Biology
Form 4 · 70 topics available
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 Compositions 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 · Immunity in Humans
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 Movement 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.
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