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.
As a result, zooplankton are primarily found in surface waters where food resources (phytoplankton or other zooplankton) are abundant. Just as any species can be limited within a geographical region, so is zooplankton. However, species of zooplankton are not dispersed uniformly or randomly within a region of the ocean.Instead âpatchesâ of zooplankton species (this also applies to phytoplankton) exist throughout the ocean.t includes holoplanktonic organisms whose complete life cycle lies within the plankton, as well as meroplanktonic organisms that spend part of their lives in the plankton before graduating to either the nekton or a sessile, benthic existence.