Why is the third line of defense consider specific and adaptive

The third line of defense is specific resistance. This system relies on antigens, which are specific substances found in foreign microbes. Most antigens are proteins that serve as the stimulus to produce an immune response. ... The activation of T-cells by a specific antigen is called cell-mediated immunity.

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Explanation:

the element that provides strength to the exoskeletons of clams and oysters is phosphorus. this is so because calcium carbonate is the main component in the shells.

explanation:

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.