31.   Such phase changes occur when minerals adopt different atomic configurations as temperatures and pressures change.

32.   Consequently the depth at which particular phase changes occur can migrate up and down within the lithosphere.

33.   At higher Rayleigh number spontaneous changes occur.

34.   Major changes occur in the mode of production, superstructure and their relationship to nature.

35.   Part of the brain contains many oestrogen receptors and when oestrogen levels fall, mood changes may occur.

36.   If changes in the distribution of income have also occurred, the improvement may only be a potential one.

37.   Although the changes do not occur overnight, positive gains often occur in a relatively brief period of time.

38.   And once the changes occur, while behavior can be altered, the pathways may never be reversed.

39.   And then the great change occurred.

40.   And that is how evolutionary changes occur.