A parent isotope has a half life of 1 million years. If a rock contained 20 mg of the parent isotope when it formed, how much parent isotope would be left after 2 million years?

Continental crust is younger than oceanic crust

If the portion of dna to be transcribed has 66 bases how many amino acids will the resulting protein have

Plants release oxygen during the day but not during the night. Explain why.

Explain how an autoimmune disease differs from an infectious disease? Similarities and differences between bacteria and viruses? Explain how the following methods can be used to assist the body's ability to fight against disease causing organisms!

You have a very heavy steel ball and a very light plastic ball. If both are dropped from the same height at the same time, and there is no air resistance, then both objects will hit the ground at the same time. True False

Which of these is an advantage of using models to study tectonic plate movements? Actual plate movements can be stopped. Actual plate movements can be made less frequent. Models of the exact material as the original can be made.

Where are the cell bodies of lower motor neurons located?

is Earth an open system or closed system? Explain your answer and provide at least one example that occurred during the Precambrian era

The human genome comprises about 3 x 109 base pairs of DNA, and no two humans, other than identical twins, ever have been or will be genetically identical. Between any two humans, the amount of genetic variation is about 0.1 percent.

Which equation represents a reduction half-react