Answer:
ecosystem
Step-by-step explanation:
The level of organization shown in the example is "ecosystem" because the example represnts interaction between two different population with acorns on the land.
Ecosystem is defined as the interaction of groups of organisms in biological domain with abiotic enviornment.
The example, groups of organisms include "squirrels and birds" and abiotic enviornment include "acorns" or "nuts".
Hence, the correct option is "ecosystem".