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Tuesday, May 18, 2010

Immune Disorders

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Immunodefeciency Disorders
Immunodefeciency means deficiency of the immune system. The children who are born without either T cells or B cells lack the ability to fight against the diseases and so are highly prone to infections.Immune Disorders

Severe Combined Immuno defeciency (SCID): In this disorder both T cells and B cells are absent at birth. Since the body lacks the immune system even a small infection can be fatal. The children have been kept alive by keeping them in the isolation suits which resemble the space suits, in the developed countries. The air inside the suits is almost sterile, without germs so that the child does not catch any infection.

Acquired Immune Defeciency Syndrome – AIDS
Cause of AIDS – Acquired Immune Defeciency Syndrome is a disease caused by a virus that can be passed from one person to another chiefly during sexual contact or through sharing of intravenous drug needles and syringes. Other names: Scientists have named the AIDS virus HIV or HTLV – III or LAV also. These abbreviations stand for information denoting a virus that attacks white blood cells (T-lymphocyte) in the human blood.
HIV – Human Immuno defeciency Virus
HTLV III – Human T-Lymphotropic Virus Type III
LAV – Lymphadenopathy Associated Virus

Sign and Symptoms: People infected with AIDS virus remain apparently well even after infection. They may not show any physical symptoms of illness for a long time. When the AIDS virus enters the blood stream, it begins to attack certain white blood cells (T-lymphocytes) and substances called antibodies are produced in the body. These antibodies can be detected by a specific blood test usually two weeks to three months after infection.
Once an individual is infected, the body may respond in many ways:

- In some people, the protective immune system may be destroyed by the virus and then other germs (like bacteria, fungi, protozoans) and cancers that ordinarily do not attack, cause opportunistic diseases (meaning using the opportunity of lowered resistance) to infect and destroy the body. Some of the common diseases are pneumonia, tuberculosis and certain cancers.
- AIDS virus may attack nervous system causing damage to the brain.
- Some may develop AIDS – Related complex (ARC) condition.
- Some early signs may be persistent cough and fever associated with difficulty in breathing.
- In some, AIDS may take years to develop and may show up as memory loss, indifference, loss of coordination, partial paralysis or mental disorder.

Symptoms of ARC (AIDS – Related complex)
ARC is a condition caused by the AIDS virus which has a specific set of clinical symptoms.
(i) Swollen lymph nodes and fever.
(ii) Night sweats and tiredness.
(iii) Weight loss, diarrhoea, loss of appetite and lack of resistance to the infection.

Mode of Infection: The infection from AIDS virus occurs only:
- When a person has sexual contact with an infected person.
- By using contaminated needles. Even the smallest amount of infected blood left in a used needle or syringe can contain live AIDS virus which can be passed on the next user.
- By the blood to blood contact as in blood transfusion.

Currently in many countries as in U.S.A., all blood donors are initially screened for AIDS virus and proper precautions are taken before blood transfusion.
Although the AIDS virus has been found in tears and saliva, no instance of transmission from these body fluids has been reported. There is no danger of infection with AIDS virus by casual social contacts or by sharing cups, towels or food. Also there are no known cases of AIDS transmission by insects like mosquitoes or pets.

High Risk groups
It is now absolutely clear that AIDS is not a black or white disease though it may be confined to a specific region. AID is not a male disease, it is found in women and children as well. But the high risk groups who become infected with the AIDS virus are found mainly among:
- Homosexual men.
- Bisexual men (who have both homosexual and heterosexual partners)
- Male and female intravenous drug users.
- Recipient of blood products.
- Sexual partners of these high risk individuals.
- Children born to women who carry the virus.

If a woman is infected with the AIDS virus and becomes pregnant, she can pass the AIDS virus to her unborn child.Immune Disorders
AIDS is a life threatening disease. At present there is no vaccine to prevent and there is no cure. However, AIDS is preventable. It can be controlled by changes in personal behaviour. AIDS is no longer the concern of any one segment of society but is the concern of all. The need of the hour is to provide care for those infected with AIDS and inform and educate others as how to prevent it.
AIDS was first recognised in USA in 1981. Although in 1984 the American and the French scientists independently identified the agent as a virus, AIDS is still a mysterious disease in many ways. We still do not know why the AIDS virus is not destroyed by man's immune system.
Organ Transplants and Immunosuppression
Transplantation means the replacement of a diseased organ or a tissue of an individual with the living healthy organ or tissue from another individual. The transplanted organs contain about forty antigens which can trigger the production of antibodies in the recipient (the person in which organ is transplanted). The recipient body recognises the transplanted organ as the foreign body or antigen and hence produces antibodies against it which cause the destruction of the transplanted organ (also called as rejection).

Ways to prevent rejection of Transplanted organ or Tissue
(i) By use of immunosuppressants. These drugs counteract the immune system and stop the production of antibodies against the transplanted organ. These drugs are not only expensive but also inhibit the body's normal immune response to disease causing microorganisms. The patient becomes prone to all kinds of infections. The research is still on to develop the immunosuppressive drugs which only stop the rejection response and do not affect the general immune system.
(ii) By taking transplanted organ from the siblings. It has been seen that if the transplanted organ like kidney is taken from the sibling (i.e. from brother or a sister) or identical twins the chances of acceptance are more as they have a comparatively similar genetic constitution.

(iii) By taking skin grafts in case of burns from one part of the body to another of the same individual.

(iv) By the use of X – irradiation on bone marrow and lymph tissues. This suppresses the blood cell production and slows the phenomenon of rejection.


Monday, May 10, 2010

Defence Mechanisms of the body

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The body of an organism is surrounded by the environment that carries numerous types of bacteria and other organisms that can cause diseases. The body has a natural defence mechanism that stops the invasion of these at various stages of attack. There are two lines of defence in the body.
(i) Non – specific defence mechanisms which try to prevent the entry of micro organisms.
(ii) Specific defence mechanisms are active processes which destroy the microorganisms once they manage to get in the body. It is also called as immune system.

