Prasanna

Students can Download Chapter 5 Through the Eyes of Travellers Notes, Plus Two History Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two History Notes Chapter 5 Through the Eyes of Travellers

1. The notes of the travellers are an important source for studying the history of middle ages. Many travellers visited different parts of India, They had various goals.

2. In the notes of these travellers there are decriptions about Indian social life. These notes have enriched our knowledge of the past. In this chapter we are trying to learn more about the middle period from the writings of the travellers.

We are especially considering the writing of three. One is Al-Biruni, who came to India from Uzbekistan in the 11^th century. The 2^nd is Ibn Battuta who came from Morocco in North Western Africa in the 14^th century. The 3^rd one is Francois Bernier, a French traveller who came here in the 17^th century.

3. Al-Biruni was born at Khwarism in Uzbekistan. Khwarism was an important centre of knowledge and so he got the best education possible. He was a linguist – a scholar in many languages. He knew Syriac, Arabic, Persian, Hebrew and Sanskrit. He was not familiar with Greek. But he had read the books of Plato and Other Geek philosophers through Arabic translations.

4. Ibn Battuta was an Arab traveller. He was born in Tangier in Morocco in 1304 and he died in 1368. His travelogue ‘Rihla’is written in Arabic. This book gives very interesting and extensive descriptions of the social and cultural life in India in the 14^th century.

5. Francois Bernier was a French traveller. He was a doctor, political thinker and historian. He came to the Mughal Empire seeking opportunities. He stayed in India for 12 years, from 1656 to 1668.

He was closely associated with the Mughal capital. He was the physician of Dara Shuko who was the eldest son of Shahjahan. He also worked with a wealthy American named Danishmand Khan when he was in the capital.

6. Ibn Battuta and Bernier wrote their notes with different viewpoints. Ibn Battuta was attracted by the novelty of everything he saw. He wrote about all those things that interested him. But Bernier was quite different. He tried to compare India with France and look for any contradictions.

7. The travelogues of these people give us very interesting and enthusiastic views about the life of the people at that time. They are very precious. But, at the same time, their descriptions had their limitations.

Their views were formulated by their attitudes which developed from the circumstances from which they came. They had failed to notice .some aspects of social life.

8. Many Indians also were adventurous enough to visit other countries grossing the seas and the mountains. But their writings have not been preserved for posterity.

Time Line
Some Travellers and their Writings

• 973-1048: Al-Biruni from Uzbekistan
• 1254-1323: Marco Polo from Italy
• 1304-1377: Ibn Battuta from Morocco
• 1413-1482: Abdul Razak Samarkhandi, from Samarkhand
• 1466-1472: Afanasy Nikitic Nikitin from Russia
• 1518: Barbosa from Portugal visited India
• 1562: Said Ali Riz from Turkey. He died that year.
• 1563-1600: Antonio Moriserrate from Spain
• 1616-31: Mahmud Vali Balki

Lived In India

• 1600-67: Peter Moonly from England
• 1605-89: Jean-Baptist Tavernier from France
• 1620-88: Francois Bernier from France

Students can Download Chapter 4 Thinkers, Beliefs and Buildings Notes, Plus Two History Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two History Notes Chapter 4 Thinkers, Beliefs and Buildings

1. In this chapter we discuss some cultural developments that took place during the period between BCE 600 to CE 600. The philosophers and thinkers of that period made great contributions to the cultural development of India.

They tried to understand the circumstances in which they lived and came forward with revolutionary principles and philosophies. Their ideas were collected orally and also in written form. Their ideas were depicted in the architectural ‘vastu’ and art of sculpture. It shows that these thinkers had exerted great influence among the people.

2. This chapter mainly talks about Buddhism. Buddhist tradition did not develop in isolation. Therefore it is necessary to know about other traditions which also grew along with Buddhism.

3. There was also the spread of Jainism in many parts of India. It spread mostly to Rajasthan, Gujarat, Malwa, Kalinga, Karnataka and Tamil Nadu. Simple principles, the use of Prakrit language, encouragement from the Kings, the energy of the Jain Sangha and Jain Ascetics helped its growth and spread.

4. The basis of Buddhist principles is the 4 ‘Arya Satyas’ and ‘Ashtanga Marga’.

(a) Buddha taught 4 fundamental truths. They are known as the 4 Arya Satyas or Noble Truths. These are the 4 Arya Satyas: The world is a sorrowful place. The reason for sorrow is desires. If one can deny his desires, he can overcome his sorrows.

By employing the Ashtanga Marga sorrows can be resisted. The ashtanga margas are: right word, right deed, right life, right efforts, right memory, right view, right decision and right meditation.

5. When Buddha was alive and even after his death, Buddhism began to spread widely. It spread abroad to China, Japan, Burma, Ceylon (Sri Lanka), Mongolia and Tibet.

6. With the 1^st century, many changes happened in Buddhism and its practice. Among the Buddha Bikshus themselves, there were different interpretations regarding the tenets of Buddhism.

During the reign of Kanishka, there was the 4th Buddhist meeting in Kashmir and in this meeting the differences became intense. It led to a split in Buddhism. One group was Hinayana and other was Mahayana.

7. In the Hindu tradition also a messiah concept developed. The ancient Hindu religion originated from this concept. There were two traditions in the ancient Hinduism: Vaishnava and Saiva.

Time Line – 1
Important Religious Happenings

• 1500-1000BC: Early Veda Traditions
• 1000-500 BC: Later Veda Traditions.
• 6^th century BC: Early Upanishads, Jainism, Buddhism
• 3^rd century BC: The first Stupas
• From 2^nd CBC: The development of Mahayana Buddhism, Vaishnava Religion, Saiva Religion and Adoration of goddesses
• 3^rd century AD: Early Temples.

Time Line – 2

• 1814: The founding of Indian Museum in Calcutta
• 1834: Ram Raja publishes his Essay on the Architecture of the Hindus. Cunningham makes excavations in Sanchi.
• 1835-42: James Fargunan makes researches in the main archaeological sites.
• 1851: Establishment of the Government museum at Madras.
• 1854: Alexander Cunningham publishes one of his early books on Sanchi entitled “Bhilsa Topes”.
• 1878: Rajendra Lai Mitra publishes “Buddha Gaya – The Heritage of Sakya Muni”.
• 1880: H.H. Kaul is appointed as the Curator of ancient monuments.
• 1888: The Treasure Trove Act is passed. This authorizes the government to acquire all ancient archaeological properties.
• 1914: John Marshal and Alfred Foucher jointly publish “The Monuments of Sanchi”.
• 1923: John Marshal publishes. ‘Conservation Manual’.
• 1955: Prime Minister Jawaharlal Nehru lays the foundation stone for the Delhi National Museum.
• 1989: Sanchi is declared a World Heritage Site.

Students can Download Chapter 3 Kinship, Caste and Classs Notes, Plus Two History Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two History Notes Chapter 3 Kinship, Caste and Class

1. Family is the basic unit of society. But all families are not alike. There are differences in the number of members, their mutual relationships and the activities they do.

