After three half-lives, a sample contains 20 grams of parent isotopes. how many grams of the parent isotope were present to start?

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen

What is a photon? a. part of a ribosome b. a light particle c. a carbon dioxide molecule d. part of a chloroplast b.a light particle

What do we call the process when two dominant alleles are expressed and do not blend? a.incomplete dominance b.codominance c.multiple alleles