Commensalism is when one organism benefits off the other one without harming it. Examples are tree frogs that use plants for protection or jackals that have been expelled from packs trailing tigers and feeding on the remains of its kill. Barnacles on whales get shelter by attaching to a whales body
A nucleus is the control center of a cell.
Gravity is the force of attraction that occurs between two objects due to their mass.
Trace evidence identifies and compares certain types of trace materials.
