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.
I believe <span>Erta Ale from Ethiopia, Hekla from Iceland, and Ol Doinyo Lengai from Congo.
Hope this helps!</span>
Answer:
Geologists use radiometric dating to estimate how long ago rocks formed, and to ... as "bracketing" the age of the sedimentary layer in which the fossils occur.
Explanation:
Answer:
Animals capable of feeding at many trophic levels will be able to survive if portions of their food supply are decreased or eliminate is not true of about trophic levels
Explanation:
This is because each trophic levels represent energy flow and supply of food to the organisms in the trophic levels. Energy are pass from one tropic levels to another as a result of source of food there. Plants majorly are the primary producers and the primary consumers depend on it. Therefore, if the source of food supply is eliminated in a trophic level, the organisms I'm the trophic level will not be able to survive.
