And introduced crab predator favors medium brown crabs while avoiding the dark brown and light brown crabs predict how this selection pressure will affect the relative frequency of the B and b
alleles in the future generations of crabs assume all other selection pressures remain the same and that there is no migration of crabs into or out of the population

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms