This chapter explores how biology is applied to improve human health and welfare. It covers human diseases, immunity, drug abuse, and microbial applications in food, industry, and agriculture — all high-yield topics in NEET Biology.

Biology and Human Welfare – NEET 2026 Complete Notes

What is Health?

Health is a state of complete physical, mental, and social well-being, not merely absence of disease.

Factors affecting health:

• Genetic disorders
• infections
• lifestyle (diet, exercise, stress).

What is Disease?

Disease is a disorder or malfunction that interferes with normal body functioning.

Types:

• Infectious: Caused by pathogens (e.g., Malaria).
• Non-infectious: Lifestyle/genetic (e.g., Cancer, Diabetes).

PATHOGENS AND PARASITES CAUSING HUMAN DISEASES

1. Malaria

• Causative agent: Plasmodium (protozoan parasite)
• Species: P. vivax, P. falciparum, P. malariae, P. ovale
• Vector: Female Anopheles mosquito
• Life cycle: Human liver → RBCs → mosquito gut
• Symptoms: Fever with chills, anemia, spleen enlargement
• Most dangerous: P. falciparum (cerebral malaria)

2. Filariasis (Elephantiasis)

• Causative agent: Wuchereria bancrofti / Brugia malayi (helminth)
• Vector: Female Culex mosquito
• Site of infection: Lymphatic vessels
• Symptoms: Swelling of limbs, scrotum; thickening of skin

3. Ascariasis

• Causative agent: Ascaris lumbricoides (intestinal roundworm)
• Transmission: Ingestion of eggs from contaminated food/water
• Symptoms: Abdominal discomfort, intestinal blockage, poor nutrient absorption

4. Typhoid

• Causative agent: Salmonella typhi (bacterium)
• Transmission: Contaminated food/water (fecal-oral route)
• Test: Widal test
• Symptoms: High fever (up to 104°F), weakness, stomach pain, constipation

5. Pneumonia

• Causative agents: Streptococcus pneumoniae and Haemophilus influenzae
• Transmission: Droplets from infected person
• Infection site: Alveoli of lungs
• Symptoms: Fever, chills, cough, difficulty breathing, chest pain

6. Common Cold

• Causative agents: Rhino viruses
• Site of infection: Nose and respiratory passages
• Symptoms: Nasal congestion, sore throat, cough, headache

7. Amoebiasis

• Causative agent: Entamoeba histolytica
• Transmission: Contaminated food/water (fecal-oral)
• Site: Large intestine
• Symptoms: Constipation, cramps, stools with mucus and blood

8. Ringworm

• Causative agent: Dermatophyte fungi (Microsporum, Trichophyton, Epidermophyton)
• Transmission: Skin contact or contaminated clothes/soil
• Symptoms: Dry, itchy lesions in skin folds (groin, armpits)

9. Dengue

• Causative agent: Dengue virus (Flavivirus)
• Vector: Aedes aegypti mosquito (day-biter)
• Symptoms: High fever, rash, muscle pain, bleeding (in severe form - Dengue Hemorrhagic Fever)

10. Chikungunya

• Causative agent: Chikungunya virus (Alphavirus)
• Vector: Aedes aegypti
• Symptoms: High fever, joint pain, fatigue

IMMUNOLOGY AND VACCINES

What is Immunity?

Body’s ability to resist harmful pathogens.

Types:

• Innate immunity: Present from birth; non-specific
• Acquired immunity: Develops after exposure; specific

Acquired Immunity:

• Humoral (B-cells produce antibodies)
• Cell-mediated (T-cells destroy infected cells)

Active vs Passive Immunity:

• Active : Vaccination, infection
• Passive : Maternal antibodies, antiserum

Vaccines:

• Contain weakened/inactivated pathogens or antigens
• Induce primary immune response and memory cell formation

CANCER

Uncontrolled cell division due to gene mutations (oncogenes).

