Unbalanced Theories

Unbalanced theories are based on the principal that it is not possible especially in a developing country that all sectors can grow simultaneously at the same rate. Therefore, developing nations must look to invest more heavily in strategic sectors. The growth  in specialized sectors will transfer to other sectors of the economy later. Since developing countries face deficiency of capital, they can not simultaneously invest in all sectors of the economy. Therefore, it is necessary that they choose few strategic sectors in which they can specialize.

These theories also suggest strong relationship between private sector and government. They have been criticized for giving way to inflation in the economy.

Balanced Theories

Balanced theories are based on the principal that growth should be sought in all sectors ofthe economy at the same level. Therefore, economic growth should be based on growth in all sector of the economy. These theories are thus termed as "Balanced Theories", which propose balanced growth achieved through growth in all sectors of the economy.

These theories suggest that size of the market is very small in developing economics. Moreover, these economies face dearth of entrepreneurs. Therefore, the role of the government is very crucial in countries where balanced theories are practiced.

Soil and Salinity Problems

When the upper layer of the soil leaves its place by wind or water, this creates the problem of "Soil Erosion". When the soil erosion is caused by wind, it is termed as "Wind Erosion". When the soil erosion is caused by excessive flood water damaging the upper surface of land, it is termed as Water Erosion". Soil Erosion decreases the fertility of land. In the worst case, it makes the land completely barren. Lands which have a grass cover are better protected against soil erosion than lands without grass. Each year, approximately 8000 hectares of land is damaged due to soil erosion.

When mineral salts dilute in the water, this creates the problem of "Water of Salinity". Lands where the composition of soil contains chemicals like sodium sulphate, magnesium chloride, magnesium sulphate etc, are more prone to salinity problems. Each year, a large part of agricultural land becomes victims to his problem.

Consumer Goods Industries

"Consumer goods industries comprise of goods which are used for consumption by final consumers".
Consumer goods are finished products. The buyers of these goods are final consumer. These goods are brought to the consumers through wholesalers and retailer. They are essential for the economy because they complement capital goods industries by consuming the industrial production.
Usually buyers of consumer goods are in much more quantity than for capital goods industries. The amount of substitutes is higher in consumer goods industries than in capital goods industries. The level of competition is much higher in consumer industries than in capital goods industries.

Major Consumer Good Industries of Pakistan are as follows:

• Cement Industry
• Confectionery Industry
• Fast Moving Consumer Goods Industry
• Hotel Industry
  

Increase In Employment

Developing countries usually suffer from unemployment. Many people are engaged with agriculture whereas; the supply of land is not enough to compensate every one for employment. Moreover, farmers growing seasonal crops remains unemployed off -season. The growth in industrial sector can provide employment opportunities to many people. Natural lands and fields are fixed but unlimited industries can be established provided there is enough investment available.

Reducing Cost of Doing Business

Investor all over the world are interested to find out cost of doing business in a particular country before investing in any country. They look for wages and utilities expenses to make an estimate of cost of doing business. Labor wage in Pakistan are low but utilities are much too expensive. In china, electricity is free. In Pakistan, electricity charges are exorbitant for commercial purpose and the recent increase in prices for gas will not make improve.Cost if doing business must decrease to attract foreign investment.

Critical Analysis of Quantity Theory of Money

In the following lines, Quantity theory of money is critically analyzed:

Analysis of Assumption in the theory:

Following are the assumptions upon which this theory is based:

• Quantity of money changes, but not the velocity of money, whereas; velocity of money also changes and brings the same result as if quantity of money changed.
• Quantity of money influences prices but the reverse is not true. In other words, quantity of money determines the level of prices. But, prices are affected by many other factors than just the quantity of money.
• Full employment prevails in the economy. This does not happen in the real world.
• Velocity of money remains constant which is not possible.
  

Financing the Savings and Investment Gap

For increasing production, one needs investment. This investment comes from saving surplus units. If the savings equal investment, then there is no need of foreign aid. But, if required investment is greater than savings, then the gap has to be financed through foreign aid. Therefore, foreign aid helps to continue production if investment requirements can not be financed with savings.

Inefficient Supply Chain

In the Supply chain of marketing agricultural products, there are a lot of people involved like weigh er, accountant, collector, commission agent etc. The goods have to pass from each one of them. It takes more time for the goods to transfer from the farmers to the consumers. This results in waste of yield as well as increase in price which consumers have to pay when the goods finally reach to them.

Importance of Capital Formation

Following points illustrate the importance of capital formation in the economic development:

• Capital formation is vital for economic growth.
• Capital resources of a country increase investment and needed finance for the industries.
• Capital formation helps in eradicating the vicious circle of poverty.
• Capital formation increase investment and production activities which results in more employment opportunities for the masses.
• Capital formation helps a country becoming self sufficient and independent all foreign pressures.
• Expenditure on Human Resource Development increases productivity and efficiency of work which later translates into better and more production.
  

Modifying Monetary Policy and Fiscal Policy

It is the need of the time that Government must modify its monetary and discal policy. Rapid increase in money supply has increased inflation to unlimited proportions. Increasing consumer credit has encouraged people to spend more on maintaining a lavish lifestyle rather than making a productive use of wealth. Moreover, the taxation system should be progressive. Indirect taxes which affect common people should be reduced and direct taxes which affect rich people should be increased.

Economic Growth

"The Increase in production that results from capital accumulation and technological change."

