One end of the figure 17-1 shows an increase in the average beak size for a population of birds. when individuals at only one end of a bell curve of phenotype frequencies have high fitness , the result is

The answer is directional selection

Although there is no figure attached, when individuals at only one end of a bell curve of phenotype frequencies have high fitness, the result is directional selection. It is a type of selection that favours a new phenotype. Ddirectional selection favors dominant or recessive (ss) homozygote, in other words those phenotypes at only one end of a bell curve

The gens present in the dna in the nucleus of the cell in the body