AP BIOLOGY

Detailed explanation-1: -If 50% of the atoms undergo decay, that means that 50% of the original sample remains after one half-life. In another 6000 years, the number of carbon-14 atoms will be equal to 25% of the original sample, in another 6000 years, to 12.5% of the original sample, and so on.

Detailed explanation-2: -Carbon-14 has a relatively short half-life of 5, 730 years, meaning that the fraction of carbon-14 in a sample is halved over the course of 5, 730 years due to radioactive decay to nitrogen-14.

Detailed explanation-3: -Carbon-14 has a half-life of 5, 730 years. After an organism dies, it stops absorbing new carbon-14 from the environment, and the isotope begins to decay at an exponential rate. Only half of the original carbon-14 isotope will remain in the fossil 5, 730 years after the organism died.

Detailed explanation-4: -The less radioactivity a carbon-14 isotope emits, the older it is. And since animals and plants stop absorbing carbon-14 when they begin to decay, the radioactivity of the carbon-14 that’s left behind reveals their age.