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 Phytoplankton: photosynthetic plankton that are usually microscopic and are also called âalgae... 2  more. 3  Zooplankton: small, sometimes microscopic animals that live in water and feed on phytoplankton (algae), other zooplankton, or detritus (dead material)...4  more. Phytoplankton: photosynthetic plankton that are usually microscopic and are also called âalgae... 2  more. 3  Zooplankton: small, sometimes microscopic animals that live in water and feed on phytoplankton (algae), other zooplankton, or detritus (dead material)... 4  more.