Biology and Human Welfare in NEET by Vipin Sir

Biology and Human Welfare is an important unit in the NEET Biology syllabus. The chapter explains how biological processes help improve human life. It covers the role of microbes in daily life, human diseases, immunity, vaccination, and drug abuse. Questions from this unit are regularly asked in NEET examinations.

A clear understanding of these topics helps students answer both factual and concept-based questions. The chapter also connects biology with healthcare, agriculture, industry, and environmental management.

Biology and Human Welfare in NEET One Shot Detailed Video

Biology and Human Welfare is an important unit for NEET preparation. It covers topics such as microbes in human welfare, biofertilizers, biocontrol agents, sewage treatment, human diseases, AIDS, cancer, immunity, vaccination, and drug abuse.

Students who want a detailed explanation of all concepts can watch the video given below. The session covers important theories, scientific names, diagrams, examples, and NEET-focused concepts in a simple manner. It can help students revise the complete unit and strengthen their understanding before the examination.

What are Microbes?

Microbes are very small organisms. They cannot be seen with the naked eye. A microscope is needed to observe them. Their size is usually in the micrometre range. Microbes include bacteria, protozoa, fungi, viruses, viroids, and prions.

Microbes are found everywhere. They live in soil, water, air, and even inside the human body. Some microbes live in extreme environments like hot springs. These are called archaebacteria or extremophiles.

Microbes are often associated with diseases. However, they also play many useful roles. They help produce food, medicines, and fertilizers. They are called both friends and foes.

Microbes in Household Products

• Curd: Curd is made with the help of Lactobacillus. This is a lactic acid bacterium. It is added to warm milk as a starter. The bacteria produce lactic acid. This coagulates the milk proteins and forms curd. Curd is easier to digest than milk. It also contains more vitamin B12.

• Idli and Dosa: The batter for idli and dosa is fermented by lactic acid bacteria such as Leuconostoc. This is different from bread fermentation.

• Bread: Bread dough is fermented by Saccharomyces cerevisiae, also called Baker's yeast. It produces carbon dioxide, which makes the dough rise.

• Toddy: Toddy is a traditional drink. It is made by fermenting the sap of palm or coconut trees.

• Cheese: Different types of cheese are made using different microbes.

1. Swiss cheese is made by Propionibacterium shermanii. It has large holes caused by CO₂ production.

2. Roquefort cheese is made by the fungus Penicillium roqueforti.

3. Camembert cheese is made by Penicillium camemberti.

Microbes in Industry

Large-scale production of microbial products takes place in fermenters. These are large vessels that hold 100 to 1000 litres or more.

• Alcoholic beverages: Saccharomyces cerevisiae ferments cereals and fruit juices to produce ethanol. Beer and wine are made without distillation. Whisky, rum, and brandy are distilled and have higher alcohol content.

• Antibiotics: Antibiotics are chemicals produced by microbes. They kill or slow the growth of disease-causing microbes. Alexander Fleming discovered penicillin in 1928. He found that the mould Penicillium notatum prevented bacterial growth. Other antibiotics like streptomycin and neomycin are produced by Streptomyces bacteria.

• Organic acids and enzymes: Several microbes produce useful chemicals.

• Lactobacillus produces lactic acid.

• Clostridium butylicum produces butyric acid.

• Acetobacter aceti produces acetic acid.

• Aspergillus niger produces citric acid.

Sewage Treatment

Sewage is wastewater from homes, hospitals, and public places. It contains organic matter and harmful microbes. It must be treated before being released into natural water bodies.

Treatment happens in two stages.

• Primary treatment is a physical process. Large solids are filtered out. Grit and sludge settle at the bottom of tanks.

• Secondary treatment is a biological process. Aerobic microbes are used in aeration tanks. They break down organic matter and form clumps called activated sludge. This sludge is then moved to anaerobic digesters. Anaerobic bacteria break it down further and produce biogas. Biogas is mainly methane, along with CO₂ and H₂S.

• BOD stands for Biochemical Oxygen Demand. It measures the amount of oxygen needed by microbes to break down organic matter in one litre of water. High BOD means more pollution. Effective sewage treatment reduces BOD.

Biogas Production

Biogas is produced in biogas plants. Animal dung and vegetable waste are used as inputs. Methanogenic archaebacteria break down the organic matter under anaerobic conditions. The main gas produced is methane. It is used for cooking and lighting. The leftover material, called spent slurry, is used as fertilizer.

Microbes as Biocontrol Agents

Biocontrol agents are living organisms used to control pests. They reduce the need for chemical pesticides. Chemical pesticides harm the environment and human health.

Some examples are:

• Ladybird beetles control aphids.

• Dragonflies control mosquito larvae.

• Bacillus thuringiensis (Bt) produces a toxin that kills butterfly caterpillars. It is used in Bt cotton.

• Trichoderma species protect plants from several pathogens.

• Baculoviruses are highly specific. They target only certain insect pests and do not harm other organisms.

Microbes as Biofertilizers

Biofertilizers are living organisms that improve soil fertility. They are safer than chemical fertilizers.

