Some isotopes, however, decay slowly, and several of these are used as geologic clocks. Dating rocks by these radioactive timekeepers is simple in theory, but the laboratory procedures are complex. <span>All methods rely on the fact that certain elements (particularly uranium and potassium) contain a number of different isotopes whose half-life is exactly known and therefore the relative concentrations of these isotopes within a rock or mineral can measure the age.</span>
Answer:
Direct observation of evolutionary change: creation of drug-resistant bacteria.
Fossil record: discovery of transitional forms of animals, discovery of shells of extinct organisms
Homology: similarities in mammalian forelimbs, identical genetic code in fireflies and tobacco plants, vestigial pelvis in right whales
Biogeography: resemblance of endangered island species to neighboring mainland species,
By tar, I think you mean nicotine. (I Hope). It affects the nerve signals that regulate breathing.
Answer:
True
Explanation:
Groundwater is the water present beneath Earth's surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.
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