NEET BIOLOGY BY SHASHI SIR

16.7 OZONE DEPLETION IN THE STRATOSPHERE  You have earlier studied in the Chemistry textbook of Class XI about ‘bad’ ozone, formed in the lower atmosphere (troposphere) that harms plants and animals.  There is ‘good’ ozone also; this ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun.  UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules.  The thickness of the ozone (300 DU) in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU).  Ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere.  There should be a balance between production and degradation of ozone in the stratosphere.  Of ...

16.6 GREENHOUSE EFFECT AND GLOBAL WARMING The term ‘Greenhouse effect’ has been derived from a phenomenon that occurs in a greenhouse.  Have you ever seen a greenhouse? It looks like a small glass house and is used for growing plants especially during winter.  In a greenhouse the glass panel lets the light in, but does not allow heat to escape.  Therefore, the greenhouse warms up, very much like inside a car that has been parked in the sun for a few hours.  The greenhouse effect is a naturally occurring phenomenon that is responsible for heating of Earth’s surface and atmosphere.  You would be surprised to know that without greenhouse effect the average temperature at surface of Earth would have been a chilly –18oC rather than the present average of 15oC.  In order to understand the greenhouse effect, it is necessary to know the fate of the energy of sunlight that reaches the outermost atmosphere (Figure16.6).  Clouds and gases r...

16.4 AGRO-CHEMICALS AND THEIR EFFECTS  In the wake of green revolution, use of inorganic fertilisers and pesticides has increased manifold for enhancing crop production.  Pesticides, herbicides, fungicides, etc., are being increasingly used.  These incidentally, are also toxic to non-target organisms,that are important components of the soil ecosystem.  Do you think these can be biomagnified in the terrestrial ecosystems?  We know what the addition of increasing amounts of chemical fertilisers can do to aquatic ecosystems vis-à-vis eutrophication.  The current problems in agriculture are, therefore, extremely grave. 16.4.1 Case Study of Organic Farming  Integrated organic farming is a cyclical, zero-waste procedure, where waste products from one process are cycled in as nutrients for other processes.  This allows the maximum utilisation of resource and increases the efficiency of production. Ramesh Chandra Dagar, a farmer in Sonipat...

16.3 SOLID WASTES Solid wastes refer to everything that goes out in trash.   Municipal solid wastes are wastes from homes, offices, stores, schools, hospitals, etc., that are collected and disposed by the municipality.  The municipal solid wastes generally comprise paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.  Burning reduces the volume of the wastes, although it is generally not burnt to completion and open dumps often serve as the breeding ground for rats and flies.  Sanitary landfills were adopted as the substitute for open-burning dumps.  In a sanitary landfill, wastes are dumped in a depression or trench after compaction, and covered with dirt everyday.  If you live in a town or city, do you know where the nearest landfill site is?  Landfills are also not really much of a solution since the amount of garbage generation specially in the metros has increased so much that these sites are getting filled too....

16.2 WATER POLLUTION AND ITS CONTROL  Human beings have been abusing the water-bodies around the world by disposing into them all kinds of waste.  We tend to believe that water can wash away everything not taking cognizance of the fact that the water bodies are our lifeline as well as that of all other living organisms.  Can you list what all we tend to try and wash away through our rivers and drains?  Due to such activities of human kind, the ponds, lakes, stream,rivers, estuaries and oceans are becoming polluted in several parts of the world.  Realising the importance of maintaining the cleanliness of the water bodies, the Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974 to safeguard our water resources. 16.2.1 Domestic Sewage and Industrial Effluents: As we work with water in our homes in the cities and towns, we wash everything into drains.  Have you ever wondered where the sewage that comes out of o...

16.3 ABSORPTION OF DIGESTED PRODUCTS  Absorption is the process by which the end products of digestion pass through the intestinal mucosa into the blood or lymph.  It is carried out by passive, active or facilitated transport mechanisms.  Small amounts of monosaccharides like glucose, amino acids and some electrolytes like chloride ions are generally absorbed by simple diffusion .  The passage of these substances into the blood depends upon the concentration gradients.  However, some substances like glucose and amino acids are absorbed with the help of carrier proteins. This mechanism is called the facilitated transport . Transport of water depends upon the osmotic gradient.  Active transport occurs against the concentration gradient and hence requires energy.  Various nutrients like amino acids, monosaccharides like glucose, electrolytes like Na+ are absorbed into the blood by Active transport  mechanism.  Fatty acids and glyc...

Deficient nutrient Disease Protein Kwashiorkar Protein and Calories Marasmus Retinol (Vitamin A) Nyctalopia and Xerophthalmia Thiamin (Vita- B1) (Beri-beri) & polyneuritis Riboflavin (Vita-B2) Cheliosis ( cracking of the corners of the mouth ) Niacin or Nicotinic acid (B3) Pellagra ( inflamed skin, diarrhea, dementia, and sores in the mouth ) Pantothenic acid (Vita-B5) Burning feet syndrome Pyridoxine (Vita-B6) Dermatitis Biotin (Vita-B7) Dermatitis Folic acid (Vita-B9) Megaloblastic anaemia Cyanocobalamin (Vita-B12) Penicious anaemia Ascorbic acid (Vita-C) Scurvy ( Bruising, bleeding gums, weakness, fatigue and rash ) Calciferol (Vita-D) Rickets and Osteomalacia & osteoporosis Tocopherol (Vita-E) Sterility Phylloqunone (Vit...

ENVIRONMENTAL ISSUES: Human population size has grown enormously over the last hundred years.  This means increase in demand for food, water, home, electricity, roads, automobiles and numerous other commodities.  These demands are exerting tremendous pressure on our natural resources, and are also contributing to pollution of air, water and soil.  The need of the hour is to check the degradation and depletion of our precious natural resources and pollution without halting the process of development.  Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil.   Agents that bring about such an undesirable change are called as pollutants.   In order to control environmental pollution, the Government of India has passed the Environment (Protection) Act, 1986 to protect and improve the quality of our environment (air, water and soil).  16.1 AIR POLLUTION AND ITS CONTROL  We are d...