Presentations for aspiring Biology students

1. SYSTEMATICS of
living organisms

2. • Systematics is the study of kinds and diversity of
organisms, their comparative & evolutionary
relationships.
• Taxonomy means classification following certain
rules/principles. (A.P. de Candolle – Swiss Botanist coined the term
Taxonomy)
• Classification is arrangement of organisms or group of
organisms in distinct categories in accordance with a
particular and well established plan. (Similarities and
dissimilarities)
• It is done in three different ways namely; Artificial ,
Natural and Phylogenetic.

3. • Artificial System : it is based on few easily observable
and non evolutionary features such as habit, colour, form
irrespective of their affinity with other organisms.
Theophrastus (370-285 BC), ‘Father of Botany’, classified plants on the
basis of their habitat, form, & texture into four
categories: trees, shrubs, under shrubs, & herbs.
Aristotle (384-322 BC) arranged animals into four major groups
like insects, birds, fishes, and whales. Aristotle also divided animals into
two groups, one having red blood (Enaima) and the others without red
blood (Anaima).
John Ray (1627-1705) divided plants into dicotyledons and
monocotyledons based on the number of cotyledons in the seed.
Carolus Linnaeus’ system was based on just a few reproductive
features. He used number, union, length, and certain other characters
of stamens as the basis of the classification of plants. Based on these
characteristics, he proposed classes as Monandria (1
stamen), Diandria (2 stamens), and Triandria and Polyandria (3 or more

4. • Natural System : It is based on natural affinities. It also
uses more number of characters rather than a single
character for determining the similarities.
A.L. de Jussieu (1748-1836) classified the plants on the basis of the
number of cotyledons along with the presence and absence of petals
and position of petals and stamens.
A.P. Candole classified the plants on the basis of the characteristics
and arrangement of vascular tissues.
The most important and the last of the natural systems for classification
of seed plants was proposed by George Bentham and Joseph
Hooker (1862-1863). This work was published in ‘Genera Plantarum’.

5. • Phylogenetic System : it is based on phylogenetic
descent. The term Taxa and Categories are used.
Category is unit of classification. It represents rank and is
commonly termed as taxon . Engler and Prantles.
Category Taxon Taxon
Kingdom Plantae Animalia
Division/Phylu
m
Angiosperm
ae
Chordata
Class Dicotyledona
e
Reptilia
Sub class Polypetalae Diapsida
Series Thalamiflora
e
--
Order Malvales Squamata
Family Malvaceae Elapidae
Genus Hibiscus Naja
Species rosa-
sinensis
naja

6. Darwin’s theory of Origin of Species is the basis of the phylogenetic
system of classification.
Engler and Prantl (1884-1930) arranged families and orders of the
flowering plants in ascending series based on the complexity of floral
morphology.
The characters like one whorl of perianth or no perianth, unisexual
flowers, and pollination by winds were considered to be primitive
compared to perianth with two whorls, bisexual flowers and pollination
by insects.
Monocots are more primitive than dicots.
As a whole, this system considered the evolution of angiosperms from a
single source, and the sequence of order and families show parallel
evolution.

7. • Domain is an unit larger than kingdom (Carl Woose 1990).
There are three domains namely;
• Archae, Bacteria have prokaryotic cells but they differ in
structure of cell wall. Archae are known for their survival
in very extreme climatic conditions of temperature,
salinity, acidity. Eukarya have eukaryotic cells. All the
three domains have very unique rRNA
• All the three domains have very unique rRNA.

8. • It is based on chemical constituents of organisms.
• It is based quantification of characters & develop an
algorithm for classification.
• It involves cluster analysis algorithms instead of
subjective evaluation. (Sokel & Sneath 1963)

9. • It is typical branching pattern, it represents a hypothetical
relationship denoting a comparison of organisms and
their common ancestor.
• It is evolutionary relationship of organism. It helps to
understand evolution & focuses on similarities of
metabolism.

10. • It is based on DNA sequence from a tiny tissue sample. It
helps in understanding ecological & evolutionary
relationships.
1) Collecting DNA barcode data of known species.
2) Matching the barcode sequence of unknown sample
against the barcode library.
Protection of endangered species.
Preservation of natural resources.
Pest control in agriculture.
Identification of disease vectors, medicinal plants.
Authentication of natural health products.

