Applicability of sec 44ad

Section 44AD is applicable to Business as distinct from Profession. However it is also  stated as per subsection 6 (inserted by Finance Act 2012)  that 44AD will not apply to Professions specified under sub section 1 of section 44AA. Does it mean that Section 44AD will be applicable to all others that are not covered by sub section 1 of section 44AA?

If income from all professions, was to be excluded, then what was the need to specifically mention only those professions that are specified in sub section 1 of section 44AA? Since 'Profession' is not elsewhere defined in I T Act, does it not indirectly mean that I T Act recognises as profession only those that are specified in sub section 1 of section 44AA?

Learned Members may kindly give their opinion.

Thanks.