<span>a cell that bears receptors for a hormone, drug, or other signaling molecule, or is the focus of contact by a virus, phagocyte, nerve fiber, etc.</span>
These fossils are very useful for us because we can use them to date the layers of rock that they are found in. Fossils that can be used in this way are called index fossils, and rock layers with the same index fossils in them can be correlated. Not my answer, link here for full
http://peter-mulroy.squarespace.com/correlating-rock-layers/
Living= 1. made of cells 2. obtain and use energy 3. grow and develop 4. reproduce 5. respond to stimuli and environment 6. adapt to environment
non-living= anything other such as stone, mountains, a watch