1. Non – specific defence mechanisms
These mechanisms guard against the entry of micro-organisms in the body.

a. Skin: Skin forms the first line of defence. It forms the hard, keratinised outer layer of the body which covers all external parts and forms an effective barrier for most bacteria and viruses. The secretions of oil and sweat glands make the surface pH acidic (pH 3 to 5) which does not let microorganisms to survive for long. Certain friendly bacteria also release acids and other metabolic wastes which also inhibit the multiplication of pathogens. The salts and fatty acids present in perspiration contain lysozymes that destroy the bacterial cell walls. Tears secreted by tear glands also contain lysozymes which prevent the eye infection. Saliva also contains the lysozymes that kill the bacteria present in the foods and drinks. Any bacteria left are killed by the secretion of the stomach. The respiratory tract is lined by the mucous membrane. First the cilia and fine hair filter out the undesired particles in the nostrils and then mucus – the slimy substance traps the bacteria. In the trachea or bronchi, the movements of cilia sweep bacteria towards the throat from where they are expelled by coughing or sneezing.

b. Phagocytic cells or W.B.C.: Phagocytic cells form the second line of defence and work when the first line of defence is broken and bacteria do gain entry through abrasion or wound in the skin. At the place of injury, clotting not only prevents bleeding but also blocks the entry of bacteria. Dilation of small blood vessels at injury increases the blood flow. The increased permeability of capillaries lets phagocytes pass out into the intercellular spaces and engulf the invading bacteria. Phagocytosis is generally carried out by neutrophils. The pus formed at he infected wound is actually the debris of the battle i.e. dead cells, digesteDefence Mechanisms of the bodyd bacteria and broken phagocytes in the blood serum. Inflammatory response: At times the phagocytosis results in a hot red, swollen inflamed area at the site of infection. Redness is due to increases flow of blood. The lymph helps by carrying bacteria and phagocytes that have engulfed bacteria to the lymph nodes where they are filtered out. The inflammatory response is due to a chemical histamine released by the lymphocytes, and the damaged tissues which causes dilation of the blood capillaries. These reactions are generally localized i.e. confined around the wound. Many a time the fight between microorganisms and W.B.C. results in rising of temperature. Such an inflammatory response is wide spread and is called a systemic reaction. High fever not only inhibits the growth of germs but also activates the body defenses and is actually beneficial if not too high and uncomfortable. The fever is caused by either the toxins released by the pathogens or by the chemicals called pyrogens (the fever producing substances) released by W.B.C. that set the body's thermostat at a higher temperature.

2. Specific defence mechanism
The first and the second line of defence were nonspecific as they acted on any type of bacteria but this third line of defence by antibodies is very specific. An antibody act against a specific bacteria or antigen only. An antigen is any foreign protein or a polysaccharide that is not found in the organism's body. Viruses, bacteria or their toxins and the cells of other person, all contain proteins not recognised in the body and hence act as antigens. An antigen stimulates the body to produce a specific antibody. The word antigen is a shorten form of antibody generating. The antibodies interact with the antigen and either destroy them or make them inactive. The antibodies are globular proteins and are called as immunoglobulins (or Ig in short form). They are produced in the lymph nodes, spleen and by the thymus gland. Entry of an antigen in the form bacteria or virus triggers a reaction in the body as a result of which the antibodies produced defend the body in various ways and try to neutralise the antigens. Antigens are not only parts of microorganisms but certain blood cells, pollen, eggs white, fruits or vegetables may also act as antigens and stimulate the immune system of the body.

The Immune System

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The most important characteristic of the immune system is that it recognises The Immune System self and nonself. The formation of antibodies in response to the antigens as described above is also a part of the immune system. The immune system has two components.

1. Humoral immune system: Humoral immune system is made up of various types of specific antibodies which are present in the blood plasma and lymph. This immune system defends the body against specific bacteria and viruses that enter the body fluids like blood and lymph. The term humors is used for body fluids. B – Lymphocytes (B-cells) are responsible for the humoral immune system.

2. Cell—mediated immune system: Cell—mediated immune system refers to highly specialized cells of the immune system that work not only against pathogens but also against fungi and protistans that invade the host cells. These cells recognise the body's own cells and react against the transplants also. This immune system also protects the body from its own cells if they become cancerous. The cell – mediated immune system is formed by the T – lymphocytes (T-cells).

Cells of the Immune System
The lymphocytes – a type of agranular W.B.C's are the main cells of immune system. These immune system are of two types: B cells and T cells
(i) Both need an exposure to antigens to trigger them into action.
(ii) Both types of cells develop from the precursor cells i.e. stem cells in the bone marrow.

Response of B – cells and the humoral immunity
When B – cells in the lymph nodes come into contact with a specific antigen, the receptors on their membrane recognise the antigen.

The B – cells are stimulated and divide repeatedly to give rise to a clone of plasma cells and memory cells. Clone is a population of cells derived from a single original cell.

All the plasma cells are genetically identical and hence they produce numerous identical antibodies which are releases into the lymph which eventually enter the blood. Most plasma cells can produce 2000 molecules of antibodies per second. They live for a few days only. The memory cells produced however remain in the lymph nodes for years and provide a rapid response during any second encounter with the same antigen.

The antibodies either stick to the surface of the bacteria and speed up phagocytosis or neutralise the toxins produced by them. Various types of B – cells, millions of these, each being specific to a particular antigen is present in the body at birth. Number of these B – cells which react with the antigens of one's own body (during embryonic development) are rendered inactive and are killed and this is the reason why antibodies are not formed to the individual's own antigens.

Response of T – cells and the cell – mediated immunity
The T – cells also have receptors on the membrane that can recognise a specific antigen. On stimulation, they also produce a clone of T cells and produce specific antibodies but the way they react is different. The T cells instead of releasing the antibodies into the bloodstream, hold on to them and the entire cell attacks the specific antigen. The life of T – cells is about 4-6 years. The body contains specific T-cell for every antigen. They are various types of T cells which perform different functions.

(i) The killer T – cells directly attack and destroy the antigens. They get attached to the specific antigen like a key fits into a lock and then destroy it. About 80% of the total lymphocyte population of human blood is of this variety only. They produce chemicals to attach other T –cells also.

(ii) Helper T – cells stimulate B cells to mature and increase their antibody production.

(iii) Suppressor T – cells suppress the total immune reaction.

Like humoral immunity some T –cells that become memory cells remain in the lymph nodes and persist even after the antigen has disappeared. They can respond to any future attack by the same antigen. The cellular immunity can also last for a life time.

Allergies
An allergy is an immune response of the body to an antigen. Some antigens may be harmless and generally do not show any reaction in most of the people. These weak antigens that cause allergy in some people are called as allergens. The allergens could be on pollen grains, dust, feathers, fur, fugal spores, etc. The symptoms of allergic reactions vary from person to person. The most common are rashes on the skin, sneezing or breathing difficulties but in severe cases it needs immediate hospitalization as it may lead to choking or anaphylactic shock. Many a times a single bee sting or a dose of penicillin may be fatal. The allergic reactions are usually very rapid. During allergy the antigen – antThe Immune Systemibody reactions occur on the membrane of the tissue cells especially the mast cells which become permeable and burst. They release histamines, which cause dilation of capillaries, redness, itching in the skin and evoke an inflammatory response. Generally the first exposure to an allergen does not cause allergy and helps in the formation of antibodies only. The second or subsequent exposures cause strong reactions and allergies. The antihistamine drugs nullify the effect of histamines. Eosinophills also increase in number during allergic reactions and are thought to have anti – inflammatory response by absorbing histamines.

Immunity
Immunity is the capacity of the body to defend against the disease. Immunity can also be defined as the ability of the body to resist the disease. The immunity can be of two types:
(i) Natural or in – born and
(ii) Acquired

Wednesday, April 21, 2010

What is a Disease?

