Think areal hard ~ how does the critter know the pressures are there, and what does he do to adjust his genome?
Where has anyone on this thread said genomes anticipate need? That is Lamarckianism -- rejected in the last century.
But all populations have variation, and all populations acquire new alleles through mutation. During any period of environmental change, the frequency of alleles in the population shifts to accommodate the change. If the necessary traits do not exist, the population goes extinct.