They are representatives between the extinction events
Protons and electrons. This is why if you have the atomic number (aka the proton number) you know both the number of protons and the number of electrons in the atom.
The answer would be underground stem.
Underground stem is located beneath the soil. It was a modified stem that allows the storage of food and nutrients. It also capable of doing asexual reproduction. Since the stem is stored underground, it is less influenced by the climate and has a higher chance to survive.
