Well depending on what the environmental change is the organisms will have to adapt, or move. if they don't they may not survive.
comment if you want an example or 2
The virus attaches itself to a specific host cell (the cell in which it will reproduce) the virus injects its genetic material into the host cell. the host cell uses the genetic material to make new viruses. the host cell splits open, releasing the viruses.
The literacy rate controls the growth of our country I think just kidding bi just want some points so I decided to answer your prob
The amount of hydrogen will decrease.