Final answer:
When classifying an organism into a kingdom, scientists look at key characteristics such as cell structure, nutrition mode, and body plan. The most inclusive category is the domain, including the diverse kingdoms within the Eukarya domain.
Step-by-step explanation:
To classify an organism into a certain kingdom, scientists must examine its key characteristics. These characteristics include aspects such as cell structure, mode of nutrition, reproduction, genetics, and overall body plan. For instance, to categorize an organism into the Animalia kingdom, one would look for traits that fit the description of Animalia: eukaryotic, multicellular, heterotrophic organisms that ingest their food, often motile, with differentiated tissues. Alternatively, organisms that are multicellular and primarily obtain energy through photosynthesis would fall into the Plantae kingdom.
With regard to the Linnaean system of classification, it utilizes a hierarchy starting from the broader groups to more specific ones, for example, from kingdom down to species. The domain is the most inclusive taxonomic category, and currently, there are three recognized domains: Archaea, Bacteria, and Eukarya. Within the domain Eukarya, there are several kingdoms including Animalia, Plantae, Fungi, and Protista. Binomial nomenclature is the system of naming species with a two-part scientific name: a genus name followed by a species identifier, such as Homo sapiens for humans.