Q. Can the heat capacity of water be considered small or large? What is the biological consequence of that characteristic?
From Thermology it is acknowledged that the quantity of exchanged heat (Q) is equal to the mass (m) multiplied by the specific heat of the substance (c) multiplied by the variation of temperature (T), Q = m.c.ΔT., and that heat capacity is Q/T, hence, m.c. Heat capacity, though, since it considers mass, relates to a specific body, where specific heat relates to the general substance. Therefore it is furthermore correct to refer to specific heat in this problem.
Water has a specific heat of 1 cal/g.oC which means that 1 oC per gram is changed in its temperature with the subtraction or addition of 1 cal of energy. This is a very important value (for example, the specific heat of ethanol is 0,58 cal/g.oC, and mercury, a metal, has a specific heat of 0,033 cal/g. oC) making water an excellent thermal protector against variations of Temperature. Even if sudden external Temperature changes happen, the internal biological conditions are kept steady in organisms which contain enough water.
High specific heat is one of the major important water properties.