Elizabeth is 90 years of age. compared to when she was 30 years of age, her now. cells require more energy arteries are less flexible stomach secretes more intrinsic factor skin is more elastic

The answer is ‘arteries are less flexible’. This is why the older you get the more predisposed you are to cardiovascular diseases such as high blood pressure. However, regular exercise may delay this development. The barometers in the blood vessels also become less sensitive hence these vessels become less responsive to blood pressure changes.

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.    

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.