Reference guide and use of this edition
What the references support
The lessons, numerical scenarios, explanations and diagrams in this guide were written for this edition. External sources were used to check scientific facts, terminology and topic scope. Their presence here does not mean they endorse this guide. This book does not reproduce external textbook exercises or artwork. Chapter questions draw on the local Pareeksha-authored science inventory with editorial corrections and original replacements. The accompanying source register records the factual references and editorial checks.
Use the following references to resolve a definition or revisit a mechanism. They are not substitutes for attempting the exercises. Scientific terms can have a broader technical definition than the simplified model used in an introductory examination. Where a problem states assumptions, solve within those assumptions and identify their limits. A numerical classroom example is not automatically a measured value for a real person, place or apparatus.
Physics and measurement
NIST, SI derived units: https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-4-two-classes-si-units-and-si-prefixes . Consult this for relationships between base and derived units. Distinguish a physical quantity from its unit: energy is the quantity and joule is an SI unit used to express it.
NIST, temperature: https://www.nist.gov/pml/owm/si-units-temperature . This supports the Celsius–kelvin relationship. A change of one degree Celsius equals a change of one kelvin, but their zero points differ. Temperature differences and absolute readings therefore require different care during conversion.
NIST, electric current: https://www.nist.gov/pml/owm/si-units-electric-current . Use the unit relationships when checking current, charge, potential difference and resistance. A result should have the requested dimensions before its numerical value is trusted.
IAEA, Radiation, People and the Environment: https://www.iaea.org/sites/default/files/radiation0204.pdf . The reference provides radiation context. This guide uses stable introductory distinctions between radiation types, without turning them into handling instructions or personal exposure guidance.
Chemistry
IUPAC periodic table: https://iupac.org/what-we-do/periodic-table-of-elements/ . This is a reference for element symbols and atomic-number arrangement. Relative atomic masses and mass numbers are different quantities; an isotope calculation should use the numbers and isotope definition supplied in the question.
IUPAC Gold Book, electronegativity: https://goldbook.iupac.org/terms/view/E01990 . Compare this term with electron affinity and ionisation energy rather than treating all three as one tendency. The chemical environment and definition determine which comparison is being made.
IUPAC Gold Book, electron affinity: https://goldbook.iupac.org/terms/view/E01977 . The sign convention and the stated process matter when discussing energy changes. Follow the question's convention and do not substitute electronegativity merely because both terms involve electrons.
IUPAC Gold Book, ionisation energy: https://goldbook.iupac.org/terms/view/I03199 . This reference helps distinguish removal of an electron from the separate process of accepting an electron. Successive ionisations refer to different charged species and need not require similar energies.
US EPA, dissolved oxygen: https://www.epa.gov/caddis/dissolved-oxygen . This supports the distinction between oxygen present in water and processes that consume it. A dissolved-oxygen measurement and a biochemical oxygen-demand measurement answer different questions.
US EPA, particulate matter: https://www.epa.gov/pm-pollution/particulate-matter-pm-basics . Use this for particulate-size terminology. A particle-size category does not specify one chemical composition, and a concentration measurement is different from the total amount emitted.
Cells, plants and heredity
NCERT textbook catalogue: https://ncert.nic.in/textbook.php . School-level topic coverage provides a useful foundation for science preparation. This guide's questions and examples are original; the catalogue is a reference route, not a claim that a particular recruitment examination follows one textbook word for word.
NHGRI, chromosomes: https://www.genome.gov/about-genomics/fact-sheets/Chromosomes-Fact-Sheet . Read this alongside the chromosome-counting diagram. Replication changes DNA quantity, while the chromosome-count convention depends on centromeres and the stage specified.
NHGRI, meiosis: https://www.genome.gov/genetics-glossary/Meiosis . The chromosome-set reduction is central to the human gamete comparison. Plant life cycles require attention to the difference between spores, gametes and generations rather than copying every human-reproduction statement unchanged.
