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ORIGIN OF LIFE

There are different theories about the origin of life on the earth.

Theory of special creationAccording to this theory, the life was created by super natural power of the god. This theory isbased on religious faith.

According to Hindu Mythology, the god of creation is Brahma. He created universe and humanbeings.According to Christian thought the god created universe, earth, plants, animals, and man withinseven days.

Theory of spontaneous generationAccording to this theory, the life originates spontaneously from the non-living things. or e!amplethe frog, toad, sna"e originated from mud. The insects and flies originated from the fruit #uicesand the microorganisms originated from air and water.

Theory of BiogenesisAccording to this theory, the life originated from pree!isting life but not spontaneously. rancis$edi and %ouis &asteur prove this

Reddi's Experiment (1688 AD

He was an 'talian biologist. He "ept dead fish, sna"e, and meat in wide mouthed flas"s and leftthem opened. He again placed same things in other flas"s and sealed the mouth. He observedlittle white worms and larvae in opened flas"s but absent in sealed flas"s. He concluded that thelife can arise from pre-e!isting life only, means some pree!isting life went in open-mouthed flas"sthen worms and larvae were developed in open mouthed flas".

!ouis "asteur's Experiment (186# ADHe was rench microbiologist. He conducted an e!periment to prove theory of biogenesis.

He poured nutrient solution into the flas".

He bent the nec" of the flas" in the shape of ( using heat.

The li)uid was boiled for several minutes so that the bacteria were either "illed or driven

out of flas".

The solution was then cooled. The dust particles remained trapped at the bend of the

tube. The solution remained sterile for months.

*hen the nec" was bro"en and flas" was tilted, li)uid came in contact with dust ormicroorganisms. Bacterial colonies or moulds appeared in the flas" within a few days.

Biochemical Theory ($odern TheoryThe scientific theory proposed by A.I. Oparin in 1923 and J.B.S. Hal Dane in + is calledbiochemical theory or modern theory or /parine and Haldane0s Theory. According to this theory,the life originated through a series of bio chemical reactions.

%rigin of earthAbout 1233 million years ago, the earth originated. The earth was a molten fireball havingtemperature of about 1333 to 333 4C. The earth began to cool down and the volume decreased.5uring the process, the heavier elements settled towards the centre forming the crust of the earthand the lighter elements remained on the outer surface-forming atmosphere. 'n the atmosphere,there were free atoms li"e C, H, /, 6 etc. The free atoms combined forming molecules li"e /,6,

and H./7/88.. / 9 67688.. 6 9 H7H88... H

%rigin of &norganic $oleculesThen these molecules started to combine to form inorganic molecules.

H7/8888 H/ H768888 6H:C7/8888.. C/9C/ C7H8888.. CH1

%rigin of imple %rganic $oleculesThe inorganic molecules combined to form simple organic molecules.

H/ 7 CH188888. (ugar9atty Acid9;lycerol

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H/76H:7CH1888. AminoAcid96itrogen Base

%rigin of omplex %rganic $oleculesThe organic molecules again combined together toform comple! molecules

(ugar 7 (ugar8888888888888

(tarch9;lycogen9Cellulose etc.atty acid 7 ;lycerol8888888888ats

Amino Acid 7Amino Acid88888888&rotein

6itrogen Base 7 (ugar 7 &hosphoricAcid88 6ucleotides06ucleotide 7 6ucleotide888888888 6ucleic Acid ? rays andelectric discharge enhanced these reactions. The nucleicacid combined with protein and nucleoprotein particleformed. 't was self-replicating particle and was first livingparticle 0the virus0.

%rigin of "rimiti)e ellThe comple! organic molecules aggregated together forming colloidal mass called coacer)ate.The nucleic acid controlled the activities of coacervate and the fats formed a layer around it. Thisstructure is called Eo*iont. 't was first cell li"e structure. The eobiont absorbed food materialsfrom the surrounding. 't was heterotroph, pro"aryotic cell, and present day bacteria.

%rigin of +eterotrophs and Autotrophs%ater on, some of the eobiont became able to ma"e food by using chemical energy. (o theybecame chemoautotroph.

