05 Origin and Evolution of life - part 01- Origin of life

05 Origin and Evolution of life - part 01- Origin of life


Origin of life  (Protobiogenesis) :
  • The living matter shows attributes or characters like - 
  1. responsiveness
  2. growth
  3. metabolism
  4. energy transformations and 
  5. reproduction.
  • As far as origin of life is considered, it has remained an enigma for intellectuals at all times. 
  • Despite of advancements in various fields like biochemistry, astrobioloy, geography, molecular biology, etc. scientists are unable to ascertain the truth. 
  • Various theories and hypotheses have been proposed to find the probable answer to this question.
 a. Theory of special creation : 
  • It is the oldest theory and is based on religious belief without any scientific proof. 
  • It states that all living organisms are created by a super-natural power. 
b. Cosmozoic theory/Theory of Panspermia: 
  • This theory advocates that life did not arise on the planet Earth. 
  • It may have descended to the earth from other planets in the form of spores or micro-organisms, called cosmozoa/ panspermia. 
  • Recently, NASA has reported fossils of bacteria-like organisms on a piece of Martian rock recovered from Antarctica. 
c. Theory of spontaneous generation (Abiogenesis) : 

  • According to this theory, life originated from non-living materialspontaneously. 
  • This theory was disproved byLouis Pasteur.
Theory of biogenesis : 
  • According to this theory, living organisms are always produced from pre-existing living forms, by process called reproduction. 
  • Theory of biogenesis however could not explain origin of first life on earth but could explain only the continuity of life. 

Comments

Post a Comment

Popular posts from this blog

9. Morphology of Flowering Plants -part 01 - ROOT

Image
  9. Morphology of Flowering Plants -part 01 - ROOT Angiosperms : Angiosperms are one of flowering plants from  phanerogams . Types of Angiosperms [on the basis of habitat] : Hydrophytes  - Growing in aquatic habitat e.g.  H ydrilla Xerophytes  - Growing in regions with scanty or no rainfall like desert e.g.  Opuntia Psammophytes  - Growing in sandy soil e.g.  Elymus Lithophytes  - Growing on rock e.g.  Couchidium Halophytes  - Growing in saline soil e.g. Mangroove plants like  Rhizophora In angiosperms seed germinates under favourable environmental conditions and produces a seedling which develops into a new plant.  Morphology : Morphologically plant shows vegetative structures like -   root, stem, leaf  and reproductive structures such as  flowers, fruits and seeds. Root :  Root is  descending axis of plant body  which is  positively geotropic and hydrotropi c but negatively photot...
Read more

6. Biomolecules - part 02 - Lipids

Image
  6. Biomolecules - part 02 - Lipids B. Lipids : These are group of substances with greasy consistency with  long hydrocarbon chain containing carbon, hydrogen and oxygen. In lipids, hydrogen to oxygen ratio is  greater than 2:1  (in carbohydrates it is always 2:1). Lipid is a broader term used for fatty acids and their derivatives.  They are soluble in organic solvents (non-polar solvents).  Fatty acids are organic acids which are composed of hydrocarbon chain  ending in carboxyl group (-COOH).  They can be  saturated fatty acids  with no double bonds between the carbon atoms of the hydrocarbon chain.  Palmitic and stearic acids  found in all animal and plant fats are examples of saturated fatty acids. Unsaturated Fatty Acids  are with one or more double bonds between the carbon atoms of the hydrocarbon chain.  Oleic acid  found in nearly all fats and  linoleic acid  found in many seed oils are example...
Read more

06 Biomolecules - part 07 - Secondary metabolites

  06 Biomolecules - part 07 - Secondary metabolites Secondary metabolites (SMs) :  Secondary metabolisms are small organic molecules produced by organisms that are not essential for their growth, development and reproductions. Several types of  bacteria, fungi and plants  produce secondary metabolism. Secondary metabolites can be classified on the basis of - chemical structure (e.g. SMs containing rings, sugar) composition (with or without nitrogen) their solubility in various solvents, or  the pathway by which they are synthesized (e.g.phenylpropanoid produces tannins) .  A simple way of classifying secondary metabolites includes three main groups such as, 1. Terpenes :  Made from mevalonic acid that is composed mainly of carbon and hydrogen 2. Phenolics :  Made from simple sugars containing benzene rings, hydrogen and oxygen. 3. Nitrogen-containg compounds : Extremely diverse class may also contain sulphur. Economic importance - Secondary metabo...
Read more