Why Darwin called non-hereditary variability definite.

In all healthy people with fair skin color, the sun’s rays cause sunburn.
Garden plants grown on soil rich in organic fertilizers grow to larger sizes.
Thus, each type of organism reacts specifically to the action of a certain environmental factor, and the reaction, in the form of a change in a trait, turns out to be similar in all individuals of this species.
This circumstance allowed Charles Darwin to call non-hereditary variability group or specific.
Non-hereditary modification variability is characterized by:
– change in phenotype;
– changes are not inherited;
– changes are massive;
– changes are adaptive;
– changes are gradual;
– changes promote survival, increase livelihoods;
– changes are adequate to environmental conditions.