Economic development and economic growth are different things. Economic growth in merely the increase in the goods and services that a country produces; whereas,economic development encompasses both the increase in production and the mechanism and structures that bring about it.
In other words, economic development is not only concerned with the increase in production but it is also concerned with making it permanent by a radical change in structure, institution or technology etc.

Boost up Economic Growth

Privatization would pave the way for a private-sector led economic growth. Recent examples of growing economies prove that private sector is the engine of growth. If private sector is strong in an economy and regulatory mechanism are functioning property, the economy is likely to prosper.

Reducing Tax Evasion

Tax evasion is a tendency not to pay taxes. People try to escape from taxes because they think the government is charging more taxes and that the tax revenue will go into the pockets of Government officials. Government has to take measures to reduce tax evasion especially from highly rich industrialists and feudal lords.

Improve Taxation Structure

The present taxation structure is very complex. People try to hide away from tax authorities because they think that Government will take a large part of their income. They give bribes to the auditors and income tax officers and pay less taxes. Government has to simplify procedure for tax calculation and collection so that the trust of people can be achieved and tax base can be increased.

Increasing the Tax Revenue

Taxes are the government's primary source of revenue. Government earns 70% to 80% of its revenue through taxes. But, it is a fact that only 10% to 15% of the population pays taxes. If Government can increase its tax base, it will generate more revenue through which it can match expenditure.

Financing Priority Sectors

The government has provided specific guidelines to banks and financial institutions to finance the priority segments and industries. This policy makes sure that the allocation of resources is directed and concentrated on areas which are more important to the progress of the country.

Other than above mentioned measures, the government has also taken following steps to promote these industries over a period of time.

• Providing loans from foreign institutions.
• Providing technical training.
• Establishing development and regulatory authorities.
• Establishing Pakistan Industrial Development corporation.
  

Relaxation of Taxes

The following relaxation in taxes has been provided by the government in the above mentioned industries.

1. Allowances to charge high rate of depreciation on plant, machinery and building.
2. Provided rebates on different occasions.
3. The relaxation in taxes for expenditure on scientific research.
4. The reduction in duty on the import of various raw materials, plants and machinery etc.
5. Income Tax incentives and tax relaxations to start a factory in a less privileged area or locality.
   

Improving Productivity through better Technology

It is not the resources but the productive use of them which increases the level of production. The technology or methods of production used in the agricultural sector are outdated and unprodcutive. By using the latest technology, the level of productivity can be increased in all sectors of the economy especially the agricultural sector. The increase in the cost of production due to the intoduction of technology will be offset by the increase in the productivity.

Deficiency of Capital

It is the capital which mutiplies and produces more wealth. If the capital is insufficient, the dream of economic development can not be realized. One essential condition of capital formation is saving. But, since ther per capital income in Pakistan is so low that majority of the people are hardly able to save anything from their income. Low savings retard investment. With low investment, the level of production decrease which creates enumployment and decrease in GDP.

Disallowing Import of Luxuries

Government can for the time being put restriction on import of luxuries goods like expensive cars etc, or it can at least levy heavy duty on it to discourage such lavishness for a developing country like Pakistan.

Increasing Import Duty:
Government must levy high import duty on consumer products which are no productive and contribute very little to the economy. An economy is not improved there are more foreign cars on the roads.

Increase in Exports

Instead of concentrating on decreasing imports, we must also not forget the importance of increasing exports. Imports in the productive areas can not be reduced and rise in the value of imports due to the rise in oil prices can also not be avoided. Therefore, we must increase exports by identifying new markets, arranging foreign and local exhibitions for Pakistani Products, providing low export refinancing rate and by exempting taxes related to exports oriented industries. Decrease In Export Duty: To increase exports, the Government must reduce export duty or in the best care remove any export duty for the time being to encourage people to produce more and export it.

Reasons of Agricultural Backwardness in Pakistan

In the following lines, few important problems in the agricultural sector of Pakistan will be discussed:

Lack of Productivity:
In is not the resources itself but the productive use of them which increases the level of production. The technology or methods of the production used in the agriculture sector are outdated and unproductive. The old method of suing carts and manually putting the pesticides in crops by traveling through the field on foot is a very slow mechanism and thus the level of productivity is very low in agriculture sector.

Natural Calamities:
Natural calamities like food, heavy rainfall and no rainfall when required are other important problems in the agriculture sector. With no artificial system in place, we rely heavily on the natural conditions and when they are not favorable, our yield for all crops is affected.

Underutillization of Resources:
The resources in agriculture sector are underutilized. A large part of agricultural land remains underutilized due to lack of water. People engaged in producing seasonal crops remains unemployed and their fields remains underutilized for that period.

Lack of Agricultural Credit:
In the recent time s, the banks have provided huge consumer credit in the area of car financing and home financing. These loans have only increased consumption. These loans have been used productively. If these loans have been granted to the poor farmers, they would utilized it for production and it would have been far better to have more agricultural production than more cards on the road.

Energy Resources of Pakistan

The major energy resources of Pakistan are as follows:

Petroleum:
Pakistan is not self sufficient in producing the required amount of petroleum for its needs. Pakistan only produces petroleum up to 15% of its requirement and the rest of the requirements are fulfilled with imports. The demand for petrol has sharply increased whereas; the production has not increased to match the needs. One of the major reasons why Pakistan is unable to extract more petroleum resources is lack of technology and its application.

