NEET Biology Notes Concept of Species
Concept of Species
Species is the fundamental or smallest unit of classification. The term ‘species’ was recognised from Genus by John Ray.
- Static concept of species or morphological concept of species was proposed by Carolus Linnaeus. He considered species as a fixed and immutable entity.
- Dynamic concept of species was proposed by Lamarck, who considered species as a mutable and dynamic entity.
- Biological concept of species was proposed by Ernst Mayr. According to this concept, a species is a group of individuals, who resemble ea#h other in morphological, physiological, biochemical and behavioural characters and are capable of interbreeding.
- • Taxonomic species are the species having a binomial name.
- Sibling species are two distinct species, which do not interbreed but are otherwise difficult to separate on the basis of morphological characters alone.
- Allopatric species are species having exclusive areas of geographical distribution.
- Sympatric species are species having overlapping areas of geographical distribution.
- Parapatric species are species with adjacent geographic ranges meeting in a very narrow zone of overlap.
- Neonatological species are living species.
- Allochronic species are s, cies belonging to different time periods.
- Synchronic species are species belonging to a same period or time.
- Polytypic species are species, which have more than one ideal types according to their geographical isolated areas.
- Linnaean species are taxonomic species distinguished on the basis of morphological grounds.
- Biospecies are species erected on the basis of reproductive and genetic isolation of a natural population.
- Macrospecies are large polymorphic species with several sub-divisions.
- Microspecies or Jordan’s species are true breedingi genetic unit below the rank of species.
- Agamospecies are species reproducing only asexually
e.g. Euglena and Amoeba. ‘
- Gamospecies are sexually reproducing species.
- Palaeospecies are species known from fossils only.
- Monotypic species are species without differentiation of sub-species or varieties.
- Keystone species plays a key role or central role in the ecology of a place.
- Mule, Hinny, Tigon and Linger are exception to biological species concept. Mule is the offspring of male donkey and female horse and Hinny is the offspring of female donkey and male horse.
- Both Mule and Hinny are sterile. Tigon is the offspring of male tiger and female lion and Linger is of female tiger and male lion. Both Tigon and Linger are fertile.
Kingdoms of Life
The study of all living organisms without placing them at appropriate place is not possible so, scientists placed the organisms into kingdoms. Kingdom is the highest taxonomic category.
Linnaeus divided all organisms into two kingdoms, i.e. plant kingdom and animal kingdom. Photosynthetic organisms were included into plant kingdom, while non-photosynthetic in animal kingdom.
- Euglena show characteristics of both plants and animals.
- Bacteria and cyanobacteria (blue-green algae) have cytological differences from plants and animals.
- Fungi which are usually classified in plants, are non-photosynthetic.
- Fungi are non-motile, multiply like plants and non-photosynthetic like animals.
- Tunicate sponges and corals are non-motile and fixed like plants.
- Some algae which are photosynthetic are either motile or produce motile reproductive cells.
E Haeckel (1866), a German biologist, suggested a third kingdom-Protista to include unicellular protozoans and algae.
Copeland (1956) developed four kingdom system with kingdoms, i.e. Monera, Protista, Plantae and Animalia.
RH Whittaker (1969), an American taxonomist, divided all the organisms into five kingdoms, i.e. Monera, Protista, Fungi, Plantae and Animalia.
The five kingdom classification is based on complexity of cell structure (prokaryotic versus eukaryotic), source of nutrition, complexity of body organisation and major ecological roles.
All organisms are classified into five kingdoms
- Kingdom-Monera includes prokaryotic, autotrophic or heterotrophic organisms.
- Archaebacteria is a primitive group of bacteria. The three main groups of archaebacteria are methanogens, halophiles and thermoacidophiles.
- Kingdom-Protista includes eukaryotic, unicellular, autotrophic or heterotrophic organisms. The members of Protista are flagellates, diatoms, dinoflagellates, slime moulds, sarcodina, etc.
- Kingdom-Fungi includes eukaryotic, multicellular, heterotrophic organisms exhibiting absorptive (assimilative) type of nutrition, spore production. Fungi are achlorophyllous, heterotrophic thallophytes, which act as decomposers, which convert complex organic molecule in to simpler inorganic forms.
- Kingdom-Plantae or Metaphyta includes all coloured, multicellular, photosynthetic organisms (plants) that occur on land, on sea shore, lakes, streams and their non-green relatives.
(a) The photoautotrophic nutrition in plants is also termed as holophytic nutrition.
(b) Kingdom-Plantae includes algae, liverworts, mosses, ferns and seed plants with or without flowers.
- Kingdom-Animalia includes all multicellular holozoic or phagotrophic or ingestive eukaryotes.
These are also known as Metazoa and include sponges, cnidarians, worms, snails and other molluscs, arthropods, insects, starfishes, amphibians, reptiles, birds and mammals.
Six Kingdoms (Three Domains of Life)
Studies of ribosomal RNA (rRNA) show that all living organisms share a common ancestor and there are three major evolutionary lineages.
These are as follows :
Each of these lineages is called domain. The domain supersedes.
Distinguishing Features of Domains
Carl Woese et. al. proposed the six kingdom system, in which Monerans are divided into Archaebacteria and Eubacteria.
Some Important Taxonomic Terms
Term Coined by
Family John Ray
Species John Ray
Tools for Study of Taxonomy
Taxonomic studies of plants, animals and other organisms are useful in agriculture, forestry, industry and in knowing our bio-resources and their diversity. Biologists have established certain procedures and techniques to store and preserve the information as well as the specimens. These procedures are called as taxonomic tools or aids. Following are the main tools for study of taxonomy
- Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets. Succulent plants or the plants, which are unsuitable for pressing and drying techniques are applied by fixing in suitable liquid preservation like 2-5% formaldehyde, acetic acid and alcohol or FAA.
- The herbarium technique involves collection, drying, poisoning (by DDT and HgCl2), mounting, stitching, labelling, deposition, etc.
- A standard herbarium sheet is 29 x 41.5 cm (11 1/2 x 6 1/2 inch) size and is made up of thick hand made paper or a card sheet.
- The biggest herbarium of th# world is Royal Botanical Garden at Kew, England, while the biggest herbarium of India is Indian botanical Garden at Kolkata.
A botanical garden is essentially a collection of living plants maintained for both pure and applied studies. The main functions of botanical gardens are
- To provide records of local flora for monographic work.
- To provide facilities for collections of living plant materials for biosystematic studies.
- To supply seeds and materials for botanical investigation.
Museums have collections of preserved plants and animals for the study and reference. These are prepared for preservation of algae, fungi, mosses, ferns, animals, etc., because they cannot be kept in herbaria.
Insects are preserved in insect boxes, after collecting, killing and pinning, whereas larger animals like birds and mammals are usually stuffed and preserved.
These are the places, where wild animals are kept in protected environments under human care.Largest zoo of the world is situated in Kruger (South Africa).
- Key is one of the taxonomical aid used for identification of plants and animals.
- The keys are based on the contrasting characters generally in pair called couplet and represents the choice made between two opposite options. One is accepted and other is rejected.
- Two types of keys are always used-indented and bracketed.
- Statement in key is called a lead.