Basque PAU General Sciences cheat sheet

Hypothesis: a falsifiable, testable statement about the relation between variables; a prediction states the expected outcome under that hypothesis.

Independent variable is manipulated by the researcher; dependent variable is measured; controlled variables are held constant to avoid confounding.

Control group receives no treatment or a placebo; it isolates the effect of the independent variable from incidental factors.

Randomisation of subjects to groups reduces selection bias; blinding (single or double) reduces observer and expectation bias.

Reproducibility requires reporting sample size, materials, procedure and analysis; replication by independent groups strengthens conclusions.

Correlation does not imply causation; causal claims need controlled manipulation or strong quasi-experimental design with confounder control.

Validity: internal validity = the design supports the causal claim; external validity = results generalise beyond the sample and setting.

Scientific method cycle: observation → question → hypothesis → prediction → experiment → analysis → conclusion → communication and revision.

Atom: protons and neutrons in the nucleus, electrons in orbitals; Z = atomic number = protons; A = mass number = protons + neutrons; isotopes differ in neutrons.

Mole: n = m/M; one mole contains 6.022×10²³ particles; molar volume of an ideal gas at STP (0 °C, 1 atm) is 22.4 L.

Molarity: M = n(solute)/V(solution in L); dilution obeys M₁V₁ = M₂V₂.

Balancing equations conserves atoms of each element; stoichiometric ratios come from coefficients, and the limiting reagent determines the maximum product yield.

Percentage yield = (actual/theoretical)×100; percentage composition by mass = (mass of element/molar mass)×100.

Bonding: ionic (metal + non-metal, electron transfer), covalent (non-metals, shared pairs, polar if ΔEN is significant), metallic (delocalised electron sea).

Acid–base: Arrhenius acids release H⁺ in water, bases release OH⁻; pH = −log[H⁺]; neutralisation acid + base → salt + water.

Redox: oxidation is loss of electrons (increase in oxidation number), reduction is gain; oxidising agent is itself reduced.

Work: W = F·d·cosθ (joules); power P = W/t; kinetic energy Eₖ = ½mv²; gravitational potential energy Eₚ = mgh.

Conservation of mechanical energy holds when only conservative forces act; friction converts mechanical energy to heat.

Ohm's law V = IR; series resistances add (R = R₁ + R₂); parallel: 1/R = 1/R₁ + 1/R₂; electrical power P = VI = I²R = V²/R.

Wave equation v = fλ; period T = 1/f; frequency is set by the source, speed by the medium.

Refraction obeys Snell's law n₁sinθ₁ = n₂sinθ₂; n = c/v; total internal reflection occurs above the critical angle sinθc = n₂/n₁.

Sound needs a material medium; light travels in vacuum at c ≈ 3×10⁸ m/s; both show reflection, refraction, diffraction and interference.

Energy sources: renewable (solar, wind, hydro, geothermal, biomass) versus non-renewable (coal, oil, gas, nuclear fuel); efficiency = useful output/total input × 100.

Prokaryotic cells lack a membrane-bound nucleus and organelles; eukaryotic cells have a nucleus, mitochondria, ER, Golgi and (in plants) chloroplasts and a cell wall.

Mitosis produces two genetically identical diploid cells for growth and repair; meiosis produces four haploid gametes with crossing over and independent assortment.

DNA replicates semi-conservatively; transcription makes mRNA from DNA, translation at ribosomes builds protein from codons (triplets); the genetic code is degenerate and universal.

Mendel's laws: segregation of alleles and independent assortment; monohybrid cross Aa × Aa gives 3:1 phenotype, 1:2:1 genotype.

Sex-linked traits sit on sex chromosomes; a carrier female (X^A X^a) can pass the allele to sons, who express it (X^a Y).

Mutations are the source of new alleles; natural selection acts on phenotypic variation, changing allele frequencies over generations.

Evidence for evolution: fossil record, homologous structures, embryology, biogeography and molecular (DNA/protein) sequence comparison.

Hardy–Weinberg p² + 2pq + q² = 1 describes allele frequencies in a non-evolving population; deviations suggest selection, drift, migration or non-random mating.

