Introduction
The subtopic "Biology — human body, diseases, nutrition, genetics" is one of the most frequently tested segments within the Science section of the BPSC (Bihar Public Service Commission) examination. Over the years, a comprehensive pool of 72 actual Previous Year Questions (PYQs) from this area has been compiled, spanning examinations from 2018 through 2025. This rich dataset reveals a consistent emphasis on factual recall, conceptual understanding, and application of fundamental biological principles. The questions range from straightforward definitions (e.g., “Pollination is the transfer of pollen grain from anther to stigma” – tested in BPSC 2022, 2021) to intermediate-level analysis (e.g., “Which part of the alimentary canal receives bile from the liver?” – BPSC 2024) and occasionally to more specialized topics like molecular genetics (“Double helix structure of DNA was discovered by James Watson and Francis Crick” – BPSC 2023) and immunology (“Which class of immunoglobulin is first produced in response to infection? IgM” – BPSC 2025).
The syllabus point for this subtopic is deliberately broad: “Biology — human body, diseases, nutrition, genetics.” However, the PYQs reveal that the Commission does not confine itself to human biology alone; it also tests plant biology (pollination, plant nutrition, gymnosperms, halophytes), ecology (habitat, mutualism, parasitism), microbiology (viruses, bacteria, fungi), and biochemistry (enzymes, hormones, vitamins). Therefore, an aspirant must adopt an integrated approach that covers all major branches of biology at a 10+2 (or introductory undergraduate) level. The difficulty level is moderate to high for some questions, especially those involving matching of sequences (e.g., the correct order of human nutrition steps: Ingestion → Digestion → Absorption → Assimilation → Egestion – BPSC 2023) or those that require distinguishing between similar concepts (e.g., “Apple is not a true fruit” – BPSC 2020).
This chapter is designed to be a comprehensive, self-contained study resource. It will build foundational concepts from first principles, define every piece of jargon, and weave the PYQs into the teaching narrative so that the student can see exactly what has been tested and how. The deep-dive sections will cover human body systems, major diseases, nutrition (macro- and micronutrients, vitamins, minerals), and genetics (from DNA structure to Mendelian inheritance and modern applications). After teaching the content, we will analyse the pattern of PYQs, identify common traps, and provide forward-looking predictions. By the end of this chapter, the student will not only be able to answer the 72 previous questions confidently but also tackle any new question that aligns with the syllabus scope.
Core Concepts & Foundations
Before diving into specific systems and diseases, we must solidify the fundamental units and processes of biology. This foundation is the bedrock upon which all higher-order questions rest.
Cell: The smallest structural and functional unit of all living organisms. It is often called the “building block of life.” Cells can be prokaryotic (lacking a nucleus, e.g., bacteria) or eukaryotic (with a membrane-bound nucleus, e.g., human cells, plant cells). Tested in BPSC 2024 (“What is the structural and functional unit of life? Cell”).
Tissue: A group of similar cells that work together to perform a specific function. Examples include epithelial tissue, connective tissue, muscle tissue, and nervous tissue in humans; and meristematic and permanent tissues in plants.
Organ: A structure composed of two or more tissue types that work together to carry out a particular function. For example, the stomach is an organ containing epithelial, muscle, and nervous tissues.
Organ System: A group of organs that work together to perform a major bodily function. The human body has 11 major systems: integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive.
Homeostasis: The ability of an organism to maintain a stable internal environment despite external changes. The hypothalamus plays a key role in regulating body temperature (tested in BPSC 2018, 2019).
Enzyme: A biological catalyst, almost always a protein, that speeds up chemical reactions in living organisms without being consumed. Most enzymes are proteins (tested in BPSC 2021, 2022). Some RNA molecules (ribozymes) also have catalytic activity, but the classic definition emphasizes protein nature.
Hormone: A chemical messenger secreted by an endocrine gland that travels through the bloodstream to target cells, where it elicits a specific response. Hormones include insulin, thyroxine, estrogen, and adrenaline. Tested with thyroxine containing iodine (BPSC 2019) and female sex hormone estrogen (BPSC 2020).
DNA (Deoxyribonucleic Acid): The hereditary material in all cellular organisms. It is a double-stranded helix composed of nucleotides (adenine, thymine, guanine, cytosine). The double helix structure was elucidated by James Watson and Francis Crick in 1953, building on X-ray crystallography data from Rosalind Franklin and Maurice Wilkins (tested in BPSC 2023). However, the discovery of DNA itself (as a substance) is credited to Friedrich Miescher (1869), not Watson and Crick – a nuance tested in BPSC 2018 where the correct answer to “Who discovered DNA?” was “None of the above/More than one of the above” because the listed choices (Watson & Crick, Mendel, Johannsen, Khorana) were all incorrect.
mRNA (Messenger Ribonucleic Acid): A single-stranded RNA molecule that carries genetic information from DNA in the nucleus to the ribosome in the cytoplasm, where it serves as a template for protein synthesis. Widely discussed during the COVID-19 pandemic (tested in BPSC 2023).
Gene: A segment of DNA that contains the instructions for producing a specific protein or RNA molecule. Genes are the units of heredity.
Allele: An alternative form of a gene. For example, the gene for flower colour may have a “red” allele and a “white” allele.
Genotype: The genetic constitution of an organism (e.g., RR, Rr, rr). Phenotype: The observable physical or biochemical characteristics of an organism (e.g., red flowers, white flowers).
Dominant vs. Recessive: A dominant allele masks the effect of a recessive allele in a heterozygous (Rr) individual. The recessive phenotype is only expressed when the individual is homozygous recessive (rr). This principle is the basis of Mendelian genetics.
Mutation: A change in the DNA sequence. Mutations can be point mutations (change of a single base), insertions, deletions, or larger chromosomal rearrangements. Non-sense codons (e.g., UAA, UAG, UGA) are stop codons that terminate translation – tested in BPSC 2025 (“Which is a non-sense codon? UAA”).
Immunity: The ability of the body to resist infection. It can be innate (non-specific, present from birth) or adaptive (specific, acquired after exposure). Vaccines work by introducing harmless antigens (like a piece of the SARS-CoV-2 spike protein) to stimulate the adaptive immune response (tested in BPSC 2023). Immunoglobulins (antibodies) are produced by B lymphocytes. IgM is the first antibody class produced during a primary infection (tested in BPSC 2025). Lymphocytes form in bone marrow (tested in BPSC 2019).
Symbiosis: A close, long-term interaction between two different biological species. It can be mutualism (both benefit, e.g., algae and fungi in lichen – tested in BPSC 2019), commensalism (one benefits, the other unaffected), or parasitism (one benefits, the other harmed, e.g., herpes simplex virus and human – tested in BPSC 2025).
Habitat: The natural environment where an organism lives (tested in BPSC 2019: “The actual location or place where an organism lives is called habitat”).
These core concepts are the building blocks. Every deeper topic – from digestion to genetics – will reference them.