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Brevet science revision sheets: biology (SVT), physics-chemistry, technology. DNA, immune system, atoms, energy, electricity, climate. Key formulas.
The science exam lasts 1 hour (50 points) and covers two of three subjects: Biology (SVT), Physics-Chemistry, and Technology. The two subjects are announced at the start of the school year.
DNA is the molecule carrying genetic information, structured as a double helix in cell nuclei. A gene is a DNA segment coding for a trait; an allele is a gene variant (dominant or recessive). Humans have 23 chromosome pairs (46 total), including XX (female) or XY (male) sex chromosomes.
Mutations are random DNA changes. Natural selection (Darwin) favours advantageous alleles in a given environment. Evolution results from mutations (diversity source) filtered by natural selection.
Meiosis produces haploid gametes (23 chromosomes). Fertilisation combines two gametes into a diploid zygote (46 chromosomes). Genetic shuffling during meiosis and random fertilisation ensure individual diversity.
Nervous system: neurons transmit electrical nerve impulses via synapses (chemical neurotransmitters). Reflex arc: stimulus → receptor → sensory nerve → spinal cord → motor nerve → effector.
Immune system: natural barriers (skin, mucous membranes), innate response (phagocytosis, inflammation), adaptive response (B lymphocytes producing antibodies, T lymphocytes destroying infected cells, immune memory). Vaccination exploits immune memory; serotherapy provides immediate but temporary protection.
Reproduction: puberty triggered by hormones. Menstrual cycle (~28 days): follicular phase → ovulation (day 14) → luteal phase. Contraception: pill (blocks ovulation), condom (barrier), IUD (prevents implantation).
Atoms: nucleus (protons+, neutrons) + electrons−. Electrically neutral. Molecules: bonded atoms (H₂O, CO₂, O₂). Ions: atoms with gained/lost electrons (Na⁺, Cl⁻).
Chemical reactions: mass is conserved (Lavoisier). Balance equations: same number of each atom on both sides. Example: 2H₂ + O₂ → 2H₂O.
pH: 0-14 scale. < 7 acidic, = 7 neutral, > 7 basic.
Speed: v = d/t (m/s). Weight: P = m × g (g ≈ 9.8 N/kg). Gravitational interaction: objects attract each other; stronger with mass, weaker with distance.
Kinetic energy: Ec = ½mv² (doubles speed → quadruples energy). Ohm's law: U = R × I. Electrical power: P = U × I. Electrical energy: E = P × t.
Light: c = 3 × 10⁸ m/s, travels in straight lines. Sound: ~340 m/s in air, requires a medium, frequency in Hz (human range: 20-20,000 Hz). Period T = 1/f. Danger above 85 dB.