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A disease is a disturbWhat is a Disease?ed state of body or mind. We generally associate word disease with physical or mental sickness. The disease can be in any part of the body and may or may not be curable. Most of the time we cure the physical illness. Mental sickness is difficult to be identified as this is a relative term and one takes notice of it only in extreme cases. Being healthy means being free of disease; both physically and mentally. It refers to the state of body and mind which is in harmony with the surroundings or environment. A perfect health is almost difficult to achieve. For time immoreal man has tried to understand the nature and causes of diseases and has tried ways to cure those diseases.

Types of Diseases
The diseases can be categorized into two basic types. Congenital, present at birth and acquired that is contracted after birth.
(i) Congenital Diseases:- Congenital diseases are present at the time of birth. Congenital diseases could be due to genetic abnormality or due to malfunctioning of any organ or system. Congenital diseases are permanent, generally not curable and may be inherited to the children.

(ii) Acquired diseases:- The acquired diseases develop after birth and can be broadly classified into two types:
(a) Communicable or infectious diseases
(b) Non communicable or non-infectious diseases. These diseases can further be divided into many types.

The agents that cause the diseases can be put in the following five categories.
(i) Biological agents or pathogens like viruses, bacteria, fungi, protozoans, etc.
(ii) Nutrient agents like minerals, carbohydrates, proteins, fats and vitamins.
(iii) Chemical agents like urea or uric acid formed in the body; or pollutants, spores and pollens present in the atmosphere.
(iv) Physical agents like heat, cold, humidity, pressure, radiation, etc.
(v) Mechanical agents like friction or other mechanical forces.

Diseases caused by Pathogens
Pathogens are disease causing living organisms like bacteria, yeasts, molds, protozoans and parasitic worms. The first study as to how they cause diseases came from the work of Robert Koch, a German physician. In 1876 he showed that the disease anthrax of sheep was due to bacteria Bacillus anthracis which existed in the pastures in the form of protective spores. He found these rod shaped bacteria in the blood vessels of infected sheep also and so came to a conclusion that sheep and cattle got these bacteria while grazing in the pastures. He isolated and grew the bacteria in the lab and inoculated them into healthy mice. The mice developed anthrax and died. On the basis of his findings, Robert Koch – the father of bacteriological technique postulated that a bacteria (microorganism) causing a disease must satisfy the following four conditions.

(i) It must found in the organisms that are infected with the disease.
(ii) One should be able to isolate it and grow it in the pure culture in the lab on the artificial medium.
(iii) When a healthy organism is inoculated with the cultured microorganism, it must contract the disease with the same symptoms.
(iv) The same microorganism should be present in huge number in the inoculated organism. It could be re-isolated from this organism

The conditions given above hold good for animal diseases as well as human diseases. They do not apply to viruses as they cannot be cultured on the artificial medium. Viruses need a living cell to multiply. The outstanding work of Koch and later of Louis Pasteur brought many infectious diseases under control.

Various ways of transmission of infectious diseases
The infectious diseases can be transmitted by various means and if not controlled can take an epidemic form and can cause many diseases. The reason for it is that each pathogen which causes the disease thrives well and multiplies in a specific medium where it does not cause the disease. Such a medium is called as reservoir of infection. The reservoir for human diseases could be other people, animals, soil or water. From these reservoirs, the diseases can be transmitted to healthy persons directly or indirectly.

(A) Direct Transmission :- The pathogens reach and infect a healthy person directly without an intermediate agent. It could be by various means like:

a. Direct contact between the infected and the healthy person. It includes diseases like small pox, chicken pox, syphilis, gonorrhea, etc. Direct contact with the discharge from the lesions, sores, skin or mucous membranes causes the infection.

b. Droplet infection: A tiny droplet is sufficient to cause an infection or a disease. Most air-borne respiratory infections like cold, influenza, whooping cough, pneumonia and tuberculosis occur in this way. The droplets emitted into the air from sneeze, cough, spit or while talking are laden with bacteria and viruses. By inhaling the air containing the droplets one gets the infection.

c. Contact with the soil containing disease causing bacteria, virusesWhat is a Disease? and other organisms. Tetanus causing bacteria thrive well in soil and enter the organism through wound or injury.

d. Bite of an animal: Rabies or hydrophobia in man is caused by a virus that is transmitted through a dog bite. The virus is present in the saliva of the rapid animal and enters the healthy person through the wound.

e. Transplacental transmission: Pathogens of certain bacteria like German measles and syphilis can pass through the placenta and if mother has these diseases during pregnancy, the foetus can also contract them.

(B) Indirect Transmission :- Many times the transmission of a pathogen to a healthy person is not direct but through an intermediate agent.

a. By vectors: It refers to arthropod carriers like houseflies, cockroaches, female anopheles mosquito, etc. which carry infectious organisms and spread the diseases. Malaria is contracted by the transfer of pathogen plasmodium by the female anopheles mosquito.

b. Vehicle borne: The pathogens present in agencies like food, water, ice or blood generally enter the body through mouth. They normally infect the digestive system and hence the wastes excreted are highly infectious. The diseases transmitted through these include cholera, dysentery, etc.

c. Air borne pathogens spread by wind currents, aerosol sprays and dust. Air and dust contain number of bacterial spores that can infect organisms.

d. Fomite-borne means one gets infection by touching any article that has been in contact with the infection. The articles could be garments, toys, crockery, door handles, soaps, taps, surgical instruments and syringes.

e. Unclean hands and fingers are the source of infection for various digestive and respiratory diseases.

Sunday, April 18, 2010

Effects of Alcohol

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Effects of AlcoholShort – term effects of Alcohol
Alcohol is rapidly absorbed in the body tissues as it does not need to be digested. It gets absorbed through the lining of the stomach and intestine and enters the blood within two minutes after being swallowed. In no time alcohol reaches all the body cells. In the cells, its oxidation begins immediately. As the cells oxidize alcohol, a large amount of heat is produced. This excess heat, not needed by the body is carried by the blood. This raises the temperature of blood and leads to increased circulation towards the skin for dissipation of heat. The skin turns rosy and the person may gets a false impression of warmth. Actually as the blood is directed towards the skin, the supply of blood to internal organs is reduced bringing a fall in their temperature. Alcohol has no value as a food as the energy released is not used in any life processes.

Long – term effects of Alcohol
Alcohol is an intoxicant and the person under its influence suffers from loss of judgement and self – control. Alcohol not only affects the individual himself but also his family and society.

Effects of Alcohol on an Individual


Effect on Central nervous system: Alcohol is a depressant and not a stimulator as many people think. Alcohol has an anaesthetic effect and releases inhibitions. Alcohol first affects the brain cortex and the person is no longer able to think clearly and judge good or bad. He suffers from loss of judgement and will power. The person may feel less inhibited. His normal restraints disappear and he loses self – control. As alcohol takes its effects, the vision gets distorted. The person may have a blurred or double vision. As alcohol reaches the cerebellum, the muscular control begins to disappear. The person is unable to walk in a straight line and walks in a clumsy gait. He becomes dizzy while standing and has a tendency to fall. Excessive intake of alcohol decreases the blood sugar level and may cause permanent damage to nerve cells.

