Final answer:
True, the absence of photosynthetic organisms would eventually lead to the suffocation of animal life due to oxygen depletion, as these organisms are essential for converting carbon dioxide into oxygen, which is critical for the survival of aerobic life forms.
Step-by-step explanation:
The statement that if all photosynthetic organisms died, animal life would eventually suffocate due to lack of oxygen is indeed true. The Earth's atmosphere was anoxic for the first two billion years or so, without molecular oxygen, and only anaerobic organisms could survive.
It was not until photosynthetic organisms, specifically cyanobacteria, evolved that the atmosphere became oxygenated, allowing for the proliferation of aerobic life forms and creating the foundation for our current ecosystem where oxygen-breathing organisms depend on the oxygen produced by photosynthetic plants and algae.
Before the existence of phototrophs and subsequent cyanobacteria, the Earth's atmosphere contained primarily carbon dioxide, a fact underscoring the importance of photosynthetic organisms in transforming it into oxygen. The absence of these organisms would halt the production of oxygen, leading to depletion of the gas in the atmosphere, making it inhospitable for current aerobic life forms.
This would profoundly affect ecological balances, disrupt food chains, and ultimately, without replenishment from photosynthesis, animal life would asphyxiate due to the eventual lack of breathable air.