Following is a list of places where surveys are conducted for the possibility of petroleum extracts:

• Tharparkar
• Hyderabad
• Waris Shah
• Districts of Mirpur
• Kohat
• Dera Ismail Khan etc

Coal:
Pakistan is not self sufficient in coal. Although coal mines exist in Pakistan but the quality of coal found in Pakistan is of very poor quality. Moreover, its only fulfills 7% of our coal requirements.

Coal Mines are found in the following places in Pakistan

• Mine of "Makarwal" which extends of Kalabagh. it approximately possesses 20 millions ton of coal.
• Lakhra
• Coal mines in Quetta , Surdag and Harnai. The coal extracted from there is used in Pakistan Steel Mills.

Natural Gas:
Pakistan is rich in possessing a substantial amount of natural gas. Natural gas as an alternative for fuel is a blessing. Since Pakistan is quite rich in natural gas, Its able to use it as an alternative for fuel in industries.

The Lip Muscles

The orbicular is orris closes the lips and, when contracting, its lateral insertions into the modioli are fixed by the contraction of the quadratus labii superioris and inferioris, zygomaticus, triangular is, and buccinator muscles. The incisal muscles also fix it to the sulci of the alveolar ridge.
During such function there is considerable inward pressure on the labial surfaces of the teeth and the labial sulci are reduced in depth. The upper denture, due to its better stability, can usually withstand such pressure provided its labial flanges have been designed correctly. The lower denture , however, particularly in cases presenting poorly formed alveolar ridges, is likely to be raised from the ridge in front and pushed backwards. Experienced denture wearers counteract this pressure of the lip by a forward pressure of the tongue but assistance can often be given to the tongue by carrying the heels of the lower denture up the ascending ramie of the mandible on such cases. The distal extension of the lower denture are often referred to as posterior stops.

Function of Tongue

Excluding taste, these are twofold. It controls the food during mastication and swallowing. It controls and directs, with the aid of the lips, teeth and palate the vibrating airstream from the larynx to form the sounds of articulate speech.
During mastication the tongue performs as follows. As the piece of food is being incised the tip of the tongue controls and steadies it. In the case of food which does not require incising the tongue is protruded slightly and its center depressed to form a shallow concavity into which the food is placed.

The Tongue

Rest Position of the Tongue

The dorsum rests against the roof of the mouth and the tip of the tongue rests in contact with the lingual surfaces of the lower incisor teeth.
The lateral borders lie against the lingual borders of the posterior teeth and protrude slightly into the free-way space between the occlusal surfaces of the upper and lower teeth.
Posteriority the soft palate rests on the dorsum of the tongue during normal nasal breathing.
When the teeth are extracted the tongue spreads laterally and the lips and cheeks fall in to meet it so filling between them the space left by the teeth, sometimes termed the neutral zone or zone of minimal conflict.

The Upper Denture

The periphery of the upper denture commencing with the posterior border is as follows.
The posterior edge should sink slightly into the non-movable tissues of the soft palate following line from the hamular notch of one side to that of the other close to the fovea palati. The posterior border then traverses the hamular notch and rises up into the sulcus on the buccal side of the tuberosity. The height to which it rises is determined by the attachment of the buccinator in this region as that muscles sweeps backwards to its attachment to the hamulus. The space is also defined distally by the mandibular coronoid process and buccally by the contracting masseter muscles.

The Lower Denture

Tracing the periphery of the lower denture, commencing with the distobuccal aspect, the outlone necessary to conferm to the associated muscles is as follows.
The periphery runs downwards and outwards from the retro molar pad to the first molar region following the attachment of the buccinator muscle as it sweeps outwards from its region along the pterygo-mandibular raphe. The periphery forms an almost straight edge because the buccinator is flattened by the contracting masseter muscle. For this reason, this part of the periphery is sometimes known as the masseteric plane.

Sulcus

The depth of the sulcus is dependent on the height of the alveolar ridge, the mobility and tension of the surrounding muscles and the alveolar mucosa lining the area. Over extension of the denture, in height or width, in the sulcus will cause instability or soreness, as will any roughness of the denture periphery. The mucogingival line forms the junction between the attached and reflected mucosa.

Frena

These move with the muscles of the lips, cheeks and tongue during speech, mastication and all activity. The peripheries of the dentures must be designed to allow for these movements, but such allowance must not be excessive otherwise the peripheral seal will be broken. The correct and incorrect method of allowing for Frena developed frena, or those which are attached too high on the alveolar ridge, may be removed surgically. In mouths exhibiting very poor retention, the removal of all the frena increases the peripheral seal.

Soft Palate

Attention has already been drawn to the correct placing of the posterior edge of the upper denture on to the non-movable tissue of the soft palate. Patients may be broadly divided into two classes with regard to this non-mobile area:

1. Those whose exhibit movement at the junction of the hard and soft palates.
2. Those whose soft palates move some distance behind the junction.
   

Palatal Vessels and Nerves

Dentures made when using certain compression impression techniques may bring pressure to bear on the foramina through which the blood vessels pass. Relief of the anterior and posterior palatine foramina should be ensured in such cases either by using the correct impression technique or by foiling the cast surface in the area of the foramina.

Rugae

These are said ti be associated with the sense of taste and the function of speech. They assist the tongue to absorb, via its papillae, the fluids containing the four primary flavors. They also enable the tongue to form a perfect seal when it is pressed against the palate in making the linguopalatal consonant stops of speech.
When a smooth, thick, artificial denture palate covers these elevations of the mucosa, difficulty is sometimes experienced with both taste and speech. The high degree if adaptability of the normal individual usually results in rapid adjustment to these problems, but the copying of rugae on the palatal surface of a denture, or especially by using the corrugation of a thin metal palate, may help to reduce the disability. In some cases ,however, these artificial rugae cause interference with speech, particularly if they are made too prominent.