Digestion: mechanical and chemical breakdown; enzymes - amylase (starch), pepsin (protein, acid pH), lipase (fats); absorption of nutrients occurs mainly in the small intestine villi.

Gas exchange occurs in alveoli by diffusion; oxygen binds haemoglobin, CO₂ is carried mainly as bicarbonate; breathing is driven by the diaphragm and intercostal muscles.

Circulation: double circuit (pulmonary and systemic); arteries carry blood away from the heart, veins return it; capillaries allow exchange; cardiac cycle = systole + diastole.

Excretion: nephrons filter blood in the glomerulus, reabsorb glucose and water, and secrete wastes; urine composition reflects homeostasis of water and ions.

Nervous system: neurons transmit electrical impulses; synapses release neurotransmitters; reflex arcs bypass conscious processing for speed.

Endocrine system: hormones act on target cells via receptors; insulin lowers blood glucose, glucagon raises it; negative feedback maintains homeostasis.

Immune response: innate barriers and phagocytes, then adaptive B lymphocytes (antibodies) and T lymphocytes (cell-mediated); vaccination creates memory cells.

Health risk factors include smoking, alcohol, poor diet, inactivity and obesity; prevention, screening and vaccination reduce incidence of major diseases.

Earth's layers: inner solid core, outer liquid core, mantle (convection drives plate motion) and lithosphere plates over the asthenosphere.

Plate boundaries: divergent (new crust, mid-ocean ridges), convergent (subduction, mountain belts, volcanism) and transform (lateral slip, earthquakes).

Rock cycle: igneous (cooling magma/lava), sedimentary (deposition, compaction, cementation) and metamorphic (heat and pressure); fossils occur mainly in sedimentary rock.

Relative dating uses superposition and cross-cutting relationships; absolute dating uses radioactive decay half-lives (e.g. ¹⁴C for recent organic remains).

Water cycle: evaporation, transpiration, condensation, precipitation, infiltration and runoff; groundwater stored in aquifers.

Carbon cycle exchanges carbon among atmosphere, oceans, biosphere and rocks; burning fossil fuels shifts carbon into the atmosphere as CO₂.

Greenhouse effect: gases such as CO₂, CH₄ and H₂O absorb outgoing infrared radiation; enhanced effect is linked to global warming and sea-level rise.

Environmental impacts of human activity: acid rain from SO₂/NOₓ, eutrophication from nitrates and phosphates, ozone depletion by CFCs, habitat loss and biodiversity decline.

Independent variable on the x-axis, dependent variable on the y-axis; label axes with quantity and unit; include units in tables and figures.

Mean = Σx/n; median is the middle value of ordered data; mode is the most frequent value; use median for skewed data.

Standard deviation quantifies spread around the mean; a large SD means high variability, and error bars show uncertainty on graphs.

Accuracy = closeness to the true value; precision = closeness of repeated measurements to each other; random errors scatter, systematic errors shift all readings.

Linear relationships give y = mx + b, where slope m is the rate of change; the slope's units are y-units per x-unit.

Interpolation estimates within the measured range; extrapolation predicts beyond it and is less reliable.

Significant figures: report results to the precision of the least precise measurement; percentage error = |measured − accepted|/accepted × 100.

Anomalous points are identified against the trend and reported or excluded with justification, not silently deleted.

Biotechnology applications: insulin from recombinant bacteria, gene therapy, PCR diagnostics, CRISPR editing and monoclonal antibodies.

Ethical frameworks for decisions: autonomy, beneficence, non-maleficence, justice; risk–benefit analysis and informed consent are central.

Genetic modification debates involve food security and yield gains versus gene flow, biodiversity risk and labelling/consumer choice.

Stem-cell research raises questions about embryo status, consent of donors and regulation; induced pluripotent cells avoid embryo use.

Data ethics: confidentiality, anonymisation, informed consent for biobanks and protection of personal genetic information against discrimination.

Renewable energy transitions raise questions of land use, cost, intermittency and equity; life-cycle assessment compares impacts, not just use-phase emissions.

Scientific literacy in society: peer review, independent replication, conflict-of-interest disclosure and communication of uncertainty to the public.

