Human biology facts for prelims: physiology, vitamins, diseases and cells

Human biology is the highest-yield static topic in prelims science. The questions repeat a small set of facts: how the heart and lungs work, which vitamin prevents which disease, how much of each mineral an adult needs, which pathogen causes which disease, and how cells divide. This article collects those facts, with mineral intakes taken from the 2020 ICMR-NIN recommended dietary allowances for adults.

Human physiology: the numbers that matter

Cardiac output is the volume of blood the heart pumps in one minute, and it equals stroke volume multiplied by heart rate. At rest an adult heart beats about 72 times a minute and pumps roughly 5 litres of blood per minute.

A healthy adult breathes about 12 to 16 times a minute at rest. Blood pressure is written as systolic over diastolic, and 120/80 mmHg is taken as normal.

Human blood groups are A, B, AB and O. Group O is the universal donor because its red cells carry no A or B antigen, and group AB is the universal recipient because its plasma carries no anti-A or anti-B antibody.

Red blood cells live for about 120 days, carry oxygen on haemoglobin, and are made in the bone marrow. Platelets help blood to clot, and white blood cells defend the body against infection.

Asked in SSC CGL 2026

Vitamins and minerals

Vitamin C and the B vitamins dissolve in water and must be taken regularly, while vitamins A, D, E and K dissolve in fat and can be stored in the body.

These are the 2020 ICMR-NIN recommended dietary allowances for adults. Older books quote much lower figures, for example 600 mg of calcium, which the 2020 revision replaced.

Asked in RRB NTPC

Diseases: pathogen, carrier and cure

A vaccine trains the immune system by exposing it to a weakened or killed pathogen, or to a part of one, so that the body can respond quickly when the real pathogen arrives. Smallpox was eradicated by vaccination in 1980, and India was declared polio-free in 2014.

Antibodies are proteins made by white blood cells that recognise and neutralise specific pathogens. The antibody titre is a measure of how much antibody is present in the blood.

Cells, chromosomes and genes

The cell is the basic unit of life. The nucleus controls the cell, mitochondria release energy from food, ribosomes make proteins, and the cell membrane controls what enters and leaves.

Human body cells carry 46 chromosomes in 23 pairs, one set from each parent. DNA, the double helix described by Watson and Crick in 1953, carries the instructions for building and running the body, and a gene is a segment of DNA that codes for a specific trait.

Cell division by mitosis doubles the number of cells at each step: one cell becomes two, then four, then eight. Meiosis, the division that makes gametes, halves the chromosome number so that fertilisation restores it.

Asked in SSC CGL 2026

Nutrition and food

Food gives energy in three forms: carbohydrate and protein each give about 4 kilocalories per gram, and fat gives about 9 kilocalories per gram. A balanced diet supplies all three, with vitamins, minerals, roughage and water.

Protein-rich algae such as Spirulina and Chlorella are used as food supplements because they pack a high share of protein into a small mass. Pulses, milk, eggs and soy are the everyday protein sources in an Indian diet.

The human genome carries about 3 billion base pairs and roughly 20,000 protein-coding genes. The Human Genome Project, completed in 2003, mapped this sequence and opened the way to precision medicine.

A biofilm is a community of microbes that sticks to a surface and protects itself with a slimy layer. Biofilms form on teeth as plaque, on medical implants and in water pipes, and they make infections harder to treat because drugs reach the microbes inside more slowly.

Prelims practice