Hamular Notch

The tissues in the hamular notch (pterygomaxillary notch) are easily compressed and the postdam line of the upper denture should be carried into this region to ensure an adequate peripheral.
In case showing gross alveolar resorption, the hamular notch flattens and the buccinator fibers in the region may become very prominent. Care should be taken in such cases that the posterior edge of the upper denture is not carried too far back on to the pterygo-mandibular.

Tuberosities

Large maxillary tuberosities bounded by deep sulci offer vary satisfactory resistance to the lateral movement of the denture.
tuberosities sometimes exhibit buccal undercut areas. If only one tuberosity is undercut this can sometimes be utilized to retain the denture on that side by slipping the distobuccal flange up over the bulge first and then rising the other side of the denture. Tuberosities exhibiting gross undercuts may require surgical treatment.

Alveolar Ridges

It must be remembered that edentulous alveolar ridges are not natural structures. They are what is left of a bone after diseases and surgery have affected it. The alveolar ridges vary greatly in size and shape and their ultimate form is dependent on the following factors.

1. Development structure:the individual variation in bone size and its degree of calcification is great.
2. The size of the natural teeth: the teeth, like the bones, show wide individual variation in size. Large teeth are usually supported by bulky ridges, small teeth by narrow ones.
3. The amount of bone lost prior to the extraction of the teeth: periodontal disease is a chronic inflammation of the supporting structures of the teeth and results in destruction of the alveolar process. If the natural teeth are retained until gross alveolar loss has occurred the resultant alveolar ridges will be narrow and shallow.
   

Oral Mucosa and Tissue Compression

The varying thickness of the mucosa and sub-mucosa covering the bones forming the palate and alveolar ridges results in the forces which are applied to the denture during clenching and mastication being transmitted unevenly to these supporting structures. In addition to this varying thickness, there are differences in the structure of the fibrous elements of the curium.
Soft tissue is compressed when a force is applied to it because some of the fluids (blood and lymph) which it contains are temporarily shifted. The amount of fluid which a soft tissue contains is dependent both on its thickness and the density of its elements.

Differences Between Natural Teeth and Artificial Dentures

The essential difference between natural and artificial teeth is that the former are firmly rooted in the bone of the jaws and in consequence they can incise, tear and finely grind food of any character because the lower teeth can move across the upper teeth with powerful shearing action. Artificial denture, on the other hand, merely rest on the alveolar redges and are held there by weak forces. In addition, they are subject to powerful displacing forces so their efficiency as a masticatory apparatus is limited. This efficiency can vary within wide limits depending on the shape and size of the edentulous jaws, the type of mucosa covering these jaws, the mental attitude of the patient to the dentures, his ability to learn to use them, and the skill of the operator.

Why are Dentures Necessary

Techniques and theories employed in and related to dental prosthesis, it is necessary to have clearly in mind the purpose which is being served. It is pertinent , therefore, to commence a articel of this nature by asking and answering the question. Why do we make dentures?
In order to answer this question the functions of the teeth must be understood. These are threefold:

1. To divide the food finely so that a large surface area is available for the action of the digestive juices.
2. To assist the tongue and lips to form some of the sounds of speech.
3. The teeth form an important feature of the face, and by supporting the lips and cheeks enable these structures to perform their functions of manipulating food and expressing emotions.

Teeth are also mutually interdependent premature loss of any tooth may cause a collapse of the dental arch and movement of individual teeth with loss of inter-proximal contacts, thus giving rise to food-packing and gingival damage.

Prosthetics

A prosthesis may be defined as " an appliance which replaces lost or congenitally missing tissue. Some prosthesis restore both the function and the appearance of the tissue they replace, other merely restore one of these factors.
Prosthetic is the art and science of designing and fitting artificial substitutes to replace lost or missing tissue. Dental prosthetic is a subdivision which deals with its application to the mouth.
By definition dental prosthetic (also known as prosthodontics or prosthetic dentistry) includes the replacement of any lost tissue and and therefore embraces the filling of teeth and the fitting of artificial crowns. In actual practice, however, the term has come to mean the fitting of appliances such as artificial dentures , bridges , obturators and surgical prostheses, and it is in this sense that the term will be used throughout this article.

Dentistry

Dentistry may be defined as:
The science concerned with the diagnosis, prevention, and treatment of diseases of the teeth, gums, and related structures of the mouth and including the repair or replacement of defective teeth is called Dentistry

Capillaries

The intimate relationship between the circulatory system and the tissues is achieved by, at the level of capillaries in the form of capillary network. the capillaries are extremely narrow (7-10u diameter), thin walled microscopic vessels. Their walls consists of a single layer of endothelium, which presents very little resistance to the diffusion of dissolved substance in or out . The cells of the tissues are bathed in tissues which provides a medium through which diffusion of materials can take place. The close approximate between the capillaries and the tissue cells facilitates the exchange of material. It is only here that exchange by diffusion or active transport can occur. The oxygen carried by the blood is diffused out into the oxygen deficient tissue and the carbon dioxide of the tissue cells is diffused in simultaneously. The nitrogenous waste is filtered through the capillaries into the excretory tubules for discharge.

