Classification of Living world

Classification systems have evolved considerably over time as biologists found new criteria to sort organisms by. Theophrastus, the 'Father of botany', used simple morphological characters to split plants into trees, shrubs and herbs, while Aristotle split animals into Enaima (possessing red blood) and Anaima (lacking it). Carl Linnaeus (1735) proposed the influential Two Kingdom system - Plantae and Animalia - based on morphology, but it broke down because it lumped prokaryotes together with eukaryotes, and lumped heterotrophic fungi together with photosynthetic plants. As tools from cytology, anatomy, embryology, molecular biology and phylogeny became available, taxonomists kept refining the picture: Ernst Haeckel (1866) split off a Three Kingdom system (adding Protista), Copeland (1956) proposed a Four Kingdom system (further splittin …