Biology
SPM · 112 topics available
Form 4
Chapter 1 · Introduction to Biology and Laboratory Rules
Biological Field and Career
Biology is a wide science with many specialised fields, and each field opens the door to different careers that help society.
OpenSafety and Rules in Biological Laboratory
A biology laboratory contains chemicals, glassware, heat and living specimens, so clear safety rules protect both people and equipment.
OpenCommunication in Biology
Scientists must share findings clearly, so biology uses reports, tables, graphs and diagrams that anyone can read and check.
OpenScientific Investigation in Biology
Biologists answer questions through a step-by-step scientific investigation that tests a hypothesis with a fair, controlled experiment.
OpenChapter 2 · Cell Biology and Cell Organisation
Cell Structure and Cell Function
The cell is the basic unit of life, and its organelles each carry out a special job that keeps the cell alive.
OpenLiving Processes in Unicellular Organisms
A unicellular organism carries out every life process inside its single cell, without any specialised organs.
OpenLiving Processes of Multicellular Organisms
In a multicellular organism, cells specialise and work together, so the body needs transport and gaseous-exchange systems to serve every cell.
OpenLevels of Organisation
In multicellular organisms, cells are organised into tissues, organs and systems that build up the whole organism.
OpenChapter 3 · Movement of Substances Across the Plasma Membrane
Structure of Plasma Membrane
How the fluid mosaic model describes the phospholipid bilayer and its proteins.
OpenConcept of Movement of Substances Across a Plasma Membrane
Diffusion, osmosis and active transport: the concepts behind moving substances across the membrane.
OpenMovement of Substances Across a Plasma Membrane in Living Organisms
How diffusion, osmosis and active transport work at exchange surfaces in animals and plants.
OpenMovement of Substances Across a Plasma Membrane and Its Application in Daily Life
How osmosis and diffusion explain food preservation, cooking, dialysis and rehydration.
OpenChapter 4 · Chemical Composition in a Cell
Water
The polar structure of water and why its properties make it essential to living cells.
OpenCarbohydrates
Monosaccharides, disaccharides and polysaccharides, and how to test for sugars and starch.
OpenProteins
Amino acids, peptide bonds, the link between shape and function, and denaturation.
OpenLipids
The structure of triglycerides and phospholipids, saturated vs unsaturated fats, and the emulsion test.
OpenNucleic Acids
Nucleotides, the structure of DNA and RNA, and complementary base pairing.
OpenChapter 5 · Metabolism and Enzymes
Metabolism
Every living cell is a busy chemical workshop. Metabolism is the whole collection of chemical reactions that keep a cell alive, from building new molecules to breaking food down for energy.
OpenEnzymes
Enzymes are the tiny protein machines that make life fast enough to work. Without them, the reactions your cells depend on would take far too long at body temperature.
OpenApplications of Enzymes in Daily Life
From the detergent that lifts stains to the cheese on your sandwich, enzymes quietly do useful work in homes and factories every day.
OpenChapter 6 · Cell Division
Cell Division
A single fertilised egg becomes a whole human body made of trillions of cells. That growth, and the daily replacement of worn-out cells, all depend on cell division.
OpenCell Cycle and Mitosis
Growing cells follow a strict schedule: grow, copy their DNA, then split neatly in two. This ordered routine is the cell cycle, and its dividing stage is mitosis.
OpenMeiosis
Sexual reproduction needs sex cells with only half the usual chromosomes. Meiosis is the special division that makes them and, at the same time, mixes the genes to create variation.
OpenChapter 7 · Cellular Respiration
Production of Energy through Cell Respiration
Food stores chemical energy, but cells cannot use it directly. Cell respiration is the process that unlocks that energy and packages it into ATP, the usable energy currency of the cell.
OpenAerobic Respiration
When oxygen is plentiful, cells extract almost all the energy locked in glucose. This is aerobic respiration, the most efficient way your body releases energy.
OpenFermentation
When oxygen runs short, cells switch to a backup plan. Fermentation keeps energy flowing without oxygen — and it is the same process that makes bread rise and turns sugar into alcohol.
OpenChapter 8 · Respiratory System in Humans and Animals
Types of Respiratory System
All living things need to exchange gases with their surroundings. Different organisms use different respiratory structures suited to their size and habitat.
