13-13= 0, 19-13= 6, so then 0-6= -6
Every 3 days the stomach starts a new lining
The cane toad was a failure as a biological control method in Australia because:
-The greyback beetle it was supposed to be eating fed at the top of the sugarcane stalks (which were 6-8 meters in height). Cane toads cannot fly or climb and therefore couldnt feed on the beetles.
-The beetles were out during the daytime, and cane toads feed at night.
-The two species are not seasonally compatible (aren't in the same place at the same time of year).
-The toads needed moist conditions to survive, and so moved away from where they were supposed to be.
-The cane toad eats many native species and often out-competes native species for food and breeding sites, leading to the decline of natives.
-Breeding habits made the cane toads a very invasive 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.
