What are the levels of organization in an ecosystem starting from the most inclusive to the least inclusive?

Ecosystem, community, population,

The levels of organization from lowest complexity to highest are: species, population, community, ecosystem, biome and biosphere.

Since you are asking specifically about the levels of organization in an ecosystem, we leave out the levels of biome and biosphere since they are both more complex than ecosystem.

The most inclusive level in an ecosystem is the ecosystem itself.

An ecosystem includes all the living organisms and nonliving (abiotic) factors such as air, water, light etc.

Community is the next level to discuss - a community in an ecosystem includes all of the living organisms which live in the defined area of the ecosystem.

Population is the next least inclusive level - a population includes all the members of one species in a defined area.

Finally the least inclusive level is that of a species. This would be one individual member of a species.