1.3: FEATURES OF ORGANISMS
SUMMARY
Classification organises living organisms into groups based on shared features. Animals and plants are distinguished by the presence or absence of cell walls, chloroplasts, and their type of nutrition — animals are heterotrophic, while plants are autotrophic. Vertebrates are divided into mammals, birds, reptiles, amphibians, and fish using features like body covering, breathing method, and reproduction. Arthropods are classified into myriapods, insects, arachnids, and crustaceans primarily by their number of legs and body sections. Using these features in a step-by-step approach allows any organism to be placed into its correct group.
🚀 At the Extended level, all organisms are placed into one of five kingdoms — animal, plant, fungus, prokaryote, and protoctist — based on cell type, cell wall composition, and nutrition. Within the plant kingdom, ferns are distinguished from flowering plants by their use of spores rather than seeds, and flowering plants are further divided into dicotyledons and monocotyledons by cotyledon number, leaf venation, and flower part arrangement. Viruses fall outside this classification system entirely because they are not cellular — they consist only of a protein coat and genetic material, and they cannot carry out life processes independently.