Answer:
The main step to prepare herbarium sheet are:
Collection and pressing of specimens. Fresh materials are pressed in plant press in herbarium press. ...
Drying of specimens. ...
Mounting of specimens on herbarium sheets. ...
Labeling of specimens. ...
The correct option is D.
The Endangered Specie Act was enacted in 1973. It is an environmental law which provides for the conservation of species that are endangered or threatened and the preservation of the ecosystem in which they live. The law prohibit the catching and killing of endangered species.
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.