2. From BCE 6^th century, most families in India followed the patriarchal system. This was a male-dominant system. After the death of the father, only the sons were entitled to his property. If the father was a king, the right to the crown belonged to the sons. This patriarchal system played a big role in marriage.

3. Since sons were the heirs to the authority and paternal property, they had much importance in this system. Daughters were not entitled to family property. It was considered best to marry them to homes which were not connected with them in any blood relationship.

4. The Dharmasutras and Dharmasastrds acknowledged 8 kinds of marriages.

5. The first 4 kinds were considered good. The remaining four were ridiculed and rejected. It is believed that these ridiculed types were practised by those who did not follow the Brahmin laws.

6. Caste or Jati shows a group in the social hierarchy. It was during the end of the Rigveda period that social divisions based on Caste distinctions came into existence.

7. There were many people in the society that did not approve the caste ideas of the Brahmins. Sanskrit Books of those times call these people, who were outside the influence Brahmin laws, uncivilized, ugly and animal-like.

8. In different parts of the subcontinent, many kinds of social classes came up at this time. There were slaves, landless agricultural workers, hunters, fishermen, shepherds, farmers, village heads, artisans, traders and royal people. Their status was determined or based on their resources.

9. Buddhists were aware of the social inequalities. Brahmins saw inequality as something divinely ordained. This.theory was rejected by the Buddhists. They believed that social inequalities were neither by birth nor ordained by God. It is possible to overcome them. Therefore Buddhists developed institutions that were capable of controlling social conflicts.

10. “Mahabharat” is considered as an “Ithihas” (Classic)of early Sanskrit literature. The literal meaning of ‘Ithihas ‘ is “Thus it was”.

11. The real writing of Mahabharata started in BCE 5^th century. It is the Brahmins who took the initiative to do it. The Mahabharata story which was in oral tradition was collected by them and it was written down.

12. The most important feature of Mahabharata is its energy. Even with the Sanskrit edition its growth did not end. Different editions of the “Ithihas” continued to be written in different languages for centuries. So many stories which were popular in certain areas or among certain sections of the people became part of the Ithihas.

Time Line – 1
Important Books

• Around 500 BC: Panini’s Ashtadhyayi, a book on grammar
• Around 500 BC: Important Dharma Sutras (Sanskrit)
• Around 500-200 BC: Tripitaka (Pali) and other early Buddhist books. Around.
• Around 500 BC to-400 AD: Ramayana and Mahabharata (Sanskrit)
• Around 500 BC to 200 AD: The writings and collection of books by Tamil Sangham’; Manusmriti (Sanskrit)
• Around 100 AD: Charakasamhita and Susruthasamhita (medical books)
• Around 300 AD: Bharata’s Natyasastra (Sanskrit), about performing arts.
• Around 300 to 6Q0 AD: Other Book on Dharmasastra (Sanskrit)
• Around 400-500AD: Sanskrit Plays including those of Kalidas; Books on Astrology and Mathematics (Sanskrit) by Varahamihira and Aryabhatta; Jain Writings in Prakrit.

Time Line – 2
Milestones in the Study of Mahabharata

• 1919-1966: Critical Studies on Mahabharata
• 1973: J.A.B. van Buitenen started the English translation of the Critical Judies of Mahabharata. But he died prematurely and the translation is incomplete.

Students can Download Chapter 2 Kings, Farmers And Towns Notes, Plus Two History Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two History Notes Chapter 2 Kings, Farmers and Towns

600 BC to 600 CE

1. The long period of 1500 years after the end of the Harappan Civilization was an important period in Indian history. During this period many important things happened in different parts of the Indian subcontinent. Rigveda was written.

Agricultural settlements came up in places like North India, Deccan Plateau and parts of Karnataka. There were new burial systems in Deccan and South India. Huge stone constructions were made. “Mahasiia’was one of them. Along with dead bodies many iron tools and weapons were also buried.

2. The Dawn of Early Nations:
Big nations known as ‘Mahajanapadas’ came into existence during this period.

3. The Coming of Cities and Towns:
This was the period of the 2^nd Urbanization in Indian history.

4. Increased use of Iron:
As the use of iron increased, forests were cleared. It led to the spread of agriculture. The iron weapons increased the importance of warriors.

5. Spread of Coin (Currency) system:
The use of metal coins helped the development of trade and commerce.

6. The political history of India from BCE 600 is also the history of fights between the Mahajanapadas for power and sovereignty. The final victory in these fights was Magadha’s. Magadha became the number one among 16 Mahajanapadas. Magadha included the present Patna and Gaya districts in Bihar.

7. With the advent of the Maurya Empire, the growth of Magadha reached its peak. The period of the Maurya Empire can be considered as a new era in Indian history. It was one of the most powerful and extensive empires in ancient India.

8. Asoka was the greatest among the Maurya Emperors. The main event during his reign was the Kalinga War and his conversion to Buddhism. It was after a bloody war in 261 BCE that he conquered Kalinga, which is known as Orissa today.

9. The Mauryas organized an extensive administration. The Mauryan Empire was quite large with extensive areas. There were different regions like mountainous areas, deserts, boundary regions and extensive shores.

10. Following the collapse of the Mauryan Empire, some political instability took place in North India. The North Eastern Region of India was occupied by the Greeks, Sakas, Parthians and Kushanas.

The administration in the Ganges Plain was captured by the Sungans. Kalinga (Orissa) came under the power of Chedi dynasty. The rule of Western Deccan went to the Satavahanas.

11. After the fall of the Mauryan Empire, many small States came into existence. By the 4^thh Century CE, some big nations also began to appear. The most important of them was the Gupta Empire. Many of these nations depended on the feudal lords, called Deputies, for administering their territories.

These feudal lords lived by controlling the land and collecting produce from the people. They gave the kings loyalty and also military support. Sometimes some powerful Lords conquered the weaker ones and themselves became kings.

Time Line – 1
The important political and economic events.

• BC 600-500: Urbanization of the Ganges Plain, Mahajanapadas (Settlements), Sealed Coins.
• BC 500-400: The Magadh rulers unify their administration.
• BC 327-325: Alexander from Macedonia attacks.
• BC 321: Chandragupta Maurya comes to power.
• BC 273-232: The rule of Emperor Asoka.
• BC 185: The end of Mauryan Dynasty.
• BC 200-100: Indo-Greek rule in the North-Western Region; In South India Cholas, Cheras and Pandyas; in Deccan Satavahanas.
• BC 100: Sakas from Central India come to power.
• AD 78: Kanishka comes to power.
• AD 100-200: The earliest inscriptions of Satavahanas and Sakas making land- gifts.
• AD 320: The beginning of Gupta Dynasty
• AD 335-375: The Reign of Samudragupta
• AD 375-415: Chandragupta II; in the Deccan Vakatakas
• AD 500-600: The rise of Chalukyas in Karnataka and Pallavas in Tamil Nadu.
• AD 606-647: Reign ofHarshavajdhana in Kanuj; the Chinese Pilgrim Huantsang comes to India seeking Chinese Religious Books.
• AD 712: Arabs conquer Sindh

Time Line – 2
Developments in ancient epigraphy

• AD 1784: Asiatic Society is established in Bengal.
• AD 1810: Colin Mackenzie collected more than 8000 inscriptions in Sanskrit and Dravidian languages.
• AD 1838: James Prinsep reads Asoka’s inscriptions in Brahmi language.
• AD 1877: Alexander Cunningham published some of the inscriptions of Asoka.
• AD 1886: The first Issue of the Journal called ‘Epigraphia Karnatica’, which discussed things about the South Indian inscriptions on lithic surfaces and copper plates, was published.
• AD 1888: The First Issue of “Epigrapia Indika” was published.
• AD 1965-66: D.C. Sircar published Indian Epigraphy and Indian Epigraphical Glossary.