Effects on Liver: Liver is the organ that gets most affected and damaged by excessive drinking of alcohol. In the liver, alcohol is converted into a more toxic substance, acetaldehyde. Also, liver synthesizes fats from alcohol. The fat lowers the production of metabolism of fat, protein and carbohydrates; it becomes a store house for fat. It leads to swelling of liver and a condition called fatty liver syndrome (75% of alcoholics suffers from this syndrome). Continued use of alcohol leads to serious degeneration of liver called cirrhosis. In this disease the fatty liver shrinks and hardens as liver cells are replaced by fibrous tissue.

Effects on Stomach: Stomach is another organ affected severely by excessive drinking alcohol. In the stomach, alcohol causes an increased flow of gastric juices. High doses of alcohol (more so if taken empty stomach) lead to painful inflammation of the stomach lining called gastritis.

Effects on Kidneys: The oxidation of alcohol in the cells produces water. This excess water is excreted in large amounts by the skin during heat elimination. But this leads to dehydration of tissues and greater concentration of nitrogenous wastes in the kidneys. Alcohol affects the normal elimination of wastes by kidneys.

Effects on other Body Organs: Cells oxidize most of the alcohol taken in but the rest is removed in a variety of ways. A part of alcohol is released in the lungs and is removed along with exhaled air. It gives an alcoholic a typical alcoholic breath odour. A small part of alcohol passes out into the kidneys and is eliminated in urine.

Alcohol Psychosis: In certain cases (about one in ten) alcoholism leads to a mental disorder called alcohol psychosis. Such people need the professional help of the doctors and psychiatrists and must be admitted in the mental hospital.

Symptoms of Alcohol Psychosis
Excessive intake of alcohol affects the nervous tissue. There is general deterioration of parts of brain. Often alcoholics starve themselves for long periods during drinking alcohol. The disease gets aggravated with the deficiency of complex vitamins necessary for normal nervous activity. The person suffering from alcoholic psychosis shows a confused personality. He is in a state of delirium and does not know who he is. The person suffers from hallucinations involving visual horror. As a result he may show uncontrolled trembling called delirium tremens (or D.T.'S). He may also suffer from the memory loss of recent events. The disorder can be treated only under medical supervision that needs the professional help of psychotherapists, doctors and dieticians.

Effects of Alcohol on the Family
An alcoholic neglects his family. Once addicted an alcoholic wants to have a drink alcohol, even if there is not enough money for food in the house. Even well-to-do families break and get ruined by alcohol drinking. The alcoholic does not care about the needs of his family members, his motto is to satisfy his own desire of drinking. It leads to his frustration and insecurity in his children. The person quarrels frequently when shown resistance and often becomes violent. The atmosphere of the house no longer remains peaceful and creates a number of domestic problems with the wife, children and other family members. The family of an alcoholic may suffer silently or show resistance. The neglected children may follow a wrong path and take to crime or drugs.

Effects of Alcohol on Society

An alcoholic not only harms himself but also the society pays a price for it. Accidents by drunken drivers are on increase in cities and highways. Alcohol impairs judgement and increases the reaction time. An alcoholic puts not only himself but also the people on roads at a greater risk. As alcohol drinking impairs judgement, even innocent youths are led to crime under its influence. As alcohol reduces the mental restrain and self – control, a number of corrupt practices in the society are linked to alcoholism directly or indirectly. Alcoholism has led to more violence in the society. Under the influence of alcohol, people become less tolerant, start using abusive language and react impulsively without about its repurcussions. Alcoholism spreads antisocial and illegal activities like distillation and sale of illicit or spurious liquor, drug trafficking and decline of moral values.

Thursday, April 15, 2010

Alcohol, Alcoholic and Alcoholism

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Alcohol

Different types of alcohol
There are various types of alcohol like methyl alcohol or wood alcohol, isopropyl alcohol and ethyl alcohol. Methyl alcohol is used as a solvent for lacquers and as an antifreeze in automobile radiators. It is highly poisonous and should not be taken. Even small quantities of it can cause blindness or death. Isopropyl alcohol is often used as rubbing alcohol. Alcohol is also poisonous and the bottles are marked as "for external use only". Ethyl alcohol or ethanol is the drinking alcohol that is consumed by the people in different forms. In this topic we will come to know about ethyl alcohol, its short term and long term effects.

Kinds of alcoholic beverages
Ethyl alcohol or ethanol (C2H5OH), also called drinking alcohol is produced by the action of yeast on sugars. The sources of sugar used are generally from fruits (like grapes) and grains (like corn, rye, barley or wheat). Ethyl alcohol is consumed as a beverage in a number of ways. Depending on the content of alcohol, there can be two types of alcoholic beverages.
(i) Fermented beverages with low content of alcohol like beer, toddy and wine.
(ii) Distilled beverages with a relatively high content of alcohol like arrack, brandy, rum, whisky, gin, vodka, etc.
Alcohol, Alcoholic and Alcoholism p
Alcoholism
The term alcoholism refers to the chronic dependence on alcohol. The person who is dependent on alcohol is called an alcoholic. An alcoholic needs proper medical supervision and help from the family and friends to break off his habit and overcome the addiction. Alcoholics can be found in all sections of society. People often begin with occasional social drinking and with small doses but soon become addictive to it and take to heavy drinking. Alcohol is an intoxicant and acts as a slow poison for the body. Most people are moderate drinkers. They can take it or leave it. They often make a single drink last for quite some time so that their body can oxidize alcohol about as fast as it enters the body. This way the alcohol is lessened and they have very few visible effects. Alcoholics are heavy drinkers. With heavy drinking the amount of alcohol in their blood keeps rising and their nervous system gets affected. Their vision becomes distorted, their walk becomes wobbly and the speech gets garbled. To overcome their habit of using alcohol, alcoholics need the cooperation of their family and friends.

Reasons for Drinking
The people take to drink alcohol for a number of reasons.
(i) Social and peer group pressure.
(ii) Just for the sake of fun and excitement.
(iii) To get a feeling of independence.
(iv) As a reaction to stress – to relieve tension.
(v) As an escape from reality when life seems unpleasant temporarily.

Alcoholism and Driving
Drinking and driving do not go together. A person under the influence of alcohol may not even realize how disastrous it can be to drive at that moment. Given below are some of the effects of alcohol that are dangerous while driving.

Impairment of Judgement of distance: A person under the influence of alcohol is not able to judge the distance accurately. His ability to judge the distance is distorted.

Poor coordination between head and eyes: A drunken driver has a poor control over the vehicle. He becomes reckless driver as the coordination between his brain and eyes is impaired.

