A bio-survey was an scientific survey completed in order to determined the biodiversity of different planets or star systems.
In 2369, the Klingon vessel IKS Toh'Kaht undertook a bio-survey mission for the Klingon High Council in the Gamma Quadrant. The crew proudly boasted about it while drinking in Quark's on Deep Space 9, something that Quark couldn't see the honor in. After emerging from the Bajoran wormhole, the Toh'Kaht was destroyed by first officer Hon-Tihl after the crew was taken over by Saltah'na energy spheres while doing the bio-survey mission. (DS9: "Dramatis Personae")
In 2372, Doctor Julian Bashir and Chief Miles O'Brien performed a bio-survey on Merik III, a planet in the Gamma Quadrant while on the runabout USS Rubicon. (DS9: "Hippocratic Oath")
Later that year, O'Brien had upgraded the sensors of a runabout, so according to him the scan resolution was good enough to perform an entire bio-survey from orbit. (DS9: "The Quickening")