Students can Download Chapter 1 Bricks, Beads and Bones Notes, Plus Two History Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two History Notes Chapter 1 Bricks, Beads and Bones

1. 4500 years ago, in the North-West region of the Indian Sub-Continent there existed a great culture. In 1921, at Harappan site, this culture was first discovered. It was known as the “Sindhu River Basin Culture”.

2. Before the coming of the Harappan Culture, there had been many other cultures. They are collectively known as Early Harappan Culture. This was the formulation of the Harappan Culture. Harappan Culture begins from here.

3. The most important feature of the Harappan Culture is the development of Urban Centres. It was during the time of the Harappan Culture that the First Urbanization began. Harappa, Mohenjo-Daro, Chanhudaro, Kalibangan, Lothal, Banwali, and Dholavira were some of the important cities of those times.

4. The most important site in Harappan Civilization is Mohenjo-Daro. This was discovered After Harappa. It was from Mohenjo-Daro most information regarding urban planning, houses, seals etc. of the Harappan Civilization were obtained. This big city was situated in the Larkana district of Sindh, on the banks of the Sindhu River. The word Mohenjo-Daro means The Mound of the Dead’. The excavations made here revealed the remains of a planned urban centre.

This city was divided into two parts:

• The Citadel, and
• The Lower Town.

5. A significant feature of the Harappan Civilization is the drainage system found in the cities.

6. The Harappan people earned their livelihood through agriculture and animal husbandry.

7. Archaeologists point out that there were social and economic inequalities among the Harappan society. It is all clear from the way they buried their dead, luxury items, and different types of residences.

8. The Harappans collected raw materials for their manufactured goods (artefacts) from faraway places. This was done mainly through commerce. The Harappan people had commercial ties with Oman, Mesopotamia, Afghanistan and Persia.

9. Seals were great artistic creations of the Harappan people. It is from these seals that we learn about their agriculture, animals, birds, trees, dress, ornaments, religious faiths, arts and foreign trade.

10. Seals are the sources from which we get information from the Harappan Script.

11. By BCE 1800, the Harappan Culture began to crumble. Most developed sites like Kolistan were abandoned. People began to migrate to new habitats in Gujarat, Haryana and Western Uttar Pradesh. The remaining habitations were subjected to great changes. The main symbols of the Harappan Civilization like the weights, seals and special beads began to disappear.

Writing, Long-distance trade, specially hand-crafted goods, etc. also disappeared. The technical skills in the building of houses also deteriorated. Construction of huge building came to a complete stop. Urban life also changed.

A rural kind of life came in its place. The goods made and the habitations give indications of this rural life. The civilizations that came up after the min of the Harappan Civilization are called “Late Harappan” or “Successor Cultures” by scholars.

12. The first person to observe things about the Harappan Civilization was Charles Masson, who was an English official. He happened to visit the Harappan village in 1826. There he observed the remains of an ancient city.

In 1856, when the railway line was being built between Karachi and Lahore, the Railway Engineers also found the remains of some ruined cities of the Harappan Civilization.

Time Line Harappan Archaeological Studies
Important Events
19^th Century:
1875: Report of Cunningham regarding the Harappan Seals.

20^th Century:

• 1921: M.S. Vats starts excavating (digging) in Harappa
• 1925: Digging starts at Mohenjo Daro
• 1946: Digging in, Harappa under the leadership of Mortimer Wheeler
• 1955: S.R. Rao starts digging at Lothal
• 1960: B.Bv Lai and B.K. Thapar begin digging at Kalibengan
• 1974: M.R. Mughal starts digging at Bahavalpur
• 1980: A group of German and Italian archaeologists start research in and around Mohenjo Daro.
• 1986: An American team begins digging at Harappa
• 1990: R.S. Bisht starts digging in Dhotaveera

Students can Download Chapter 8 Biodiversity and Conservation Notes, Plus Two Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two Zoology Notes Chapter 8 Biodiversity and Conservation

Biodiversity
The diversity is not only at the species level but at all levels from macromolecules within cells to biomes. Edward Wilson has described the biodiversity as follows

(i) Genetic diversity:
It is diversity at the genetic level. For example the Rauwolfia vomitoria growing in different Himalayan ranges shows the genetic variation i.e due to the concentration of the active chemical (reserpine) that the plant produces.

India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.

(ii) Species diversity:
It is the diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

(iii) Ecological diversity:
It is the diversity at the ecosystem level. For example, the different type of ecosystems within India are deserts, rain forests, mangroves, coral reefs, wetlands, estuaries.

Alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway. Internationally, the biodiversity and its conservation are vital environmental issues because it is important for survival of human beings.

1. How Many Species are there on Earth and How Many in India?
According to the IUCN (2004), the total number of plant and animal species described is slightly more than 1.5 million.

But several species of plants and animals would have to be discovered in tropics and temperate regions.

Among animals, insects are the most species-rich, it is more than 70 per cent of the total. This indicates that out of every 10 animals on this planet, 7 are insects.

The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles, and mammals.

Nearly 45,000 species of plants and twice as many of animals have been recorded from India.
May’s global estimates shows that 22 percent of the total species have been recorded so far and more than 1,00,000 plant species and more than 3,00, 000 animal species yet to be discovered.

Representing global biodiversity: proportionate number of species of major taxa of plants, invertebrates and vertebrates:

2. (i) Latitudinal gradients:
The species diversity decreases from the equator towards the poles. Tropics (latitudinal range of 23.5° N to 23.5° S) have more species than temperate or polar areas.

Colombia (near the equator) has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at 710 N only 56 species.

India (tropical latitudes) has more than 1,200 species of birds. Equador forest in a tropical region has 10 times species of vascular plants than temperate region, the Midwest of the USA.

Topical Amazonian rain forest in South America has the greatest biodiversity on earth. It possess more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and of more than 1,25,000 invertebrates. About two million insect species have to be discovered in rain forests.

The reason for the greatest biodiversity in tropics

(ii) Species-Area relationships:
German naturalist and geographer, Alexander von Humboldt observed that relation between species richness and area to be a rectangular hyperbola. It is a straight line in logarithmic-spate. The relationship is given below as equation.

log S = log C + Z log A whereS = Species richness A = Area Z = slope of the line (regression coefficient) C = Y-intercept

The value of Z lies in the range of 0.1 to 0.2, (whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are similar).

