The assemblage of plants, animals, and microbes that constitute the living portions of ecosystems are collectively referred to as the biota.

Here's a breakdown of why:

* Biota is a collective term for all living organisms in a particular region or time period. It encompasses plants, animals, fungi, bacteria, and all other living things.

* Ecosystem refers to the community of living organisms (biota) in a particular environment, interacting with each other and with their non-living surroundings (abiotic factors).

So, the biota represents the living components of an ecosystem, interacting and shaping the environment.