Final answer:
The assertion that photosynthetic organisms only release oxygen and nonphotosynthetic organisms only release carbon dioxide is false. Both types of organisms can produce CO₂, and photosynthetic organisms such as cyanobacteria were responsible for the oxygenation of the early Earth's atmosphere after non-photosynthetic, anaerobic organisms.
Step-by-step explanation:
The statement that 'photosynthetic organisms release only O₂ into the atmosphere, while nonphotosynthetic organisms release only CO₂' is false. Photosynthetic organisms, like plants, do release oxygen (O₂) as a by-product of photosynthesis, but they can also release carbon dioxide (CO₂) through cellular respiration, especially during the night when photosynthesis does not take place. Nonphotosynthetic organisms, such as animals, predominantly release CO₂ as a product of cellular respiration. However, there are exceptions, such as anaerobic bacteria that can release different by-products.
When considering the history of life on Earth, it is believed that non-photosynthetic organisms evolved before photosynthetic organisms because there was no free oxygen in the atmosphere when life began. The presence of carbon dioxide (CO₂) suggests that the first organisms were likely anaerobic.
Oxygen began accumulating in the atmosphere after the evolution of photosynthetic organisms like cyanobacteria, which produced oxygen as a by-product. This significant event, known as the Great Oxidation Event, marked a critical point in Earth's history and paved the way for the evolution of aerobic life forms that utilize oxygen for cellular respiration.