Types:

• Benign: Localized, non-spreading
• Malignant: Invasive, spreads (metastasis)
• Agents: Carcinogens (radiation, chemicals), viruses (EBV, HPV)
• Detection: Biopsy, imaging, tumor markers
• Treatment: Surgery, radiotherapy, chemotherapy, immunotherapy

HIV & AIDS

HIV (Human Immunodeficiency Virus):

• Retrovirus that attacks helper T-cells (CD4+)
• Genome: RNA, reverse transcriptase enzyme

AIDS (Acquired ImmunoDeficiency Syndrome):

• Final stage of HIV infection; immune system fails
• Transmission: Unprotected sex, blood transfusion, sharing needles, mother-to-child
• Symptoms: Opportunistic infections, weight loss, fever, fatigue

ADOLESCENCE, DRUG & ALCOHOL ABUSE

Adolescence:

• Period of rapid physical, mental, emotional development (age: 12-18)
• Increased risk-taking behavior

Drug Abuse:

• Common drugs: Cannabis (marijuana), heroin (smack), cocaine, morphine
• Routes: Injection, smoking, inhalation
• Effects:
• Short-term: Euphoria, altered perception
• Long-term: Organ damage, addiction, behavior issues

Alcohol Abuse:

• Affects liver (cirrhosis), brain, heart
• Causes physical dependency, social and mental issues

Tobacco Use:

• Contains nicotine – stimulant and addictive
• Increases risk of cancer, heart diseases, bronchitis
• Passive smoking is also harmful

MICROBES IN HUMAN WELFARE

Microbes in Household Products

• Lactobacillus (curd formation)
• Aspergillus (fermented food like dosa, idli)

Microbes in Industrial Production

• Alcohol: Saccharomyces cerevisiae (yeast)

Antibiotics:

• Penicillin (from Penicillium notatum)
• Streptomycin (from Streptomyces)

Microbes in Sewage Treatment

• Primary treatment: Physical removal of waste
• Secondary (biological) treatment: Aerobic microbes (e.g., floc) decompose organic matter
• By-product: Biogas generation

Microbes in Energy Generation

• Methanogens (e.g., Methanobacterium) – used in biogas plants
• Break down dung anaerobically to release methane-rich biogas

Microbes as Biocontrol Agents

• Bacillus thuringiensis (Bt): Used against insect larvae (e.g., in Bt cotton)
• Predatory insects: Ladybird, Dragonflies (against aphids, mosquitoes)

Microbes as Biofertilizers

• Bacteria: Rhizobium (in legume roots), Azospirillum, Azotobacter
• Cyanobacteria: Anabaena, Nostoc – fix nitrogen in rice fields
• Fungi: Mycorrhiza (Glomus) – phosphorus absorption

NEET PYQs & TRICKS (Previous Year Highlights)

• Most frequently asked: HIV transmission, Plasmodium life cycle, Types of immunity
• Match-the-column on: Microbe → Product
• Assertion-Reason questions on: Bt Cotton, vaccines, sewage treatment steps

PRO TIPS FOR NEET:

These smart strategies can boost your NEET Biology score drastically:

1. Master NCERT Diagrams:

• Malaria life cycle – Plasmodium stages in human & mosquito
• HIV replication – Entry, reverse transcription, integration, release
• Sewage Treatment Plant (STP) – Primary, secondary treatment, sludge handling

2. Revise Charts and Tables:

• Disease summary tables: Causative agents, vectors, symptoms
• Microbes & Products Table:
• Lactobacillus – curd
• Aspergillus – citric acid
• Methanobacterium – biogas
• Flashcards or sticky notes can help in last-moment quick recall.

3. Practice PYQs (Previous Year Questions):

• Solve at least last 10 years’ NEET Biology papers
• Focus on repeating concepts and question patterns
• Prioritize Health & Disease, Immunology, Microbes in Human Welfare

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FINAL REVISION TABLE (Quick Recall)

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Thank You for Reading!

Thank you for going through our Complete NEET 2026 Notes on Biology and Human Welfare. We hope this resource has helped you revise important concepts like Health & Disease, Immunology, Microbes in Human Welfare, and more — all aligned with the latest NEET syllabus and NCERT focus.

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