Which part of an amino acid makes each of the 20 amino acids different? a. carboxyl group b. r-group c. phosphate tail

According to the cladogram, which organisms have roundworms as a common ancestor?

Compare the composition of the moon's surface with the composition of the earth's surface.

Which of these is an example of land degradation? a. containers designed to store pollutants leak. b. fertilizers provide too many nutrients to crops. c. garbage is buried so the land can be reclaimed later. d. a drought kills all the plants in an area, leaving bare land