The third kingdom contains all organisms whose cells have a nucleus, including plants, animals, algae, and even fungi. So evolutionarily speaking, humans and fungi are cousins.
If you’ve ever seen movies about World War I, you know that the soldiers in the trenches often wore bulbous gas masks that made them look like human insects. The masks were necessary to protect them from chemical weapons such as chlorine gas, a noxious substance that could almost instantly suffocate unprotected victims.
We all know we need iron to live. How else would our blood carry oxygen to our lungs? And cells need iron in order to multiply. The problem is that our cells aren’t the only ones who need iron in order to thrive. Cancer cells and microorganisms like E. Coli and staph need iron too.