Chapter 11 Cell Communication Overview: The Cellular Internet essential for multicellular organism the combined effects of multiple signals determine cell response Concept 11.1: External signals are converted into responses within the cell Evolution of Cell Signaling yeast cells identify their mates by cell signaling a signal transduction pathway is a series of steps by which a signal on a cell?s surface is converted into a specific cellular response pathway similarities suggest that ancestral signaling molecules evolved in prokaryotes and were modified later in eukaryotes Local and Long Distance Signaling the concentration of signaling molecules allows bacteria to detect population density cells in a multicellular organism communicate via chemical messengers