General Science II — Biology, Health, and Everyday Science

Why This Chapter Matters

Biology and health-related general science questions are especially significant for the Village/Ward Secretariat examination because several posts — most directly the ANM (Auxiliary Nurse Midwife) and allied health functionaries, but also Welfare and Education Assistants who deal with nutrition and school-health-linked schemes — require working familiarity with the human body, common diseases, nutrition, and basic hygiene and sanitation practices as part of their actual job duties. Beyond these specific posts, every candidate benefits from a firm grounding in this material because General Science sections across nearly all these exams draw heavily on human biology, disease prevention, and everyday applied science. This chapter builds that foundation in clear, exam-ready prose.

Cell Biology and Levels of Organisation

All living organisms are composed of cells, the basic structural and functional unit of life, a principle formally established as part of what is called cell theory. Cells are broadly classified into two types: prokaryotic cells, which lack a defined nucleus and membrane-bound organelles (found in simple organisms such as bacteria), and eukaryotic cells, which have a true, membrane-bound nucleus containing the cell's genetic material along with various specialised membrane-bound organelles (found in plants, animals, fungi, and protists). Within a typical eukaryotic cell, several structures recur in exam questions: the nucleus houses the cell's DNA and controls cellular activities; mitochondria, often called the "powerhouse of the cell," generate the energy the cell needs through cellular respiration; the cell membrane regulates what enters and leaves the cell; and, in plant cells specifically (but not animal cells), a rigid cell wall provides structural support outside the cell membrane, and chloroplasts, containing the green pigment chlorophyll, enable photosynthesis. This distinction between plant and animal cells — the presence of a cell wall and chloroplasts in plant cells but not in animal cells — is one of the most commonly tested basic biology facts.

Multicellular organisms are organised in a clear hierarchy that exam questions sometimes test directly: cells group together to form tissues (a group of similar cells performing a common function, such as muscle tissue or nervous tissue), tissues combine to form organs (a structure made of different tissues working together for a specific function, such as the heart or the liver), organs work together as organ systems (such as the digestive system or circulatory system, in which several organs cooperate toward a broader physiological goal), and organ systems together constitute a complete organism.

Human Body Systems

The digestive system breaks down the food we eat into simpler nutrients that the body can absorb and use for energy, growth, and repair. Digestion begins in the mouth, where chewing and saliva (containing the enzyme amylase, which begins breaking down starch) start the process; food then travels down the oesophagus to the stomach, where gastric juices, including hydrochloric acid and the enzyme pepsin, break down proteins and where the highly acidic environment also helps kill many ingested pathogens. Partially digested food then moves into the small intestine, the primary site of nutrient absorption into the bloodstream, aided by digestive secretions from the liver (bile, which emulsifies fats) and the pancreas (which produces enzymes that break down carbohydrates, proteins, and fats). Remaining undigested material passes into the large intestine, where water is reabsorbed and the residue is compacted and eventually eliminated as waste.

The circulatory (cardiovascular) system transports blood, and with it oxygen, nutrients, hormones, and waste products, throughout the body. The heart, a muscular pumping organ with four chambers (two atria and two ventricles), drives this circulation: blood returning from the body (low in oxygen) enters the right side of the heart and is pumped to the lungs to pick up oxygen and release carbon dioxide, then returns to the left side of the heart, which pumps this oxygen-rich blood out to the rest of the body through arteries; blood returns to the heart through veins, and this simple distinction — arteries generally carry blood away from the heart while veins generally carry blood back toward it — is a frequently tested basic fact (with the pulmonary artery and pulmonary vein being notable exceptions to the usual oxygenated/deoxygenated pattern, since the pulmonary artery carries deoxygenated blood to the lungs and the pulmonary vein carries oxygenated blood back to the heart). Blood itself is composed of red blood cells (which carry oxygen using the protein haemoglobin), white blood cells (which are central to the body's immune defence against infection), platelets (which are essential for blood clotting), and plasma (the liquid component carrying all of these along with dissolved nutrients, hormones, and waste products).

The respiratory system is responsible for the exchange of oxygen and carbon dioxide between the body and the environment. Air is inhaled through the nose or mouth, travels down the trachea (windpipe), and branches into the bronchi and progressively smaller bronchioles within the lungs, ultimately reaching tiny air sacs called alveoli, where the actual gas exchange happens: oxygen diffuses from inhaled air into the surrounding blood capillaries, while carbon dioxide diffuses in the opposite direction, from the blood into the alveoli, to be exhaled. The large surface area and thin walls of the millions of alveoli in each lung are what make this gas exchange efficient.

