Definition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT.Greek plak-, plax flat surface.First Known Use: 1842.efinition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT. Greek plak-, plax flat surface. First Known Use: 1842.
A tree pruner is a class 1 lever. The fulcrum is where the two blades cross, and the load is what you are cutting. The effort is applied to the two handles.
The crown is made up of the leaves and branches at the top of a tree. The crown shades the roots, collects energy from the sun (photosynthesis) and allows the tree to remove extra water to keep it cool (transpiration -- similar to sweating in animals).rown: The crown is made up of the leaves and branches at the top of a tree. The crown shades the roots, collects energy from the sun (photosynthesis) and allows the tree to remove extra water to keep it cool (transpiration -- similar to sweating in animals). The crowns of trees come in many shapes and sizes!