Medical brain notes 33

  Reasons for the Explosion   The main reason for slow and fluctuating population growth prior to early 1800's was the prevalence of diseases such as small pox, diphtheria, measles and scarlet fever. In addition, epidemics of diseases such as typhoid fever, cholera and plague eliminated large number of adults. Famines also were not unusual. Biologically speaking, prior to 180s the population was essentially in a dynamic balance with natural enemies and other aspects of environmental resistance. High reproductive rates were largely balanced by high mortality.   Since the 19th centuary   �    discoveries of vaccination provides protections to many of the infectious agents   �    discovery of antibiotics is a major breakthrough in the medical history,   �    improvements in agricultural techniques,   �    improvements in the nutrition and   �    better sanitation and personal hygiene   brought ab...

  Global warming : Green house effect Global warming refers to an average increase in the earth's temperature, which in turn causes changes in climate. During the past 4.65 billion years of its history, earth has warmed many times. But at present it is facing a rapid warming mainly due to human activities. The average temperature of earth is about 59 0 F (15 0 C). During the last century this average has risen by about 1 0 F. By the year 2100, it is believed that the rise would be between 2.5 and 10.4 0 F. This will cause dramatic changes such as rise in sea level, changes in rainfall patterns, wide range of impacts on plants, wildlife and humans.   Green house gases and Green house effect :-   The trapping of energy from the sun by certain gases in the atmosphere leading to the rise in earth's temperature is known as Green   house effect . Hence these gases are known as green house gases. Some   gases such as water vapour, carbon dioxide, nitrous oxide and meth...

  Types of Greenhouse Gases :-   In the environment, greenhouse gases occur (i) naturally or (ii) from human activities.   The most abundant greenhouse gas is  carbon dioxide . It reaches the atmosphere due to volcanic eruptions, respiration of animals, burning and decay of organic matter such as plants. Normally carbon-dioxide is removed by the plants by photosynthesis. Carbon-dioxide is also absorbed into ocean water. But humans by their activities increase the release of carbon dioxide into the atmosphere . Such activities include burning of fossil fuels, solid wastes, wood and wood products to drive vehicles, generate electricity etc. At the same time due to deforestation, the number of trees available to absorb carbon-dioxide through photosynthesis has been greatly reduced.   Human activities have caused carbon - dioxide to be released to the atmosphere at rates much faster than that at which earth's natural processes can recycle this gas. There were about ...

  Effects of Global warming :-   1.     Due to the warming of oceans, sea level will rise. Glacier ice will also melt, causing further rise in sea level. As a result in the 21 st  century sea level will rise from 9 to 88 cm. Such a rise will submerge many parts of countries. 2.   Seasons will be longer in some areas.   3.    The warmed world will be generally more humid and greater humidity will increases the rainfall.   4.   Storms are expected to be more frequent and intense. 5.   Some regions of the world would become dry.   6.     Wind blows will be harder and in different patterns. Hurricane would be more severer.   7.   Weather patterns would be less prediclable and more extreme.   8.     Crops and forests may be affected by more insects and plant diseases.   9.     Animals and plants will find it difficult to adjust to the changed environment. Animals will ...

  Carbon sequestration :-   The simple technique is to preserve trees and plants more. Trees, take up carbon-dioxide, break it down in photosynthesis, and store carbon in new wood. It need massive reforestation. Carbon-dioxide can also be sequestrated directly into deep ocean water or into oil wells or some aquifer form which it cannot escape.   Usage of alternate fuels such as nuclear energy, solar power, wind power and hydrogen fuel cells which emit no greenhouse gases are being considered.   Ozone layer depletion   Ozone is a form of oxygen (O 3 ). In the stratosphere (ozonosphere), ozone blocks out the sun's ultraviolet rays and is a lifesaver.   Ozone as a natural sun block   The electromagnetic radiation emitted from the sun includes ultraviolet radiation, which is potentially harmful to most living things since it can damage DNA. The ozone layer screens out the sun's harmful ultraviolet radiation. Even 1% reduction in the amount of ozone in the ...

  Waste management   Human activities related to livelihood and welfare generate waste. All wastes are pollutants and they create pollution in one way or other. Fundamentally air, land and water pollution results mostly due to improper disposal of wastes. Classification of wastes   1. Bio - degradable waste   These are wastes capable of being removed or degraded by biological or microbial action. Waste from agricultural products, animal wastes and waste from food processing, leather, fibre, paper and wood etc. come under this group.   2. Non bio-degradable waste   The substances which are normally not acted upon and decomposed by microbes are non-bio degradable wastes. It includes mineral waste, mining waste and industrial waste and non-degradable metallic and plastics substances.   3. Mixture of biodegradable and non-biodegraded wastes   It includes municipal waste and industrial waste. Municipal waste contains household garbage, piles of food sc...