But, the species-area relationships among large areas like continents, the slope of the line to be much steeper.

Here the Z value lies in the range of 0.6 to 1.2. For example, for fruit-eating birds and mammals in the tropical forests of different continents, the slope is found to be 1.15.

3. The importance of Species Diversity to the Ecosystem:
The communities with more species are more stable than those with less species. The stable community shows much variation in productivity from year to year; they are resistant to disturbances and spreading of foreign species.

David Tilman found that plots with more species showed less year-to-year variation in total biomass. He also showed that increased diversity leads to higher productivity. The rich biodiversity is not only for ecosystem health but helpful to the survival of the human race.

4. Loss of Biodiversity:
The colonisation of tropical Pacific Islands by humans led to the extinction of more than 2,000 species of native birds.

The IUCN Red List (2004) included 784 species undergoes extinction.

It was noticed that the disappearance of 27 species in recent days. The 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31 per cent of all gymnosperm species in the world face the threat of extinction. Here amphibians are more vulnerable to extinction.

The study fossil records indicates the mass extinction. It is estimated to be 100 to 1,000 times faster than in the pre-human times.

Causes of biodiversity losses: It is mainly due to human activities.
There are four major causes

(i) Habitat loss and fragmentation:
This is the most important cause of extinction of animals and plants. This was mainly in tropical rain forests. More than 1000 hectares of rain forest have been lost in recent decades.

The Amazon rain forest is cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle.

The degradation of many habitats by pollution affects the survival of many species. It results large habitats are broken up into small fragments. So the mammals and birds requiring large areas are affected, it leads to the reduction in population.

(ii) Over-exploitation:
It leads to the over-exploitation of natural resources. For example the extinction of Steller’s sea cow, passenger pigeon was due to humans. The overexploitation of marine fish populations leads to the reduction of commercially important species.

(iii) Alien species invasions:
The introduction of foreign species cause the reduction or extinction of indigenous species. The Nile perch introduced into Lake Victoria in east Africa led to the extinction of more than 200 species of cichlid fish in the lake.

The introduction of weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchomia) seriously affected the land and aquatic population respectively.

Introduction of African catfish Clarias gariepinus for aquaculture purposes is a threat to the indigenous catfishesin river.

(iv) Co-extinctions:
If two species are in obligatory relation ship the extinction of one species affect the other. Eg-coevolved plant-pollinator mutualism where extinction of one species leads to the extinction of the other

Biodiversity conservation
1. Why Should We Conserve Biodiversity?
It is mainly based on three concepts narrowly utilitarian, broadly utilitarian, and ethical.

(1) Narrowly utilitarian:
Humans get economic benefits from nature food (cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance.

More than 25 per cent of the drugs are obtained from plants. Many medicinally useful plants would have to be discovered from the tropical rain forests.

(2) Broadly utilitarian:
Biodiversity plays a major role in ecosystem services . Amazon forest is through photosynthesis produce 20 per cent of the total oxygen in the earth’s atmosphere.

Pollination is another ecosystems service by bees, bumblebees, birds and bats. Nature provides aesthetic pleasures of watching spring flowers in full bloom and bulbul’s song in the morning.

(3) Ethical:
Every species has an intrinsic value so they are conserved for future generations.

2. How do we conserve Biodiversity?
It is through in situ (on site) conservation and ex situ (off site) conservation
In situ conservation:
Some areas of country are identified as ‘biodiversity hotspots’ These region shows high species richness and high degree of endemism.

Besides these the sacred groves such as in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western Ghat regions of Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh conserve and protect large number of rare and threatened plants.

Ex-situ Conservation:
It is the conservation of threatened animals and plants outside their natural habitat. Examples are Zoological parks, botanical gardens and wildlife safari parks.

As a part of conservation gametes of threatened species can be preserved in viable and fertile condition for long periods using cryopreservation techniques. In this technique, fertilized eggs, embryos, seeds etc are also stored.

In the Convention on Biological Diversity (The Earth Summit’) held in Rio de Janeiro in 1992, nations taken measures for conservation of biodiversity and its sustainable utilisation.

In a follow-up, the World Summit on Sustainable Development held in 2002 in Johannesburg, South Africa, 190 countries taken the decision to achieve biodiversity at 2010 and decrease the current rate of reduction.

Students can Download Chapter 7 Microbes in Human Welfare Notes, Plus Two Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two Zoology Notes Chapter 7 Microbes in Human Welfare

Microbes In Household Products

The traditional drink ‘Toddy’ is made by fermenting sap from palms.

Microbes In Industrial Products
Microbes are used to synthesise a number of products such as beverages and antibiotics. These are produced in large scale by using large vessels called fermentors.

1. Fermented Beverages:
Fermentors:

Fermentation plant:

Yeasts ( brewer’s yeast-Saccharomyces cerevisiae) is used for the production of beverages like wine, beer, whisky, brandy or rum.

Different type of alcoholic drinks are made depending on the type of the raw material used for fermentation and the type of processing.

2. Antibiotics:
Antibiotics are chemical substances, they are isolated form some microbes and used to kill or destroy the growth of other (disease-causing) microbes.

Penicillin was the first discovered antibiotic from the mould Penicillium notatum. Alexander Fleming while working on Staphylococci bacteria, observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. It was due to a chemical produced by the mould and he named it as Penicillin.

Chain and Florey developed penicillin for commercial use. This antibiotic was used to treat American soldiers wounded in World War II. Fleming, Chain and Florey were awarded the Nobel Prize in 1945, for this discovery. Many antibiotics are used to treat diseases such as plague, whooping cough, diphtheria leprosy etc.

3. Chemicals, Enzymes and other Bioactive Molecules:

• Aspergillus niger(a fungus)- citric acid
• Acetobacter aceti(a bacterium) – acetic acid
• Clostridium butylicum (a bacterium)- butyric acid
• Lactobacillus (a bacterium)- lactic acid
• Yeast (Saccharomyces cerevisiae)- ethanol

1. Lipases:
They are used in detergent, helpful in removing oily stains from the laundry.

2. Streptokinase:
It is obtained from bacterium Streptococcus used as a ‘clot buster’ for removing clots from the blood vessels of patients.

3. Cyclosporin A (Immunosuppressive agent):
It is produced by the fungus Trichodermapolysporum. It is helpful to patients subjected to organ-transplant.

4. Statins:
It is obtained from yeast Monascus purpureus used to lower blood-cholesterol level It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

Microbes In Sewage Treatment
The waste water generated in cities and towns contain large quantity of human excreta and waste materials called as sewage. It contains organic matter and microbes. It is treated in sewage treatment plants (STPs). It is done by two stages.

Primary treatment:
It is the removal of large and small particles from the sewage through filtration and sedimentation.; Initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge, and the supernatant forms the effluent.

