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A species is a named unit of biological classification. The useful criteria vary among groups: reproductive compatibility can inform classification in many animals, while microbial comparisons also use genomes and other characters. Escherichia coli is a species; K-12 MG1655 identifies a particular strain within it. See OpenStax Biology 2e, 18.2: species concepts.

Zooplankton are drifting aquatic consumers, including small animals. In the illustrative food web, the chosen zooplankton feed on algae and serve as prey for small fish; this assumed diet is not a claim about every kind of zooplankton.