1. Domain: The highest level of classification, grouping organisms based on fundamental cellular differences. The three domains are Bacteria, Archaea, and Eukarya.
2. Kingdom: Within a domain, organisms are further classified into kingdoms based on shared characteristics. Examples include Animalia (animals), Plantae (plants), Fungi (fungi), and Protista (single-celled eukaryotes).
3. Phylum: Organisms within a kingdom are grouped into phyla based on their body plans and other significant features. For example, within Animalia, there are phyla like Chordata (animals with a backbone), Arthropoda (insects, spiders, crustaceans), and Mollusca (snails, clams, squid).