Combined Science,
one step at a time.

A scientific biological drawing uses clear, unbroken lines, no artistic shading and ruled label lines. It should represent the observed specimen and include scale or magnification where appropriate.

Watch for: Do not repeat the wording of Key concepts in biology. Explain the underlying rule or relationship, apply it to the context and check the command word.

Embryonic stem cells are pluripotent and can produce many specialised cell types. Adult stem cells are usually more restricted; treatment still requires evaluation of rejection, tumour and ethical risks.

Watch for: Do not repeat the wording of Cells and control. Explain the underlying rule or relationship, apply it to the context and check the command word.

Genome data can help identify disease-associated variants, trace migration and ancestry, and guide research. It does not remove environmental effects or ethical concerns about privacy and discrimination.

Watch for: Do not repeat the wording of Genetics. Explain the underlying rule or relationship, apply it to the context and check the command word.

Hominin fossils, including Ardi and Lucy, anatomical evidence and the dating and sophistication of stone tools associated with early humans help reconstruct changes through human evolution.

Watch for: Do not repeat the wording of Natural selection and genetic modification. Explain the underlying rule or relationship, apply it to the context and check the command word.

Randomisation balances groups and double blinding reduces expectation and measurement bias. A control or placebo helps attribute differences to the medicine; safety monitoring remains essential.

Watch for: Do not repeat the wording of Health, disease and the development of medicines. Explain the underlying rule or relationship, apply it to the context and check the command word.

Translocation is the movement of dissolved assimilates, especially sucrose, through phloem from sources such as leaves to sinks such as roots, fruits and growing tissues.

Watch for: Do not repeat the wording of Plant structures and their functions. Explain the underlying rule or relationship, apply it to the context and check the command word.

Oestrogen and progesterone in the pill maintain hormonal feedback that inhibits FSH and LH, preventing normal follicle maturation and ovulation. IVF instead uses fertility hormones to stimulate egg maturation and release.

Watch for: Do not repeat the wording of Animal coordination, control and homeostasis. Explain the underlying rule or relationship, apply it to the context and check the command word.

Arteries withstand and maintain higher pressure using thick muscular elastic walls. Veins return blood at lower pressure, have wider lumens and valves that reduce backflow.

Watch for: Do not repeat the wording of Exchange and transport in animals. Explain the underlying rule or relationship, apply it to the context and check the command word.

Transpiration releases water vapour from leaves. Water cycles through evaporation, transpiration, condensation, precipitation and flows, while decomposers and microorganisms also drive carbon and nitrogen cycling.

Watch for: Do not repeat the wording of Ecosystems and material cycles. Explain the underlying rule or relationship, apply it to the context and check the command word.

Most alpha particles passed through, showing atoms are mostly empty space, but rare large deflections required a tiny, dense, positively charged nucleus. Later work identified protons and neutrons in the nucleus.

Watch for: Do not repeat the wording of Key concepts in chemistry. Explain the underlying rule or relationship, apply it to the context and check the command word.

Two spots show the sample contains at least two soluble components. A matching Rf under the same conditions supports the presence of the reference dye, though additional evidence can strengthen identification.

Watch for: Do not repeat the wording of States of matter and mixtures. Explain the underlying rule or relationship, apply it to the context and check the command word.

Drying and weighing the cathode before and after gives the mass of copper deposited. Current, time, electrode area and concentration should be controlled or measured for a valid comparison.

Watch for: Do not repeat the wording of Chemical changes. Explain the underlying rule or relationship, apply it to the context and check the command word.

Lower temperature favours exothermic ammonia formation but is slow. Higher pressure favours ammonia but requires costly strong equipment. Industrial conditions and an iron catalyst balance rate, yield, safety and cost.

Watch for: Do not repeat the wording of Extracting metals and equilibria. Explain the underlying rule or relationship, apply it to the context and check the command word.

Chlorine dissolves in moisture, making the litmus acidic before bleaching the dye. The other observations test oxygen, carbon dioxide and hydrogen respectively.

Watch for: Do not repeat the wording of Groups in the periodic table. Explain the underlying rule or relationship, apply it to the context and check the command word.

Exothermic products have lower energy than reactants. Activation energy is the minimum energy barrier from the reactant level to the profile peak; a catalyst lowers this barrier without changing the overall energy change.

Watch for: Do not repeat the wording of Rates of reaction and energy changes. Explain the underlying rule or relationship, apply it to the context and check the command word.

Volcanic outgassing supplied water vapour, carbon dioxide and nitrogen. Cooling condensed water to oceans; carbon dioxide decreased through dissolution, carbonate formation and photosynthesis, while photosynthetic organisms raised oxygen.

Watch for: Do not repeat the wording of Fuels and Earth science. Explain the underlying rule or relationship, apply it to the context and check the command word.

Energy is measured in joules and power in watts. Force uses newtons, mass kilograms, charge coulombs, current amperes, pressure pascals and distance metres.

Watch for: Do not repeat the wording of Key concepts of physics. Explain the underlying rule or relationship, apply it to the context and check the command word.

Reaction time varies naturally, but an outlier may reflect anticipation, distraction or measurement error. Repeats improve reliability; a justified treatment of anomalies produces a more representative mean.

Watch for: Do not repeat the wording of Motion and forces. Explain the underlying rule or relationship, apply it to the context and check the command word.

Nuclear stations can deliver continuous high output with low operational carbon emissions, but waste management, accident risk and lifecycle costs require evaluation.

Watch for: Do not repeat the wording of Conservation of energy. Explain the underlying rule or relationship, apply it to the context and check the command word.

A microphone converts the sound to an electrical signal displayed against time. Measuring several cycles reduces percentage uncertainty; frequency is the reciprocal of period.

Watch for: Do not repeat the wording of Waves. Explain the underlying rule or relationship, apply it to the context and check the command word.

Alternating currents accelerate charges in an aerial, producing radio waves. Their electric fields drive oscillating currents in a receiving aerial. Atomic and nuclear changes can produce higher-frequency electromagnetic radiation.

Watch for: Do not repeat the wording of Light and the electromagnetic spectrum. Explain the underlying rule or relationship, apply it to the context and check the command word.

Contamination continues to expose tissue until material is removed or decays and may irradiate internally. Irradiation from an external source stops when exposure ends and does not usually make the target radioactive.

Watch for: Do not repeat the wording of Radioactivity. Explain the underlying rule or relationship, apply it to the context and check the command word.

Energy is transferred from the spring's elastic store to the trolley's kinetic store, with some dissipated thermally. Energy is conserved in the complete system.

Watch for: Do not repeat the wording of Energy: forces doing work. Explain the underlying rule or relationship, apply it to the context and check the command word.

The diagram includes forces acting on the book: Earth's gravitational force downward and the table's normal contact force upward. The force on the table acts on a different object.

Watch for: Do not repeat the wording of Forces and their effects. Explain the underlying rule or relationship, apply it to the context and check the command word.

Adding a parallel branch increases total conductance. Both branches have the same potential difference and junction currents add, so total current is greater and R = V/I is below either branch resistance.

Watch for: Do not repeat the wording of Electricity and circuits. Explain the underlying rule or relationship, apply it to the context and check the command word.

Soft magnetic materials respond strongly while current flows but lose most magnetism when current stops, which suits switchable electromagnets.

Watch for: Do not repeat the wording of Magnetism and the motor effect. Explain the underlying rule or relationship, apply it to the context and check the command word.

Soft iron has high magnetic permeability and low retentivity, concentrating the changing flux linking both coils while reversing magnetisation with the a.c.

Watch for: Do not repeat the wording of Electromagnetic induction. Explain the underlying rule or relationship, apply it to the context and check the command word.

At the boiling point, energy increases particle potential energy by overcoming attractions; average kinetic energy and temperature stay constant during the change.

Watch for: Do not repeat the wording of Particle model. Explain the underlying rule or relationship, apply it to the context and check the command word.

A fixed reference and initial-length reading avoid systematic offset. Gradual loading, repeats and an unloading check improve reliability and reveal permanent deformation.

Watch for: Do not repeat the wording of Forces and matter. Explain the underlying rule or relationship, apply it to the context and check the command word.