The Big Bang theory

The Big Bang theory:

• The Big Bang is a singular huge explosion which is unimaginable in physical term.

• The universe expanded and hence the temperature came down.

• Hydrogen and Helium formed sometime later.

• The gases condensed under gravitation. They formed the galaxies of the present day universe.

• In the solar system, earth was formed about 4.5 billion years back.

Condition of primitive earth:

• Earth formed about 4.5 billion years ago.

• There was no atmosphere on early earth.

• Water vapor, methane, carbon dioxide and ammonia released from molten mass covered the surface.

• The UV rays from the sun broke up water into Hydrogen and oxygen. The lighter H2 escaped.

• The ozone layer was formed by O3.

• As earth cooled, the water vapor fell as rain. It fill all the depressions and form oceans.

Origin of life:

• Special creation theory: According to this theory God created earth and living organism. But it does not had any scientific prof.

• Theory of spontaneous generation: According to this theory living organism are originated from decaying and rotting matter like straw, mud etc.

• Theory of biogenisis: Louis Pasteur experimentation demonstrated that life comes only from pre-existing life.

• He showed that, in pre-sterilized flasks life did not come from killed yeast. The new living microorganism arose from ‘killed yeast when flask open in to air.

• Oparin – Haldane theory of Biochemical origin of life:

• A.I. Oparin and Haldane proposed that life could have come from pre- existing non-living organic molecule (e.g. RNA, protein etc.).

• According to them life originated from non-living matter by a gradual process of physicochemical reaction on primordial earth.

• The conditions on primitive earth were –

1. High temperature.

2. Volcanic storms.

3. Absence of oxygen.

4. Reducing atmosphere containing CH4, NH3 etc.

• Urey and Miller experiment:• Stanley Miller conducted an

experiment in self-designed spark discharging apparatus. In 1953 he conducted physicochemical test for origin of life.

• Miller created similar conditions of primordial earth in a laboratory scale.

• He created electric discharge in a closed flask to raise temperature upto 800oC . It was in primitive earth.

• He Used CH4 H2, NH3 and water vapor inside the flask.

• He observed the formation of amino acids in condensed liquid water.

• Origin of first cell:

• The first non-cellular forms of life may originated 3 billion years back.

• They have been giant molecules like RNA, proteins, Polysaccharides etc.

• These giant molecules are called capsules. They reproduced their molecules to form coaservates.

• The first cellular life formed are unicellular.

• All life forms were in water environment only. This simple cell evolved into complex form of present diversified life

• Evolution of life: Theories.• Evolution is the process that results in heritable

changes in a population. It spread over many generations leading to diversity of organisms on earth.

• Charles Darwin made a sea voyage in HMS Begale ship.

• First voyage (1826–1830)• Second voyage (1831–1836)• Third voyage (1837–1843)

• Darwin on his observation and collection during voyage proposed theory of Natural selection.

• He observed that various form of life exist on earth share some similarities. There had bean extinction of old one and evolution of new one.

• The struggle for existence and survival fittest leads to reproductive fitness. Over a period of time it leads to formation of new species.

12 February 1809 – 19 April 1882

• EVIDENCES FOR EVOLUTION

• Paleontological evidence:

• Fossils are hard parts of life found in rocks.

• Different-aged rock sediments contain fossils of different life-forms.

• A study of fossils in different sedimentary layers indicates the geological period in which they existed.

• The study showed life forms are restricted to certain geological time-span.

• Hence new lives have arisen at different times in the history of earth.

• Comparative anatomy and morphological evidence:

• It is the Comparison of body structures among different species

• It shows similarities and differences among organisms of today and those that existed years ago.

• Certain anatomical similarities among species are the same.

• Ex skeletal elements make up the forelimbs of man, horse, whale and bat are same. But each of them performing different function.

• All of them have humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs.

• Homologous organ: These are the organs having same basic structure but different function.

• Ex 1. fore limb of human, cheetah, whales and bat.

• Ex 2. Thorn of Bougainvillea and tendrils of Cucurbita represent homology.

• Analogous organ: These are the organs having different anatomical structure but same function.

• Ex 1: wings of butterfly, bird and bat.

• Ex 2. Eye of octopus and eye of mammals.

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• Ex 3. Flippers of Penguins and Dolphins.

• Ex 4. Sweet potato (root modification) and potato (stem modification)

• Divergent evolution:

• It is the origin of new species from common ancestors.

• Homologous organs supports common ancestor.

• Convergent evolution:

• It is the independent development of species having similarities to adopt similar environment.

• Analogous organs supports it.

• Biochemical evidences:

• Similarities in proteins and genes performing a same function among different organisms.

• Embryological support for evolution:

• Certain features during embryonic stage common to all vertebrates that are absent in adult.

• Ex gill slits of vertebrates found in embryo.

• Evolution by natural selection:

• observation of moth population in England 1850 supports it.

• Before industrialization, it was observed that there were more white-winged moths on trees than dark-winged or melanised moths.

• Because white easily escaped from predators as it blends with trunk colour and lichens.

• After industrialization 1920 there were more dark-winged moths in the same area.

• Because of smoke, tree trunk become dark after industrial revolution. The white months are easily noticed and captured by predators. The dark winged were escaped.

• Adaptive radiation:

• It is the process of evolution of different species in a given geographical area radiating to other areas.

• Ex :Darwin's finches in the Galapagos Island.Finches are sparrow like small birds found in Galapagos island.

• 14 different species of finches are observed by Darwin.

• They have same body plan and short tail. But differes in beak shape and size which is adopted to different food habit.

• Theories of evolution:

• Three major theories explains the mechanism of evolution.

• 1. Theory of inheritance of acquired character by Lamarck.

