Biology 101: Complete O Level Revision Course for Beginners

Explore ecological study techniques for estimating species abundance using quadrats, transects, nets, and traps. Learn sampling, density calculations, and mark-recapture to estimate populations across an area.

Explore how minerals like iron, calcium, phosphorus, and sodium support blood, bones, nerves, and metabolism, and examine malnutrition, obesity, diabetes, and starvation.

Enzymes act as biological catalysts, speeding up cellular reactions and remaining unchanged. They are proteins with a specific active site that binds substrates in a lock-and-key model, forming enzyme-substrate complexes.

Explore the transport system—blood vessels, blood, and heart—and its link to immunity, including red and white blood cells, plasma, and platelets, and how antibodies fight antigens.

Explore the anatomy and roles of arteries, veins, and capillaries, detailing wall structure, pressure differences, oxygen transport, diffusion, valves, and how circulation returns blood to the heart.

Explore heart structure and function, including four chambers, key valves, and the flow of blood through pulmonary and systemic circulation, plus heartbeat and blood pressure.

Explore phloem translocation of manufactured food through sieve tube elements and companion cells, powered by living cells and mitochondria, with bidirectional systemic transport from source leaves to sink roots.

Explore the basics of plant transpiration, including how water moves from roots to leaves and evaporates from stomata. Understand its role in plant water balance and cooling.

Describe the deamination of amino acids into ammonia and urea, liver processing via the hepatic portal vein, and how excretion and homeostasis are maintained in plants and animals.

Explore osmoregulation, showing how the hypothalamus and pituitary use antidiuretic hormone to regulate kidney absorption and urine concentration, and examine food storage as starch and glycogen in plants and animals.

Examine reflex action as a rapid, involuntary response via the reflex arc, outlining stimulus, receptors, sensory and motor neurons, spinal and cranial reflexes, and pupil reflex.

Explore how the endocrine system and nervous system coordinate hormones from glands such as pituitary, pancreas, thyroid, ovaries, and testes to regulate metabolism and reproduction.

An overview of the skeletal system, its protective and supportive roles, how it enables movement with muscles, stores calcium and phosphorus, and produces blood cells, plus axial and appendicular skeleton.

Grow organisms by increasing cell number or enlarging existing cells, producing irreversible size changes. Develop complexity through stages like metamorphosis, and measure growth by dry mass, height, and leaf number.

Explore the menstrual cycle and its three phases—follicular, ovulation, and luteal—highlighting FSH, estrogen, and the uterine lining. Learn how menstruation marks the cycle start, understand cycle duration, and recognize menopause.

Explore sexually transmitted infections within a beginner biology course designed for an O level revision.

Explore the history of genetics and how inheritance and environment shape living organisms. Trace beliefs from ancient Egypt to Mendel's plant experiments and the discovery of DNA.

Biotechnology applies biological and engineering principles to improve health and ecosystems. Genetic engineering, a biotechnology branch, manipulates genes via plasmids and DNA vectors to produce insulin and other products.