Lack of alertness: A drunken driver may fail to recognize the objects outside his vehicle. His mind is not attentive and cannot concentrate on driving.

Blurred vision: the driver has as unsteady and blurred vision. He fails to recognize various road signals like stop lights, road flashers, dividers or turns.

Increased reaction time: Reaction time is the length of a time a person takes to respond to a stimulus. The normal reaction time is about 2/3rd of a second. A drunken driver with an increased reaction time takes longer to respond to an emergency situation. Along with poor judgement, it leads to tragic accidents. If the driver suddenly sees something on the road ahead of him, he takes longer to apply brakes resulting in the accident. Many innocent people get killed or are disabled by the accidents caused by the drunken drivers and alcohol.

Careless and discourteous behaviour: A drunken driver is an erratic, and a rash driver. He seldom gives right of way and often speeds and takes risks.

Dealcoholism
An alcoholic needs a sympathetic understanding and cooperation of the family members and friends to overcome drinking. An alcoholic uses alcohol as an escape from reality problem of life. So the foremost thing during Dealcoholism is to find the problem that underlies his drinking. Alcoholic needs volunteers to help him overcome the problem rather than take to alcohol. Dealcoholism is a gradual process. A person does not leave alcohol all of sudden. He may undergo withdrawal symptoms and may need proper medical care. There are a number of voluntary and private organizations that help people overcome the habit of taking alcohol and help them lead a healthy fulfilling life. They teach them how to cope up with stress and advise not to take alcohol. Some alcoholics with mental delirium may need to be admitted to hospitals and under the care of psychologists and doctors. It may take longer for these people to overcome the problem.

Tuesday, April 13, 2010

Drugs as a Social Stigma

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Life of the drug addicts
Drug addiction drains the body both physically and emotionally. Drug addicts feel that drugs help them, to reduce stress but actually they go through harrowing times. The drugs are expensive and are sold illegally. The whole energy of an addict is diverted to obtain the drugs by hook or crook. He becomes useless for himself and for the society. He is forced to steal, to pay the hefty price for the drugs from illegal narcotic traffic. Once addicted, a number of them take to crime to satisfy the drugs craving. The body of an addict develops tolerance and he needs larger and larger doDrugs as a Social Stigmases. As the person develops physical and psychological dependence on drugs, he craves more for the drugs and the vicious circle begins. He gets withdrawal from his family and friends and prefers the company of other addicts. Today there are thousands of addicts and a large number of them are teenagers. They get involved in the illegal activities, drug – trafficking and crime. The drug addicts are unable to work at jobs. They are always in look out for an easy way to get money which they have to get the drugs. They often suffer from malnutrition and deliberately take overdoses to forget their problems. Drug addicts not only ruin their life but their families and society also pay a heavy price for them. Drug addicts also suffer the danger of infection. Since drugs are always procured illegally, they are not prepared in sterile conditions. Also they are diluted or mixed with substances which are not sterile. Further the syringes used are dirty, hence infection is common. It could be blood infection, jaundice, hepatitis or AIDS. The moment a person chooses a path of drugs, he is on a shortest and a surest way to disaster.

Factors Leading to Drug Addiction
There are a number of factors which lead to drug addiction. Some of these are mentioned below:-

(i) Biochemical changes caused by the drugs
Large group addictive drugs even when taken in small amounts and within a short time of their use, produce noticeable biological and chemical changes in the body. These changes called as feeling of high are then desired by the person either to escape from disturbing life problems or to get relief from stress. The person then starts desiring these small short – lived high moments and starts taking more and more drugs.
(ii) Peer group and personality influence
So many youngsters take to drugs just out of curiosity and adventure to have a new sensation or a new thrill. Sometimes they fear that if they resist, their friends may reject them. Also the people who are emotionally unstable, immature or impulsive fall easily for drugs.

(iii) Environmental, social and cultural influence
There are a number of multifarious social factors that lead the people to take drugs. All sections of society, from lower to upper class can fall prey to drug addiction. It could be due to broken homes, unhealthy parental attitudes, loneliness, lack of affection, negative attitude of people around, easy access to money, living near crime dominated spots, behavioral problems at home and work place, stressful life, etc. The addicts use drugs as an escape from the problem and in the process get addicted.

Some precautionary measures to avoid drug addiction
Drug addiction is directly related to stress. Once addicted, it is a long process before one comes back to normal life. So to avoid addiction, one should try to overcome the stress by other means like:
(i) Talk to oneself and understand and accept oneself as one is.
(ii) Try to face the problem, rather than avoid or forget it by taking drugs.
(iii) Talk to the family members, friends or teachers and other adults in the community. It is always possible to avoid drugs and sort out the problems and look for ways to overcome the stress.

Deaddiction and Rehabilitation
The road to recovery of drug addicts is long and often discouragingly slow. Family members, friends and society on the whole have a very important role to play. The drug abuse is generally not found in happy, well adjusted families. It is more among people who feel insecure and stressed. Once addicted, they need proper medical care and a sympathetic attitude. Management of deaddiction is a complicated and difficult task. It cannot be done single – handedly by a psychiatrist, psychologist or a social worker. It needs an integrated approach, and a concerted effort of a group of specialists. The treatment for deaddiction occurs in phases.

Deaddiction:
The first phase of treatment is detoxification. Here, gradually the drugs are stopped and the addict is helped to overcome the withdrawal symptoms. The addict undergoes severe physical and emotional disturbances. These are taken care by giving specific medicines. Then begins the next stage of psychotherapy and counseling in which the clinical psychologist uses his/her special ways to understand and help the addict overcome his drug addiction. The individual and group counseling is given by psychologists and counselors. The treatment includes an effort to reduce the addict's stress. An addict is taught new ways to solve everyday problems. It also needs strict supervision that an addict gets adequate diet, rest and is able to relax. They pay home visits for motivating the addicts and their family members to continue the treatment. So many times if family cooperation is not there the addicts when left on their own start taking the drugs again. The family counseling is done by efficient social workers in order to change the attitude of rejection and hostility of the neighbours and other family members towards the addict. An addict needs to be accepted by the family and society.

Rehabilitation:
Once an addict has undergoes deaddiction and is accepted by the family and society, begins the next step of rehabilitation. They are given proper vocational training so that they can lead a healthy and meaningful life. The attempts are made to help them becomeDrugs as a Social Stigma p useful members of the society. Deaddiction and rehabilitation of addicts is a long drawn process. There are a number of volunteer and government organizations that work towards this cause. In last two decades, drug addiction has spread to societies all over the world though initially it was confined to a few developing countries. Now it has become a global problem. To signify the magnitude of problem, United Nations Organization observed 26th June 1989, as the International Day Against Drug Abuse and Alcoholism.

CLASSIFICATION AND EFFECTS OF DRUGS ON HUMAN HEALTH

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The psychotropic drugs act on the mind in various ways. Depending on how they act, they have been classified into four major groups given below.
(i) Sedatives and tranquillizers, e.g. valium, etc.
(ii) Opiate narcotics, e.g. opium, morphine, heroin, etc.
(iii) Stimulants, e.g. caffeine, cocaine, amphetamines, etc.
(iv) Hallucinogens, e.g. LSD, mescaline, charas, bhang, hashish, marijuana, etc.
Effects of the drugs according to classification are given below:

1 Sedatives and tranquillizers (depressant)

a. Valium, Calmpose, Trytanol
They depress the activity of central nervous system and produce a feeling of calmness and relaxation. They decrease anxiety temporarily and reduce the sensitivity to the world around the user. They bring drowsiness and in higher doses induce deep sleep. They help to relieve pain. So they are used by doctors to relieve pain, induce sleep and to reduce emotional anxiety. Tranquillizers are the drugs that reduce tension and anxiety, bring calmness without inducing sleep.

b. Barbiturates

Barbiturates are synthetic drugs commonly called as sleeping pills. They are used to decrease anxiety and induce sleep. As such they are not addictive but a person may develoCLASSIFICATION AND EFFECTS OF DRUGS ON HUMAN HEALTHp emotional dependence on them. In such cases it is difficult to withdraw from them as the person suffers from withdrawal symptoms when deprived of the drug. Barbiturates have two more severe hazards in the society: They are frequently used in higher doses for suicide. They are lethal for the body when taken with alcohol, can lead to tragic death.

2 Opiate narcotics or narcotic drugs

a. Opium
It can be taken orally in powder form, or inhaled (smoked) or taken in the form of injections. Opium is extracted from the juice of white poppy capsule Papaver somniferum. It is reddish brown, has strong smell and is bitter in taste. It is eaten or smoked. People addicted to opium, show loss of weight, sterility and total loss of interest in work. They show severe withdrawal symptoms if drug is not made available thus they degrade the human health. An overdose may stop respiration and lead to death.

b. Morphine and Codeine

Morphine is the active ingredient of opium and is used to relieve pain. It is valuable as an analgesic. It leads to addiction. Codeine is a mild analgesic. In small doses it does not cause addiction. It is an ingredient of certain medicines like cough syrups.

c. Heroin

Heroin is highly addictive and so dangerous to human health that its use in medicine is also illegal. It is taken orally, inhaled or injected. It is often diluted with harmful substances before injected into the human body. Also the needles or syringes used are not sterile. Hence these drugs addicts often suffer from secondary illness like blood poisoning, formation of abscess, serum hepatitis and AIDS. As heroin addicts are dependent on the drug, failure to get it causes severe withdrawal symptoms like vomiting, diarrhea, shivering, twitching, perspiration, abdominal cramps and muscle cramps.

3 Stimulants


a. Caffeine
Caffeine is a mild stimulant and is found in the leaves of tea plant, seeds of coffee and cocoa plant. It is commonly taken in the form of beverages like tea, coffee, cocoa and cold drinks. It increases alertness and thought. Excessive use of caffeine causes addiction.

b. Cocaine

Cocaine is extracted from the leaves of the South American cocoa plant. (It is different from the beverage cocoa). Cocaine causes a feeling of excitement and increases self-confidence. It causes temporary stimulation of nervous system and feeling of enlightment. Later person gets a feeling of fear and turns violent. It is also used as local anesthesia by doctors.

c. Amphetemines

Amphetemines are synthetic drugs often used as pep pills. These are often taken by truck drivers and night workers to keep themselves awake, without realizing that these also cause blurred vision and impair judgement. Higher doses can cause hallucinations. Weight watchers use them to reduce their appetite.

4 Hallucinogens
Hallucinogens are also known as psychedelic, or mind expanding drugs. LSD, mescaline, psilocybin and products of hemp plants like charas, bhang, marijuana, hashish. Hallucinogens alter a person's thoughts, feeling and perceptions. The person claims to see sounds, and hear things that do not exist.

a. LSD (Lysergic acid diethylamide)
LSD is the most dangerous hallucinogen. It is obtained from the argot fungus. An LSD drug even in very small amounts like 1 µg per kg of body weight induces psychedelic trips. The user sees bright lights, strange shapes and a feeling of outside their bodies. It causes severe damage to the nervous system.

b. Mescaline
Mescaline is extracted from the spineless cactus that grows in south – west America. The drug is used to get kicks CLASSIFICATION AND EFFECTS OF DRUGS ON HUMAN HEALTH pand has similar effects like other hallucinogens.
c. Psilocybin
Psilocybin is extracted from certain mushrooms. It is also taken to get kick and causes hallucinations.
d. Products of hemp plant charas, bhang and ganja, marijuana and hashish
All these are obtained from the dried leaves and flowers parts of the hemp plant Cannabis sativa. These drugs are commonly taken by drug users in India. The reaction depends upon the amount and strength of drug used. The user feels relaxed, elated and high. However may become moody and violent. They lose the sense of timing and judgement and see and hear objects. These drugs have dangerous often fatal effects when taken along with other drugs like heroin and when taken in combination with alcohol.

Wednesday, April 7, 2010

Introduction to Drugs

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Drugs
Definition: By the definition, the term drug can be defined as any substance used in the composition of a medicine. In medical terms a drug is defined as any chemical substance which taken into the body, alters the way the body functions. It means a drug may modify one or more of the body's physical or mental functions.

Uses of Drugs
Drugs are used in a number of ways.
Drugs are prescribed as medicines to prevent or cure a variety of disease. Some drugs help to fight against infections.
Drugs may be used to promote better physical and mental health.
A number of drugs are used to alleviate anxiety, reduce pain or insomnia.
Drugs may be used to alter the mood. Such drugs are termed as mood – altering drugs.

The drugs should be used under medical advice only. Self – medication may be very harmful because drugs do have harmful side – effects. Some drugs like mood – altering drugs have a particular risk of a patient becoming totally dependent on them called drug dependence. They are habit forming drugs, also called as psychotropic drugs.
In this topic we will only come to know about the habit forming drugs in detail.

Psychotropic Drugs
(i) Psychotropic drugs act on the brain and affect its normal functioning. They slow down and interfere in the functioning of the nervous system.
(ii) Psychotropic drugs alter behavior, consciousness and powers of perception. They alter the mood of a person, hence are called as mood – altering drugs.
(iii) Psychotropic drugs have a visible effect on the behaviour of a person.
(iv) Psychotropic drugs impair the person's judgments.
(v) Psychotropic drugs make a person increasingly dependent on them. Therefore they are called as habit forming or addictive drugs. They lead to both physical and mendrugstal addiction.
Certain Terms Related to Habit Forming Drugs
Given below are certain terms to drug addiction which will often used in this topic.

Tolerance: - Tolerance to a drug means less response to a specific dose with repeated use. That means body has developed resistance to the effect of the drug. Now the person needs more of the drug to get the desired effect. For example, when a person takes 1 microgram of a drug for the first time, the response he gets is far more than when he takes it the hundredth time. Now he needs to take much more the amount for the same effect.

Drug Addiction: - Drug addiction means that after a drug has been taken for some time, it is very hard to give up its use. It is state of periodic and persistent urge, deterimental to the health of individual and society. The person who becomes addicted is known as addict.
An addict shows the following characteristics:
(i) A strong urge to continue taking the drug.
(ii) Progressive tolerance to the drug, that is increasing the dose of drug to get desired effects.
(iii) Physical and mental dependence on the drug.

Withdrawal Symptoms: When a drug is taken regularly for sometime, two types of addiction may occur – physical and emotional or psychological.
In physical addiction the body develops a need for the drug. When drug supply is cut off, the body reacts violently and a number of withdrawal symptoms starts appearing. These include:
(i) Severe abdominal pain or severe body ache
(ii) Muscular cramps
(iii) Headache
(iv) Fever
(v) Watering of eyes and nose
(vi) Vomiting and pain in stomach
(vii) Sleeplessness, difficulty in breathing, irregular heartbeat, etc. Such a person gets relief only when he gets more of the drugs.

Emotional or Psychological addiction:
It means a person has a strong craving or urge for the drug either for pleasure r to avoid the intense physical disturbance. If the drug is not given, the addict faces severe depression and derangement. If a person is not physically addicted to a drug, he may overcome his addiction without suffering from withdrawal sickness. But usually people are addicted to a drug physically as well as emotionally. They need proper medical care to overcome their addiction.

Psychological Drug Dependence:
It refers to the state of mind of a person who is so dependent on the drug that his life or activities are centered around in ensuring the supply of drug. The drug itself may or may not be addictive but the person wants to take it continuously just to enjoy its effects or to avoid the discomfort caused by its absence. Repeated use of the drug makes a patient totally dependent on them. World Health Organization (WHO) suggested the use of the term drug dependence to include the terms drug addiction or drug abuse. The drugs that cause drug dependence are called as psychotropic drugs as they act on the brain and alter behavior, consciousness power of perception.

Wednesday, March 31, 2010

LEVELS OF ORGANIZATION – SPECIES AND POPULATION

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Levels of Organization

The living organism is a system of interwoven and overlapping hierarchies of organization. Starting from atom, each level makes the base for the next higher level and thus forms different levels of organization. The properties of those levels of organization are unique and are different from any levels of organization, e.g. water is a molecule of hydrogen and oxygen. It has its own properties which are different from hydrogen and oxygen, both. Each level of organization is more complex and has fewer units than the previous one i.e. there are lesser tissues than cells. The molecules of life are packed into highly organized, self enclosed units called cells. Each cell has a complex structure that gives it the capability of self-reproduction a unique characteristic of living things. Cell is the lowest level among the levels of organization that is considered to be alive. The structural hierarchy represents how matter has become more and more organized with each levels of organization. At every shift of organizational level, energy is required. This new level of organization has its own properties. Energy is necessary to maintain that level of organization. There is an intimate relationship between organism and environment in every levels of organization. Levels of organization are the basis of evolution. Levels of organization has determined the kind of life that existed in past and is existing today however, the activities of an organism also produce changes in environment so the relationship is in both ways.

A living organism – the most observable unit can be studied at various levels as given:

Genes → Cells → Tissues → Organs → Organisms → Populations → Biotic Community → Ecosystem

In this part headed "Levels of Organization" we will study the living organisms at the species and population level.Levels of Organization.jpg

The Individual Organism

A living organism is able to carry out its life processes within its body independently. The individuals can be counted, measured and studied as they are the most concrete objects. The individual organism is always derived from the pre – existing ones through vegetative, asexual or sexual reproduction. An individual always has a life span with a definite beginning and a definite end. An individual is able to transmit its characters to the offspring. The aggregation of individuals of one kind forms the population.


Population
Population is a geographically isolated group of the same kind (so called species). It is a group of organisms of same species that occupy a specific area. The population may be closer or widely dispersed geographically. The number of population distributed over a large geographical area may form one species.


Species
Species is supposed to be the basis unit of taxonomy. A species may be defined in number of ways in various biological aspects.

Genetically – A species having group of organisms that show a distinct similarity in the generelationshiptic karyotype.
Morphologically – A species is a distinct and recognizable group of organisms.
Ecological – A species having group of organisms that share the same ecological niche. (No two species can have the same niche)
Interbreeding – A species having group of organisms that can interbreed and produce a fertile offspring in nature. The criteria is too simple to understand a species. There are number of species where the organisms may look different and yet they belong to the same species.

Monday, March 29, 2010

Amazing Biology

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Amazing biology man.jpg
Amazing biology frog

Thursday, March 11, 2010

Biotic Community

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Characteristics of a Biotic Community

In any natural environment of only one species cannot exist by themselves. It is always a group of population that live together in the same area. An association of a number of different inter-related populations of different species in a common environment in a nature forms a Biotic Community. The members of a biotic community can be producers, consumers or decomposers. The members of a biotic community are all interdependent. A biotic community may be small or large e.g. pond community occupies a limited area while the desert or grass land communities could spread to miles. A biotic community may primarily be of plants or animals and generally includes both. As different species share a common environment, number of direct or indirect interactions exists between them inside a biotic community. A biotic community interacts with the abiotic factors and forms an ecosystem.

Cells – Tissues – Organs – Organisms – Population = Biotic Community


Every biotic community needs abiotic factors for survival. At times the dominance of one factor determines the predominance of particular kind of population in a biotic community. For example: In a biotic community of fruit bearing trees the frugivorous bats and insects would be in plenty. A grass land biotic community has seed eating birds, mice and predatory birds living on small insects. A damp marsh has frogs, toads, fish, water insects and water birds that feed on small creatures. Aquatic plants of different kinds adapted for different intensities of light at the surface or at different depths would be present in a biotic community.


Interspecific Interact

ions in a Biotic Community

When various species live together in a biotic community, numbers of interactions take place according to specific needs of food, shelter and habits. We will discuss some of these in this chapter.

1. Predation 2. Scavenging 3. Parasitism 4. Commensalism 5. Symbiosis 6. Competition


1. Predation

Predation is a direct and often complex interaction of two species in a biotic community. The stronger animal called predator captures and feeds on the weak animal called prey. The decline in number of predators leads to a increase in number of the prey. An increase in the predator population leads to decrease in the prey population in a biotic community. These fluctuations play an important part in regulating natural population. Examples: Tiger feeds on deer, owls on rats etc. At times an animal could be a predator as well as a prey.


2. Scavenging

Scavenging is a direct food relationship where animals called scavengers feed on other dead animals which have either died naturally or have been killed by another animal in a biotic community. They play an important role in a biotic community as food is not wasted and also is disposed off. Examples: - Vulture feeds on dead bodies. Hyenas and jackals feed on left over killed animals by lion. They may feed on big animals like zebra and giraffe killed by other animals.