The effluent ready for secondary treatment:
Secondary treatment:

An aerial view of sewage plant:

Secondary treatment or Biological treatment:
The primary effluent is passed into large aeration tanks that is agitated and air is pumped into it. It results the vigorous growth of useful aerobic microbes into floes (bacteria associated with fungal filaments forms mesh like structures).

The growing microbes consume the organic matter in the effluent. It reduces the BOD (biochemical oxygen demand) of the effluent.

This treatment is continued till the BOD is reduced. After reducing the BOD, the effluent is passed into a settling tank where the bacterial ‘floes’ are allowed to sediment. This sediment is called activated sludge.

A small part of the activated sludge is pumped back into the aeration tank to.serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here the bacteria and the fungi are digested. This process releases gases such as methane, hydrogen sulphide and carbon dioxide.

These gases form biogas and used as source of energy Later the effluent is released into natural water bodies like rivers and streams.

The Ministry of Environment and Forests has initiated Ganga Action Plan and Yamuna Action Plan to save these major rivers of our country from pollution.

Microbes In Production Of Biogas
Bacteria which grow anaerobically on cellulosic material, produce large amount of methane along with CO₂ and H₂. They are called as methanogens. eg Methanobacterium.

These bacteria are commonly found in the anaerobic sludge during sewage treatment and in the rumen (a part of stomach) of cattle.

The excreta (dung) of cattle is rich in these bacteria. It is used for generation of biogas, commonly called gobar gas.

The biogas plant consists of a concrete tank (10 – 15 feet deep) in which bio-wastes are collected and a slurry of dung is fed. The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. The spent slurry is removed through another outlet and used as fertiliser.
A typical biogas plant:

The biogas thus produced is used for cooking and lighting.

Microbes As Biocontrol Agents
Biocontrol is controlling of plant diseases and pests by biological methods instead of using insecticides pesticides and weedicides.

Biological control of pests and diseases:
In agriculture, natural predation is practiced instead of using chemicals. So it is called sustainable agriculture

1. The beetle with red and black markings – the Ladybird, and Dragonflies are useful to eliminate aphids and mosquitoes, respectively.

2. Bacillus thuringiensis is used to control butterfly caterpillars is an example of microbial biocontrol. Here cry gene of bacteria introduced into cotton plant and it is called as Bt cotton.

If these plants are eaten by the insect larvae. In the gut of the larvae, the oxin is released and the larvae get killed.

3. Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective bio control agents of several plant pathogens.

4. Baculoviruses are pathogens that attack insects and other arthropods.

5. The genus Nucleopolyhedrovirus are species-specific and have narrow spectrum insecticidal applications

This is better in the area having beneficial insects that are coming under integrated pest management (IPM) programme.

Microbes As Biofertilisers
1. For example, the root nodules of leguminous plants have the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen which is used by the plant as nutrient. Other bacteria can fix atmospheric nitrogen eg- Azospirillum and Azotobacter( free-living in the soil) enriching the nitrogen content of the soil.

2. Fungi form symbiotic associations with plants (mycorrhiza). The genus Glomus form mycorrhiza. The fungal symbiont absorbs phosphorus from soil and passes it to the plant. In addition to these plants are resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.

3. Cyanobacteria which can fix atmospheric nitrogen, eg. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. These add organic matter to the soil and increase its fertility. Biofertilisers are used to reduce dependence on chemical fertilisers.

Students can Download Chapter 5 Evolution Notes, Plus Two Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two Zoology Notes Chapter 5 Evolution

Origin Of Life
In the solar system, earth was originated 4.5 billion years back. There was no atmosphere on early earth.

The UV rays from the sun broke up water into Hydrogen and Oxygen. Oxygen combined with ammonia and methane to form water, CO₂ and others.

Life originated four billion years. Earlier it was believed that life originated from non living things. This is the theory of spontaneous generation.

Later Louis Pasteur demonstrated that life comes only from pre-existing life. He showed that in presterilised flasks, life did not come from killed yeast while in another flask open to air, new living organisms arose from ‘killed yeast’.

Oparin and Haldane proposed that the first form of life that arose from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) and it is followed by chemical evolution.

In 1953, S.L. Miller, an American scientist created similar conditions in a laboratory He created electric discharge in a closed flask containing CH4, H2, NH3 and water vapaur at 800°C. He observed the formation of amino acids.

The first non-cellular forms of life could have originated 3 billion years back i.e RNA, Protein, Polysaccharides, etc…

Later the first cellular forms (single-celled) were originated. These were occurred in water environment only.
Diagrammatic Representation of Miller’s Experiment:

Evolution Of Life Forms – A Theory
Charles Darwin was conducted a voyage ship called H.M.S. Beagle round the world and reach the conclusion that existing living forms share similarities not only among themselves but also with life forms that existed millions of years ago. There has been gradual evolution of life forms.

According to the concept of reproductive fitness, those who are better fit in an environment, produce more progeny than others and survived more. He called it as natural selection an important mechanism of evolution.

In the same time Alfred Wallace naturalist of Malay Archepelago had the same conclusion as Darvin, that all the existing life forms share similarities and share common ancestors.

What Are The Evidences For Evolution?
Evidence of evolution of life comes from fossils that found in sedimentary rocks. Different-aged rock sediments contain fossils of different life-forms. They represent extinct organisms (e.g., Dinosaurs).This type of evidence is called paleontological evidence.

Analysing the comparative anatomy and morphology, shows similarities and differences among organisms of today and those that existed years ago.

Example of homologous organs in (a) Plants and (b) Animals:

For example whales, bats, Cheetah and human share similarities in the pattern of bones of forelimbs (similar anatomical structure).

It contains the bones like humerus, radius, ulna, carpals, metacarpals and phalanges. The same structure developed along different directions due to adaptions to different needs. So they have different functions.

These structures are homologous. This type of evolution is called divergent evolution. Other examples are vertebrate hearts or brains and the thorn and tendrils of Bougainvillea.

Wings of butterfly and of birds anatomically dissimilar but they perform similar functions. These are analogous structures arise due to convergent evolution.

Other examples are the eye of the octopus and of mammals or the flippers of Penguins and Dolphins: Sweet potato (root modification) and potato (stem modification) etc.

Another evidence supporting evolution by natural selection comes from England. Before industrialisation there are more white-winged moths on trees than dark-winged.

This is due to white-coloured lichen covered the trees – in that background the white winged moth survived But after industrialisation, there were more dark-winged moths in the same area because the tree trunks became dark due to industrial smoke and soots.

Under this condition the white-winged moth did not survive due to predators, dark-winged or melanised moth survived.

Lichen are pollution indicators they cannot grow in areas that are polluted. Hence, moths that were able to camouflage themselves.

What Is Adaptive Radiation?
In this, the small black birds -Darwin’s Finches are examples. Darwin found that there were many varieties of finches in the same island.

Their original seed-eating features are changed and become insectivorous and Variety of beaks of finches that Darwin found in Galapagos Island vegetarian finches.

Here the evolution starting from a point and radiating to other areas of geography (habitats) is called adaptive radiation.

Another example is Australian marsupials. A number of different marsupials evolved from an ancestral stock within the Australian island.

