Biology Revision

Cell structure and organization

Cell theory states that all living organisms are composed of cells, the cell is the structural and functional unit of life, and all cells…

Chemical and Physical Basis of Life

Water's unique life-supporting properties derive from polarity and extensive hydrogen bonding: high specific heat capacity, high heat of…

Mendel's experiments

Gregor Mendel established classical genetics using true-breeding garden pea plants (Pisum sativum) studying seven discrete pairs of…

Non-Mendelian genetics

Incomplete dominance (Intermediate inheritance): Heterozygote displays an intermediate phenotype between the two homozygotes (e.g.,…

Evolution and gene frequencies

Microevolution is defined as a change in allele frequencies in a population's gene pool over successive generations.

Structure and function of genetic materials

DNA secondary structure: Double-stranded, antiparallel polynucleotide chains (5' to 3' opposite 3' to 5') forming a right-handed double…

Genes and gene expression

Central Dogma of Molecular Biology: Genetic information flows unidirectional from DNA (replication) to mRNA (transcription) to polypeptide…

Molecular basis of mutations

A mutation is a permanent, heritable alteration in the nucleotide sequence of an organism's genome.

Gene technology tools and methods

Recombinant DNA technology involves isolating, cutting, joining, and transferring genes into host organisms using molecular tools.

Applications of gene technology

Medical applications: Production of recombinant human insulin (Humulin), human growth hormone, monoclonal antibodies, subunit vaccines, and…

Diversity of organisms

The three-domain classification system (Woese): Domain Bacteria, Domain Archaea, and Domain Eukarya based on rRNA sequence analysis and…

Diversity of microorganisms

Microorganisms comprise diverse microscopic cellular (bacteria, archaea, fungi, protozoa, microalgae) and acellular biological entities…

Basic microbiology techniques

Sterilization eliminates all forms of microbial life including bacterial endospores: Heat sterilization (autoclaving: moist heat at 121°C,…

Resource acquisition and transport in plants

Water potential (Ψw) is the free energy of water per unit volume, determined by solute potential (Ψs) and pressure potential (Ψp): Ψw = Ψs…

Plant reproduction

Angiosperms exhibit alternation of generations with a dominant diploid sporophyte (2n) and a reduced microscopic haploid gametophyte (n)…

Plant responses to signals

Plant hormones (phytohormones) are organic regulators synthesized in low concentrations that coordinate growth, development, and…

Nervous coordination overview

Coordination is the integration of diverse bodily activities to respond effectively to internal and external stimuli, mediated by two…

Human nervous system structure

The human nervous system is divided anatomically into the Central Nervous System (CNS: Brain and Spinal Cord) and the Peripheral Nervous…

Nerve impulse generation and transmission

Resting Membrane Potential (-70 mV): Maintained by the active Na+/K+ ATPase pump (pumping 3 Na+ out for every 2 K+ in) and differential…

Nervous system disorders

Alzheimer's Disease is a progressive neurodegenerative disorder marked by memory loss, cognitive decline, and personality changes,…

Sensory structures

Sensory receptors are specialized cells or modified dendritic endings that convert environmental stimuli into electrical receptor…

Eye and ear structure and function

Eye tunic architecture: Outer fibrous tunic (opaque sclera and transparent cornea), middle vascular tunic (choroid, ciliary body, and…

Immunity

Immunity is the body's defense against infectious pathogens and foreign substances, categorized into non-specific Innate Immunity and…

Endocrine system

The endocrine system consists of ductless glands that secrete chemical messengers (hormones) directly into the bloodstream to act on target…

Homeostasis

Homeostasis is the physiological maintenance of a dynamic, steady internal environment (extracellular fluid: interstitial fluid and plasma)…

Types of reproduction in animals

Reproduction is the biological process by which new individual organisms are produced, classified broadly into Asexual and Sexual…

Male reproductive system

The male reproductive system consists of primary sex organs (paired testes) and accessory structures: epididymides, vas deferens,…

Female reproductive system

The female reproductive system consists of paired ovaries, Fallopian tubes (oviducts), uterus, vagina, and external genitalia (vulva: labia…

Fertilization to birth

Fertilization begins with capacitation of sperm in female tract, followed by Acrosome reaction releasing enzymes (hyaluronidase, acrosin)…

Reproductive health

Reproductive health encompasses complete physical, mental, and social well-being in all matters relating to the reproductive system, not…

Skeletal systems and movement

Supporting systems in animals provide mechanical body support, maintain shape, protect vital organs, and serve as rigid anchor points for…

Axial skeleton

The human axial skeleton consists of 80 bones organized along the central vertical longitudinal axis: the Skull (22 bones: 8 cranial + 14…

Appendicular skeleton

The human appendicular skeleton consists of 126 bones organized into the Pectoral (Shoulder) Girdles, Upper Limbs, Pelvic (Hip) Girdle, and…

Joints and muscle movement

Joints (articulations) are junctions between bones classified structurally by binding material: Fibrous joints (immovable / synarthroses,…

Ecosystem components

An ecosystem is a dynamic functional community comprising living biotic components interacting with their physical abiotic environment…

Ecosystem processes

The two foundational processes sustaining all ecosystems are unidirectional Energy Flow (governed by the laws of thermodynamics) and…

World biomes

A biome is a vast, macro-scale terrestrial or aquatic ecological region characterized by distinct climactic patterns, soil types, and…

Ecosystems of Sri Lanka

Sri Lanka, despite its compact territorial size (65,610 km²), exhibits exceptional ecosystem diversity driven by topographic elevation…

Biodiversity and threats

Biodiversity (biological diversity) is the variety of life on Earth across three hierarchical levels: Genetic Diversity (allelic variation…

Global environmental problems

Enhanced Greenhouse Effect and Anthropogenic Global Warming: Greenhouse gases (CO2 from fossil fuel combustion/deforestation, CH4 from…

Biodiversity and environmental conservation

Biodiversity conservation strategies are broadly classified into In-situ (on-site conservation within natural ecosystems) and Ex-situ…

Microorganisms as pathogens

Infectious diseases are caused by transmissible biological pathogens (viruses, bacteria, fungi, protozoa, helminths) capable of colonizing…

Microbial control methods

Microbial control aims to prevent infection, food spoilage, and contamination through physical, chemical, and antimicrobial pharmacological…

Use of microorganisms in industry and agriculture

Microorganisms are exploited across diverse industrial, agricultural, and environmental biotechnology applications due to their immense…

Soil microorganisms and soil health

Soil health is the sustained capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans, maintained…

Microbiology in water and waste management

Potable water must be free of pathogenic microorganisms, hazardous chemicals, and turbidity; municipal water purification follows…

Recycling of solid wastes

Solid waste management constitutes a major global environmental and public health imperative, governed by the Waste Hierarchy framework:…

Microbes and food spoilage

Food spoilage is the sensory, biochemical, and nutritional deterioration of food rendering it unpalatable or unsafe for human consumption,…

Ornamental fish culture

Ornamental aquaculture (floriculture / aquarium fish culture) is a high-value export sector in Sri Lanka, generating foreign exchange and…

Horticultural practices

Horticulture is the intensive branch of agriculture focused on the art, science, technology, and commercial cultivation of fruits,…

Vector-borne diseases

Vector-borne diseases are human illnesses caused by parasites, viruses, and bacteria transmitted primarily by hematophagous arthropod…

Food preservation and postharvest losses

Postharvest losses refer to the measurable quantitative and qualitative degradation of agricultural foodstuffs occurring along the supply…

Emerging biotechnologies

Emerging biotechnologies are revolutionizing medicine, agriculture, forensics, and industrial environmental sustainability through…