Features of organisms

Classification organises living organisms into groups based on shared features.

Animals

• Are heterotrophic, obtaining their nutrients by feeding on other organisms

Plants

• Are autotrophic, making their own food by photosynthesis

Animals and plants are distinguished by the presence or absence of cell walls and chloroplasts, and by their type of nutrition.

Vertebrates

• Are divided into mammals, birds, reptiles, amphibians, and fish
• Classified using features such as body covering, method of breathing (gas exchange), and method of reproduction

Arthropods

• Are classified into myriapods, insects, arachnids, and crustaceans
• Distinguished primarily by their number of legs and number of body sections

Using these features in a step-by-step approach (such as a dichotomous key) allows any organism to be placed into its correct group.

Extended 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.

Ferns

• Are distinguished from flowering plants by reproducing using spores rather than seeds

Flowering plants

• Are further divided into dicotyledons (dicots) and monocotyledons (monocots)
• Distinguished by cotyledon number, type of leaf venation, and the arrangement of flower parts

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
• Consist only of a protein coat surrounding genetic material (DNA or RNA)
• Cannot carry out life processes independently and reproduce only inside living host cells

At a Glance