Placental mammals in Australia also exhibit adaptive radiation i.e they evolved into varieties (e.g., Placental wolf and Tasmanian wolf marsupial).

Variety of beaks of finches that Darwin found in Galapagos Island:

Biological Evolution
The importance of Darwinian theory of evolution lies in natural selection.

A colony of bacteria (say A) growing on a given medium show variation in terms of feed component. A change in the medium composition results the population (say B) that can survive under the new conditions.

Here the fitness of B is better than that of A under the new conditions. Nature selects for fitness. Adaptive ability is inherited. It has a genetic basis. Fitness is the ability to adapt and get selected by nature.

Branching descent and natural selection are the two key concepts of Darwinian Theory of Evolution Before Darwin, Lamarck had conducted experiments and proposed the use and disuse of organs.

He gave the examples of Giraffes who in an attempt to forage leaves on tall trees had to adapt by elongation of their necks. As they passed on this acquired character of elongated neck to succeeding generations.

The work of Thomas Malthus on populations was influenced Darwin For example, natural resources are limited, populations are stable in size except for seasonal fluctuation.

The population size grow exponentially if reproduced maximally. Darwin was pointed that variations which are heritable, when the resource utilisation better for few, they reproduce more progeny. Hence for a period of time survivors leave more progeny and there would be a change in population characteristics.

Mechanism Of Evolution
Mendel had studied only inheritable ‘factors’ influencing phenotype, But Hugo deVries conducted experiments on evening primrose and proposed the idea of mutation. Mutations are random and directionless while Darwinian variations are small and directional.

Mutation leads to speciation called as saltation (single step large mutation).

Hardy-Weinberg Principle
Diagrammatic representation of the operation of natural selection on different traits:

(a) Stabilising
(b) Directional and
(c) Disruptive

According to Hardy-Weinberg principle allele frequencies in a population are stable and is constant from generation to generation. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1.

For example, p and q represent the frequency of allele A and allele a. The frequency of AA individuals in a population is simply p2. The frequency of p appear on both the chromosomes of a diploid individual, Similarly of aa is q2, and of Aa is 2pq.

Hence, p2 + 2pq + q2 = 1. This is a binomial expansion of (p+q)2.

Disturbance in genetic equilibrium, or Hardy – Weinberg equilibrium, i.e., change of frequency of alleles in a population affected by five factors.

These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

When migration of population occurs, gene frequencies change in the original as well as in the new population. If the same change occurs by chance, it is called genetic drift.

Sometimes the change in allele frequency is different in the new sample of population that they become a different species. The original drifted population becomes founders and the effect is called founder effect.

The variation due to mutation or variation due to recombination during gametogenesis, or due to gene flow or genetic drift results in changed frequency of genes and alleles in future generation.

A Brief Account Of Evolution
About 2000 million years ago (mya) the first cellular forms of life appeared on earth. From this the cells with membranous envelop evolved and developed Some of these cells had the ability to release O₂. Slowly single-celled organisms became multi-cellular life forms.

In 1938, a fish caught in South Africa happened to be a Coelacanth which was thought to be extinct. These animals called lobefins evolved into the first amphibians that lived on both land and water.

The amphibians evolved into reptiles. They lay thick shelled eggs. Their modern descendents are the turtles, tortoises and crocodiles.

In the next 200 millions years reptiles of different shapes and sizes dominated on earth.In this period Giant ferns (pteridophytes) were present.

Land reptiles dinosaurs (biggest i.e., Tyrannosaurus rex) went back into water to evolve into fish like reptiles 200 mya (e.g. Ichthyosaurs). About 65 mya, the dinosaurs suddenly disappeared from the earth.

After the reptiles, mammals evolved on this earth. The first mammals were like shrews. Their fossils are small sized. Mammals were viviparous and protected their unborn young inside the mother’s body.

There were in South America mammals resembling horse, hippopotamus, bear, rabbit, etc. Due to continental drift, when South America joined North America, these animals were overridden by North American fauna.

Due to the same continental drift pouched mammals of Australia survived because of lack of competition. Some mammals live wholly in water are Whales, dolphins, seals and sea cows.

Origin And Evolution Of Man

Students can Download Chapter 4 Molecular Basis of Inheritance Notes, Plus Two Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus Two Zoology Notes Chapter 4 Molecular Basis of Inheritance

The Dna
DNA is a long nucleotides polymer of deoxyribonucleotides.

1. Structure of Polynucleotide Chain:
A nucleotide has three components

1. Nitrogenous base
2. Pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and
3. Phosphate group.

There are two types of nitrogenous bases.

Cytosine is common for both DNA and RNA and Thymine is present in DNA.

Uracil is present in RNA at the place of Thymine.

A nitrogenous base is linked to the pentose sugar through a N – glycosidic linkage to form a nucleoside, When a phosphate group is linked to 5′-OH of a nucleoside through phosphor ester linkage, to form nucleotide. Two nucleotides are linked through 3′-5′ phosphodiester linkage to form a dinucleotide.

Polynucleotide chain has at one end a free phosphate moiety at 5′-end of ribose sugar and other end of the polynucleotide chin the ribose has a free 3′-OH group The backbone in a polynucleotide chain is formed due to sugar and phosphates.

RNA has an additional-OH group present at 2′-position in the ribose and the uracil is found at the place of thymine.

Acidic nature of DNA was first identified by Friedrich Meischer in 1869 and it called as ‘Nuclein’.

Each strand from a DNA acts as a template for synthesis of a new strand. The two double stranded DNA thus, produced would be identical to the parental DNA molecule.

The salient features of the Double-helix DNA are

Francis Crick proposed the Central dogma in molecular biology, which states that the genetic information flows from DNA to RNA and RNA to protein. But in some viruses the flow of information is reverse direction, that is from RNA to DNA.

2. Packaging of DNA Helix:
In E. coli, they do not have a defined nucleus it is termed as ‘nucleoid’. The DNA in nucleoid is organised in large loops held by proteins.

In eukaryotes, this organisation is much more complex. Here the positively charged, basic proteins called histones are associated with DNA.

Histones are rich in the basic amino acid residues lysines and arginines. Histones are organised to form a unit of eight molecules called as histone octamer.

The beads-on-string structure in chromatin is packaged to form chromatin fibers that are further coiled and condensed at metaphase stage of cell division to form chromosomes.

The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called Nucleosome. It contains 200 bp of DNA helix.

Nucleosomes constitute the repeating unit of a structure in nucleus called chromatin, it is thread-like stained (coloured) bodies seen in nucleus. The nucleosomes in chromatin are seen as ‘beads-on- string’ structure when viewed under electron microscope (EM).

The packaging of chromatin at higher level with proteins that are called as Non-histone Chromosomal (NHC) proteins.

The Search For Genetic Material
This is the work of identification of DNA that acts as a genetic material and responsible for inheritance.

Transforming Principle:
In 1928, Frederick Griffith, in a series of experiments with Streptococcus pneumoniae (bacterium responsible for pneumonia), showed the trasformation in the bacteria.

