The eye is a complex sensory organ that allows us to see the world around us. The eye works by gathering light from the environment and converting it into electrical signals that can be interpreted by the brain. The basic structure of the eye includes the cornea, iris, pupil, lens, retina, and optic nerve. The cornea is the transparent outer layer of the eye that helps to focus incoming light. The iris is the colored part of the eye that regulates the amount of light that enters the eye through the pupil, which is the black circular opening in the center of the iris. The lens is a clear, flexible structure located behind the iris that helps to focus light onto the retina. The retina is a thin layer of tissue that lines the back of the eye and contains photoreceptor cells called rods and cones. These cells convert light into electrical signals that are sent to the brain via the optic nerve. The rods are responsible for the low light vision and detecting motion, while the cones are resp
Chemical evolution on primitive earth
In previous post we talk about various theories which were try to solve the puzzle of life i.e. how first life appear on earth. In the race of these theories, The modern theory were come which is the most acceptable theory of origin of life.This theory was given by two scientist Oparin and Haldane, so it is also known as Oparin-Haldane theory. This theory was published by Oparin in his book 'Origin of life'. He told that life originated in sea water, so water is very essential for origin of life. They divided the origin of life in two major process, first the Chemical Evolution and second one is the Biological Evolution. In this post we talk about the Chemical Evolution, so lets begin.
Chemical Evolution also known as chemogeny. This is the story after the big bang when our earth was too hot and we called this the Primitive earth.On primitive earth the atmosphere was very adverse, High temperature, volcanic storms, lightening and reducing atmosphere. and on primitive earth every atom are in free state which are essential for formation of protoplasm i.e. C, H, O, N, e.t.c.
On primitive earth Hydrogen was in maximum quantity among all the other atoms and, so it start reacting with other atoms to make molecules. Hydrogen reacted with almost all oxygen to make water vapour and no free oxygen left which made the atmosphere reducing. Hydrogen also reacted with Nitrogen and formed Ammonia. Hence, Water and Ammonia were probably the first inorganic compounds formed on earth and Methane was the first organic compound formed on earth. Now if a question arise in your mind that where is the energy for these reactions comes from then I will told you that on primitive earth the temperature was very high, lightening, volcanic storms and direct sunlight comes on earth so it will gives the more than enough amount of energy to carry out these reactions.
Now, as the earth cooled down, the water vapour fell as rain, to fill all the depressions on earth and form primitive oceans. During this the molecules continued to react with each other and formed various simple compounds, (like aldehydes, ketones, alcohols, amino acids, fatty acids, purines, pyrimidines, e.t.c,) and complex compounds (proteins, polysaccharides, fats/lipids, nucleic acids e.t.c.). But here note that the these proteins are non structural and non enzymatic and nucleic acids are non replicable.
Now, the water of oceans became a rich mixture of macro molecules/complex organic compounds. Haldane called it Hot dilute soup/ pre biotic soup.
Hence the possibilities of life were established in the water of primitive oceans because these macromolecules form the main component of protoplasm.
However we have no clear idea about how the first self replicating metabolic capsule of life arose, but many experiments made to solve the mystery of arise of life on earth. From these macromolecules how first life was originated, we will study in next part in The Biological Evolution
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