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.
1 Zooplankton depends on the phytoplankton and other particulate matter that is found in the water for food. 2  Phytoplankton is the chief food source for the zooplankton! 3  Difference in habitat. 4  As phytoplankton is primarily dependant on sunlight as their food source, they tend to prefer the surface of the water.hese are planktons-tiny organisms that drift along the surface of fresh water. The word plankton originates from the Greek word that means a drifter or a wanderer. There are basically two categories of plankton. Though they are similar in size and ecological importance, there is a world of difference between them.