Killer whales are an endangered species. The decline in the whales’ numbers has been linked to poor nutrition, resulting in the inability to maintain a pregnancy. This risk to developing whale embryos is most likely a result of
(1) an environmental factor not associated with the embryo’s genes
(2) an infection caused by the embryo’s exposure to a pathogen
(3) faults in the genes of the embryo itself
(4) toxins that are introduced into the mother
from the embryo’s blood