OpenMechanisms of Breathing
Breathing moves air in and out of the lungs. It depends on muscles that change the volume, and therefore the pressure, of the chest cavity.
OpenGaseous Exchange in Humans
After air reaches the lungs, oxygen and carbon dioxide are swapped between the air sacs and the blood. This exchange happens by diffusion across very thin surfaces.
OpenHealth Issues Related to the Human Respiratory System
Smoking, air pollution and infections can damage the respiratory system. Knowing the causes and effects helps us protect our lungs.
OpenChapter 9 · Nutrition and the Human Digestive System
Digestive System
An overview of the human digestive system: the alimentary canal, the accessory organs and the five main processes of nutrition.
OpenDigestion
How food is broken down physically and chemically along the gut, and which enzymes act on carbohydrates, proteins and fats.
OpenAbsorption
How digested nutrients pass from the small intestine into the blood and lymph, and the adaptations of the villi that make absorption efficient.
OpenAssimilation
How body cells use absorbed nutrients for energy, growth and storage, and the central role of the liver.
OpenDefaecation
How the body removes undigested and indigestible material as faeces, and why defaecation is not the same as excretion.
OpenBalanced Diet
The classes of food a balanced diet must contain, and the factors that change how much energy and nutrients a person needs.
OpenHealth Issues Related to the Digestive System and Eating Habits
Common disorders of the digestive system, how poor eating habits cause them, and habits that keep the gut healthy.
OpenChapter 10 · Transport in Humans and Animals
Types of Circulatory System
How animals move materials around the body depends on their size and complexity. This subtopic compares transport by diffusion, open and closed circulatory systems, and single versus double circulation.
OpenCirculatory System of Humans
The human circulatory system is a closed, double circulation built from the heart, blood vessels and blood. This subtopic traces the route of blood and compares the structure of arteries, veins and capillaries.
OpenMechanism of Heartbeat
The heart beats on its own, driven by an electrical pacemaker and coordinated by valves that keep blood flowing one way. This subtopic explains the cardiac cycle and how heart rate is controlled.
OpenMechanism of Blood Clotting
When a blood vessel is cut, the body seals it quickly with a clot. This subtopic follows the chain of reactions from platelets to the fibrin mesh, and why clotting matters for health.
OpenBlood Group of Humans
Human blood is classified into groups by the antigens on red blood cells. This subtopic explains the ABO system, why some transfusions clump the blood, and the meaning of universal donor and recipient.
OpenHealth Issues Related to The Blood Circulatory System of Humans
Diseases of the heart and blood vessels are among the leading causes of death worldwide. This subtopic looks at atherosclerosis, hypertension, heart attack, stroke and anaemia, and how lifestyle affects them.
OpenLymphatic System
The lymphatic system works alongside the blood to drain excess tissue fluid, absorb fats and fight infection. This subtopic explains how tissue fluid forms and how lymph returns to the blood.
OpenHealth Issues Related to The Lymphatic System of Humans
When lymph cannot drain or lymph tissue becomes diseased, swelling and infection follow. This subtopic covers lymphoedema, elephantiasis, lymphoma and swollen lymph nodes, and how they are prevented.
OpenChapter 11 · Human Immunity
Body Defence
The body defends itself against pathogens using three lines of defence, from physical barriers to the specific action of white blood cells.
OpenActions of Antibodies
Antibodies are proteins made by lymphocytes that bind to specific antigens and destroy or neutralise pathogens in several ways.
OpenTypes of Immunity
Immunity is the body's ability to resist a pathogen. It can be active or passive, and each of these can arise naturally or artificially.
OpenHealth Issues Related to The Human Immune System
The immune system can sometimes overreact, attack the body itself, or become too weak. These problems lead to allergies, autoimmune diseases and immunodeficiency.
OpenChapter 12 · Coordination and Response in Humans
Coordinate and Response
How the body detects change and organises a matching response through nervous and hormonal control.
OpenNervous System
The layout of the human nervous system: the central control centre and the nerves that reach every part of the body.
OpenNeurones and Synapse
The cells that carry nerve impulses and the tiny gaps where one neurone passes a message to the next.
OpenVoluntary and Involuntary Actions
Actions you choose to make versus automatic ones, and the reflex arc that gives rapid protective responses.
