About 1.7–1.8 million species have been described; taxonomy names and arranges them using binomial nomenclature and a hierarchy of categories from species to kingdom.
How it's asked: Rules of writing scientific names, the order of taxonomic categories, which family/order a familiar organism belongs to (mango, wheat, man, housefly), and ICBN vs ICZN.
Why this is true
Common names differ from place to place, so scientists needed one universal, unambiguous name for each organism. Linnaeus's binomial system gives each a generic name and a specific epithet, written in Latin (or Latinised) because a dead language does not change, and it is governed by codes — ICBN for plants and ICZN for animals — so a name means the same thing everywhere. Classification then groups organisms by shared characters into ranks; each rank (taxon) is broader than the one below it. As you move up from species to kingdom, the number of shared characters decreases, which is why two species in the same genus resemble each other far more than two members of the same class. Taxonomy rests on four steps — characterisation, identification, nomenclature and classification.
Key points
Organisms with their taxonomic categories (NCERT examples)
| Common name | Genus species | Family | Order | Class | Phylum / Division |
|---|---|---|---|---|---|
| Man | Homo sapiens | Hominidae | Primata | Mammalia | Chordata |
| Housefly | Musca domestica | Muscidae | Diptera | Insecta | Arthropoda |
| Mango | Mangifera indica | Anacardiaceae | Sapindales | Dicotyledonae | Angiospermae |
| Wheat | Triticum aestivum | Poaceae | Poales | Monocotyledonae | Angiospermae |
Common traps
- In plants the rank between class and kingdom is called division, not phylum.
- Mango belongs to order Sapindales and family Anacardiaceae; Poales/Poaceae belong to wheat — these pairs are often swapped in options.
Worked example
A student writes the scientific name of mango on a chart as 'mangifera Indica' in plain handwriting without underlining.
High-yield
Species → genus → family → order → class → phylum/division → kingdom. Mango: Anacardiaceae, Sapindales; wheat: Poaceae, Poales.
Quick check
Q1.Which taxonomic category contains the most closely similar organisms?
Q2.Families Convolvulaceae and Solanaceae are included in the order: