic hetorotrophs. Those that survived evolved over time into the aerobic heterotrophs that could carry out cellular respiration. The aerobic organisms became dominant and gave rise to the dominant species on the planet today.