OpenHealth Issues Related to the Nervous System
Disorders and injuries that damage the nervous system, and choices that help keep it healthy.
OpenEndocrine System
The glands that release hormones into the blood and the roles of key hormones such as insulin and adrenaline.
OpenHealth Issue Related to the Endocrine System
What happens when hormone levels are too high or too low, using diabetes and thyroid disorders as key examples.
OpenChapter 13 · Homeostasis and the Human Urinary System
Homeostasis
How the body keeps its internal conditions steady while the outside world changes.
OpenThe Urinary System
The organs that filter the blood and make urine, keeping water and wastes in balance.
OpenHealth Issues Related to the Urinary System
Common kidney and urinary problems, and the treatments that keep patients alive.
OpenChapter 14 · Support and Locomotion in Humans and Animals
Types of Skeleton
The three main kinds of skeleton in animals and what each is good for.
OpenMusculoskeletal System of Humans
How bones, joints and muscles work together to hold up the body and make it move.
OpenMovement and Locomotion
The difference between moving a body part and moving the whole body from place to place.
OpenHealth Issue Related to the Human Musculoskeletal System
Common bone, joint and muscle problems, and how to keep the musculoskeletal system healthy.
OpenChapter 15 · Sexual Reproduction, Development and Growth in Humans and Animals
Reproductive System of Humans
The human reproductive system produces gametes and allows fertilisation to occur, forming the biological basis for continuing the species.
OpenGametogenesis in Humans
Gametogenesis is the process by which the body makes haploid gametes through meiosis, ensuring that fertilisation restores the normal diploid chromosome number.
OpenMenstrual Cycle
The menstrual cycle is a roughly 28-day hormonal cycle that prepares the female body for a possible pregnancy each month.
OpenDevelopment of Human Foetus
After fertilisation the zygote develops through embryo and foetus stages inside the uterus, nourished and protected by the placenta and amniotic fluid.
OpenFormation of Twins
Twins form either when one fertilised egg splits or when two eggs are fertilised separately, giving identical or fraternal twins.
OpenHealth Issues Related to the Human Reproductive System
The reproductive system can be affected by infections, hormonal problems and lifestyle factors; understanding these helps in prevention and treatment.
OpenGrowth in Humans and Animals
Growth is a permanent increase in size and mass of an organism, following characteristic patterns that can be shown on growth curves.
OpenForm 5
Chapter 1 · Organisation of Plant Tissues and Growth
Organisation of Plant Tissue
How specialised cells are grouped into tissues that build the plant body.
OpenMeristematic Tissues and Growth
The dividing tissues that let plants grow longer and thicker throughout life.
OpenGrowth Curves
Reading the shapes that describe how organisms increase in size over time.
OpenChapter 2 · Leaf Structure and Function
Leaf Structure
The internal layers of a leaf and how each part is suited to its job.
OpenMain Organ for Gaseous Exchange
How the leaf is adapted to exchange gases with the surrounding air.
OpenMain Organ for Transpiration
Why the leaf loses water vapour, and what controls the rate.
OpenMain Organ for Photosynthesis
How the leaf captures light and raw materials to build glucose.
OpenCompensation Point
The light level where photosynthesis exactly balances respiration.
OpenChapter 3 · Nutrition in Plants
Main Inorganic Nutrients
Green plants build their own food by photosynthesis, but they still need a supply of inorganic nutrients — mineral ions absorbed from the soil — to grow healthily. This subtopic looks at the main macronutrients and micronutrients and the roles they play.
OpenOrgan for Water and Mineral Salts Uptake
Water and dissolved mineral salts enter a plant through its roots. The root, and especially the tiny root hair cells near its tip, is beautifully adapted for this job. This subtopic explains how uptake happens and why root hairs are so effective.
OpenDiversity in Plant Nutrition
Most plants are autotrophs that make food by photosynthesis, but some have evolved unusual ways of obtaining nutrients. This subtopic explores carnivorous, parasitic and saprophytic plants, and mutually helpful partnerships such as nitrogen-fixing bacteria in root nodules.
OpenChapter 4 · Transport in Plants
Vascular Tissues
Plants have two transport tissues that together form the vascular system: xylem and phloem. This subtopic compares their structure and function — xylem carrying water upward, phloem carrying food both ways.