• 2. Theory of natural selection by Darwin.

• 3. Mutation theory by Hugo De Vries.

Theory of inheritance of acquired character by Lamarck.

• Lamarck was a French Naturalist.

• He said that evolution of life had occurred by use and disuse of organs and inheritance of acquired character

• He gave the example of Giraffes .the ancistor giraffe are small donkey like animals.

• In first attempt to get leaves on tall trees had to adapt by elongation of their necks.

• This character has acquired and elongated neck inherited to succeeding generations.

• Giraffes, slowly over the years, came to acquire long necks.

Theory of natural selection by Darwin.

• The main concept of Darwin's theory are,

1. Over production.

2. Limitation of food and space.

3. Struggle for existence.

4. Variations.

5. Survival of fittest.

6. Natural selection.

7. Speciation.

• But Darwin did not explained the mechanism of variation and inheritance of characters.

. Mutation theory by Hugo De Vries.• According to De Vries, mutaions are

the main cause of evolution and speciation.

• The sudden change in gene that results in variation in phenotype is called mutation.

• According to him speciation occurs in a sudden change in a single step.

• Mutations are random and directionless

• The main objections of this theory are

• Mutations are negative and retrogressive.

• Rate of mutation is slow compare to evolution.

Hardy-Weinberg principle:

• It states that allele frequencies in a population are stable and constant from generation to generation, if a population has no selection, no mutation, no migration, no genetic drift, and are random mating.

• (p + q)2 = p2 + 2pq + q2 = 1.

• Five factors are known to affect Hardy-Weinberg equilibrium:

• Gene migration or gene flow.

• Genetic drift.

• Mutation.

• Genetic recombination.

• Natural selection.

• Gene flow: movement of genes into or through a population by interbreeding or by migration.

• Genetic drift: Changes in the frequencies of alleles in a population that occur by chance, rather than because of natural selection.

• Gene pool: All the genes in a population at a particular time.

• The geologic time scale (GTS):

• It is a system of chronological measurement of Earth's history and evolition of life.

• It is constructed by geological and paleontological studies.

• Geologic time scale has 6 divisions or era.

• Eras are subdivided into periods.

• periods are subdivided into epochs.

• The 6 ears are:

• 1. Azoic era: 4600 to 4200 mya. no life

• 2. Archaeozoic era: 4200 to 3800 mya.- origin of life. Evolution of prokaryotes.

• 3. Proterozoic era: 1600 to 600 mya –origin of first animal, evolution of algae and insect.

• 4. Paleozoic era: 600 to 280 mya.

• In this Cambrian period all invertebrates and marine algae evolved.

• In Devonian period 400 to 345 mya fishes evolved. It is the golden age of fishes.

• In carboniferous period 345 to 280 mya amphibians and retails evolved.

• 5. Mesozoic era: 280 to 65 mya origin of mammals, ferns, gymnosperms and birds occurred.

• In this, Jurassic period is the golden age of reptiles and dinosaurs are dominant.

• In cretaceous period birds are evolved.

• 6. Coenozoic era: 65 to 2 mya origin of placental mammals and angiosperms seen.

• Origin of man occurs in 2 mya.

• The modern man evolved 1 mya. The culture and agricultural practices started in 10,000 years ago.

• A BRIEF ACCOUNT OF EVOLUTION:

• About 2000 million years ago the first cellular forms of life appeared on earth.

• Some cellular form had the ability to release O2.

• Slowly single cell organisms became multi-cellular life forms.

• By the time of 500 million years ago invertebrates were formed and active.

• Jawless fish probably evolved around 350 million years ago.

• Sea weeds and few plants existed probably around 320 million years ago.

• in 1938 Coelacanth a lobe finned fish discovered in South Africa. It evolved into first amphibians.. These were ancestors of modern day frogs and salamanders.

• The amphibian evolved into reptiles.

• Reptiles’ lays eggs which don not dry up in sun unlike those of amphibians.

• Giant ferns (pteridophytes) were present but they fell to form coal deposits slowly..

• The land reptiles were the dinosaurs.

• The biggest dinosaurs are Tyrannosaurus was about 20 feet in height and had huge fearsome dagger like teeth.

• About 65 million years ago the dinosaurs suddenly disappeared from the earth.

• Some of them evolved into birds.

• The first mammals were like shrews. Their fossils were small sized.

• Mammals were viviparous and protected their unborn young ones inside the mother’s body.

• Due to continental drift, pouched mammals of Australia survived. Because of lack of competition from any other mammals.

ORIGIN AND EVOLUTION OF MAN:

• ORIGIN AND EVOLUTION OF MAN.

• Human are belongs to the order primates of class mammals.

• Primates also includes monkeys, gibbons, gorilla, chimpanzee, loris etc.

• About 15 mya primates Dryopithecusand Ramapithecus were existing.

• They were hairy and walked like gorillas and chimpanzees.

• Ramapithecus was more man like while Dryopithecus was more ape-like.

• 2 mya Australopithecines is found in East African grasslands.

• They hunted with stone weapons.

• Essentially ate fruit.

• The first human-like being the hominid was Homo habilis.

• Brain capacity was between 650 – 800 cc.

• They did not eat meat.

• in 1891 Fossils discovered in Java focus on the next stage i.e. Homo erectus. It lived about 1.5 mya.

• Had large brain around 900 cc.

• Probably ate meat.

• Neanderthal man:

• Lived in east and central Asia between 1, 00,000-40,000 years back.

• Brain size 1400 cc

• They used hides to protect their body.

• Buried their dead.

• Homo sapiens:

• Evolved in Africa. As they moved across continents and developed distinct races.

• Pre historic cave art developed about 18,000 years ago are found.

• Agriculture and human settlement came around 10,000 years back.