Final answer:
Two members of the same kingdom share only basic similarities and can belong to different species, while members of the same species can interbreed and must belong to the same kingdom. The Linnaean taxonomy groups living organisms into a hierarchy from kingdom to species based on shared characteristics and evolutionary relationships.
Step-by-step explanation:
In the Linnaean system of classification, organisms are grouped into hierarchical categories known as taxa, which range from the broadest category, kingdom, to the most specific, species. Members of the same kingdom, such as the Kingdom Animalia or Kingdom Plantae, share only basic similarities and can belong to vastly different species. For instance, a human and a butterfly are both part of the Kingdom Animalia, yet they are different species. Conversely, two organisms of the same species, like two domestic dogs (Canis lupus familiaris), would necessarily belong to the same kingdom because they are capable of interbreeding and producing fertile offspring, which is a key characteristic that defines a species.
The kingdom is the largest taxonomic category and includes a diverse array of organisms. For example, the Kingdom Animalia encompasses humans, primates, insects, fish, and reptiles, all of which are heterotrophic and multicellular. On the other hand, the species level is the most exclusive, representing organisms that are closely related enough to reproduce successfully. Organisms that appear similar, such as the bald eagle (Haliaeetus leucocephalus) and the African fish eagle (Haliaeetus vocifer), may not be of the same species and thus, are not capable of producing fertile offspring naturally.
Classifying different species based on evolutionary relationships can be complex, as it involves tracing back divergences to a common ancestor. Species that are evolutionarily related evolved from this common ancestor over time, such as how lions and tigers are more closely related to each other than to bears, despite all being large carnivores.