OpenTransport of Water and Mineral Salts
Water absorbed by the roots must travel all the way up to the leaves, sometimes tens of metres in a tall tree. This subtopic explains the pathway of water, the transpiration pull that drives it, and the factors that affect the rate of transpiration.
OpenTranslocation
The food made in the leaves must reach every growing and storing part of the plant. This movement of organic products through the phloem is called translocation. This subtopic explains what is moved, where, and how the process is powered.
OpenPhytoremediation
Because plants absorb water and dissolved substances so effectively, they can also be used to clean up pollution. Phytoremediation uses living plants to remove, trap or break down harmful substances in soil and water. This subtopic explains how it works and its advantages and limitations.
OpenChapter 5 · Response in Plants
Types of Responses
How rooted plants respond to directional stimuli such as light, gravity and water through tropisms.
OpenPhytohormone
The chemical growth regulators that control plant growth, development and tropic responses.
OpenApplication of Phytohormones in Agriculture
How farmers and growers use natural and synthetic plant hormones to control crop growth.
OpenChapter 6 · Sexual Reproduction in Flowering Plants
Structure of a Flower
The parts of a flower and how each is adapted for sexual reproduction in flowering plants.
OpenDevelopment of Pollen Grains and Embryo Sac
How the male gametes in pollen grains and the female gametes in the embryo sac are formed.
OpenPollination and Fertilisation
How pollen reaches the stigma and how the male gametes fuse with the female gametes in double fertilisation.
OpenDevelopment of Seeds and Fruits
What happens to the ovule and ovary after fertilisation as seeds and fruits are formed.
OpenImportance of Seeds for Survival
Why seeds are vital for the survival and spread of flowering plants, including dormancy and dispersal.
OpenChapter 7 · Adaptations of Plants
Chapter 8 · Biodiversity
Classification System and Naming of Organisms
How living things are grouped into a hierarchy and given standard scientific names using binomial nomenclature.
OpenBiodiversity
The variety of life at genetic, species and ecosystem levels, and why protecting it matters.
OpenMicroorganisms and Viruses
The main groups of microorganisms, the special nature of viruses, and their useful and harmful roles.
OpenChapter 9 · Ecosystem
Chapter 10 · Environmental Sustainability
Threats to the Environment
Human activities that damage the environment — pollution, deforestation and global warming — and their effects.
OpenPreservation, Conservation and Restoration of Ecosystems
Ways to protect natural ecosystems: keeping them untouched, using them wisely, and repairing damaged ones.
OpenPractices in Environmental Sustainability
Everyday practices and larger strategies that reduce our impact on the environment and keep resources for the future.
OpenGreen Technology
Technology designed to reduce harm to the environment through clean energy, efficiency and low emissions.
OpenChapter 11 · Inheritance
Monohybrid Inheritance
A monohybrid cross follows how a single characteristic controlled by one gene is passed from parents to offspring, revealing dominant and recessive patterns.
OpenDihybrid Inheritance
A dihybrid cross tracks two characteristics at once, showing how genes on different chromosomes are inherited independently to give the classic 9:3:3:1 ratio.
OpenGenes and Alleles
Genes are the units of heredity carried on chromosomes, and alleles are their alternative forms — together they explain dominant and recessive traits, genotype and phenotype.
OpenInheritance in Humans
Human inheritance includes multiple-allele traits such as ABO blood groups, sex determination by the X and Y chromosomes, and sex-linked disorders like colour blindness and haemophilia.
OpenChapter 12 · Variation
Types and Factors of Variation
Variation is the difference in characteristics among individuals of the same species, classed as continuous or discontinuous and caused by genetic and environmental factors.
OpenVariation in Humans
Humans show both continuous variation such as height and body mass, and discontinuous variation such as blood group and tongue rolling, shaped by genes and the environment.
OpenMutation
Mutation is a sudden, permanent change in the genetic material — either in a gene or in the number or structure of chromosomes — and is a source of new variation.
OpenChapter 13 · Genetic Technology
Genetic Engineering
Genetic engineering transfers a chosen gene from one organism into another using recombinant DNA technology, for example to make bacteria produce human insulin.
OpenBiotechnology
Biotechnology uses living organisms or their products in industry, medicine and agriculture — from traditional fermentation to modern gene technology and tissue culture.
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