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Natural science



Science - this term has been derived from a Greek verb scire, meaning to know and a Latin noun scientia, meaning knowledge. It is an orderly and systematized body of knowledge based on observations, reasoning and experimental verification. The scientific knowledge is gathered by observations, inquiry and investigations. The main thing that distinguishes science from humanities such as art and culture is the use of the experiments to answer the questions.

The scientific reasoning and the experiments are often simple not mysterious at all. They are merely logical ways of trying to answer the problem as are used by business people, historians and each of us in everyday life. There is no need of any scientific training or knowledge to decide whether conclusions are justified from the data presented or not. We can request further tests of a theory that not appear to be well supported by evidence, and we can agree or disagree with the predictions from a theory.

The term science when used without any descriptive adjective refers to natural science. It deals with natural phenomena. It is different from social science such as sociology which deals with human relations or an abstract science such mathematics which deals with abstract relations.

Natural science is taken into a position of great importance in modern society. Scientific inventions and discoveries are inseparable from human life and welfare. Their applications in day to day problem provide solutions for them. Many decisions affecting our future depend on appropriate interpretation of scientific discoveries.

The government of a country requires that every one participate in decisions on such subjects as population control, pollution standards, protection of wildlife and immunization. The body of scientific knowledge is already so vast that everyone can not understand it all. However, as a responsible citizen, we can follow some studies that bear on public issues. By doing so, we can apply scientific reasoning to decide our own positions on these issues.

However, the natural sciences can be categorized into physical sciences and biological sciences. The physical sciences primarily deal with non-living matter and include subjects like Physics, Chemistry, geology, astronomy etc. The biological sciences include the living organisms, their interactions and relationship with the non – living things. It includes the subjects like Botany, Zoology and microbiology etc.





Scientific Method


The knowledge imparted by any science includes facts, laws and principles of the nature. The knowledge about these is acquired by a typical procedure which is sometimes called scientific method or method of science. This method is used to know about an unknown object or an unknown happening (event or phenomenon) in any science. Sequence of steps of this procedure are broadly classified as

• Observation
• Hypothesis
• Experimentation
• Conclusion
• Sometimes retesting


The scientific method begins with a set of observations with respect to an unknown object or an unknown happening (event or phenomenon) the set of observations activate observer’s (scientist’s or researcher’s ) mind and he wants to know about the unknown object or unknown happening. His natural reaction is to ask questions about it. Then considering his own thought, colleagues’ suggestion and information of the literature, he recognizes a problem to investigate on his observations.

With these information, the scientist or researcher puts forth a hypothesis. Hypothesis is an explanation of what he expects in the underlying original observation or a set or observations. The hypothesis is a tentative explanation or observations or event. It is confirmed through the experiment or refused.

The hypothesis is tested through experiment. It is called experimentation. The experiment is carried out in a specified fashion. The scientist attempts to hold all conditions constant except the one he is manipulating so that any result he observes should be exclusive function of the changed conditions. The result is compared with that of a control, an experiment that depicted all natural conditions.

From the data of experiment, a conclusion is arrived at. If the conclusion is contrary to the hypothesis the hypothesis is refuted, otherwise the conclusion establishes a fact law or principle about the unknown object or happening.










Physics, major science, dealing with the fundamental constituents of the universe, the forces they exert on one another, and the results produced by these forces. Sometimes in modern physics a more sophisticated approach is taken that incorporates elements of the three areas listed above; it relates to the laws of symmetry and conservation, such as those pertaining to energy, momentum, charge, and parity. See Atom; Energy.
Scopes of Natural Science
Divisible into pure science and applied science
Study , understanding of different laws, facts and principles of natural sciences is pure science
Application of the knowledge of pure science for the welfare of human beings is applied science
Scopes of physics
Simple machines
Lever pulley trolley wheel and axel screw wedge, water lifting pump
Computer which work like human brain
Light
Heat
Sound
Electricity
Magnet
Scopes of chemistry
Scopes of biology











Theories of origin of life

Theory of Special Creation

This theory was proposed by Hebrew et al and strongly supported by Father Suarez. According to Bible, God created this universe, all animals and plants including ocear, mountain etc. The life was created during 4004 BC in six consecutive days. The heaven and earth were created on 1st day. Sky was separated from water on the 2nd day. On the 3rd day, the land and plants were created. On the 4th day, the Sun, Moon and Stars were created. Te 5th day, fish and fowl were created. Animals were created on 6th day. The first human was Adam created from inanimate matter the clay which was furnished with soul. Then it started breathing. The first woman was Eve who was created from one of his ribs.
All existing animals and plants were created by God. According to Hindu Mythology, Brahma( God of Creation) created different forms of life. The body of all living beings was made up of five elements( pancha maha bhut) like the earth(Prithvi), water(jala), fire(Teja), sky(Akash) and air(Bayu). After the death, all these elements will be returned to pancha maha bhuta.

