The smallest thing they study is cells, i think!
hoped this helped!!
 
        
                    
             
        
        
        
Answer: They do affect the health of an ecosystem.
Explanation: In an ecosystem there are many things that are biotic and abiotic. For an example: water is abiotic and plants/animals are all biotic, the water is not living but it keeps the ecosystem alive by quenching the thirst of the plants growing from the ground and the animals roaming around on the land. Dead animals and plants are not abiotic and they are now providing food for fungi and bacteria. Without the abiotic factors, it would be difficult for the biotic to survive. 
 
        
             
        
        
        
Fungi contain many different microscopic organisms compared to regular plants, Fungi can be very poisonous compared to plant too and also a regular plant contains a cell wall where as Fungi don't. Most importantly plants use the process photosynthesis to make their own food, Fungi don't.