Darwinism designates a distinctive form of evolutionary explanation for the history and diversity of life on earth. Its original formulation is provided in the first edition of On the Origin of Species in 1859.
The enthalpy - or internal energy - of a substance is a function of its temperature and pressure. The change in internal energy with respect to change in temperature at fixed pressure is the Specific Heat at constant pressure - cp.
The change in enthalpy of a reaction can be generally understood as the change in heat of a reaction. If this change is negative, the system gives off heat energy; the reaction is exothermic. If the change in enthalpy is positive, the system absorbs heat energy; the reaction is endothermic.