What is innate immunity? discuss the barriers associated with innate immunity.

Innate immunity is a nonspecific defense mechanisms that play its role as soon as an antigen appear in the body (it is relatively rapid but nonspecific and because of that it is not always effective)

Explanation:

The barries of innate immunity are:

Skin: At Epidermal surface, its protective aspect are keratinized cells that lives on the surface, known as Langerhans cells.

Skin sweat or secretions: Their specific defense is sweat glands and sebaceous glands, and their protective aspect is low ph and washing action.

Mucosal surfaces: they are at the mucosal epithelium, and their protect aspects are nonkeratinized epithelial cells.

Oral cavity: They defend salivary glands through Lysozyme

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .