Biology — Human Physiology, Health, Diseases and Nutrition

Introduction

Biology, as a science subject in the CGPSC Paper 1 syllabus, spans a wide canvas that includes the fundamental mechanisms of life — how the human body functions, how it fights disease, how nutrients sustain it, and how plants and microorganisms interact with human health and agriculture. The subtopic "Biology — human physiology, health, diseases and nutrition" sits at the crossroads of pure science and applied knowledge, making it one of the most practically relevant sections for aspirants.

This subtopic has generated 11 questions across the CGPSC examinations from 2019 through 2024, appearing in every single year of that window. That consistent presence — six consecutive years with questions — signals that the examiners regard this area as a permanent and non-negotiable component of the paper. The frequency is among the highest in the Science section, placing it on par with Physics and Chemistry clusters. An aspirant who masters this chapter comprehensively is virtually guaranteed to correctly answer two or three questions in any given year's paper.

The scope of what has actually been tested reveals the examiners' intellectual priorities. Questions from this subtopic have probed plant physiology (stomata, photosynthesis, transpiration), cellular biology (chromosomes, glucose breakdown, anaerobic respiration), nutrition science (macro- and micronutrients, vitamin deficiency diseases), microbiology and infectious disease (viruses, vaccine dosages, rice blast disease), and the misuse of hormones in agriculture. That breadth means aspirants cannot safely "focus" on only one narrow area — the examiner draws from the full palette.

There is also a Chhattisgarh-specific dimension to appreciate. Chhattisgarh is India's "rice bowl" — the state grows paddy on millions of hectares and rice blast disease (caused by the fungus Magnaporthe oryzae) is a direct threat to its agricultural economy. A CGPSC question on rice blast disease is not academic curiosity; it tests whether an aspirant understands the diseases that threaten the state's food security. Similarly, questions on biofertilizers (Rhizobium, Azolla, blue-green algae) are deeply relevant to Chhattisgarh's push for organic and sustainable farming, given that large areas under tribal cultivation still rely on traditional and low-input agriculture.

Nutritional diseases matter enormously in the CG context as well. The state has historically high rates of malnutrition, anaemia, and vitamin deficiency diseases, particularly in tribal and rural districts. Scurvy (Vitamin C deficiency), night blindness (Vitamin A deficiency), and anaemia (iron deficiency) are public health problems that state government schemes actively address. When CGPSC asks about scurvy and Vitamin C (tested in 2023), it is simultaneously testing science knowledge and policy awareness.

The difficulty level of questions from this subtopic ranges from direct recall (Vitamin C → Scurvy; Covishield dose = 0.5 ml) to multi-statement evaluation (all three statements about stomata; statements about glucose breakdown). The multi-statement format is a favourite device because it requires not just knowing the main fact, but being able to precisely identify which supporting facts are true or false. This chapter teaches all the building blocks needed to handle both straightforward and composite question formats.

The note is structured to move from the foundational concepts outward into progressively richer territory: core definitions first, then plant physiology, then human physiology and cellular respiration, then nutrition and deficiency diseases, then infectious diseases and vaccines, then the worked examples drawn from actual PYQs, and finally the predictive and revision material.

Core Concepts & Foundations

Before diving into any specific system of biology, every aspirant must be comfortable with the vocabulary and conceptual scaffolding. Biology is a terminology-heavy discipline, and imprecise understanding of a single term can cause a cascade of errors on multi-statement questions.

Cell: The fundamental structural and functional unit of all living organisms. Every physiological process — digestion, respiration, immunity, hormone signalling — ultimately takes place at the cellular level.

Nucleus: The membrane-bound organelle within a eukaryotic cell that houses the genetic material (DNA organised into chromosomes). It is the control centre of the cell, directing protein synthesis and cell division.

Chromosome: A thread-like structure made of DNA and protein found inside the nucleus. Each chromosome carries genes in a linear sequence. The chromosome number is a fixed, species-specific constant — a cornerstone of genetics. Humans have 46 chromosomes (23 pairs); the constant chromosome number per species was tested directly in CGPSC 2019.

Gene: A specific sequence of DNA that codes for a functional product, usually a protein. Genes determine inherited traits.

Photosynthesis: The biochemical process by which green plants, algae, and some bacteria convert light energy into chemical energy (glucose), using carbon dioxide and water, releasing oxygen as a by-product. It is the foundational energy capture process for almost all life on Earth.

Respiration: The biochemical process by which cells break down glucose (or other organic molecules) to release energy in the form of ATP (adenosine triphosphate). Respiration can be aerobic (using oxygen) or anaerobic (without oxygen).

ATP (Adenosine Triphosphate): The universal energy currency of cells. Energy released from glucose breakdown is captured in the phosphate bonds of ATP and spent when those bonds are broken.

Stomata (singular: stoma): Microscopic pores found mainly in the epidermis of leaves (and sometimes stems). Each pore is flanked by two guard cells that regulate its opening and closing. Stomata serve three linked functions: gas exchange (CO₂ in, O₂ out during photosynthesis; O₂ in, CO₂ out during respiration), water vapour release (transpiration), and uptake of atmospheric CO₂ for photosynthesis.

Transpiration: The process by which water is lost from the aerial parts of a plant as water vapour, primarily through stomata. It creates a tension that pulls water upward from roots — the transpiration pull — and also cools the plant.

Guard Cells: Specialised kidney-shaped (or dumbbell-shaped in grasses) epidermal cells that flank each stoma. Their turgor pressure controls stomatal opening: when guard cells absorb water, they swell and curve, opening the pore; when they lose water, they collapse and close it.

Hormone: A chemical messenger produced in one tissue and transported (usually via blood in animals, or vascular tissue in plants) to target tissues, where it regulates specific physiological processes.

Virus: An acellular infectious agent composed of a nucleic acid genome (either DNA or RNA, never both simultaneously) enclosed in a protein coat called a capsid. Viruses are not considered alive by many definitions because they lack independent metabolism and must hijack host cell machinery to replicate.

Vaccine: A biological preparation that stimulates an individual's immune system to recognise and combat a specific pathogen, providing immunity without causing the disease itself.

Nutrient: A substance that an organism requires for energy, growth, and the maintenance of vital processes. Nutrients are classified as macronutrients (required in large quantities) and micronutrients (required in trace amounts).

Deficiency Disease: A disease caused by the absence or insufficient supply of one or more essential nutrients. Examples include scurvy (Vitamin C deficiency), rickets (Vitamin D deficiency), and anaemia (iron or Vitamin B12 deficiency).

Biofertilizer: A substance that contains living microorganisms which, when applied to seeds, plant surfaces, or soil, colonise the rhizosphere or the interior of the plant and promote growth by increasing the supply of primary nutrients to the host plant.

Chromosome Number Constancy: One of the most important principles of genetics — the number of chromosomes in somatic (body) cells of any given species is fixed and constant for that species, regardless of age, sex, weight, or environmental conditions. This constancy is maintained by mitotic cell division.

The Cell: Structural Overview

A typical animal cell contains a plasma membrane enclosing cytoplasm with embedded organelles: nucleus (genetic control), mitochondria (ATP generation via aerobic respiration), ribosomes (protein synthesis), endoplasmic reticulum (transport network), and Golgi apparatus (packaging and secretion). The plasma membrane is a phospholipid bilayer with embedded proteins that regulate which substances enter and exit the cell — this selective permeability is fundamental to all physiological processes.

A typical plant cell differs in possessing a rigid cellulose cell wall outside the plasma membrane, a large central vacuole for turgor and storage, and chloroplasts — the organelles where photosynthesis occurs. The double membrane of chloroplasts encloses a fluid matrix (stroma) and internal membranous sacs called thylakoids; light-dependent reactions occur on thylakoid membranes, and the Calvin Cycle (carbon fixation) occurs in the stroma.

The comparison between animal and plant cells is a common examination topic:

Prokaryotic vs. Eukaryotic Cells

A foundational distinction that underpins the entire tree of life:

Prokaryotes (bacteria, cyanobacteria/blue-green algae): no membrane-bound nucleus; genetic material as a nucleoid region; no membrane-bound organelles; generally smaller (1–10 µm); divide by binary fission.

Eukaryotes (animals, plants, fungi, protists): true membrane-bound nucleus; membrane-bound organelles; generally larger (10–100 µm); divide by mitosis or meiosis.

Cyanobacteria — one of the key biofertilizers — are prokaryotes. They lack a nucleus but still possess the molecular machinery for nitrogen fixation and photosynthesis. This is an important nuance: "blue-green algae" is a common name, but they are not true algae (which are eukaryotic). They are prokaryotic bacteria capable of photosynthesis.

The Immune System: Basic Concepts

Since "health and diseases" is explicitly part of the subtopic, aspirants need a working understanding of how the human body fights pathogens.

Immunity: The ability of an organism to resist infection and disease. It operates through two broad arms: innate (non-specific, immediate) and adaptive (specific, memory-based).

Antigen: Any molecule — usually a protein on the surface of a pathogen — that the immune system recognises as foreign and mounts a response against.

Antibody: A Y-shaped protein (immunoglobulin) produced by B lymphocytes (B cells) in response to a specific antigen. Each antibody binds specifically to the antigen that triggered its production, neutralising or flagging the pathogen for destruction.

Lymphocytes: White blood cells (a type of leukocyte) that are the central players in adaptive immunity. B cells produce antibodies (humoral immunity); T cells directly kill infected cells or coordinate the immune response (cell-mediated immunity).

Vaccination works by introducing a harmless form of an antigen (killed pathogen, attenuated pathogen, protein subunit, or — as with Covishield — a viral vector carrying the antigen gene) to train the immune system to produce memory cells. When the real pathogen arrives, the memory response is fast and strong, preventing disease.

Classification of Nutrients: Macro vs. Micro

For plants, nutrients are divided based on the quantity required:

Macronutrients are needed in relatively large amounts and include: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulphur (S). Potassium is a macronutrient — this was directly tested in CGPSC 2020, where aspirants had to distinguish potassium from micronutrients like zinc, boron, and chlorine.

Micronutrients (trace elements) are required in tiny amounts but are still essential: iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), molybdenum (Mo), chlorine (Cl), and nickel (Ni).

A common exam trap is placing potassium (K) or calcium (Ca) — clearly macronutrients — alongside micronutrients and testing whether the aspirant knows the difference.