Mice infected with the S strain (virulent) die from pneumonia infection but mice infected with the R strain do not develop pneumonia.

When Griffith was injected heat-killed S strain into mice, bacteria did not kill them. But he injected a mixture of heat-killed S and live R bacteria, the mice died and he recovered living S bacteria from the dead mice.

Biochemical Characterisation of Transforming Principle:
Oswald Avery, Colin MacLeod, and Maclyn McCarty worked on the ‘transforming principle’ of Griffith’s experiment and noticed that DNA alone from S bacteria caused R bacteria to become transformed.

They also discovered that protein-digesting enzymes (proteases) and RNA-digesting enzymes (RNases) did not affect transformation.

But the digestion with DNase inhibited transformation.

1. The Genetic Material is DNA:
Alfred Hershey and Martha Chase (1952) grew bacteriophages on a medium that contained radioactive phosphorus and some others on medium that contained radioactive sulfur.

Viruses grown in the presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus but protein does not. Similarly, viruses grown on radioactive sulfur contained radioactive protein but not radioactive DNA because DNA does not contain sulfur.

After the infection the viral coats were removed from the bacteria by agitating them in a blender. It is concluded that proteins did not enter the bacteria from the viruses. But the DNA is the genetic material that passed from virus to bacteria.

The Hershey-Chase experiment:

2. Properties of Genetic Material (DNA versus RNA):
A molecule that act as a genetic material must possess the following features

Therefore, among the two nucleic acids, the DNA is a better genetic material.
The presence of thymine at the place of uracil also gives additional stability to DNA.
In fact, RNA being unstable, mutate at a faster rate. So the viruses having RNA genome having shorter life span mutate and evolve faster.

Rna World
RNA is genetic material as well as a catalyst. But it is reactive and hence unstable. Therefore, DNA has evolved from RNA with chemical modifications that make it more stable.

Replication
Watson and Crick (1953) proposed replication of DNA. They suggested that the two strands separate and act as a template for the synthesis of new complementary strands.

Waste-click model for semiconservative DNA replication:

1. The Experimental Proof:
DNA replicates in semi conservative manner was first shown in Escherichia coli by Matthew Meselson and Franklin Stahl performed the following experiment in 1958:

After the completion of replication, each DNA molecule have one Watson-Crick model for parental and one newly synthesised strand. This is termed as semiconservative DNA replication. semiconservative DNA replication.

Then they transferred the cells into a medium with normal 14NH4Cl and took samples at various definite time intervals as the cells multiplied, and extracted the DNA that remained as double-stranded helices.

The DNA that was extracted from the culture one generation after the transfer from 15N to 14N medium [E. coli divides in 20 minutes] had a hybrid DNA.
(Separation of DNA by Centrifugation):

DNA extracted from the culture after another generation [that is after 40 minutes, II generation] was composed of equal amounts of this hybrid DNA and of ‘light’ DNA.

In an another experiment radioactive thymidine is incorporated into DNA and was observed the semi conservative replication of DNA in Vicia faba (faba beans) by Taylor and colleagues in 1958.

2. The Machinery and the Enzymes:
In E. coli, the process of replication takes place with the help of DNA-dependent DNA polymerase, because it uses a DNA template to catalyse the polymerization of deoxynucleotides.

E. coli that has only 4.6 × 106 bp completes the process of replication within 38 minutes. Deoxyribonucleoside triphosphates have double role. Besides acting as substrates, they provide energy for polymerization reaction same as in case of ATP.

Initially the replication occur within a small opening of the DNA helix (origin of replication) called as replication fork. The DNA- dependent DNA polymerases catalyse polymerization only in one direction, that is 5¹-3’.

Here on one strand (the template with polarity 3’-5′), the replication is continuous, while on the other (the template with polarity 5′-3′), it is discontinuous. The discontinuously synthesized fragments are later joined by the enzyme DNA ligase.

In eukaryotes, the replication of DNA takes place at S-phase of the cell-cycle. A failure in cell division after DNA replication results into polyploidy(a chromosomal anomaly).

Transcription
The process of copying genetic information from one strand of the DNA into RNA is termed as transcription. In transcription only a segment of DNA is copied into RNA.

Only single stranded RNA is produced by transcription process. If the two RNA molecules are produced simultaneously it would be complementary to each other, hence would form a double stranded RNA. This would prevent the translation.

1. Transcription Unit:
DNA has three regions as transcription unit

1. A Promoter
2. The Structural gene
3. A Terminator

The two strands have opposite polarity and the DNA-dependent RNA polymerase catalyse the polymerisation in only one direction, that is, 5′-3′, the strand that has the polarity 3′-5’acts as a template, and is also referred to as template strand.

The other strand which has the polarity (5′-3′) and the sequence same as RNA (except thymine at the place of uracil), is displaced during transcription. This strand (which does not code for anything) is referred to as coding strand.
For example

The promoter is located towards 5′ – end (upstream) of the structural gene. It provides binding site for RNA polymerase.

The terminator is located towards 3′ – end (downstream) of the coding strand and it usually defines the end of the process of transcription.

2. Transcription Unit and the Gene:
A gene is the functional unit of inheritance. The DNA sequence coding for tRNA or rRNA molecule also define a gene.

Cistron is a segment of DNA coding for a polypeptide, the structural gene in a transcription unit is called as monocistronic (mostly in eukaryotes) or polycistronic (mostly in bacteria or prokaryotes).

3. Types of RNA and the process of Transcription:
In bacteria, there are three major types of RNAs:

• mRNA (messenger RNA)
• tRNA (transfer RNA), and
• rRNA (ribosomal RNA).

All three RNAs are needed to synthesise a protein in a cell. The mRNA provides the template, tRNA brings aminoacids and reads the genetic code, and RNAs play structural and catalytic role during translation.

DNA- dependent RNA polymerase that catalyses transcription of all types of RNA in bacteria. RNA polymerase binds to promoter and initiates transcription (Initiation). It uses nucleoside triphosphates as substrate and polymerises in a template and follow the rule of complementarity.

Once the polymerases reaches the terminator region, the nascent RNA and RNA polymerase falls off. This results in termination of transcription.

RNA polymerase catalyse all the three steps, which are initiation, elongation and termination.

The RNA polymerase bind with initiation factor and termination-factor to initiate and terminate the transcription, respectively.

In bacteria, the mRNA does not require any processing and transcription and translation take place in the same compartment.

In eukaryotes, there are 3 RNA polymerases in the nucleus. The RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S).

RNA polymerase III is responsible for transcription of tRNA, 5srRNA, and snRNAs (small nuclear RNAs).

The RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hnRNA).

Genetic Code
The process of translation requires transfer of genetic information from a polymer of nucleotides to a polymer of amino acids.
codons for various aminoacids:

For this, George Gamow, who proposed only 4 bases they have to code for 20 amino acids, the code should constitute a combination of bases.

The code should be made up of three nucleotides( triplet) and in various combination would generate 64 codons, 4³ (4 × 4 × 4) Marshall Nirenberg’s cell-free system for protein synthesis helped the code to be deciphered.

