Final answer:
Food availability directly influences Paramecium populations with abundant food allowing for growth, and scarcity leading to competition, where Paramecium aurelia outcompetes Paramecium caudatum when resources are limited.
Step-by-step explanation:
The way food availability affects the populations of Paramecium can be observed in an experimental setting where different species, such as Paramecium aurelia and Paramecium caudatum, are grown together and compete for resources.
Individually, each species grows well, suggesting that when food is abundant and not a limiting factor, they can both thrive.
However, when these two species are placed together, the presence of competition evidently results in P. aurelia outcompeting P. caudatum for available food resources. This demonstrates that Paramecium populations are directly influenced by food accessibility—abundant food allows for better survival and reproduction, but limited food leads to competition and potential population decline of the less competitive species.