What is Systematics?
Systematics is the study of the historical relationships among groups of biological organisms. It involves the recognition and understanding of biodiversity.
The term systematics was coined by Linnaeus in 1735.
Although the terms systematics, taxonomy, and classification are often used interchangeably, technically they have different meanings.
G. Simpson (1961) distinguished between these three terms.
Taxonomy
Taxonomy is the branch of biology that deals with the identification, nomenclature, and classification of organisms.
The term taxonomy was first introduced by the French botanist A.P. de Candolle (1778–1841) for the theory of plant classification.
Taxonomy is also known as systematic botany.
Carolus Linnaeus is known as the Father of Taxonomy, and H. Santapau is called the Father of Indian Taxonomy.
Types of Taxonomy
There are three types of taxonomy:
- Alpha Taxonomy
- Beta Taxonomy
- Omega Taxonomy
- Alpha Taxonomy: When only morphological characters are used for the identification and classification of plants, it is called alpha taxonomy.
- Beta Taxonomy: It includes genetic, anatomical, cytological, palynological, physiological, and other characteristics. It is also called biosystematics.
- The terms alpha and beta taxonomy were given by Turill.
- Omega Taxonomy: The analysis and synthesis of all types of information and data to create a classification system based on phylogenetic relationships is called omega taxonomy.
Classification
Classification refers to the process of placing an organism or a group of organisms into a particular category according to a systematic and nomenclature-based structure.
Aristotle, known as the Father of Zoology, made the first recorded attempt to classify animals in his book Historia Animalium.
He divided animals into two main groups:
- Anaima – animals without red blood cells (invertebrates)
- Enaima – animals with red blood cells (vertebrates)
Theophrastus and Plant Classification
Theophrastus (372–287 BC), known as the Father of Botany, classified plants based on their form and texture, and described around 480 plant species in his book Historia Plantarum.
Identification
Identification is the process of determining the exact place or position of an organism in a set plan of classification. It is done using taxonomic keys.
A key is a helpful tool that allows for easy identification of an organism using diagnostic or distinguishing characters.
Difference between Taxonomy and Systematics
- Taxonomy focuses on discovering and describing new species.
- Systematics uses evolutionary relationships to understand biogeography, coevolution, adaptation, and strategies for biological conservation.
Systematists or taxonomists are scientists who provide data on the identification, description, distribution, and relationships of life forms on Earth.
New Systematics (Biosystematics)
New Systematics, also known as Biosystematics, is a concept in systematics that emphasizes taxonomic affinity based on evolutionary, genetic, and morphological traits.
The term New Systematics was proposed by Julian Huxley in 1940.
Nomenclature
Nomenclature refers to the process of assigning unique scientific names to various structures, including living organisms, for their identification.
🔹 Types of Biological Nomenclature:
- Vernacular Names
- Scientific Names
Vernacular names are the common or local names by which plants and animals are known in specific regions.
For example: Kandiali (a thorny plant).
Scientific names are those assigned according to universally accepted principles and rules so that they are valid worldwide. These names are distinct, specific, and have standardized spellings that remain unchanged.
🔹 Types of Nomenclature:
- Polynomial Nomenclature
- Trinomial Nomenclature
- Binomial Nomenclature
✅ 1. Polynomial Nomenclature
This was the earliest scientific attempt at naming organisms. In this method, an organism was given a multi-word name that described all its key features.
This system was complicated and lengthy.
✅ 2. Trinomial Nomenclature
This system extends binomial nomenclature by adding a third taxon. It is used when a species has subspecies or subdivisions that must be identified separately.
🐾 In animals:
The trinomen or trinomial name refers to the subspecies.
It includes:
- Generic name
- Specific name
- Subspecies name
All three names are written in italics, with only the generic name capitalized.
🌿 In plants:
Trinomial nomenclature provides a three-part name (ternary name) for taxa below the species level.
✅ 3. Binomial Nomenclature
This is the standard system of assigning proper scientific names to organisms. Each name consists of two words:
- Generic name (genus)
- Specific name (species)
These names are given in Latin, as it is a dead language, meaning no changes occur in it.
🔹 Rules of Binomial Nomenclature:
- The name consists of two words:
- First: Generic name (starts with a capital letter)
- Second: Specific name (starts with a lowercase letter)
- Both names should be italicized (when printed) or underlined separately (when handwritten).
- No comma, hyphen, or punctuation is used between the two names.
- The scientist’s name who discovered and described the species is added at the end.
Example: Ficus bengalensis L., Homo sapiens L.
🔹 Synonyms:
If multiple names are given to the same species by different scientists, the name that was first validly published is accepted as the valid name, provided the publication was effective and valid.
🔹 Codes and Concepts in Nomenclature:
- The International Code of Botanical Nomenclature (ICBN) is based on Philosophia Botanica, a book written by Carl Linnaeus.
- The current botanical nomenclature code was published in 1978.
- Botanical nomenclature is independent of zoological and bacteriological nomenclature, which follow their own codes.
🔹 Types of Type Specimens:
- Lectotype:
A specimen or element chosen from the original material when no holotype was designated, or the holotype is lost. - Neotype:
A specimen selected to serve as the name-bearing type when all original material is missing. - Epitype:
A specimen chosen to clarify the application of a name when the existing types (holotype, lectotype, or neotype) are ambiguous or not sufficient for identification. - Topotype:
A specimen collected from the same locality as the original holotype.
Taxonomic Hierarchy or Linnaean Hierarchy
Taxonomic hierarchy is the stepwise arrangement of taxonomic categories in descending order, followed during the classification of an organism.
The term taxa refers to taxonomic groups of any rank, i.e., any unit of classification.
🔹 Linnaean Hierarchy
In the original Linnaean system, five major taxa were used:
- Class
- Order
- Genus
- Species
- Variety
In the modern system, the complete hierarchical order is as follows:
➡️ Species
➡️ Genus
➡️ Tribe
➡️ Family
➡️ Order
➡️ Series
➡️ Class
➡️ Division (for plants) / Phylum (for animals)
➡️ Kingdom
This arrangement is called a hierarchy, where each category is ranked above or below another.
- Kingdom is the highest taxonomic category.
- Species is the lowest and basic unit of taxonomy.
🔹 Types of Specification (Types of Type Specimens)
- Holotype:
The single specimen designated by the author to represent the species. - Isotype:
A duplicate of the holotype, collected at the same place, same time, and by the same person. - Syntype:
Any of two or more specimens cited when no holotype was designated, or all specimens equally designated as types. - Paratype:
A specimen cited in the protologue that is not the holotype, isotype, or syntype, but still mentioned.
🔹 Systems of Biological Classification
There are four main classification systems used by taxonomists:
- Artificial System
- Natural System
- Phylogenetic System
- Phenetic System
✅ 1. Artificial Classification System
This system is based on one or a few superficial characteristics, like flower color, leaf shape, etc.
✅ 2. Natural Classification System
Organisms are grouped based on natural affinities using multiple permanent and significant characteristics, such as:
- Structural
- Cytological (Chromosomal)
- Reproductive
- Biochemical
✅ 3. Phylogenetic Classification System
Based on evolutionary relationships, it arranges organisms according to their ancestral lineage.
✅ 4. Phenetic Classification System
It classifies organisms based on overall observable similarities, regardless of ancestry.
🔹 Concepts of Species
- Genetic Species Concept (Lotsy, 1918):
A species is a group of individuals that are genetically identical. - Biological Species Concept (Ernst Mayr, 1942):
A species is a group of naturally interbreeding populations that are reproductively isolated from other such groups.
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