the three general classifications are sensory neurons, motor neurons and interneurons. I don't know how they work together to produce a response to an environmental stimulus:( sorry
The various types of cells making up the structural composition of your body (skin cells, muscle cells, cells of your stomach lining, etc.) are all Epithelial cells. The only other class of cells in your body are Gametes (sperm and egg cells).
MASS: because it is the measure of the amount of matter in an object
Flu vaccines need to be revised and changed every year because the flu virus constantly mutates. Flu viruses can change in two ways: drift or shift. Antigenic drift occurs when genes of the virus slowly change during replication until the immune system no longer recognizes it. On the other hand, antigenic shift occurs when a major change in the virus happens. This usually leads to a totally different kind of virus. This is what happened during the H1N1 scare in 2009.
DNA viruses like mumps are less prone to mutation due to the presence of DNA polymerase. RNA viruses are more prone to mutation because they undergo reverse transcription to simulate the role of DNA.
