Medical definition of posterior median sulcus: a shallow groove along the midline of the posterior part of the spinal cord that separates the twoâ¦ a shallow groove along the midline of the posterior part of the spinal cord that separates the two posterior funiculi and is the externalâ¦
Zooplankton Fact Sheet. Zooplankton are microscopic invertebrate animals that swim or drift in water. They are at the base of the food chain, feeding on microscopic plants and being fed upon by aquatic insects, fish and salamanders.ooplankton Fact Sheet. Zooplankton are microscopic invertebrate animals that swim or drift in water. They are at the base of the food chain, feeding on microscopic plants and being fed upon by aquatic insects, fish and salamanders.
The plant-like organisms are phytoplankton (from phytos, Greek for plant); small animal plankton are zooplankton (from zoios, Greek for animal); and bacteria and archaea, minuscule cells that decompose material and recycle chemicals in the ocean, make up the bacterioplankton. But these categories are far from perfect.