This theory states that
1. The life was created by God or Creater
2. Formed all of a sudden, out of nothing
3. No interrelationship among living beings and
4. Have not undergone any change
The life is a mysterious force or vital spirit that set living things completely apart from non living and originated due to some supernatural event. It is accepted on basis of faith. One should believe in the existence of God. However, this theory can not be proved experimentally. So biologists do not believe in this theory.



Objections
Charles Darwin condemned special creation theory saying that earth has not always been inhabited by plants and animals as we know now. It means there is always a change. This theory lacks sound logic, scientifically sound evidence, it could not convince scientists.


Theory of Spontaneous generation or abiogenesis

Before the end of the Seventeenth century, both biologists and philosophers believed that non living things could arise from the non living(inanimate) substance spontaneously. This remained true for centuries in the past. This theory was proposed by Von Helmont(1577-1644). In China, even from earliest time, there was belief that aphid and other insects under the influence of heat and moisture, come into existence. In sacred books of India, there are indication of sudden emergence of different parasites, flies, beetles from sweat and manure. The Babylonian cuneiform text showed the worms and other creatures were formed form the mud of canals. In ancient Egypt, the conviction prevailed that layer of humus deposited by Nile river in its flood gave birth to living creatures like toads and frogs.

o Frogs, toads, snakes etc were believed to be developed from mud
o Parasites, beetles flies etc from sweat and manures
o Aphids and other insects arose under the influence of heat and moisture
o Fly maggots from flesh
o Young mice could arise from wheat grains and when these are kept in a dark room along with dirty clothes
Anaximenes (586-524 BC) proposed that air as sole cause of life.
Aristtotle (384-322BC proposed that worms, insects, fish, tape worm from excreta, crab, salamanders from earth can be developed.

Experiment of Von Helmont
Von Helmont kept dirty shirt and few grains of wheat in a cup board for 21 days. He observed mice developed from sweat and wheat. So, he proposed that both sexes of mice will be developed directly from non living things. He conducted this experiment in the support of spontaneous generation.
We find the repetition of these tales in the writings of ancient Greeks like Thales(624-547 BC), Empedocles(485-425 BC), Democritus (460-370 BC), Plato (427-347BC ) and Aristotle(384-322 BC).
William Harvey(1578-1627) despite the statement that all life come from egg was not able to tear himself from the concept that lower forms of life may aboriginate by spontaneous generation from non living precursors.

Theory of biogenesis

This theory states that life is originated not from inanimate substance but from the preexisting forms only.

Redi’s Classical Experiment

Italian Physician Sir Francisco Redi (1621-1697) demonstrated that maggots were not created from meat or fishes. In his classical experiment, he placed lumps of boiled meat in jars, some uncovered, some covered with muslin cloth and some with parchment paper. After few day, he observed fly maggots only in the uncovered jars.









The discovery of microbs by Van Leeuwenhoek (1632-1723) brought the question that microbs are so simple and could arise by Spontaneous Generation. This idea was authoritatively maintained by German philosopher Leibniz (1646-1716), French naturalist Buffon (1707-1788) and Englishman John Ne dham (1713-1781).


The decline and fall of the theory of Spontaneous Generation

An Italian scholar Abbe Spallanzani tested the theory of Spontaneous Generation. In 1765, he prepared flasks of meat broth which were boiled for several hours and then sealed. This broth remained clear for months and when seals were broken and broth tested, it was shown to be free of microbs.

Spallanzani’s experiment were neither conclusive nor satisfying to many of his contemporary scientist. They claimed that by boiling, he had driven out the vital force needed for Spontaneous generation. And also the sealed flask contained no oxygen.


The period of Louis Pasteur(1822-1895) : Pasteur devised several experiment means by which Spontaneous Generation of microbs was disproved. The simplest and most sophisticated one was with the use of a swan- neck flask. He prepared meat broth in this flask and boiled for several hours. He then left the flask unsealed. The flask was not sealed and there was free exchange of air with environment and system did not lack oxygen. Still the swan –neck remained free of microbial contamination for months because their swan neck were so shaped to trap the viable microbial particles and allow only air to enter the flask. After several months, he broke the neck of the flask and did not find the microbs. This simple experiment thus altogether disproved the concept of Spontaneous Generation. Thus it was proved that life could arise only from the pre existing life which is known as Biogenesis.

Cosmozoic theory
This theory was proposed by Richter 1865 AD and supported by Arrhenius 1908 AD. It states that life came on this earth from other planet in the form of seed or spore or panspermia. So, spore theory finding the suitable environment it grows into life. He could not explain mechanism by which panspermia survived adverse condition of high temp and lethal radiation of inter planatery space during migration.