The nervous system coordinates and controls the body's activities and consists of the central nervous system (the brain and spinal cord) and the peripheral nervous system (nerves branching throughout the rest of the body). The brain itself has specialised regions, and a few are commonly tested: the cerebrum, the largest part, is responsible for higher functions such as thought, voluntary movement, sensory perception, and language; the cerebellum coordinates balance, posture, and fine motor coordination; and the medulla oblongata, part of the brainstem, regulates essential involuntary functions such as heartbeat, breathing, and blood pressure. Nerve impulses travel through specialised cells called neurons, and the reflex arc — the rapid, involuntary response to a stimulus, such as pulling a hand away instantly from a hot surface, occurring through the spinal cord without needing to wait for the brain to consciously process the danger first — is a commonly tested example illustrating how the nervous system can act with life-protecting speed.

The skeletal and muscular systems provide structural support, protection for internal organs, and enable movement. The adult human skeleton typically contains 206 bones, providing a rigid but living framework, protecting vital organs (the skull protects the brain, the rib cage protects the heart and lungs), and serving, along with bone marrow, as a site for blood cell production. Muscles work in coordination with bones, generally in pairs that pull in opposite directions since muscles can only actively contract (pull) and not push, to produce the wide range of body movements humans are capable of.

The excretory system removes metabolic waste products from the body, with the kidneys playing the central role by filtering blood to remove excess water, salts, and nitrogenous waste products such as urea, producing urine, which is then stored in the bladder before elimination. The kidneys also play an important role in regulating the body's overall water and salt balance and blood pressure, which is why kidney health is closely linked to broader cardiovascular and metabolic health.

The endocrine system, working alongside but distinct from the nervous system, regulates body functions through hormones — chemical messengers released directly into the bloodstream by specialised glands. Commonly tested glands include the pancreas, which produces insulin (a hormone essential for regulating blood sugar levels, whose insufficient production or ineffective use leads to diabetes mellitus); the thyroid gland, which regulates metabolic rate and whose disorders (either underactive or overactive thyroid function) are common and frequently referenced in health-awareness contexts; and the pituitary gland, often called the "master gland" because it regulates the activity of several other endocrine glands throughout the body.

Nutrition, Vitamins, and Deficiency Diseases

A balanced diet provides the body with all essential nutrients in appropriate proportions: carbohydrates and fats, which primarily provide energy; proteins, essential for growth, tissue repair, and the building of enzymes and other essential molecules; and vitamins and minerals, required in small quantities but essential for numerous specific bodily functions, along with adequate water and dietary fibre. Deficiency diseases, caused by inadequate intake of a specific nutrient, are a heavily and reliably tested topic, and candidates should be comfortable with a core list of vitamin deficiencies and their associated conditions. Vitamin A deficiency causes night blindness and, if severe and prolonged, can contribute to more serious eye damage; good dietary sources include carrots, green leafy vegetables, and dairy products. Vitamin B1 (thiamine) deficiency causes beriberi, a condition affecting the nervous and cardiovascular systems. Vitamin B3 (niacin) deficiency causes pellagra, characterised classically by dermatitis, diarrhoea, and dementia. Vitamin C deficiency causes scurvy, characterised by bleeding gums, joint pain, and poor wound healing, and is classically associated with sailors on long voyages who lacked access to fresh fruits and vegetables; citrus fruits like lemons and oranges are well-known rich sources of vitamin C. Vitamin D deficiency causes rickets in children (leading to soft, weakened, and deformed bones) and osteomalacia in adults; vitamin D is unusual among vitamins in that the human body can synthesise it in the skin on exposure to sunlight, in addition to obtaining it from dietary sources. Vitamin K deficiency impairs the blood's ability to clot properly, since vitamin K is essential for producing several clotting factors.

Mineral deficiencies are also commonly tested: iron deficiency causes anaemia, characterised by fatigue and reduced oxygen-carrying capacity of the blood due to insufficient haemoglobin, and is one of the most widespread nutritional deficiencies in India, particularly among women and children, making it a frequent target of government nutrition and welfare schemes. Iodine deficiency causes goitre (an enlargement of the thyroid gland) and, in severe cases during pregnancy and early childhood, can impair physical and mental development, which is why iodised salt was mandated as a public health measure. Calcium deficiency affects bone health and can contribute to conditions such as osteoporosis, particularly in older adults. Protein-energy malnutrition in children can result in two related but distinct severe conditions: kwashiorkor, associated primarily with protein deficiency and characterised by swelling (oedema) despite sometimes adequate calorie intake, and marasmus, associated with an overall severe deficiency of both calories and protein, characterised by extreme wasting. Given that several secretariat-linked posts, particularly ANM and Welfare and Education Assistant roles, deal directly with nutrition monitoring, child health, and welfare scheme implementation, this deficiency-disease list is worth memorising thoroughly rather than only superficially.

Microorganisms and Common Diseases

Microorganisms — bacteria, viruses, fungi, and protozoa — are responsible for a wide range of human diseases, and understanding the basic distinctions between these categories helps with both exam questions and practical health awareness. Bacteria are single-celled prokaryotic organisms; while many bacteria are harmless or even beneficial (such as certain gut bacteria that aid digestion), some cause disease, and bacterial infections are generally treatable with antibiotics, a class of medicine that specifically targets bacterial cell structures or processes and is not effective against viral infections, a distinction that is important both for exam purposes and for general public health awareness about responsible antibiotic use. Viruses are much smaller than bacteria and cannot reproduce independently; they must invade a living host cell and hijack its machinery to replicate, and viral infections are generally managed through antiviral medications, supportive care, or, most effectively at a population level, prevention through vaccination, rather than antibiotics. Fungi and protozoa are also responsible for various human diseases, though generally less prominent in these exam syllabi than bacterial and viral diseases.

A number of commonly tested diseases are worth knowing along with their causative agent and mode of transmission, since exam questions frequently test exactly this pairing. Malaria is caused by Plasmodium parasites (a protozoan) and transmitted through the bite of an infected female Anopheles mosquito; it remains a significant public health concern in parts of India, and prevention focuses on mosquito control (eliminating stagnant water breeding sites, using mosquito nets, and insecticide spraying) alongside prompt diagnosis and treatment. Dengue and chikungunya are viral diseases transmitted by the Aedes mosquito, which characteristically breeds in clean, stagnant water (such as water collected in discarded containers, coolers, or tyres) and typically bites during daytime, a contrast worth remembering against the Anopheles mosquito responsible for malaria, which typically bites at dusk and night. Tuberculosis (TB) is a bacterial disease caused by Mycobacterium tuberculosis, primarily affecting the lungs, and is spread through airborne droplets when an infected person coughs or sneezes; it remains a major public health priority in India, with sustained government programmes aimed at its detection and treatment. Typhoid and cholera are both bacterial diseases transmitted through contaminated food or water, underscoring the importance of safe drinking water and proper sanitation as basic disease-prevention measures. Hepatitis refers to inflammation of the liver and can be caused by several different viruses (commonly designated A, B, C, D, and E), with Hepatitis A and E typically transmitted through contaminated food or water, while Hepatitis B and C are typically transmitted through contact with infected blood or bodily fluids, a distinction that matters for both exam purposes and practical prevention advice.

Vaccination, or immunisation, works by exposing the immune system to a harmless form or component of a pathogen (or, in some modern vaccine technologies, genetic instructions for the body to produce a harmless piece of the pathogen), training the immune system to recognise and mount a rapid, effective defence if it later encounters the actual disease-causing organism, without the person having to suffer the actual disease first. India runs a Universal Immunisation Programme that provides vaccines free of cost against several serious childhood diseases, including tuberculosis (via the BCG vaccine), diphtheria, pertussis (whooping cough), and tetanus (commonly bundled together), poliomyelitis, measles, and hepatitis B, among others, and this programme is one of the largest public health immunisation efforts in the world by the sheer number of children covered annually. India was officially certified polio-free in 2014, a landmark public health achievement resulting from decades of sustained vaccination campaigns, and this fact is frequently tested as a point of public health pride and historical significance. Given that ANM and other health-linked secretariat functionaries are directly involved in immunisation delivery and maternal-child health services at the grassroots level, this area deserves particularly careful attention from candidates preparing for those specific posts, though it is tested broadly across the exam as general knowledge as well.