Artificial Pace Maker

It is a device that supplies electrical impulses to the heart to maintain the heart beat at a regular rate. It consists of a small electronic device and power source connected to heart via an electrical wire. It is implanted beneath the skin in the chest when a person's SAN is not functioning properly or when there is some impairment to the passage of the normal electrical impulses.

Blood Flow

Blood flow through the vessels at an uneven speed. It flow much faster in large arteries and much slower in capillaries. Although an individual capillary is much narrower, but the capillary beds have an enormous number of such capillaries. So that the total diameter of these vessels is much greater than the arteries. For this reason the blood flows slowly in the capillaries, permitting the exchange of materials between the blood and interstitial fluids. As blood leaves the capillary bed and passes to the venules and veins, it speeds up again due to the reduction in total cross sectional area.

Blood Pressure

Blood pressure is the hydrostatic force exerted by the blood against unit area of the vessel wall. It is measured in millimeters of mercury (mm Hg). Mercury manometers are being used for measuring the blood pressure which are known as Sphygmomanometer. Blood pressure is determined of the arterioles. When wall of the arterioles are constricted (vasoconstriction), the blood pressure rises; when they are dilated (vasodilation). the blood pressure falls. The constriction and the dilation of arterioles are due to the constriction and relaxation of the smooth muscles of the arterioles, respectively. These muscles are largely under the control of nerve impulses and hormones.

Veins

Veins are thin walled blood vessels. They are also composed of the same three layers as that arteries, but possess less muscles and less elastic fibers. Their lumen is large. Semi lunar valves are present which prevent the back flow of blood. The pressure of blood flowing through them is low and are non-pulsatile. The blood flows slowly and smoothly. The veins carry de-oxygenated blood except the pulmonary veins which transport oxygenated blood from the lungs to the heart. The veins are super-facial and collapse when empty.

Heart Beats

The contractions of the heart chambers are known as heart beats which are rhythmically and regular. A human normal heart beats 72 times per minute at rest. These beast are audible and are known as heart sounds.
During the ventricular systole blood is forced against the closed AV-valves. This procedures the first heart sound LUB. Ventricular systole is followed by ventricular diastole. The high pressure developed in the aorta, tends to force some blood back towards the ventricles which closes the aorta valves. This impact of the back flow against the valves causes the second heart sound DUP.

Human Heart

The human heart is the most powerful organ in the circulatory system. It works continuously like a muscular pump and keeps the blood in circulation. The heart lies in the thoracic cavity between the lungs slightly towards left, enclosed with in the rib cage with the sternum in front and vertebral column behind. It is surrounded by a double layered Pericardium. A pericardia l fluid is secreted in between the two. It functions as a lubricant and reduces friction between the heart walls and surrounding tissue during the beating of heart.

Transport In Man

Blood Circulatory System (Cardio-vascular system)
The fluid circulatory system, with blood as the transporting material has assumed its highest development in man. It consists of a powerful heart, arteries, veins and capillaries.

Blood: Blood is viscous, red fluid connective tissues, comprising a colorless plasma in which the blood corpuscles float.

Plasma: It constitutes about 55% of the blood. It is a viscous fluid containing a mixture of inorganic salts in true solution form and blood proteins (albumins, globulins and fibrinogen) in colloidal form. In addition, plasma contains glucose, amino acids, triglycerides, urea, hormones, enzymes and auto toxins. The water is the most abundant component and forms 90% of plasma. The dissolved substances are only 10%.
Blood Corpuscles: These are the blood cells which form the remaining 45% of the blood.

Pyramid of Energy

The quantitative studies of an ecosystem are carried out by two way i.e by studying the food chain or food web, and by ecological pyramids. The ecological pyramids are the pyramids of number. It is diagrammatic representation of tropic levels. i.e. producers, herbivores and carnivores. Pyramid is drawn on the basis of their number. The second way is the use of pyramid of biomass, instead of numbers are each level it involves total mass of the living organisms present at each tropic level. The third way of study is pyramid energy.

Sun as a Source of Energy

The ultimate source of energy in an ecosystem is the sun light. It travels as electromagnetic waves and about 40% is reflected back from clouds and other 15% is absorbed by Ozone layer and is converted to heat energy by the atmosphere; remaining 45% reaches to earth, of which a small fragment i.e 2-3% is absorbed by green plants while rest reflected and dispersed.

Energy Flow Through The Ecosystem

In an ecosystem, organism are linked together in energy and nutrient relationship. The energy can be defined as the capacity so do work. The term work can be used to any energy consuming process such as living cells maintain electrical gradient across membrane and the active transport process which requires expenditure of energy. However, the ecological studies relating food requirement and energy relationship among living components of an ecosystem are referred as bio-energetics. Energy is found in four main forms i.e , radiant energy, heat energy, chemical energy and mechanical energy. Only a small part of solar energy is visible spectrum.

Need for Energy in Living Organisms

All living cells carry out numerous activities e.g, they generally assemble macromolecules of all types, from raw materials, waste products are produced and excreted, genetic instructions flow from the nucleus to cytoplasm, vesicles are moved from Golgi bodies to the plasma membrane, ions are pumped across the membranes etc. For these high level of activities, a cell needs energy. The energy is used as fuel for life which is derived from light energy trapped by plant cells and converted into energy rich compounds. Other organisms, which do not have the ability to trap light energy, obtain their energy by eating plants or by eating the organism that eat plants. Capturing and conversion of this energy from one form to another in the living system and its utilization in metabolic activities is called bio-energetics.