3. Parasitism

Parasitism is a negative interaction in a biotic community where one not only derives nourishment but also lives a part or the whole of life on another organism. The parasite is an organism that lives on another organism, the host from which it obtains food as well as shelter in a biotic community. It could be between animals between plants or between animals and plants in a biotic community. In the host – parasite relationship the weak attacks the stronger. It is beneficial to parasite and harmful to host. Generally a parasite may cause an illness but not kill the host except in severe cases. There may be number of parasites on one host.


4. CommensalismBiotic Community shark

In Commensalism one organism or a population is benefited while the other is neither benefited nor harmed. In some cases the host may be able to derive some minor benefit. There is no physiological exchange of any kind. The association may be temporary or permanent in a biotic community. Example

: Remora – a small fish attaches itself to the lower side of a shark. Remora feeds on scraps of shark's food and is not harmed.


5. Symbiosis

Symbiosis is an association of two populations in a biotic community where both the populations are benefited. There is often a close or permanent association. In some cases both are so interdependent that neither can live alone in that biotic community.


6. Competition

The two species in a biotic community interact in such a way that it affects their growth and survival. Both the species share the same resources like water, nutrients, space, sunlight, food, etc of a biotic community. Members of both species compete to survive in that respective biotic community. There is a direct inhibition of one by another. Many a times there is no set pattern as any one can succeed. Examples:- Carnivorous animals like tiger and lion compete for the prey. Trees, herbs and shrubs compete for sunlight and nutrients in a biotic community.


7. Some Passive Interactions

There are many interactions that exist in nature of a biotic community in between the animals, or between animals and the surrounding, which also help an organism to survive in that biotic community. Camouflaging – The blending of an animal with its surrounding is called camouflaging. It is also known as protective coloration. They camouflage their body shape and colour to suit the environment. Examples:- Stick insect Carausius morosus resembles a thin dry branch. Dead Leaf butterfly Kalima parolecta resembles a dry leaf. Praying mantis Mantis religiosa resembles the green foliage. Mimicry – Mimicry is also a type of protective resemblance in a biotic community. In this an animal mimics another animal so as to avoid predation. The viceroy butterfly mimics the common Monarch butterfly which is avoided by birds for its unpleasant taste.


Other Interactions

There may be many other interactions which may not be apparent. The association of birds and animals bringing about seed dispersal and pollination. The birds feeding on ticks – the parasites on the body of cattle. The red billed and yellow billed ox peckers perch on the black rhinoceros of Africa and feed on ticks and thus make the animal rid of the parasites to survive in a biotic community. They also warn the animal of the approaching danger. The rufus woodpecker makes a nest in a hole in the ball shaped nest of the ants. The ferocious ants do not harm the eggs or young ones but the birds feed on these ants and keep a check on their population to continue their generation in a biotic community.


Biotic Stability

A biotic community is a naturally occurring assemblage of plants and animals living in the same environment. They all interact to make the

community stable. It has been seen that more the number of species, more stable is the community. For example a biotic community containing a large population of Eucalyptus or any other plant may be totally wiped out by a fungal disease or insect infestation. But if a biotic community contains many species and kinds of plants, only one would wiped out at a time and the rest would survive. Example – In Serengeti plains of Africa, 20 species of antelope graze in the same area. Each species eats on a different kind of grass or shrubs. Some that feed on the same species, feed at different stages of grass. This makes the biotic community rich and stable.


Changes in a Biotic Community – Ecological Succession

A community is built up over a period of time. As the time passes, communities change. In a biotic community there are interactions among the organisms (biotic factors) and between the biotic and abiotic factors (climate, light, soil, etc) All these bring about changes in a biotic community. A biotic community is a dynamic unit where tropic levels exist, there is

a flow of energy and cycling of nutrients. It is a living part of an ecosystem. The wind, fire, volcanic activity or any other event in nature or man may destroy the organisms living in a biotic community. Now if this area is left alone, a succession would start and ultimately a permanent biotic community would take shape. This process from the beginning to the climax may take many years. During this time there will be an orderly and progressive replacement of one biotic community by another till a relatively stable biotic community is established. This is called as ecological succession. A complete succession is called as Sere. A Sere is made up of a number of seral stages. A climax community is the final or the seral stage.


Kinds of Ecological Succession

(1) Primary Succession (2) Secondary Succession.


1. Primary Succession

Primary Succession occurs where no biotic community has previously existed like sand dunes, volcanic islands, lava flows, etc. The area is devoid of any organisms. It may take upto 1000 years before climax community gets established.

Various stages in a Primary Succession – Let us take an example of a bare rock or volcanic islands. Trees, herbs or shrubs can not grow because of absence of good soil. The first organisms often called pioneer organisms are lichens that invade the rocky area. The fungal component holds and the algae provides food. The usually rode the rock surface and tiny crevices or fissures open in the rock in a biotic community. The erosion of rock, sand, dead and decayed lichens provide sufficient soil for larger plant species to invade. Next mosses, ferns and grasses grow on the rocky surface. Certain insects and small animals are also seen. Then the herbs, shrubs and trees replace the earlier vegetation and new animals continue to invade. Ultimately these plants will be succeeded by large seed bearing plants, tall grasses. This would also support number of different kinds of animals populations in a biotic community. This final stable self growing community is called as climax community. The animals also show a succession but these are governed by the plant succession.


Climax Community

It may take hundreds of years for a climax forest community to be established on a sand dune. A climax community is in equilibrium with the environment. A climax community often has one or more dominant species. It is generally referred to those species which collectively form a greater biomass and are generally larger in size. Climax community supports large number of species. Climax community has a high bio mass and rich organic soil. Climax community provides a wide range of food material. Climax community has a diverse variety of niches for animals.


2. Secondary Succession

It occurs when a biotic community has been disrupted and the surface is completely or largely devoid of vegetation. It may be due to earthquake, fire or even clearing of forest by man. As the spores, seeds, rhizomes the organs of vegetative reproduction are present beneath the soil, often grasses, shrubs, weeds are first to appear. The same principle of primary succession applies but it occurs at a much faster pace. It has been observed that a destroyed grass

land may take 50 – 100 years and a destroyed forest about 200 years. Overgrazing of grasslands is like reversion of the community succession. The introduction of exotic weeds in a cleared forest seriously affects the succession and it may become impossible to regenerate the same old type of forest in a biotic community.


Dominance of Species

Biotic Community oak

Each sere has one or more dominant species which are a part of climax community. These could be Pine, Oak, Sal or Teak depending on the area and climatic conditions in that biotic community. The dominant species are the most numerous plants. They are generally large in size and have the greatest biomass. They influence the local environment. The species may be fewer in number in temperate forests – 90% of trees may be pines and oaks of a biotic community. The species may be more in tropical rain forests like Andaman group of islands where there are about 12 dominant species.

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