Which changing external condition triggers the salivary glands?

Why are fossils not found in igneous rocks? igneous rocks are made from cooling of lava or magma. igneous rocks are found too deep underground. igneous rocks are too dark in color to contain fossils. igneous rocks are too dense to contain fossils.

Body temperature is tightly regulated in mammals for example when external temperatures drop too much the body of a mammal responds by in order to its core temperature?

3differences between bacteria and other 2 cells