Yup. Ecosystems can be understood at different scales, though conventionally when biologists use the term they mean landscape scale interactions. Still, I remember a professor who took the metaphor of human-body-as-ecosystem to make an interesting point about overuse of topical anti-bacterials. They likened using those to clear cutting a forest - a wholesale destruction of an entire functional ecosystem dominated by benign actors just for the sake of removing a handful of weeds. And, just like clear cutting a forest, it's the weedy stuff that grows back first - the stuff that's more aggressive, pioneering, or invasive. The benign stuff of that forest takes longer to come back and recreate a healthy ecosystem. Since understanding this, I more or less refuse to use those topical anti-bacterial products unless there's extenuating circumstances to justify it (e.g., the pandemic).
"Kills 99.9% of germs!" Yeah, well, 99.9% of those "germs" are benign and not a problem to begin with and won't make you ill! Not that the capitalist marketers care about that little detail.
As for non-heterotrophic organisms, pretty sure there's some deep sea life that's autotrophic but not photosynthetic. Also, folks forget that microorganisms exist. Bacteria and the like. They're the overwhelmingly vast majority of life on this planet and sustain themselves through all sorts of methods - chemistry masterminds of the planet. Not really my area of expertise, though. But remembering our single-celled friends just makes me laugh whenever some human says something to the degree of "our species could destroy all life on earth." No. No, we really couldn't.
