The can survive fr a long period of time outside a persons body.
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.
Answer:
True
Explanation:
According to the law of conservation of mass, mass can not be created nor destroyed.
The implication of this is that the total mass on both sides of the reaction equation must be the same.
Thus, the number of atoms of each element on both sides of the reaction arrow must be the same.
Answer:
6, 3, 4, 5, 7, 2, 1
Explanation:
Here, speciation occurs because the original butterfly population gets separated into two populations, each facing a different set of environmental conditions. Initially, there was just a single population of butterflies in the valley and all butterflies were able to mate with each other. A fire destroyed their habitat so they had to migrate to other areas. Some butterflies migrated to eastern side of mountain and some to western side of mountain.
Now there were two butterfly populations and they faced different environment from each other. Over the time, the populations adapted to their local surroundings and started to accumulate changes in their genome. Their gene pools started to separate from each other. Eventually they evolved into two different species. When their old habitat was restored in the valley, they returned once again. However, this time they were not able to interbreed because they were now two different species.