Precautionary principle: when evidence of serious harm exists, lack of full certainty is not a reason to postpone cost-effective protective measures.

Safety: goggles and lab coat; know the location of the eyewash, shower, fire extinguisher and fume hood; never pipette by mouth; add acid to water, not water to acid.

Measuring volume: graduated cylinder for approximate volumes, volumetric pipette and burette for precise delivery; read the meniscus at eye level.

Weighing: use a balance calibrated to zero; record mass to the instrument's precision; use weighing paper or a tared container.

Titration: rinse the burette with titrant, add indicator, reach the endpoint (colour change) and record the volume; repeat for concordant results.

Microscopy: start at low power, focus with the coarse knob then fine knob; magnification = eyepiece × objective; stain to increase contrast.

Separation: filtration (insoluble solid from liquid), distillation (liquids with different boiling points), chromatography (different affinities for stationary/mobile phases).

Heating and cooling: use a water bath for controlled heating; never heat a closed system; allow hot glassware to cool before handling.

Waste disposal: organic solvents and heavy-metal solutions go to labelled waste containers, never the sink; record observations and results in a lab notebook.

Photosynthesis links physics (light absorption), chemistry (CO₂ fixation, redox) and biology (chloroplast structure): 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.

Cellular respiration reverses energy flow: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP, connecting biochemistry, gas exchange and energy transfer.

Climate change integrates physics (radiative forcing), chemistry (greenhouse gases), biology (ecosystem shifts) and geology (ice cores, sea level).

Energy in food is measured in kJ and traced through trophic levels; ecological pyramids connect thermodynamics with ecosystem ecology.

Medical imaging (X-ray, MRI, ultrasound) applies wave physics and electromagnetic principles to anatomy and diagnosis.

Water quality assessment combines chemistry (pH, nitrates, dissolved oxygen), biology (bioindicators) and geology (aquifer properties).

Environmental impact assessment combines measurement, statistical analysis and modelling, and must report uncertainty before policy decisions.

Modelling in science: models simplify reality, have assumptions and limits; validation against independent data determines their reliability.

Hypothesis: a falsifiable, testable statement about the relation between variables; a prediction states the expected outcome under that hypothesis.

Independent variable is manipulated by the researcher; dependent variable is measured; controlled variables are held constant to avoid confounding.

Control group receives no treatment or a placebo; it isolates the effect of the independent variable from incidental factors.

Randomisation of subjects to groups reduces selection bias; blinding (single or double) reduces observer and expectation bias.

Reproducibility requires reporting sample size, materials, procedure and analysis; replication by independent groups strengthens conclusions.

Correlation does not imply causation; causal claims need controlled manipulation or strong quasi-experimental design with confounder control.

Validity: internal validity = the design supports the causal claim; external validity = results generalise beyond the sample and setting.

Scientific method cycle: observation → question → hypothesis → prediction → experiment → analysis → conclusion → communication and revision.

Atom: protons and neutrons in the nucleus, electrons in orbitals; Z = atomic number = protons; A = mass number = protons + neutrons; isotopes differ in neutrons.

Mole: n = m/M; one mole contains 6.022×10²³ particles; molar volume of an ideal gas at STP (0 °C, 1 atm) is 22.4 L.

Molarity: M = n(solute)/V(solution in L); dilution obeys M₁V₁ = M₂V₂.

Balancing equations conserves atoms of each element; stoichiometric ratios come from coefficients, and the limiting reagent determines the maximum product yield.

Percentage yield = (actual/theoretical)×100; percentage composition by mass = (mass of element/molar mass)×100.

Bonding: ionic (metal + non-metal, electron transfer), covalent (non-metals, shared pairs, polar if ΔEN is significant), metallic (delocalised electron sea).

Acid–base: Arrhenius acids release H⁺ in water, bases release OH⁻; pH = −log[H⁺]; neutralisation acid + base → salt + water.

Redox: oxidation is loss of electrons (increase in oxidation number), reduction is gain; oxidising agent is itself reduced.

Work: W = F·d·cosθ (joules); power P = W/t; kinetic energy Eₖ = ½mv²; gravitational potential energy Eₚ = mgh.