Severo Ochoa enzyme- polynucleotide phosphorylase was also helpful in polymerising RNA with defined sequences.

1. Mutations and Genetic Code:
Deletions and rearrangements in a segment of DNA result in loss or gain of a gene function.

Insertion or deletion of one or two bases, changes the reading frame from the point of insertion or deletion. Such mutations are referred to as frame-shift insertion or deletion mutations.

2. tRNA- the Adapter Molecule:
Francis Crick proposed that an adapter molecule would bind to specific amino acids. tRNA has an anticodon loop and an amino acid accepter end to which it binds to amino acids. tRNAs are specific for each amino acid.

For initiation, there is another specific tRNA that is referred to as initiator tRNA. There are no tRNAs for stop codons.

Two-dimensional structure of tRNA looks like a clover-leaf. But in three-dimensional structure of tRNA looks like inverted L.

Translation
Translation is the process of polymerisation of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence of bases in the mRNA. The amino acids are joined by a bond which is known as a peptide bond. Formation of a peptide bond requires energy.

The activation of amino acids with ATP and linked to tRNA- a process commonly called as charging of tRNA or aminoacylation of tRNA. If two such charged tRNAs are brought close together the peptide bond is formed.

The ribosome also acts as a catalyst (23S rRNA in bacteria is the enzyme- ribozyme) for the formation of peptide bond.

A translational unit in mRNA is start codon (AUG) and the stop codon. mRNA also has some additional sequences that are not translated they are called as untranslated regions (UTR). The UTRs are present at both 5′-end (before start codon) and at 3′-end (after stop codon). They are required for efficient translation process.

The ribosome consists two subunits; a large subunit and a small subunit. For initiation, the ribosome binds to the mRNA at the start codon (AUG) that is recognised only by the initiator tRNA.

In elongation , amino acid linked to tRNA, and bind to the codon in mRNA by forming complementary base pairs with the tRNA anticodon. The ribosome moves from codon to codon along the mRNA.

Amino acids are added one by one and translated into Polypeptide. At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome.

Regulation Of Gene Expression
The Lac operon:
In eukaryotes, the regulation is possible in

1. transcriptional level (formation of primary transcript),
2. processing level (regulation of splicing),
3. transport of mRNA from nucleus to the cytoplasm,
4. translational level.

For example E. coli synthesised the enzyme beta-galactosidase in the medium if the disaccharide, lactose is present.

Enzyme breakdown the lactose into galactose and glucose; the bacteria use them as a source of energy. The development and differentiation of embryo into adult organisms are also a result of the coordinated regulation of expression of several sets of genes.

In a transcription unit, the activity of RNA polymerase at a promoter is regulated by proteins. These regulatory proteins act both positively (activators) and negatively (repressors). The promoter regions of prokaryotic DNA is regulated by the interaction of adjacent operators. Each operon has its specific operator and specific repressor.

For example, lac operator is present only in the lac operon and it interacts specifically with lac repressor only.

1. The Lac operon:
The function of lac operon was first shown by Jacob and Monod.

Other examples are trp operon, ara operon, his operon, val operon, etc.

The lac operon consists of one regulatory gene (i gene) and three structural genes (z, y, and a).

Hence, all the three gene products in lac operon are required for metabolism of lactose. Lactose (inducer) is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon.

In the presence of an inducer, such as lactose, the repressor is inactivated by the inducer. Then RNA polymerase bind to the promoter and transcription proceeds. Regulation of lac operon by repressor is referred to as negative regulation.

Human Genome Project
This is mainly aims to find out the complete DNA sequence of human genome If two individuals differ, then their DNA sequences should also be different, at least at some places.

Human Genome Project was launched in the year 1990 (HGP). Human genome consists of approximately 3 × 109 bp.

HGP was coordinated by the U.S. Department of Energy and the National Institute of Health. The project was completed in 2003.

This project also aims to solve challenges in health care, agriculture, energy production, environmental remediation.

Methodologies:
For sequencing, the total DNA from a cell is isolated and converted into random fragments of relatively smaller sizes and cloned in suitable host using vectors. The cloning resulted into amplification of each piece of DNA fragment so that it could be sequenced with ease.

The commonly used hosts are bacteria and yeast, and the vectors are called as BAC (bacterial artificial chromosomes), and YAC (yeast artificial chromosomes). The fragments are sequenced using automated DNA sequencers that was developed by Frederick Sanger.

These sequences are then arranged based on some overlapping regions present in them. Alignment of these sequences are done with computer based programs. These sequences are annotated and assigned to each chromosome. The sequence of chromosome 1 was completed only in May 2006.

Another task was the construction of genetic and physical maps on the genpme. This was made possible by knowing the polymorphism of restriction endonuclease recognition sites, and some repetitive DNA sequences.

1. Salient Features of Human Genome:

Dna Fingerprinting
The 99.9 per cent of base sequence among humans is the same. The genetic differences between two individuals is calculated by comparing the two sets of 3 × 10⁶ base pairs.

It is the identification of differences in some specific regions in DNA sequence called as repetitive DNA,
These repetitive DNA are separated from bulk genomic DNA as different pegks during density gradient centrifugation.

The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA. Depending on base composition, length of segment, and number of repetitive units, the satellite DNA is classified into many categories,

1. Micro-satellites,
2. Mini-satellites etc.

These sequences do not code for any proteins and show high degree of polymorphism. DNA from every tissue (such as blood, hair-follicle, skin, bone, saliva, sperm etc.), of an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications.

The polymorphisms are inheritable from parents to children DNA fingerprinting is the basis of paternity testing, in case of disputes.

The polymorphism in DNA sequence is the basis of genetic mapping and DNA fingerprinting, Polymorphism arises due to mutations. Allelic sequence variation results inheritable mutation.

Such variation are observed in non coding DNA sequence. These mutations accumulating generation after generation, and form one of the basis of variability/polymorphism.

The different types of polymorphisms ranging from single nucleotide change to very large scale changes. For evolution and speciation, such polymorphisms play very important role.

The technique of DNA Fingerprinting was initially developed by Alec Jeffreys. He used a satellite DNA as probe. It is called as Variable Number of Tandem Repeats (VNTR).

The technique, is based on Southern blot hybridisation using radiolabeled VNTR as probe.

It involves

1. isolation of DNA,
2. digestion of DNA by restriction endonucleases,
3. separation of DNA fragments by electrophoresis,
4. transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon,
5. hybridisation using labelled VNTR probe, and
6. detection of hybridised DNA fragments by autoradiography.

The VNTR belongs mini-satellite.lt is the small DNA sequence. Its copy number varies from chromosome to chromosome in an individual. The numbers of repeat show very high degree of polymorphism.

The size of VNTR varies in size from 0.1 to 20 kb. So after hybridisation with VNTR probe, the autoradiogram gives many bands of differing sizes.

These bands give a characteristic pattern for an individual DNA. It differs from individual to individual in a population except in the case of monozygotic (identical) twins.