Answer: Mycorrhiza
Explanation: Mycorrhiza is a symbiotic relationship between a plant and a fungi. Nearly 80 percent of all plants with root systems participate in this mutualistic relationship. In mycorrhiza, the fungus forms a haustoria that penetrates the cell walls of the plant's roots. The fungus absorbs all the nutrients from the roots as they are transported to the plant. In return, the fungus gives the plant necessary chemicals and minerals that it cannot properly reach on its own.
I believe the term for an observable trait of an organism would be called or noted as the organism's phenotype.
Answer:
1. They keep casts to preserve the real fossils.
2. Maybe someone would steal a fossil and sell it on the dark web?
3. They keep casts to keep the real fossils in prime condition, by that I mean like undamaged.