Conservation of mechanical energy holds when only conservative forces act; friction converts mechanical energy to heat.

Ohm's law V = IR; series resistances add (R = R₁ + R₂); parallel: 1/R = 1/R₁ + 1/R₂; electrical power P = VI = I²R = V²/R.

Wave equation v = fλ; period T = 1/f; frequency is set by the source, speed by the medium.

Refraction obeys Snell's law n₁sinθ₁ = n₂sinθ₂; n = c/v; total internal reflection occurs above the critical angle sinθc = n₂/n₁.

Sound needs a material medium; light travels in vacuum at c ≈ 3×10⁸ m/s; both show reflection, refraction, diffraction and interference.

Energy sources: renewable (solar, wind, hydro, geothermal, biomass) versus non-renewable (coal, oil, gas, nuclear fuel); efficiency = useful output/total input × 100.

Prokaryotic cells lack a membrane-bound nucleus and organelles; eukaryotic cells have a nucleus, mitochondria, ER, Golgi and (in plants) chloroplasts and a cell wall.

Mitosis produces two genetically identical diploid cells for growth and repair; meiosis produces four haploid gametes with crossing over and independent assortment.

DNA replicates semi-conservatively; transcription makes mRNA from DNA, translation at ribosomes builds protein from codons (triplets); the genetic code is degenerate and universal.

Mendel's laws: segregation of alleles and independent assortment; monohybrid cross Aa × Aa gives 3:1 phenotype, 1:2:1 genotype.

Sex-linked traits sit on sex chromosomes; a carrier female (X^A X^a) can pass the allele to sons, who express it (X^a Y).

Mutations are the source of new alleles; natural selection acts on phenotypic variation, changing allele frequencies over generations.

Evidence for evolution: fossil record, homologous structures, embryology, biogeography and molecular (DNA/protein) sequence comparison.

Hardy–Weinberg p² + 2pq + q² = 1 describes allele frequencies in a non-evolving population; deviations suggest selection, drift, migration or non-random mating.

Digestion: mechanical and chemical breakdown; enzymes - amylase (starch), pepsin (protein, acid pH), lipase (fats); absorption of nutrients occurs mainly in the small intestine villi.

Gas exchange occurs in alveoli by diffusion; oxygen binds haemoglobin, CO₂ is carried mainly as bicarbonate; breathing is driven by the diaphragm and intercostal muscles.

Circulation: double circuit (pulmonary and systemic); arteries carry blood away from the heart, veins return it; capillaries allow exchange; cardiac cycle = systole + diastole.

Excretion: nephrons filter blood in the glomerulus, reabsorb glucose and water, and secrete wastes; urine composition reflects homeostasis of water and ions.

Nervous system: neurons transmit electrical impulses; synapses release neurotransmitters; reflex arcs bypass conscious processing for speed.

Endocrine system: hormones act on target cells via receptors; insulin lowers blood glucose, glucagon raises it; negative feedback maintains homeostasis.

Immune response: innate barriers and phagocytes, then adaptive B lymphocytes (antibodies) and T lymphocytes (cell-mediated); vaccination creates memory cells.

Health risk factors include smoking, alcohol, poor diet, inactivity and obesity; prevention, screening and vaccination reduce incidence of major diseases.

Earth's layers: inner solid core, outer liquid core, mantle (convection drives plate motion) and lithosphere plates over the asthenosphere.

Plate boundaries: divergent (new crust, mid-ocean ridges), convergent (subduction, mountain belts, volcanism) and transform (lateral slip, earthquakes).

Rock cycle: igneous (cooling magma/lava), sedimentary (deposition, compaction, cementation) and metamorphic (heat and pressure); fossils occur mainly in sedimentary rock.

Relative dating uses superposition and cross-cutting relationships; absolute dating uses radioactive decay half-lives (e.g. ¹⁴C for recent organic remains).

Water cycle: evaporation, transpiration, condensation, precipitation, infiltration and runoff; groundwater stored in aquifers.

Carbon cycle exchanges carbon among atmosphere, oceans, biosphere and rocks; burning fossil fuels shifts carbon into the atmosphere as CO₂.

