Explain how covalent bonds and hydrogen bonds hold together a strand of DNA

Covalent bonds appear inside every linear chain and connect bases, sugars, and phosphate groups.

Hydrogen bonds appear between two strands and involve the base from one strand with the base from another strand in the complementary pairing.

Explanation:

A covalent bond is a chemical bond formed by joining electrons of two non-metal atoms into one or more common pairs.

A hydrogen bond (X-bond) is a type of weak chemical bond based on electrostatic attraction between a hydrogen atom and a nucleophilic atom that contains free electron pairs.

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

i thinking chemical change