11. Category Taxon Taxon
Kingdom Plantae Animalia
Division/Phylu
m
Angiosperm
ae
Chordata
Class Dicotyledona
e
Reptilia
Sub class Polypetalae Diapsida
Series Thalamiflora
e
--
Order Malvales Squamata
Family Malvaceae Elapidae
Genus Hibiscus Naja
Species rosa-
sinensis
naja
Categories together constitute taxonomic hierarchy. Some
Categories like kingdom, genus, species are compulsory
categories whereas categories like suborder, sub family are
facultative.

12. Taxonomy hierarchy is the scientific grouping of the various
taxonomic categories in a descending order on the basis of
their position and ranks in classification. Taxon is a group of
any rank.
• Species is the basic unit in the system of classification.
the members of species resemble with each other in
their morphological and reproductive characteristics and
breed freely among themselves.
• Genus is group of related species which resemble each
other in certain characteristics but they do not
interbreed.
Eg: Panthera includes Lion (leo), Tiger (tigris), Leopard (pardus)
Solanum includes Brinjal (melongena) & Potato (tuberosum)
A genus having only single species is called monotypic while a genus

13. • Family is a group of closely related genera. For eg. Family
Malvaceae includes genera like Hibiscus, Malva, Sida,
Gossypium, Abutilon,etc. Felidae includes Cats, Leopards,
Lion, Tigers, Cheetah. Dogs belong to another family
Canidae
• Order is a group of related families which resembles with
each other in major characteristics. For eg. The order
Carnivora includes families of cats and dogs (Felidae &
Canidae).
• Subclass is a group of different order having some
similarities. For eg. The Subclass polypetalae includes
orders like Malvales, Ranales, Parietales etc.
• Class is a group of related subclasses constitute a class.
For eg. class Dicotyledonae includes subclasses like
polypetalae and Gamopetalae.

14. • Division is a category consisting of related classes. For
eg. Division : Angiospermae includes classes like
Dicotyledonae & Monocotyledonae.
[Note : In case of animals the category “Phylum” is used instead of
“Division”.]
• Subkingdom is divisions possessing some similarities.
For eg. The subkingdom Spermatophyta or Phanerogams
includes the divisions Angiospermae and Gymnospermae.
• Kingdom is the highest taxonomic category consisting of
different sub kingdoms. For eg. kingdom plantae or plant
kingdom consists of the sub-kingdoms phanerogams and
cryptogams.

15.  The art of naming an object is infact a science called as
nomenclature. The system of nomenclature of plants and
animals in which the scientific name consists of two
words or epithets is called binomial nomenclature.
For eg. The scientific name of sunflower is Helianthus
annus Helianthus indicates genus (generic name) & annus
indicates species (specific name).
• Binomial names are simple, precise and meaningful.
• Binomial names are standard as they are accepted
universally.
• Binomial names are easy to understand and remember.
• Binomial names indicate phylogeny of organisms.

16. • Name is composed of two latin/greek words.
• Generic name is a simple noun. It should come first &
begin with capital letter.
• Specific name is adjective and should come later and
begin with small letter.
• Both the names should be separately underlined if
handwritten and if printed it should be in italics.
• The generic and specific name should not have less than
three or more than thirteen letters.
• Usually the name of the author who names a plant or an
animal is written in full/abbreviated form after scientific
name eg. Mangifera indica L. L stands for Linnaeus.
“Mentioning of author’s name after the name of the species is called
citation.”
• ICBN (International Code of Botanical Nomenclature) has been
changed to ICNAFP (26th June 2018) (International Code of
Nomenclature for Algae, Fungi & plants)

17. • Mangifera indica – mango
• Solanum tuberosum – potato
• Solanum melongena – brinjal
• Pathera leo – Lion
• Homo sapiens – Humans
• Panthera pardus – leopard
• Panthera tigris – Tiger
• Acinonyx jubatus -- Cheetah
• Felis is the genus for Cats