Bioenergetics

Energy is defined as the capacity to do work. It exists in a number of different forms :heat, light, electrical, magnetic, chemical, atomic, mechanical and sound, The laws which apply to energy conversion are the laws of thermodynamics.

Animal Classification

In order to better understand such a large number of organisms, it is necessary to arrange them in groups. This arrangement presents a great deal of information in an orderly way. In the traditional two-kingdom system of classification (not followed these days) the multi-cellular animals were referred to as Metazoa to distinguish them from one-celled Protozoa. In modern five kingdom classification scheme the Protozoa belongs to kingdom Protoctista whereas the true animals are placed in kingdom Animalia. A true animal is now defined as a Eukaryotic, multi-cellular, heterotrophic organisms which is diploid and developed from an embryo formed by the fusion of two different haploid gametes, a large egg and a small sperm. Most of animals are motile, a few, however, are sessile.

Evolution of Seed

We have studied in Selaginella that two types of spores are present. One is smaller in size called micro spore and the other bigger in size called megaspore. This type condition is known as Heterospory. These spores have different functions to perform. Instead of growing into a gametophyte of similar structure, the heteros porous plants produce two different gametophytes. Micro spore grows into a sperm forming gametophyte. The other kind mega spore, grows into egg forming gametophyte. The two kind of spores are formed in two different kinds of sporangia. These like the sporangia of club mosses, horse tails and ferns have become protected as a result of the evolution of various enveloping structure.

Evolution of the Leaf

The leaf is the most important organ of a green plant because of its photosynthetic activity. It is very interesting to trace the origin of leaf in the green plants.
The evolution of one-veined leaf (microphyllous) can be explained by assuming that a thorn like outgrowth (E-nation) emerged on the surface of the naked stem. With an increase in size of the out growth, the vascular tissues were also formed for the supply of water and support to the leaf. Another possibility is that a single veined leaf originated by a reduction in size of a part of the leafless branching system of the primitive vascular plant. This is how the leaf of Lycopodium (club mosses) and equistium (horse tail) came into existence.
Many veined leaf (megaphylious) originated much later. These are the evolutionary modifications of the forked branching system in the primitive plants. The first step in the evolution of this leaf was the restriction of forked branches to a single plane. The branching system became flat. The next step in the evolution was filling the space between the branching and the vascular tissue. The leaf so formed looked like the web foot of a duck.

Classification of Plants

Plant biologist use the term division for the major plant groups within the plant kingdom. The taxonomic category corresponds to phylum, the highest unit of classification within the animal kingdom. Divisions, like phyla, are further subdivided into classes, order, families and genera. The classification scheme used in this book recognizes two main groups called bryophyta (non vascular plants) and tracheophyta (vascular plants) This division is based on the presence or absence of vascular tissues.

Plant biologist use the term division for the major plant groups within the plant kingdom. The taxonomic category corresponds to phylum, the highest unit of classification within the animal kingdom. Divisions, like phyla, are further subdivided into classes, order, families and genera.

The classification scheme used in this book recognizes two main groups called bryophyta (non vascular plants) and tracheophyta (vascular plants) This division is based on the presence or absence of vascular tissues.

An Outline of Classification of plantae:
Division I: Bryophyta (Non-vascular plants)

Class Hepaticae (Liverworts)
Class Musci (Mosses)
Class Anthocerotae (Hornworts)

Division II: Tracheophyta (Vascular Plants)

Subdivision Psilopsida (Psilopdsids)
Subdivision Lycopsida ( Club Mosses)
Subdivision Sphenospsida ( Horse Tails)
Subdivision Pteropsida (Ferns)
Subdivision Spermopsida ( Seed Plants)

Yeasts

Yeasts which are unicellular, are none of the most interesting and economically important groups of microscopic ascomycota. Most of their reproduction is asexual and takes place by cell fission or budding( the formation of a smaller cell from a larger one). Sometimes, however, whole yeasts cells may fuse. One of these cells, containing two nuclei, may then function as an ascus with syn gamy followed immediately by meiosis; the resulting ascospores function directly as new yeast cells.

Nutrition In Fungi

All fungi lack chorophyll and are heterotrophs (obtaining carbon and energy from organic matter). They obtain their food by direct absorption from the immediate environment and are thus absorptive heterotrophs. Most fungi are saprotrophs, decomposes that obtain their food (energy, carbon and nitrogen) directly from dead organic matter. and the organic molecules thus produced are absorbed back into the fungus. Saprobic fungi anchor to the subtract by modified hyphae, the rhizoid. Fungi are the principal decomposes of cellulose and lignin, the main components of plant cell walls ( most bacteria cannot break them). Extensive system of fast growing hyphae provides enormous surface for absorptive mode of nutrition. Saprobic fungi, along with bacteria, are the major decomposers of the biosphere, contributing to the recycling of the elements (C, N, P, O, H etc.) used by living things.

The Body Of Fungus

The body of a fungus, called my-celium, consist of long, slender, branched tubular thread filaments called the hyphae ( Singular Hypha) Hyphae spread extensively over the surface of substratum. Chitin in their wall is more resistant to decay than are cellulose and lignin which make up plant cell wall. Hyphae may be septet or non-septet. Septet hyphae are divided by cross-walls called septa (Singular Septum) into individual cells containing one or more nuclei. Non-septet hyphae lack septa and are not divided into individual cless, instead these are in the form of an elongated multi-nucleated large cell. Such hyphae are called coenocytic hyphae, in which cytoplasm moves effectively, distributing the materials throughout.

Symptoms of Malaria

The Symptoms of Malaria first appear after several days of infection in man. The time taken by the parasite before it appears in the blood is called incubation period. The symptoms that appear in this period of infection include nausea, loss of appetite, constipation and insomnia. Soon headache, muscular pains, aches in the joints develops followed by chills.
At he onset of malarial fever the patient, suffers from shaking chills and sweating.The body temperature may rise as high as 106 o F.

Economics Importance of Phytophthora Infestans

The most important species phytophthora infest ants cause the late blight of potato. This is a havoc to potato crop and causes sufficient damage. The symptoms of the disease appear both upon aerial and underground parts. The whole plant becomes blighted in severe conditions. Dry and wet rots damage the tubers.
The First sign of the disease is appearance of small brown patches on leaves which in cloudy and muggy weather rapidly increase to the whole leaf surface.
In bad cases the crown also shows similar symptoms which becomes a rotten pulpy mass emitting foul odor. On the under surface of such infected leaves a cotton growth of my-cilium consisting of fortification of the fungus is seen. This growth is absent in dry weather.

The underground parts especially the tubers are also affected which often remain smaller in size and show dry rot with rusty brown markings in the flesh and brown depressions at certain places, in the skin.

Chlorella

It is fresh water algae found floating in stagnant water of ponds, pools ditches etc. It is easily cultured and has been used as an experimental organism in research on photosynthesis as well as being investigated as an alternate source of food.
The body is one-celled spherical in outline and solitary. It contains a single nucleus and a cup-shaped chloroplast usually without a pyridine.

The Sole method of reproduction is by aplanospores, which involves the division of protoplast into 8-16 daughter protoplast. Each daughter protoplast secrets a wall to produce a nonmotile aplanospore. On release from the parent cell each aplanospore forms a new vegetative cell. Zoo spores and gametes are unknown. It is of great economic importance as recently an antibiotic called chlopellin useful for the control of bacterial diseases has been prepared from the plant.

Use and Misuse of Antibiotics

Antibiotics are chemical substance produced by certain micro-organisms that inhibit or kill some other micro-organism. They have a dramatic impact on the treatment of infectious diseases. Since the discovery of the first Antibiotic, penicillin which was derived from Fungi in 1940, a large number of antibiotics have been discovered from other Fungi and Bacteria, while many are synthesized artificially.
Some antibiotic drugs are effective against only certain types of bacteria while other known as broad spectrum antibiotics are effective against wide range of bacteria. The targets of antibiotics in bacteria are cell-wall, plasma membrane and bio synthetic processes of protein and nucleic acid.

Locomotion

Some Bacteria can move using simple flagella that are attached with a unique wheel-like structure.
These are simpler in structure than the flagella seen in some eukaryote cells. Bacteria flagella, which may either cover the cell or from a tuft at one end can rotate rapidly, propelling the bacterium through its liquid environment. Recent research has revealed a unique wheel-like structure embedded in the bacterial membrane and cell wall that allows the flagellum to rotate. Flagella allow bacteria to disperse into new habitats to migrate toward nutrients, and to leave unfavorable environment. Flagellated bacteria show orientation toward various stimuli, a behavior called Taxis. Some are chemo tactic, moving toward chemicals given off by food or away from toxic chemicals.

Saprophytic Bacteria

They get their food from dead organic matter. The soil is full of organic compounds in the form of Humus. Bacteria living in the soil have large number of enzymes that break down the complex substances of humus to simpler compounds. These bacteria absorb and utilize simple compounds as a source of energy. Many other saprophytic bacteria cause decay of dead animal and plant material as they convert complex organic compounds to simpler ones.

Bacteria ( Discovery)

Advances in our understanding of living things often depend on the invention of special instruments. Because of their extremely small size, viruses could not be detected by the optical microscope. Their presence was assumed, however from evidence of their effects on living tissue. The electron microscope later confirmed their existence. It was not so with bacteria. Before the invention of the optical microscope, men lived in ignorance of the presence of these micro organism.

Hepatitis : A Serious Health Risk

Hepatitis is an inflammation of the liver. It may be due to viral infection, toxic agents on drugs. It is characterized by jaundice, abdominal pain, liver enlargement, fatigue and some times fever.
There are various types of Hepatitis.

HEPATITIS --- A
Hepatitis A is transmitted by contact with faces from infected individuals. It is caused by non-enveloped RNA virus.

HEPATITIS --- B (serum hepatitis is caused by unusual DNA virus.

The causative agent of hepatitis B, contains a small, circular molecule of partly, but not completely, double standard DNA. The viral genome encodes two kind of proteins, a core protein and a surface protein, as well as DNA polymerase.

The amount of genetic information in the hepatitis B viral genome-359 nucleotides-is less than that of any other pathogen, except of the viroids.

The hepatitis B virus poses a serious public health problem, particularly among Asian, Africans, and male homosexuals. It often persists in carriers without causing any symptoms, but it may still be highly infections. People infected early in life often become carriers, and it is estimated that there are about 200 million such carriers worldwide. Since most of these people are not recognized as carriers, there is a real possibility of the frequent transmission of Hepatitis through skin contacts, blood transfusion, and similar medical procedures.

HEPATITIS --- C
Hepatitis C pass through blood from mother to child during pregnancy and afterward by sexual contact.

