Fossil records show that the size of black bears in europe increased during each glacial period and decreased during the interglacial periods. identify the type of selection that occurred during each period and discuss how the type of selection supports the claim that a single environmental factor can yield a variety of phenotypic responses from different genotypes within a population.

The answer is directional selection
It is the mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction. The advantageous allele increases in frequency independently of its dominance relative to other alleles; that is even if the advantageous allele is recessive, it will eventually become fixed, changes the average value of a trait. Occurs most often under environmental changes and when populations migrate to new areas with different environmental pressures. 

Ithink the answer is c. i’m not sure though i’ll notify you when i have an exact answer!