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.
At the base of the aquatic food web are: 1  Plankton Plankton are microscopic plants and animals whose movements are largely dependent upon currents. 2  Phytoplankton Plant plankton are called phytoplankton and may be single cells or colonies. 3  Zooplankton Animal plankton are called zooplankton. In the Great Lakes, most producers are phytoplankton, or microscopic floating plants. 2  An example of phytoplankton is green algae. 3  Large rooted plants, another type of producer, provide food and shelter for different organisms, fish and wildlife.