Primary succession occurs when vegetation occurs in a place for the very first time, i.e there was no vegetation there before.
The causes are:
-Erosion
-Physiography
-Elevation
For an organism to function properly all the physiological factors should be favorable. These physiological factors include water level, pH, temperature etc. To perform the basic function of the life, it is important to maintain the physiological parameter in a particular range.
In case, these physiological parameters are not balanced, then the body of the organism does not perform well and causes illness.
So, the first blank can be filled with temperature and the second blank can be filled with range.
Is this like on a test or like homeowork?
