Fertilization by more than one sperm would result in a polyploidy and an inviable zygote. What is the first line of defense against polyspermy?a. species specific recognition of proteins on the outer coat of the egg. b. changes in the membrane potential of the egg prohibiting additional sperm from entering.
c. capacitation in the sperm fertilizing the egg.
d. products released from the egg changing the zona pellucida of the egg and prohibiting additional sperm from entering.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

it creates acid rain

ever get the answers? im stuck on this as well