C/7H(888888..C2H+/27 H/ 7 ((ome other eobionts developed chlorophyll molecules, which trapped solar energy tomanufacture food from C/and H/. They became photoautotroph.

C/7H(888888..C2H+/27 H/ 7 /

'n this way, photosynthetic organisms were originated on the earth. /n other hand theheterotrophs modified and different types of animals evolved. They started to consumeautotrophs and used / to brea" down food material to release energy.

$&!!ER A,D -RE.' E/"ER&$E,TTo prove /parin and Haldance biochemical theory of origin of life Miller and >rey in +@conducted an e!periment. They designed an apparatus containing glass tube, flas", and gaschamber. They "ept 6H:, CH1,H, C/ in gas chamber and water is boiled in the flas" to producewater vapor. The energy was supplied by heating and by electric spar"s.

The condenser was used to cool reaction. They run the e!periment for a wee". inally, theyanalyed the products formed within the tube. They found different organic compounds li"e fattyacid, amino acid, sugar, glycerol etc in the tube. Then they proved /parin and Haldance0s theory

of origin of life through a series of chemical reaction among the inorganic gases under theinfluence of temperature, electric discharges, and cooling.

E0%!-T&%,

The orderly and gradual change in ob#ect from one form to another form is called evolution. Theorderly and gradual change in living things is organic evolution li"e plant evolution and animalevolution. The orderly and gradual change in non-living things is called inorganic evolution li"ethe evolution of earth and stars.

Evolution of Man

Fig: Miller and Urey's Apparatus

Chlorophylls

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E)olution of Early $ammal

About +3 million years ago, the early mammalevolved from the reptiles. They were small rat li"eanimals having long snout. The 5inosaurs were alsoevolved from it.

E)olution of "rimates

About 2@ million years ago, primates evolved from theearly mammal. The primates have long snout long and busy tail. 't was insectivorous. 't was li"epresent day tree shrew. At that, time dinosaurs were e!tinct.

E)olution of Anthropoid Ape

About :2 million years ago anthropoid ape evolved from primates. They were ancestors ofmon"ey, ape, and man. rom the primates new world mon"ey diverged about @3 million yearsago. The nose of the new world mon"ey0s nose was very flat, nostrils were directed upward, andtail is long and prehensile.

E)olution of +ominid

About 1 million years ago, the hominid evolved from anthropoid ape. The hominid was ancestorsof man and ape. About @ to :3 million years ago from the anthropoid ape old world mon"eydiverged. The old world mon"ey0s nose is raised, the nostrils directed downward and the tail isshort and non-prehensile.

E)olution of Ramapithecus and i)apithecus (the earliest ancestor of manAbout +3-+1 million years ago, $amapithacus and (ivapithecus evolved from the hominid. Theywere earliest ancestors of man. The $amapithecus was found in Asia and Africa. 'ts tooth wasfound in Butwal of 6epal. The (ivapithecus was found in Asia.

About 1-+3 million years ago Apes diverged from the hominid. They include Chimpanee, ;orilla,/rangutan, and ;ibbon.

E)olution of Australopithecus

About @ million years ago, the Australopithecus was evolved from the $amapithecus and(ivapithecus. They were first human li"e animal. Their brain capacity was 133 233 cc. 't couldwal" upright and about : @ ft tall and 13 @3 g in weight. The Australopithecus has twospecies. They areA. AfricansandA. robustus.

E)olution of Homo erectus

About +.D million years ago, Homo erectus evolved fromA. africanus.The Homo erectus includes

Eava man found in 5ubai and &ec"ing Man found in China.The Eava man0s cranial capacity was 33 cc. 't was @ ft tall and used fire, tools. The locomotionwas bipedal. The chin was absent.The &e"ing man0s cranial capacity was +3D@ cc.'t was supposed that Homo erectus was evolved from Homo habilis about million years ago andthe Homo habiliswas evolved formA. Africanus. The Homo habiliscranial capacity was D33 cc. 'twas about 1-@ feet tall, bipedal, the chin was absent.

