What allows receptors for extracellular signaling molecules present on the responding cell's surface to recognize such molecules so readily

How does a gymnosperm prevent itself from pollinating the same tree

The earths core is made up mainly of what 2 substances? 2. like an egg, earth has a core, a layer surrounding the core, and a thin, hard outer layer. which layers of the earth match the layers of an egg?

The two main stages of cell division are called