General Science: Biology, Human Body and Health

Cell and classification

• The cell is the basic unit of life (Robert Hooke, 1665). There are prokaryotes, with no true nucleus (bacteria), and eukaryotes.
• Organelles:
  • mitochondria: make ATP, the "powerhouse";
  • ribosomes: make protein;
  • chloroplasts: carry out photosynthesis in plants;
  • lysosomes: digest waste, the "suicide bags";
  • the nucleus holds DNA.
• Plant vs animal cells: plant cells have a cell wall (cellulose), chloroplasts and a large vacuole.
• Cell division: mitosis gives growth; meiosis makes gametes and halves the chromosome number.
• Classification: Whittaker's five kingdoms are Monera, Protista, Fungi, Plantae and Animalia. Viruses are not placed in any kingdom.

Plant biology

• Photosynthesis takes place in chloroplasts and releases oxygen. Transpiration happens through the stomata.
• Plant hormones:
  • auxins (growth);
  • gibberellins (stem elongation);
  • cytokinins (cell division);
  • abscisic acid (dormancy, the "stress hormone");
  • ethylene (fruit ripening).
• Nitrogen fixation: Rhizobium in the root nodules of legumes, and blue-green algae in rice fields.

Human body systems

System	Key facts
Digestive	Digestion starts in the mouth (salivary amylase acts on starch); the stomach makes HCl and pepsin; the small intestine absorbs most nutrients; the liver makes bile and is the largest gland
Circulatory	The heart has 4 chambers; a normal adult pulse is about 72 per minute; normal blood pressure is about 120/80 mm Hg; red cells carry O₂ (haemoglobin) and live about 120 days; white cells fight infection; platelets help clotting
Blood groups	ABO and Rh (Landsteiner). O negative is the universal donor; AB positive is the universal recipient
Respiratory	Gas exchange happens in the alveoli of the lungs
Excretory	The kidneys (nephrons) filter blood and make urine
Nervous	The brain: the cerebrum (thinking), cerebellum (balance) and medulla (involuntary actions); neurons
Endocrine	Pituitary (the "master gland"), thyroid (thyroxine, needs iodine), pancreas (insulin), adrenal (adrenaline, "fight or flight")
Skeletal	206 bones in adults; the femur is the longest; the stapes (ear) is the smallest

Facts to remember: the skin is the largest organ. Normal body temperature is 37 °C (98.6 °F).

Nutrition and deficiency diseases

Nutrient	Source	Deficiency causes
Vitamin A	Carrot, green leaves, milk	Night blindness, xerophthalmia
B1 (thiamine)	Whole grains	Beriberi
B3 (niacin)	Groundnut, meat	Pellagra
B12	Animal foods	Pernicious anaemia
Vitamin C	Citrus, amla	Scurvy (bleeding gums)
Vitamin D	Sunlight, fish oil	Rickets (children), osteomalacia
Vitamin K	Green vegetables	Poor blood clotting
Iron	Leafy greens, jaggery, meat	Anaemia
Iodine	Iodised salt, sea food	Goitre
Protein	Pulses, milk, eggs	Kwashiorkor; marasmus (energy and protein)

• Fat-soluble vitamins: A, D, E and K. Water-soluble vitamins: B and C.
• NFHS-5 (2019–21) data:
  • Anaemia affects 57% of women aged 15–49 and 67% of children aged 6–59 months.
  • Stunting is 35.5%.
  • Bihar and Jharkhand have among the highest rates of child undernutrition.
• Programmes:
  • Anaemia Mukt Bharat;
  • POSHAN Abhiyaan and Mission Poshan 2.0;
  • fortified rice distributed through the PDS (2024);
  • PM POSHAN (school meals).

Diseases

Cause	Diseases
Virus	Common cold, influenza, COVID-19, measles, polio, rabies, dengue, chikungunya, hepatitis, HIV/AIDS, Japanese encephalitis, Nipah, mpox
Bacteria	Tuberculosis, typhoid, cholera, leprosy, diphtheria, tetanus, plague, pneumonia (often)
Protozoa	Malaria (Plasmodium, female Anopheles), kala-azar (Leishmania, sandfly), amoebic dysentery
Fungi	Ringworm, athlete's foot, "black fungus" (mucormycosis)
Worms	Filaria (elephantiasis, Culex mosquito), roundworm

Bihar health issues

• Kala-azar has been concentrated in Bihar, Jharkhand, West Bengal and UP. India reached the elimination target in 2023.
• Acute Encephalitis Syndrome (AES) in Muzaffarpur has been linked to litchi toxins combined with malnutrition and hypoglycaemia.
• Japanese encephalitis.

Non-communicable diseases (diabetes, hypertension, cancer, heart disease) now cause more than 60% of deaths in India.

Immunity, vaccines and genetics

• Innate vs acquired immunity. Active immunity comes from infection or vaccination; passive immunity comes from ready-made antibodies, as in antivenom.
• Vaccines: Edward Jenner (smallpox, 1796).
  • Types: inactivated, live-attenuated, subunit and mRNA.
  • Indian COVID vaccines: Covaxin, Covishield and ZyCoV-D (the first DNA vaccine).
• Universal Immunisation Programme (1985) and Mission Indradhanush (2014). The U-WIN portal records vaccinations.
• Milestones: smallpox eradicated (1980); India declared polio-free (2014); maternal and neonatal tetanus eliminated (2015).
• Genetics:
  • Mendel's laws.
  • DNA is a double helix (Watson and Crick, 1953).
  • Humans have 46 chromosomes, in 23 pairs.
  • XY is male and XX is female, so the father determines the child's sex.
  • Genetic disorders: sickle cell anaemia (common in tribal populations; National Sickle Cell Anaemia Elimination Mission, 2023), haemophilia, thalassaemia and Down syndrome (trisomy 21).

Public health programmes

• National Health Mission: NRHM 2005 plus NUHM 2013, with ASHA workers.
• Ayushman Bharat (2018): PM-JAY gives ₹5 lakh per family per year, and all people aged 70+ have been covered since 2024. Ayushman Arogya Mandirs provide primary care.
• Ayushman Bharat Digital Mission: ABHA health IDs.
• TB Mukt Bharat: target of 2025. The Ni-kshay Poshan Yojana gives nutrition support.
• Jan Aushadhi Kendras sell generic medicines.
• Indicators:
  • IMR about 26 per 1,000 live births (SRS 2021).
  • MMR 97 per lakh (2018–20).
  • Life expectancy about 70 years.
  • Bihar's IMR and MMR are above the national average.

Exam tip: Disease, cause and carrier make an easy table that is asked every year. For Bihar and Jharkhand also learn kala-azar, AES (Muzaffarpur), sickle cell anaemia in tribals, and anaemia data from NFHS-5.