last part of the small intestine; connects the small intestine to the large intestine; important for absorption of B-12

acquired ability to prevent an unnecessary or harmful immune response to a detected foreign body known not to cause disease or to self-antigens

failure, insufficiency, or delay at any level of the immune system, which may be acquired or inherited

identification of parents by newborns as the first organism they see after birth

mating of closely related individuals

increase in abnormalities and disease in inbreeding populations

in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype

(also, anvil) second of the three bones of the middle ear

cleavage pattern in which individual blastomeres have the character of "stem cells," and are not yet predetermined to develop into specific cell types

dynamic fit between the enzyme and its substrate, in which both components modify their structures to allow for ideal binding

mutation that results from exposure to chemicals or environmental agents

operon that can be activated or repressed depending on cellular needs and the surrounding environment

form of logical thinking that uses related observations to arrive at a general conclusion

(also, noble gas) element with filled outer electron shell that is unreactive with other atoms

drains blood from the veins that come from the lower organs and the legs