Coffee with NEET Day - 6



Living world

 Homeostasis 

  • Gk, homoios-same Stasis- standing is the maintenance of a constant internal environment or steady state (blood plasma, haemolymph, extracellular fluid, etc). 
  • The French physiologist Claude Bernard (1857) realized the importance of stability in the internal environment (milieu interieur). 
  • The term was first coined by the American physiologist Walter Bradford Cannon in 1929.


      Type of specification 

1.Holotype.

     The original type specimen from which the description of a new species is established. 

2. Isotype. 

    Duplicate of holotype, as another branch of the same tree. 

3. Lectotype. 

      Specimen selected from original material to serve as Nomenclatural type where there is no holotype. 

4. Neotype. 

     New nomenclatural type when the original type is missing. 

5. Paratype. 

      Any other specimen described along with holotype. 

6. Syntype. 

      Any of two or more specimens cited by an author when there is no holotype. 


Species concept. 

 1. Species is the basic unit of taxonomy. 

2. Modern concept of species is biological species concept introduced by Ernst Mayr (1942). 

3. Mayr defined species as groups of interbreeding natural populations that are reproductively isolated from each other group. 

4. The traditional concept of species was given by Linnaeus in Systema naturae; this is based on morphology and is also known as 'Morphological concept'

5. Species inhabiting the same geographical area (identical or overlapping) are  sympatric. 

6. Species inhabiting different geographical areas  are allopatric. 

7. Related species which are reproductively isolated but morphologically similar are called sibling species. 

8. Classical systematics is based on the 'Typological concept' by Plato and Aristotle. 

9. Genetic species concept was given by Lotsy (1918), according to which, a species is a group of genetically identical individuals. 

10. Species that contain two or more subspecies are called polytypic species. 

11. Species that are not sub- divided into subspecies are called monotypic species.


Dr. A. KINGSLIN M.Sc, BEd, Phd

Post Graduate Teacher in Botany
St. Mary Goretty Hr. Sec School, Manalikarai 
Kanyakumari district



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