Some common elements that are gaseous state at room temperature are:
Oxygen Nitorgen Fluorine Chlorine Hydrogen Helium
In addition, all of the elements in group VIII are gases too, they have an octet of electrons (complete outer electron shell) , they're really stable and therefore they're called noble gases. Some examples from group VIII include helium, krypton, xenon etc.
Substance exist as gases in room temperature is due to their boiling point, where is it lower than the room temperature (usually around 25°C). If their boiling point is higher than room temperature, they should exist as either solid or liquid, which is how the majority of the elements in the periodic table is.
The deer and wolf population would decrease because the deer have less plants to feed on while already being eaten by the wolves, and eventually the wolves will have less deer to feed on which will decrease their population
