Taxonomy, Systematics and Taxonomic Categories

TAXONOMY = process of classification based on characteristics: characterisation, identification, classification and nomenclature. SYSTEMATICS = study of diversity and evolutionary relationships ('systema' = systematic arrangement of organisms); coined from the title of Linnaeus's 'Systema Naturae'. The TAXONOMIC HIERARCHY (descending): Kingdom > Phylum (animals)/Division (plants) > Class > Order > Family > Genus > Species. Memory aid: 'King Philip Came Over For Good Soup' (Kingdom, Phylum, Class, Order, Family, Genus, Species). SPECIES is the lowest/basic unit; KINGDOM is the highest. As we go up the hierarchy, number of common characters DECREASES and the category becomes more abstract.

SPECIES = group of individual organisms with fundamental similarities, capable of interbreeding to produce fertile offspring. In a binomial name, the species is the specific epithet. Example: in Panthera leo (lion) and Panthera tigris (tiger), 'leo' and 'tigris' are species while Panthera is the genus. Mangifera (genus) has one species indica. GENUS = group of related species having more characters in common than other genera. As you move from species → kingdom: number of organisms INCREASES, common characteristics DECREASE. Remember: lower category = more similar organisms; higher category = fewer common features.

HUMAN: Species sapiens → Genus Homo → Family Hominidae → Order Primata → Class Mammalia → Phylum Chordata → Kingdom Animalia. HOUSEFLY: Musca domestica → Family Muscidae → Order Diptera → Class Insecta → Phylum Arthropoda → Kingdom Animalia. WHEAT: Triticum aestivum → Family Poaceae (Graminae) → Order Poales → Class Monocotyledonae → Division Angiospermae → Kingdom Plantae. Note: animals use PHYLUM, plants use DIVISION. Mango and wheat share kingdom Plantae but differ at lower categories. The more categories two organisms share, the closer their relationship.

Cover the answer, recall, then check. 12 cards on the NCERT must-know facts for NEET.

Q1. What four processes make up taxonomy?
A1. Characterisation, identification, classification and nomenclature.

Q2. From where is the word 'Systematics' derived, and what does it include?
A2. From the Latin word 'systema' (systematic arrangement of organisms). Linnaeus used 'Systema Naturae'. Systematics also takes into account evolutionary relationships between organisms.

Q3. List the taxonomic hierarchy from lowest to highest.
A3. Species → Genus → Family → Order → Class → Phylum (Division in plants) → Kingdom.

Q4. Define species as a taxonomic category.
A4. A group of individual organisms with fundamental similarities; the lowest/basic taxonomic category. E.g. indica in Mangifera indica; leo in Panthera leo.

Q5. Give the genus and species for lion, tiger and leopard.
A5. Genus = Panthera. Lion = Panthera leo, tiger = Panthera tigris, leopard = Panthera pardus.

Q6. Name three species of the genus Solanum.
A6. Solanum nigrum, Solanum melongena (brinjal), Solanum tuberosum (potato).

Q7. To which family do Solanum, Petunia and Datura belong?
A7. Family Solanaceae.

Q8. Which order includes families Convolvulaceae and Solanaceae, and on what basis?
A8. Order Polymoniales — grouped on the basis of floral characters.

Q9. Give an example of a Class and its included Orders.
A9. Class Mammalia includes orders Primata (monkeys, gorillas, gibbons) and Carnivora (tiger, cat, dog).

Q10. What character unites all members of Phylum Chordata?
A10. Presence of a notochord and a dorsal hollow neural (nerve) cord — shared by fishes, amphibians, reptiles, birds and mammals.

Q11. What is used for Phylum in plant classification?
A11. Division is used in place of Phylum for plants.

Q12. How do common characters change as you go up the taxonomic hierarchy?
A12. The higher the category, the fewer the characters in common. Number of common characteristics decreases from species to kingdom.