Catastrophic theory
It was proposed by G Cuvier 1769-1832 and Orbigney 1802-1837. This theory states that there have been several creation each preceded by a catastrophy due to some major geological changes. Each catastrophy destroyed previous life completely and was followed by next advanced creation.

Steady state theory
This theory states that organisms have been unchangeable not only through out existence but also they have existed and continue to exist unchanging till eternity. Hutton says there is no beginning and end. This theory was supported by Richter and Arrhenius etc.

Modern or Natural or chemosynthetic theory of origin of life
This theory was proposed by Russian biochemist Alexander Ivanovich Oparin (1923) and supported by JBS Haldane (1928). This theory is popularly known as Oparin Haldane theory. This theory has been explained in detail in Oparin’s book “The Origin of life on the earth” published in 1936.

It states that primitive life originated in the water bodies on the primitive earth by chemical evolution through a series of chemical reaction about 4200 million years ago.
Steps
A. Origin of Earth (Biopoiesis)
The earth is supposed to be originated about 4.6 billion (4x109) years ago. The sphere was filled with cloud masses of dust particles called ylem. The rotation and gravity caused condensation and formed entire solar system. The earth when formed was very hot (4000 – 8000 oC ), like a ball of fire. Gradually cooled in next few million of years. They started condensing forming solids, liquids and gases. Heavy elements shank at the centre forming core. The lighter one (Aluminum, silicon, sodium, potassium ) formed the middle core of earth. Thus, lithosphere was formed. Lightest gases N2 H2 CO2 He etc including water vapor with dust particle rose above the land surface and turned finally into atmosphere.
B. Origin of life on earth
It is expected that life originated on earth nearly 3.7 billion years ago and involved following changes.
I. Chemogeny
Volcanic gases like H2 N2 CO2 H2O He underwent many changes (chemical evolution) which took place in following steps.
i. Formation of original gases
The original gases like NH3, CH4, HCN etc would have formed by interaction of volcanic gases when primitive earth cooled down from 100 oC. The formation of prime component was the start of life in primitive earth
N2 + 3H2 ……… 2NH3
C + 2H2 ……… CH4
2C + N2 + H2 ….. 2HCN
ii. Formation of key bio micro compounds
Simple key bio micro compounds like pentose sugar, glycerol. Fatty acids aminoacids, nitrogen bases( adenine, cytosine, thymine, Guanine etc would have formed by interaction of original gases( NH3 CH4 HCN ) when the temp further went down to about 50 to 60 oC Such reaction took place under the action of heat coming from energy radiation of Sun lightning, lava, radio active elements like radium, uranium of rocks etc.
6CH4 + H2O …………….. C6H12O6 + 12H2
CO2 + 2NH3 …………….. CO(NH2)2 + H20
CH4 + H2O + NH3 +HCN ……….. Nitrogen bases
CH4 saturated hydrocarbon reacted with water there by forming unsaturated hydrocarbon like acetylene, ethylene etc. From these, aldehydes, ketones, alcohol, acid were formed spontaneously, still more complex organic compounds like glucose, amino acid, fatty acids etc and purine and pyrimidine were formed as key bio micro compounds.
iii. Formation of complex bio macro compounds
Complex bio macro compounds like starch, protein, lipid, nucleic acid would have formed by polymerization of key simple bio micro compounds in the presence of water.
C6H12O6 + C6H12O6+ + C6H12O6 + … Polysaccharides
Fatty acids + glycerol ……………………. Lipid(fat)
Amino acids + amino acids + amino acids + ……..Protein
Complex bio macro compounds thus formed did not undergo oxidation because primitive earth was reducing, no free O2 and no microbes present.
iv. Formation of coacervates
When earth further cooled down, water vapour turned into rain, earth surface shrunk and formed depression where rain water filled up and turned into lakes, sea, as hydrosphere. Up lands turned into mountains. In sea, bio macro compounds when mixed with sea water formed thin hot soup called “broth”. To this Haldane 1992 called ‘pre biotic soup’.



Miller Urey experiment

Stanley Miller and Harold C Urey in 1953 performed series of experiments and tested Oparin and Haldane theory. They devised an apparatus that simulated the conditions of the surface of pre biological earth and analyzed the molecular forms that arose. The apparatus consisted of exposing water vapor to electric spark of 75,000 volts(to represent the lightning of thunder storms) in an ammonia, methane and hydrogen atmosphere of the early earth. After two weeks of treatment, Miller chromatographed the final solution and found many organic compounds including both carbohydrates and amino acids. Many of the compounds were important metabolic intermediates of present day organisms.

Since free oxygen destroys most of the intermediate products, the presence of intermediate products supported the Oparin and Haldane’s hypothesis of reducing atmosphere of primitive earth. Abiotic synthesis of molecules is possible only in reducing atmosphere and abundance of free oxygen (as in earth today) prevents the abiotic origin of life. So, life is originated from the earth’s inorganic atmosphere in the past but is no longer happens today.