Re: why aren't fungi classified in the plant kingdom?

Originally there were only two kingdoms - plants and animals. If an organism 
didn't move, it was usually placed in the plant kingdom. The current five 
kingdom system didn't become common in biology textbooks until the 1980s. 
Fungi are placed in a separate kingdom because they share many characteristics 
and have different characteristics than plants and animals. 

- Almost all plant species are photosynthetic. No fungi are photosynthetic.
- Plants have cellulose in their cell walls. Many fungi have chitin in their 
cell walls.
- The majority of plant species reproduce via seeds. Fungi reproduce via 
spores. 
- Fungi digest food outside their bodies, unlike most animals which ingest 
food and digest it inside their bodies.

References



The Fungus Kingdom


Fun Facts About Fungi


Introduction to the Fungi