Greenhouse effect: gases such as CO₂, CH₄ and H₂O absorb outgoing infrared radiation; enhanced effect is linked to global warming and sea-level rise.

Environmental impacts of human activity: acid rain from SO₂/NOₓ, eutrophication from nitrates and phosphates, ozone depletion by CFCs, habitat loss and biodiversity decline.

Independent variable on the x-axis, dependent variable on the y-axis; label axes with quantity and unit; include units in tables and figures.

Mean = Σx/n; median is the middle value of ordered data; mode is the most frequent value; use median for skewed data.

Standard deviation quantifies spread around the mean; a large SD means high variability, and error bars show uncertainty on graphs.

Accuracy = closeness to the true value; precision = closeness of repeated measurements to each other; random errors scatter, systematic errors shift all readings.

Linear relationships give y = mx + b, where slope m is the rate of change; the slope's units are y-units per x-unit.

Interpolation estimates within the measured range; extrapolation predicts beyond it and is less reliable.

Significant figures: report results to the precision of the least precise measurement; percentage error = |measured − accepted|/accepted × 100.

Anomalous points are identified against the trend and reported or excluded with justification, not silently deleted.

Biotechnology applications: insulin from recombinant bacteria, gene therapy, PCR diagnostics, CRISPR editing and monoclonal antibodies.

Ethical frameworks for decisions: autonomy, beneficence, non-maleficence, justice; risk–benefit analysis and informed consent are central.

Genetic modification debates involve food security and yield gains versus gene flow, biodiversity risk and labelling/consumer choice.

Stem-cell research raises questions about embryo status, consent of donors and regulation; induced pluripotent cells avoid embryo use.

Data ethics: confidentiality, anonymisation, informed consent for biobanks and protection of personal genetic information against discrimination.

Renewable energy transitions raise questions of land use, cost, intermittency and equity; life-cycle assessment compares impacts, not just use-phase emissions.

Scientific literacy in society: peer review, independent replication, conflict-of-interest disclosure and communication of uncertainty to the public.

Precautionary principle: when evidence of serious harm exists, lack of full certainty is not a reason to postpone cost-effective protective measures.

Safety: goggles and lab coat; know the location of the eyewash, shower, fire extinguisher and fume hood; never pipette by mouth; add acid to water, not water to acid.

Measuring volume: graduated cylinder for approximate volumes, volumetric pipette and burette for precise delivery; read the meniscus at eye level.

Weighing: use a balance calibrated to zero; record mass to the instrument's precision; use weighing paper or a tared container.

Titration: rinse the burette with titrant, add indicator, reach the endpoint (colour change) and record the volume; repeat for concordant results.

Microscopy: start at low power, focus with the coarse knob then fine knob; magnification = eyepiece × objective; stain to increase contrast.

Separation: filtration (insoluble solid from liquid), distillation (liquids with different boiling points), chromatography (different affinities for stationary/mobile phases).

Heating and cooling: use a water bath for controlled heating; never heat a closed system; allow hot glassware to cool before handling.

Waste disposal: organic solvents and heavy-metal solutions go to labelled waste containers, never the sink; record observations and results in a lab notebook.

Photosynthesis links physics (light absorption), chemistry (CO₂ fixation, redox) and biology (chloroplast structure): 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.

Cellular respiration reverses energy flow: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP, connecting biochemistry, gas exchange and energy transfer.

Climate change integrates physics (radiative forcing), chemistry (greenhouse gases), biology (ecosystem shifts) and geology (ice cores, sea level).

Energy in food is measured in kJ and traced through trophic levels; ecological pyramids connect thermodynamics with ecosystem ecology.

Medical imaging (X-ray, MRI, ultrasound) applies wave physics and electromagnetic principles to anatomy and diagnosis.

Water quality assessment combines chemistry (pH, nitrates, dissolved oxygen), biology (bioindicators) and geology (aquifer properties).

Environmental impact assessment combines measurement, statistical analysis and modelling, and must report uncertainty before policy decisions.

Modelling in science: models simplify reality, have assumptions and limits; validation against independent data determines their reliability.