- Taxonomy A branch of science that deals
with identification, naming and classification of plants as well
as animals is called taxonomy.
- Importance of taxonomy
a. Collective study of organisms.
b. Identification scheme for organisms.
c. Universally accepted scientific names.
d. Classifying and putting the plants and animals into definite
e. Evolutionary relationship.
- 'Species' is regarded as the basic unit of
- Species: Groups of interbreeding natural
populations which are reproductively isolated from other groups,
are called species.
Taxa and Categories
- Classification includes a hierarchical system of
different ranks, with 'kingdom' at the top and 'species'
at the bottom.
- Categories: All the ranks of
classification are called categories.
- Taxon: All the members of a category
belong to one taxon.
- Various categories used in classification, from the
bottom to the top, are:
- Species: It is the smallest unit. The
potentially interbreeding group.
- Genus: Group of closely related species.
- Family: Group of closely related genera.
- Order/Cohort: Group of closely
- Series: Group of closely related orders.
- Subclass: Group of closely
- Class: Group of closely related sub - classes.
- Subdivision: Group of closely
- Division: Group of closely
- Kingdom: Group of closely related
- Units of classification:
1. Species: The species
is the smallest unit of classification. The species refers to a group
of plants or animals which have close resemblance with one another in
their morphological characters and breed freely among themselves. For
example, all banyan trees belong to the species bengalensis while all
pipal trees belong to the species religiosa. John Ray was first to
use the term species.
2. Genus: The genus
is a unit of classification higher than the species. The genus is a
group of related species which show resemblance in their reproductive
characters but differ in their vegetative characters. For example,
banyan and pipal are two different species belonging to the same
3. Family: The family
is a unit of classification higher than the genus. The family is a
collection of genera (singular±genus) showing similar reproductive
characters. For example, Hibiscus and Sida are two different genera
showing resemblance in their floral characters belonging to the same
4. Cohort or
Order: The cohort or order is a unit of classification higher
than the family. A group of closely related families forms a cohort
or order. For example, families Malvaceae and Tiliaceae belong to the
same cohort (order) Malvales.
5. Class: The class
is a broad unit of classification which includes all related
subclasses. For example, class Dicotyledonae consists of subclasses
like Polypetalae, Gamopetalae and Apetalae.
6. Division or
Phylum: The division or phylum (for animals) is the largest
unit of classification. The division consists of closely related
classes. For example, division Angiospermae includes classes like
Dicotyledonae and Monocotyledonae.
Levels of Classification
of Hibiscus plant according to the hierarchical levels of
Kingdom à Plantae - Multicellular autotroph.
Division à Spermatophyta - Seed producing plant.
Sub-division à Angiospermae - Ovules
enclosed inside ovary.
Class à Dicotyledonae - Two cotyledons in the embryo.
Sub-class à Polypetalae - Petals of
flowers are free.
Series à Thalamiflorae - Distinct thalamus, hypogynous
Order à Malvales - Monadelphous stamens, axile
Family à Malvaceae - Stipulate leaves, Reniform anthers.
Genus à Hibiscus - Epicalyx present, capitate stigma.
Species à rosa - sinensis - Flower
stalk presents (pedicel), long staminal tube.
- Carlous Linnaeus was a Swedish botanist who established
a naming system consisting of two words called binomial
- The first part of the name indicates genus while the
second part indicates species. Example: For the mango plant, the
binomial nomenclature is Mangifera indica Linn,
where Mangifera is genus, the indica is
species and Linn is the short form of the name of scientist
Linnaeus who discovered it.
- Importance of Binomial Nomenclature
a. Simple, meaningful, standard and universally accepted names.
b. Helps in identification and grouping of organisms in any part
of the world.
- Taxonomy makes use of information from all the branches
of biology such as morphology, cytology, phylogeny, molecular
- Morphological Criteria: Plants with
identical morphological characters are grouped together.
- Phylogenetic Considerations: Phylogeny is
evolutionary history. According to phylogeny, each group of plants
is a product of modifications of different characters. If plants
resemble each other, then they are of common origin.
- Numerical Taxonomy: Resemblance in
characters is considered to be the index of closeness while
differences indicate separation of plants into different groups.
- Chemotaxonomy: Here, the plants
are classified according to their chemical composition into
different groups. If two species are identical in their chemical
substances, then they are closely related.
of Botany and Medicine.
span:1707 - 1781.
Naturalist, studied at the university
and described 5,900 species of plants and 4,200 species of
binomial nomenclature and artificial system of classification
based on sexual characteristics, viz., stamens and carpels.
Plantarum (2)Species Plantarum.