NHGRI, dominance: https://www.genome.gov/genetics-glossary/Dominant-Traits-and-Alleles . Dominance describes expression in a genetic context. It does not by itself describe how frequent an allele is in a population or whether its effect is advantageous.
NHGRI, codominance: https://www.genome.gov/genetics-glossary/Codominance . Compare codominance with complete dominance and incomplete dominance. The expected phenotype ratio depends on the expression rule given in the problem, even when the genotype combinations have the same 1:2:1 pattern.
Human physiology and public health
NIDDK, digestive system: https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works . This provides organ–function context for digestion and absorption. Production, storage, secretion, absorption and assimilation are separate verbs and often require different answers.
NHLBI, blood flow: https://www.nhlbi.nih.gov/health/heart/blood-flow . Trace the two connected circuits and identify vessels by direction relative to the heart. Oxygen content is a separate property and does not define the words artery and vein.
NHLBI, respiratory system: https://www.nhlbi.nih.gov/health/lungs/respiratory-system . This supports the distinction between conducting airways and gas-exchange structures. Ventilation, diffusion and cellular respiration are connected processes with different meanings.
NIDDK, kidneys: https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work . Use this to review filtration and tubular adjustment. Final urine composition cannot be inferred from filtration alone because reabsorption and secretion also contribute.
NIDDK, diabetes insipidus: https://www.niddk.nih.gov/health-information/kidney-disease/diabetes-insipidus . The factual use here is vasopressin and water regulation, including the distinction between hormone production and release. No personal diagnosis or treatment schedule is supplied by this book.
WHO, vaccines: https://www.who.int/news-room/feature-stories/detail/how-do-vaccines-work . This supports antigen recognition and immune memory. Vaccine schedules and product-specific recommendations are date-sensitive and should be checked against the relevant current official programme.
WHO, antimicrobial resistance: https://www.who.int/news-room/fact-sheets/detail/antimicrobial-resistance . Distinguish antibiotic resistance from the wider antimicrobial category. Resistance concerns microorganisms and their response to medicines; it is not a claim that a person's body becomes a resistant microbe.
CDC, ringworm: https://www.cdc.gov/ringworm/about/ . The factual association used here is fungal cause. A common name can be misleading, so classify a pathogen from established biology rather than from one word in the illness name.
CDC, tuberculosis: https://www.cdc.gov/tb/causes/index.html . The reference supports bacterial cause and airborne transmission. Matching a disease with a pathogen in an examination is different from diagnosing a person from symptoms.
Biotechnology and ecological reasoning
NHGRI, PCR: https://www.genome.gov/about-genomics/fact-sheets/Polymerase-Chain-Reaction-Fact-Sheet . This supports the amplification concept. Ideal doubling exercises are mathematical models; a real reaction's efficiency and controls determine how results should be interpreted.
NIST, DNA mixture interpretation: https://www.nist.gov/publications/dna-mixture-interpretation-nist-scientific-foundation-review . This provides context for distinguishing evidence about a biological source from claims about the activity that deposited material. A profile comparison must be interpreted with its uncertainty and case context.
NCERT, ecosystem: https://ncert.nic.in/textbook/pdf/lebo112.pdf . This provides introductory context for productivity and trophic relationships. In calculations, retain time and area units where supplied, distinguish a standing stock from a flow, and use transfer efficiencies stated in the question.
Recruitment and currency
This is a subject guide, not an official recruitment notification. Chapter lengths and practice counts represent an editorial study plan. Check the applicable Andhra Pradesh State Level Police Recruitment Board notice for the post, examination stage, paper structure, language rules and syllabus. No chapter allocation in this guide should be read as a promise of official question weight.
Reference checks for this edition were recorded on 30 September–1 October 2026. Stable scientific concepts and invented practice data should be distinguished from dated policy, law, programme, observance or current-affairs facts. Recheck dated facts against the relevant official source when using this edition for a later examination.