1. explain what the ""biological species"" definition is. describe its strengths and weaknesses. 2. why does a biological species have to be reproductively isolated from other organisms? 3. compare allopatric and sympatric speciation. 4. briefly explain the following species barriers a. habitat isolation b. temporal isolation c. behavioral isolation d. mechanic isolation e. gametic isolation f. reduced hybrid viability g. reduced hybrid fertility h. hybrid breakdown 5. compare the concepts of gradualism and punctuated equilibrium.