Quick Review — 10 Sentences — Summary

Metabolism — the totality of anabolic and catabolic reactions — is the only universally accepted defining feature of living organisms because no non-living entity exhibits it.
Growth cannot define life because non-living crystals also grow by accumulation of material from outside.
Reproduction cannot define life because mules (horse × donkey hybrids), worker bees, and infertile humans are alive yet cannot reproduce.
Taxonomy, a term coined by A.P. de Candolle, is the science of identification, nomenclature, and classification of organisms.
Systematics is the broader discipline that adds the study of evolutionary (phylogenetic) relationships to the operations of taxonomy.
The mandatory taxonomic hierarchy from most to least inclusive is: Kingdom → Phylum/Division → Class → Order → Family → Genus → Species.
Binomial nomenclature, established by Carolus Linnaeus in Systema Naturae, gives every organism a two-part name comprising a capitalised genus and a lowercase specific epithet.
In print, scientific names are italicised; when handwritten, the genus and specific epithet are each underlined separately — never with one continuous line.
The species is the basic unit of classification, defined as organisms that interbreed to produce fertile offspring; the kingdom is the most inclusive category.
The nine taxonomic aids are: herbarium, botanical garden, museum, zoological park, dichotomous key, flora, monograph, manual, and catalogue — with the type specimen serving as the nomenclatural reference standard for species identity.