• Rhizobium lives in the root nodules of leguminous plants. It fixes atmospheric nitrogen.

• Azospirillum and Azotobacter are free-living bacteria. They fix nitrogen in the soil.

• Cyanobacteria like Anabaena, Nostoc, and Oscillatoria fix nitrogen in paddy fields.

• Glomus species are mycorrhizal fungi. They live in association with plant roots and improve phosphorus absorption.

What is Health?

Health is not just the absence of disease. It is a state of complete physical, mental, and social well-being. Factors like balanced diet, hygiene, exercise, and vaccination help maintain good health.

A disease is a condition where the normal functioning of one or more organs is disturbed. Diseases can be non-infectious, like cancer, or infectious, like typhoid and AIDS.

Common Diseases

• Typhoid is caused by Salmonella typhi. It spreads through contaminated food and water. It affects the small intestine. It is confirmed using the Widal test.

• Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae. It affects the lungs. Fluid fills the alveoli, making breathing difficult. It spreads through airborne droplets.

• Common cold is caused by rhinoviruses. It affects the nose and upper respiratory tract. Recovery usually takes three to seven days.

• Malaria is caused by Plasmodium species. It is transmitted by the bite of a female Anopheles mosquito. The parasite first infects the liver, then the red blood cells. When RBCs rupture, a toxin called haemozoin is released. This causes the cyclic fever seen in malaria patients.

• Amoebiasis is caused by Entamoeba histolytica. It affects the large intestine. Symptoms include abdominal pain and stool with mucus and blood. The housefly acts as a carrier.

• Filariasis is caused by Wuchereria bancrofti. It affects the lymphatic vessels. Chronic inflammation leads to severe swelling of the limbs, a condition called elephantiasis. It is transmitted by mosquitoes.

• Ringworm is a fungal infection. It is caused by Microsporum, Trichophyton, and Epidermophyton. It affects the skin, nails, and scalp. It thrives in warm and humid conditions.

AIDS

AIDS stands for Acquired Immunodeficiency Syndrome. It is caused by HIV, the Human Immunodeficiency Virus. HIV is a retrovirus. It contains RNA and uses reverse transcriptase to convert RNA into DNA inside the host cell.

HIV infects macrophages and helper T-cells. As helper T-cells are destroyed, the immune system weakens. The person becomes vulnerable to opportunistic infections.

HIV spreads through sexual contact, infected blood transfusions, shared needles, and from mother to child during pregnancy.

It is detected using the ELISA test. Treatment involves antiretroviral drugs like AZT. These slow viral replication but do not cure the disease.

Cancer

Cancer is a non-communicable disease. It is caused by uncontrolled cell division. Normal cells stop dividing when they come into contact with each other. This is called contact inhibition. Cancer cells lose this ability and continue to divide.

Benign tumours stay at the original site. Malignant tumours spread to other parts of the body. This spreading is called metastasis.

Cancer is caused by radiation, certain chemicals like tobacco, and some viruses. It is diagnosed by biopsy, CT scan, or MRI. Treatment includes surgery, radiotherapy, chemotherapy, and immunotherapy.

Immunity

Immunity is the body's ability to fight disease.

• Innate immunity is present from birth. It is non-specific. It includes physical barriers like skin, physiological barriers like stomach acid, and cellular barriers like neutrophils and macrophages.

• Acquired immunity develops after exposure to a pathogen. It is specific and has memory. It involves B-lymphocytes and T-lymphocytes. The first response to an antigen is slow. Subsequent responses are faster and stronger due to memory cells.

• Antibodies are Y-shaped molecules. They are made of two heavy chains and two light chains. The variable region binds to antigens. The main types are IgG, IgA, IgM, and IgE.

• Active immunity means the body produces its own antibodies. It is slow but long-lasting.

• Passive immunity means ready-made antibodies are transferred. For example, IgG passes from mother to foetus through the placenta. IgA is found in breast milk. Passive immunity is immediate but does not last long.

Vaccination

Vaccines contain weakened or inactivated pathogens or their proteins. They stimulate the immune system to produce antibodies and memory cells. If the real pathogen enters the body later, the immune response is fast and effective. Some modern vaccines are made using recombinant DNA technology.

Drug and Alcohol Abuse

Drug abuse means using a substance beyond its medicinal purpose in a way that harms health.

• Opioids are derived from the poppy plant Papaver somniferum. Examples are morphine and heroin. They act as sedatives and painkillers.

• Cannabinoids are derived from Cannabis sativa. Examples are marijuana and hashish. They affect the brain and cardiovascular system.

• Cocaine is derived from Erythroxylum coca. It stimulates the central nervous system and causes euphoria. High doses can cause hallucinations.

• Tobacco contains nicotine. It stimulates the adrenal glands and raises blood pressure and heart rate. Carbon monoxide in tobacco smoke reduces oxygen delivery to the body. Tobacco is linked to lung, oral, and bladder cancer.

Biology and Human Welfare covers important concepts related to microbes and human health. Microbes play both harmful and helpful roles in our lives. Understanding diseases, immunity, and drug abuse is equally important for health awareness. These topics are also frequently tested in the NEET examination.