- There were 3 conditions for the origin of life
⇒ continuous supply of replicators
⇒ copying error during replication
⇒ system must have required a continuous supply of free energy.
- Biological evolution started with the formation of pre/protobionts which are non living structures that led to the formation of first living cells from which the more complex cells have evolved.
- The 2 prebionts are
Oparin ⇒ coacervates [aggregation of colloidal particles in liquid phase that consists of carbohydrates, proteins, lipids and nucleic acids surrounded by a non-biological membranes
Sydney Fox ⇒ Micro spheres [Microscopic membrane bound spheres formed when protenoids are boiled in water and allowed to cool. Protenoids are produced by dehydration synthesis of amino acids at 180°C]
- Oldest known fossil ⇒ Stromatollites [sheet formed over sedimentary rocks which contained a species of Blue green Algae, called Archaeospheroides barbetonensis].
- Evolution of modes of Nutrition
(Photo auto trophs) - Eg. Cyanobacteria
- As the number of photoautotrophs increased, O2 was released in the sea and atmosphere which is termed as O2 revolution.
- As O2 accumulated in atmosphere, the UV light changed some of the O2 into Ozone.
2O2 + O2 → 2O3
- Origin of Eukaryotes is of two types
⇒ Symbiosis [Margulis]
⇒ Origin by Invagination
- Symbiotic origin :
⇒ Predator host cell + aerobic bacteria ⇒ Eukaryotic animal cell
⇒ Predator host cell + aerobic bacteria + cyanobacteria ⇒ Eukaryotic plant cell.
- Three domains of life [Carl Woese]
- Finally, it is concluded that the life originated from ocean.
⇒ Evidences for organic Evolution
- The study of fossils is called as Palaeontology.
⇒ Leonardo da Vinci [The Father of Palaeontology]
⇒ George Cuvier [The Founder of modern Palaeontology]
- The fossils of spores, Pollen grains and other microscopic structures are called micro fossils (or) Palyno fossils.
- Age of the fossils can be determined by following methods
⇒ Clock of the rock method / Radioactive clock
⇒ Radioactive carbon method
⇒ Potassium - argon method
- The first geological time scale was developed by Gioranni Avdesina. The history of the earth has been divided into a number of major divisions called eras, which are sub divided into periods. The modern periods are further divided into epochs.
- The fossil record contains some transitional link forms called missing links [also called as connecting links].
Eg. Archaeopteryx [connecting link between birds and reptiles]
- Evolution of Vertebrates :
- Evolution of horse :
Eohippus [renamed as Hyracotherium]
Mesohippus [Intermediate horse]
Merychippus [ruminating horse]
Pliohippus [first, one toed horse]
Equus [modern horse]
Watch this video for the topic from 1:18 to 12:40
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