After a volcanic eruption, lava flowed over an area and then cooled to form a thick layer of new rock. One thousand years later, a thriving forest with diverse flora and fauna is found in that area, even though evidence suggests that several large forest fires have occurred. Which statement best describes what happened? Secondary succession occurred, followed by several primary successions. Only secondary successions occurred. Primary succession occurred, followed by several secondary successions. Only primary successions occurred.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

cell division is not regulated in tumor cells.

1. amino acid refers to the fundamental building block of proteins, comprising of an amino group and a carboxyl group.

2. catalyst refers to any substance, which increases the rate of chemical reaction without being used up in the reaction.

3. a complex molecule containing he genetic code is dna or deoxyribonucleic acid.

4. an enzyme refers to a molecule of protein, which is unique in accelerating up a particular chemical reaction in the biological systems.

5. nucleic acid refers to an sequence of sugars, phosphates, and nitrogenous bases, for example, dna and rna.

6. a protein refers to a large, composite organic molecule comprising of a huge number of amino acids associated together with the of peptide bonds.

7. rna refers to a nucleic acid that takes part in the production of proteins.

8. substrate refers to a compound, which takes part in a chemical reaction, and is chemically modified by the reaction.