Fungi Kingdom

Fungi — the kingdom Fungi comprising mushrooms, yeasts, molds, and lichens — are neither plants nor animals but a separate kingdom with over 100,000 described species (estimated 2.2-3.8 million total). Their cell walls are made of chitin (like insect exoskeletons, not cellulose like plants); they obtain nutrients by secreting digestive enzymes and absorbing the products (external digestion). The 'wood wide web' — mycorrhizal networks of fungal hyphae connecting tree roots — transmits water, nutrients, and chemical signals between trees (including between different species). Trees can preferentially send sugar to struggling neighbors through these networks. The largest known organism on Earth is a honey fungus (Armillaria ostoyae) in Oregon covering 9.65 km² — estimated to be 8,650 years old. Penicillin (from Penicillium mold), LSD (from ergot fungus), immunosuppressants (cyclosporine, from soil fungus), and statins (from Aspergillus) are medically essential fungal products.