Hygiene, Sanitation, and Preventive Health

Many of the most impactful public health interventions are not complex medical treatments but simple, consistent hygiene and sanitation practices, and this theme runs strongly through both general science questions and the welfare-scheme knowledge relevant to secretariat posts. Handwashing with soap at key moments — before eating or preparing food, and after using the toilet — is one of the single most effective and low-cost measures for preventing the spread of diarrhoeal diseases and respiratory infections, because it physically removes pathogens before they can be transferred to the mouth, nose, or food. Safe disposal of human waste through proper toilets and sewage systems, rather than open defecation, prevents faecal-oral transmission of disease-causing organisms into drinking water sources and food, which is why sanitation infrastructure has been such a major public health and government policy focus in India in recent decades, closely tied to the Swachh Bharat Mission's broader goals of eliminating open defecation and improving overall cleanliness. Access to safe drinking water — free from contamination by pathogens and harmful chemicals — is similarly foundational, since waterborne diseases such as cholera, typhoid, and various forms of diarrhoeal illness remain significant causes of preventable illness, particularly among young children, in areas lacking reliable safe water access.

Vector control — reducing populations of disease-carrying organisms such as mosquitoes — is another major preventive health theme, since diseases like malaria, dengue, and chikungunya can often be prevented more effectively by eliminating mosquito breeding sites and using protective measures (nets, repellents) than by treating the disease after infection occurs. At the household and community level, simple measures such as ensuring stagnant water does not accumulate in containers, coolers, or discarded items, and covering water storage containers, meaningfully reduce mosquito breeding opportunities.

Basic first aid knowledge is also occasionally tested and is genuinely useful in a secretariat functionary's daily work, given how often such staff are the first responders to minor injuries or medical situations in their community. Key general principles include: for minor cuts and wounds, cleaning the wound and applying pressure to stop bleeding before covering it; for burns, cooling the affected area with clean, cool (not ice-cold) running water rather than applying substances like toothpaste or oil, which can worsen the injury or increase infection risk; for suspected fractures, immobilising the affected area and avoiding unnecessary movement before the person can reach proper medical care; and for choking, methods such as back blows and abdominal thrusts to help dislodge an obstructing object from the airway. Basic awareness of common medical emergencies — recognising the signs of a heart attack (chest pain, shortness of breath), stroke (sudden weakness or numbness, especially on one side of the body, slurred speech, facial drooping), or severe allergic reactions — and the importance of promptly seeking professional medical help rather than delay, is also a practically important and occasionally tested theme, since prompt recognition and referral can be genuinely life-saving.

Everyday Science and Common Sense Applications

Finally, this section of the exam frequently draws on general "everyday science" knowledge that blends biology, chemistry, and physics in practical contexts, and candidates benefit from being comfortable applying basic scientific reasoning to familiar situations rather than only recalling isolated facts. Photosynthesis, the process by which green plants convert carbon dioxide and water into glucose and oxygen using light energy captured by chlorophyll, is fundamental not just as a biology fact but as the basis of virtually all food chains and much of the oxygen in Earth's atmosphere, and its importance extends into environmental science discussions about carbon cycles and climate. Food preservation techniques — refrigeration (slowing microbial growth and enzymatic spoilage by lowering temperature), drying (removing the moisture microorganisms need to grow), salting and sugaring (drawing water out of food and microbial cells through osmosis, inhibiting microbial growth), pasteurisation (brief heating to kill most harmful microorganisms without fully cooking the food, most familiar in the context of milk), and canning (sealing food after heat treatment to prevent recontamination) — are commonly tested applied-science topics that connect basic microbiology to everyday household practice.

Blood groups are another recurring topic: the ABO blood group system classifies human blood into types A, B, AB, and O based on the presence or absence of specific antigens on red blood cells, and the separate Rh factor classifies blood as positive or negative based on the presence or absence of the Rh antigen, together giving the familiar blood group designations such as A positive, O negative, and so on; O negative blood is often referred to as a "universal donor" type because it lacks the antigens that would trigger a reaction in most recipients, while AB positive is often called a "universal recipient" type for the corresponding reason, though real-world blood transfusion practice always requires careful cross-matching regardless of these general compatibility rules.

Understanding this chapter well means treating biology and health science not as an isolated academic subject but as directly practical knowledge — the same knowledge that underlies vaccination drives, nutrition monitoring, sanitation campaigns, and grassroots health services that secretariat functionaries, particularly ANMs and welfare-linked staff, deliver every day. Approach your revision by connecting each fact to its practical relevance: not just what causes a disease, but how it spreads and how it is prevented; not just which vitamin prevents which deficiency, but which foods provide it and why that matters for a government nutrition scheme. This applied, connected approach will serve you well both in the examination hall and in the work that follows it.