Two-Kingdom Classification:

·         Oldest system:

The two-kingdom system is the oldest classification system, dividing organisms into Plantae (plants) and Animalia (animals).

·         Autotrophs and Heterotrophs:

Organisms were classified based on their ability to produce their own food (autotrophs) or rely on others (heterotrophs).

·         Limitations:

This system faced criticism for including bacteria, fungi, and algae in Plantae, despite their distinct characteristics.