Prevention

The reduction in the spread of HIV could be brought about by the use if clean needles and sterile syringes by drug addicts.
Education about the disease has an important part to play particularly in reassuring the public about the real risk. There is no evidence that infection can occur by droplet infection through the nose or mouth, or by casual contact such as shaking hands etc.

Control and Treatment Of AIDS

An enormous international effort is being made to devise methods of treating and preventing the diseases. There are two lines of research, one into developing drugs which can be used to cure the disease, and one into developing a vaccine, Both approaches are at an early stage and require heavy financial investment. In the short-term the aim is to develop drugs to inactivate the virus, by blocking the pathogen's metabolism.

The best known drug used by 1987 was azidothymidine or zidovudine (formerly known as AZT) which slows progression of the disease and can attack the virus even in the brain (a major reservoir of infection) other drugs are being examined such as Ribavarrin a drug used to treat other viral infection which has been found to suppose the AIDS virus under laboratory conditions. Submarine, an anti parasitic drug has also shown encouraging results inhibiting viral reproduction in host.

Human Immune Deficiency Virus (HIV)

A RETROVIRUS AIDS--Symptoms, Transmission and its control

In HIV, the infections agent that causes AIDS, the glyco-proteins of the envelope enable the virus to bind to specific receptors on the surface of certain white blood cells, although there are two RNA molecules. They are identical, not complementary strands.
Acquired Immune Deficiency Symptoms (AIDS ) is a disorder which impairs the body's lymphocyte cell T4 immune system in humans, in that the virus replicates within the T4 or helper cell. Thus these cells can no longer help or induce other T cell, called Killers, to fight invaders. The body's immune system breaks down, leaving the patient exposed to a variety of diseases.

It is important to realize, however, that infection with the virus (HIV) does not necessarily result in AIDS. As with other diseases, some people remain symptoms less and are therefore termed carriers.

Plant Diseases

We have already discussed one of the best known plant diseases called tobacco mosaic virus. Plant viruses can stunt any plant growth and diminish crop yields. There are two major routes by which a plant viral disease can spread either by Horizontal Transmission or Vertical Transmission. In the first, a plant is infected from an external source of virus through injured parts or through insects. In the second, a plant inherits a viral infection from a parent. Agriculturists have not yet devised cure for most viral diseases of plants. Therefore, their efforts have focused largely on reducing the incidence and transmission of such diseases and on breeding genetic varieties of crop plants that are relatively resistant to certain viruses.

Viral Diseases ( Transmission / Spread and Control )

1. Animal Diseases: Several of the animal viruses cause important diseases. Poliomyelitis cause by polio-virus was a wide spread, cropping disease through the first half of the twentieth century. Although poliomyelitis is now largely under control by vaccination in the industrialized countries, it remains a serious and common disease in the tropics and elsewhere in the less developed parts of the world. Colds are viral infection of the upper respiratory tract. About one third of all colds are caused by the rhino-viruses which are unenveloped plus-strand RNA viruses. There are dozens of different strains of clod-causing rhino-viruses alone, each of them with different properties and none conferring cross-immunity to the others. More than 200 of viruses that cause colds have been identified, which makes the development of appropriate immunization methods very difficult, if not impossible.

Bacteriophage

They are among the most complex viruses. Each of them is made up of at least five separate proteins; these make up the head, the tail core, the molecules of the capsid, the base -plate of the tail, and the tail fibers. A long DNA molecule is coiled within the head.
One the basis of morphology viruses are classified into rod shaped (T.M.V), spherical (Polio-virus) and tadpole like bacteriophage viruses etc.

Classification of Virus

Viruses are generally classified on the basis of morphology and nucleic acid. they contain. On the basis of morphology, viruses are classified into rod-shaped (T.M.V), spherical (Polio virus) and tadpole ( Bacteriophage ). The nucleic acid present may be DNA or RNA which may be naked enveloped or complex. Recently, viruses are classified on the pattern to their diversity. The diversity of the viruses is great and is almost certainly related to their modes of origin. To provide a systematic idea of some of this diversity, we will discuss the viruses under eight main headings.

Structure of Viruses

They appear like little spheres of golf-balls, rod shaped, like tadpoles and may be polyhedral.

Viruses may consists of Viral-Genomes, Capsids, Envelopes and Tail-Fibers. Their Genomes (set of genes) may consists of a single or several molecules of DNA or RNA. The smallest viruses have only four genes while the largest have several hundreds.

The protein coat that encloses that virul genome is called a Capsid. It may be of different shapes. Capsid is made up of protein subunits called Capsomeres. The number of capsomeres is characteristic of a particular virus.

Some viruses have accessory structures called viral-envelops that help them infect their hosts. They are membranous cloaking their capsids. Bacteriophages have tail piece with Tail Fibers.

Characteristics of Virus

Viruses are non cellular parasitic entities. They cannot line and reproduce outside of living cells since they lack the machinery to do so by themselves. They range in size from 20nm to 250nm.
Viruses are either virulent, destroying the cell in which they occur or temperature, becoming integrated into their host genomes and remaining stable there for long periods of time.
The adhesion properties of viruses are determined by those of the proteins that make up their coats and envelops. The simplest viruses use the enzymes of the host cell for both their protein synthesis and gene replication; the more complex ones contains up to 200 genes and are capable of synthesizing through their host may structural proteins and enzymes.

AIDS is caused by HIV ( Human Immunodeficiency Virus ), which possesses a Glycoprotein on its surface that penetrates the cell membrane, sheds its protective coat and reproduce.