E)olution of the ro$agnon man

About :133 years ago, the Cro-Magnon man evolved from Homo erectus. The Cro-Magnon manwas li"e modern man. Their cranial capacity was +233 cc. They were @ ft tall, have prominentchin, broad or flat forehead, raised nose, superior intelligence. They made weapons, lived incaves and he was artist.

E)olution of ,eanderthal man

About D3-13 thousand years ago, The 6eanderthal man Homo sapiens neanderthalensisdiverged from Homo erectus. Their cranial capacity was +1@3 cc. They resemble to modern man.They were @ ft tall, chin was absent, they used tools for hunting used animal hides as clothes,capable of communicating, and they made tradition to bury dead bodies.

E)olution of $odern man

The modern man

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Differences *et2een Ape and $anApe $an

The apes have semi erect bodyThe vertebral column is curvedThe bipedal locomotion need support offorelimb

The fore limb is longer than hind limbThe thumb does not e!tend up to the baseof fore finger.They have flat noseCanine incisor teeth are longer and thic"erThe chin is absentThe eye brow ridges are heavy andprominentThey have short nec" embedded inshoulderThe body is covered with hairs

The man has erect body?ertebral column is straightThe bipedal locomotion do not need support offore limb

The fore limb is shorter than the hind limbThe thumb e!tends up to the base of fore fingerThey have raised noseThe canine and incisor teeth are shorter

The chin is prominentThe Fye brow ridges are not so prominent

They have long nec"ewer amounts of hairs are present on thebody.

+omology of $an

(imilarities in chromosome number of apes and man is called homology.

The chromosomes number of apes is 1.

The chromosome number of man is 12.

(imilar amount of 56A.

Banding pattern of chromosome is similar.

Chromosome number :, 2 have similar banding pattern

Banding pattern means arrangement of 56A in chromosome.

T+E E0&DE,E %3 E0%!-T&%,

To convince about the truth of evolution there are several evidences, which support the validity of evolution

(A TR-T-RA! A,D A,AT%$&A! E0&DE,EThe types of organs li"e homologous organs, analogous organ and vestigial organsprovide the evidences about structure.+omologous organ

The organs, which are similar in structures and origin, called homologous organ.or e.g. human hand, Birds wing, bats wing, Horse0s front foot are homologous

organ.Analogous %rgan

The organs, which are not similar in structure and origin but function is same are called analogous organ.or e.g. Bird0s wing and insect0s wing, ishes eye and mollus"0s eyeThe analogous organs are developed due to similar habitat in evolutionary process.

0estigial %rganThe useless and reduced organ are called vestigial organs are called vestigial organ. 'n human body,there are about 33 types of vestigial organ. or eg. 6ictitating membrane, ?ermiform appendi!, Canine

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teeth, Caudal ?ertebrae, (ome sna"es have vestige of limbs, ishes lived in dar" caves have reducedeyes.

(B A,AT%$&A! E0&DE,EThe arrangement of different types of system li"e blood vessels, alimentary canal, s"eletal system, e!cretorysystem etc is similar in vertebrates. Thus, the anatomy suggests in favor of organic evolution showing thatthe anatomical similarities become more and more comple! progressively as one proceeds from loweranimals to higher animals. All the varieties of animals have inherited the anatomical similarities from a

common ancestor. ( "A!E%,T%!%4&A! E0&DE,EThe paleontology deals with the study of fossils thus pale ontological evidences are the evidences ofevolution from the fossil record suggesting that the evolution occur from simple form to the comple! form.a) Archaeopteryx

The most favorable evidence, which prove pale ontological evidence, is a"ind of fossil bird named Archaeopter!. This provides connecting lin"between reptiles and birds suggesting that the birds might have beenevolved from reptiles. 't represented the characteristics of both a bird andthe reptile. 't possessed following characters't had a bea" li"e a bird but the bea" contained teeth li"e reptiles.'ts forelimbs were modified into wings li"e birds but claws on its wing li"ereptiles.'t had feathers li"e birds but also had scales li"e reptiles. 't had featherytail li"e birds but had vertebrae li"e reptiles. Therefore, it is proved that the

birds were evolved from reptiles and therefore the birds are called glorifiedreptiles.* +orse's "hylogenyThe evolutionary history of horse is termed as horse0s phylogeny. The first horse