All the individuals of a particular organism, such as rose plants, belong to a taxonomic category called
- (a)species
- (b)genus
- (c)family
- (d)order
Correct — A, species. Species is the basic and lowest unit of the taxonomic hierarchy, and it is the only rank that gathers individuals rather than groups. A species is the set of organisms that share the same fundamental features and that interbreed among themselves to produce fertile offspring; every level above it — genus, family, order, class, phylum, kingdom — is a container for lower groups, not for individuals. So the moment the stem says 'all the individuals of a particular organism', the answer has to be the bottom rung. The ranks above only widen the net: genus holds several related species, family several related genera, order several related families.
- (b)genus — A genus is a group of closely related species, not of individuals — Solanum, for instance, holds the potato, the brinjal and the black nightshade. It is one rank too high for what the stem describes.
- (c)family — A family gathers related genera. Rosaceae, the rose family, takes in apple, pear, peach, strawberry and almond alongside the roses — plainly a far wider net than 'a particular organism'.
- (d)order — An order gathers related families and is wider still. Rosales includes not only Rosaceae but also the fig and mulberry family and the hemp family.
Taxonomy arranges living things in a nested ladder of ranks: kingdom, phylum or division, class, order, family, genus, species — widest at the top, narrowest at the bottom. Each organism has a two-word scientific name made of its genus and its species, a convention called binomial nomenclature and credited to Carolus Linnaeus. Mangifera indica is the mango: Mangifera the genus, indica the species.
Two things decide this item. First, direction — the taxonomic ladder narrows downward, so 'all the individuals of one kind' must sit at the bottom, and species is the bottom rank offered. Second, the definition of species itself, which is stated in terms of individuals: organisms of one species share fundamental similarities and can breed among themselves. No other rank is defined that way. One honest note about the paper's example: the rose is not a species but a genus, Rosa, holding well over a hundred wild species and thousands of cultivated hybrids, so 'rose plants' is a loose illustration of what the stem means by 'a particular organism'. The rank being asked for is still species, and that is what the key marks.
- The descending order of the main taxonomic ranks is kingdom, phylum or division, class, order, family, genus, species.
- Species is the basic unit of classification — the only rank whose definition is framed in terms of individual organisms interbreeding.
- Binomial nomenclature, given its modern form by Carolus Linnaeus, names an organism by genus followed by species: Homo sapiens, Mangifera indica, Panthera leo.
- Genus is one step above species and contains several related species; Panthera holds the lion, the tiger and the leopard.
- The rose is the genus Rosa, in the family Rosaceae and the order Rosales.
Every rank above species is a container for groups. Only species is a container for organisms.
- Reading the everyday name of a plant or animal as a species when it is really a genus — rose is Rosa, a genus.
- Inverting the ladder and treating kingdom as the smallest unit.
- Confusing a variety or cultivar, which is below species, with the species itself.
As a one-line rank identification, as an ordering item asking for the hierarchy from higher to lower, or as a name-parsing item asking what the two words of a scientific name stand for.
Which one of the following is the correct sequence of levels of hierarchy of classification of organisms from higher to lower ?
- (a) Phylum – Class – Order – Family – Genus
- (b) Phylum – Class – Family – Order – Genus
- (c) Family – Order – Class – Species – Genus
- (d) Class – Family – Order – Species – Genus
Answer(a) Phylum – Class – Order – Family – Genus
The same ladder, asked as an ordering item instead of a placement item. Knowing that the sequence runs phylum, class, order, family, genus and finally species is what tells you the bottom rung is where individuals of one kind gather.
- practice — not a real PYQ
In the scientific name Mangifera indica, the word 'Mangifera' denotes which taxonomic rank?
- (a)Species
- (b)Genus
- (c)Family
- (d)Order
Answer(b) Genus — in binomial nomenclature the first word is the genus and the second, 'indica' here, is the species.
- practice — not a real PYQ
Which one of the following is the correct sequence of taxonomic ranks from the widest to the narrowest?
- (a)Class, Order, Family, Genus, Species
- (b)Order, Class, Genus, Family, Species
- (c)Family, Order, Class, Species, Genus
- (d)Class, Family, Order, Species, Genus
Answer(a) Class, Order, Family, Genus, Species — the standard descending order of ranks below phylum or division.