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Artificial selection of living organisms

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 The term “artificial selection” was expressed by the Persian scientist Abu Rayhan Biruni in the 11th century. Charles Darwin also used this term in his work on natural selection. He noted that many domesticated animals and plants had special properties that were developed by: •  Intentional breeding among individuals with desirable characteristics; and •  Discouraging the breeding of individuals with less desirable characteristics Artificial selection (or selective breeding) means intentional breeding between individuals for certain traits, or combination of traits. Selective breeding has revolutionized agricultural and livestock production throughout the world. Animals or plants having desirable characteristics are selected for breeding. In this way, many new generations with desirable characteristics are produced. In artificial selection, the bred animals are known as breeds, while bred plants are known as varieties or cultivars. Numerous breeds of sheep, goat, cow, hen etc. have be
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Water pollution and its effects on life

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 Water pollution is a contamination of water bodies (e.g. lakes, rivers, oceans and ground water). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds. Industrial Effluents Industrial units are installed to produce the desired substances (chemicals, cloth, leather goods, paper, plastic items, petrochemicals and rubber items) on commercial scale to meet the needs of the society. But unfortunately all the industrial units discharge their wastes (chemicals and solid materials) either to open ground or to water channels. This is called industrial effluent. The industrial effluent may be highly toxic organic chemicals, inorganic salts, heavy metals, mineral acids, oil and greases, etc. On the other hand, water used as cleaning agent in industries is directly discharged out. This water contains all kinds of toxic chemicals and detergents. When these effluents and used water enter lakes, streams,
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History of economy

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  History of economics Economics is the science that concerns itself with economies; that is, it studies how societies produce goods and services as well as how they consume them. It has influenced global finance at many important junctions throughout history and is a vital part of our everyday lives. However, the assumptions that guide the study of economics have changed dramatically throughout history. Here we take just a brief look at the history of modern economic thought. What we present is just a narrow snapshot, which focuses primarily on Western European and American strands of thought.   KEY TAKEAWAYS Economics is the science of how goods and services are produced and consumed.  Adam Smith used the ideas of French writers to create a thesis on how economies should work, while Karl Marx and Thomas Malthus expanded on his work—focusing on how scarcity drives economies. Leon Walras and Alfred Marshall used statistics and mathematics to express economic concepts, such as economies
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How nitrogen recycle in our environment

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 Nitrogen is an important component of many biomolecules, like proteins and nucleic acids (DNA and RNA). Atmosphere is the reservoir of free gaseous nitrogen. Living organisms cannot pickup this gaseous nitrogen directly from atmosphere (except for nitrogen fixing bacteria). It has to be converted into nitrates to be utilized by plants. Nitrogen cycling involves several stages: a- Formation of Nitrates It is done by the following ways: i. Nitrogen Fixation Conversion of nitrogen gas into nitrates is called nitrogen fixation. It occurs in the following ways.  •  Thunderstorms and lightning convert atmospheric gaseous nitrogen to oxides of nitrogen. These oxides dissolve in water and form nitrous acid and nitric acid. The acids in turn combine with other salts to produce ‘nitrates’. It is called as atmospheric nitrogen fixation. •  Some bacteria also have the ability to transform gaseous nitrogen into nitrates. It is called biological nitrogen fixation. Some of these nitrogen fixing bact
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Basic Information about Dengue Fever

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 Basic Information about Dengue Fever Dengue fever is a viral infection transmitted through a mosquito Aedes aegypti. It has become a major health problem in tropical and sub-tropical countries, including Pakistan. There are four types of dengue virus. Recovery from infection by one provides lifelong immunity against that virus but provides no protection against infection by the other three viruses. According to the World Health Organization, there are 50 million dengue infections worldwide every year. Now, there are 2.5 billion people at risk from dengue. The female Aedes mosquito gets the virus when it bites an infected person. When an infected mosquito bites another person, viruses enter his / her blood and attack white blood cells. Inside WBCs, viruses reproduce and destroy them. In severe cases, the virus affects liver and bone marrow. As a result there is a decrease in the production of blood platelets and patient suffers from bleeding. Other symptoms of dengue include high fever
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Water pollution and its effects

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 It is the change in the composition of water by the addition of harmful substances. Water pollution severely affects the health of people. Sewage is one of the major pollutants of water. It contains organic matter and the excreta of human and other animals. Organic matter encourages the growth of microorganisms which spread diseases. The wastes of industries (acids, alkalis, dyes and other chemicals) are disposed in nearby water bodies. These wastes change the pH of water and are harmful or even fatal to aquatic organisms. Certain industries release a lot of hot water from their cooling plants. It results in heating up of water bodies and kills aquatic life. Fertilizers and pesticides enter into water bodies with the rain water flow and the ground water by seepage. These chemicals remain in water for a long time and can enter food chains. They cause a number of diseases in animals. Oil tankers and offshore petroleum refineries cause oil leakage into water. Oil floats on the water surf
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How acid rain forms and its effect on living things.

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Acid rain  Acid rain: When oxides of sulphur and oxides of nitrogen mix with rain water and forms sulphuric acid and nitric acid its is called acid rain. Causes of acid rain. We use fossils fuel in our automobiles and factories to power them by the burning of this fuel oxides of sulphur and oxides of nitrogen released in to our atmosphere and became the part of atmosphere . These are very dangerous air pollutant which cause of acid rain. How acid rain forms: When oxides of sulphur and oxides of nitrogen combines with rain water they form sulphuric acid and nitric acid .These acid comes into our earth in the form of acid rain .And we called this rain the acid rain because it is the mixture of water and acid . Effects of acid rain : Aquatic life:Acid rain badly effects our aquatic life because it changes the PH of water which was neutral before acid rain and after rain this water becomes acid because acid rain changes its PH. The aquatic life like fishes etc start to die .it badly effect
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