Answer:
an ecosystem
Explanation:
All of the living things in San Fransisco make up an ecosystem.
A biological ecosystem, by definition, is a system of all the living organisms occupying an area who are in constant interaction with themselves and the non-living portion of their environments. In other words, an ecosystem is a community of all organisms in an area that interacts with each other and with the non-living components of their communities.
All the living things in San Fransisco, California would be made up of different communities of plants, animals, and microbes. These communities would definitely be interacting with themselves in one way or another and also interact with the abiotic components of their environment. Hence, they together constitute an ecosystem.
