Dna is comprised of four different types of nucleotides. each one is made up of a pentose sugar, a phosphate group, and one of four nucleosides. 2. adenine, guanine, cytosine and thymine are nitrogenous bases. 3. adenine and guanine, which have a nine-member double-ring, are called purines. 4. cytosine and thymine, which have a six-member single-ring, are called pyrimidines.

The hypothesis of continental drift states that earth's continents, which are located on tectonic plates, move relative to each other. which of the following is true of the movement of the tectonic plates? a. tectonic plates only move once every million years. b. they move at a rate of approximately 5 centimeters per year. c. tectonic plates never move, only the continents located on them do. d. their movements are very rapid and occur at random times.

What is the phylum of soft bodied animals with a true bosy cavity and a three part body consisting of a foot visceral mass and a mantle

What is thought to have caused the mass extinction at the end of the cretaceous period?