Basque PAU General Sciences flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Falsifiable hypothesis

A testable statement that predicts a specific outcome and can in principle be shown false by observation or experiment; this is what distinguishes scientific claims from unfalsifiable ones.

Control group

The group in an experiment that receives no treatment or a placebo, providing a baseline against which the treated group is compared to isolate the independent variable's effect.

Blind and double-blind design

In a blind design participants do not know their group; in a double-blind design neither participants nor the researchers measuring outcomes know, reducing expectation and observer bias.

Limiting reagent

The reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product that can form according to the stoichiometric coefficients of the balanced equation.

Mole and Avogadro constant

The mole is the amount of substance containing 6.022×10²³ elementary entities; mass in grams divided by molar mass gives moles, n = m/M.

pH scale

pH = −log[H⁺] in aqueous solution; values below 7 are acidic, 7 is neutral at 25 °C, and above 7 is basic; each unit represents a tenfold change in H⁺ concentration.

Oxidation and reduction

Oxidation is loss of electrons and an increase in oxidation number; reduction is gain of electrons and a decrease; both always occur together in a redox reaction.

Ohm's law

For a conductor at constant temperature, current is directly proportional to potential difference: V = IR, where V is volts, I is amperes and R is ohms.

Wave equation

For any periodic wave, speed equals frequency multiplied by wavelength, v = fλ; frequency is determined by the source and speed by the medium.

Total internal reflection

When light travels from a denser to a less dense medium beyond the critical angle, it is entirely reflected back inside; sinθc = n₂/n₁, used in optical fibres.

Meiosis

A two-division process producing four haploid daughter cells from one diploid cell, with crossing over and independent assortment generating genetic variation in gametes.

Monohybrid cross ratio

Crossing two heterozygotes Aa × Aa gives a 3:1 phenotypic ratio for a dominant trait and a 1:2:1 genotypic ratio (AA:Aa:aa) in the offspring.

Natural selection

Heritable variation among individuals, combined with differential survival and reproduction, changes allele frequencies in a population over generations, adapting it to its environment.

Hardy–Weinberg equilibrium

In a large, randomly mating population without selection, mutation, migration or drift, allele frequencies stay constant and genotype frequencies follow p² + 2pq + q² = 1.

Alveolar gas exchange

Oxygen diffuses from alveolar air into blood across thin walls, and carbon dioxide diffuses out; large surface area and short diffusion distance make the exchange efficient.

Insulin and glucagon

Pancreatic hormones with opposite effects: insulin lowers blood glucose by promoting uptake and glycogen formation; glucagon raises it by releasing glucose, maintaining homeostasis by negative feedback.

Adaptive immune response

B lymphocytes produce specific antibodies against antigens, while T lymphocytes destroy infected cells; memory cells formed after infection or vaccination give faster future responses.

Plate tectonics

The lithosphere is divided into plates moving over the asthenosphere; divergent, convergent and transform boundaries produce earthquakes, volcanism, mountain belts and ocean ridges.

Radiometric dating

Absolute dating uses the known half-life of a radioactive isotope to calculate age from the ratio of parent to daughter atoms, for example carbon-14 for recent organic remains.

Eutrophication

Excess nitrates and phosphates entering water cause algal blooms; decomposition then depletes dissolved oxygen, killing fish and reducing biodiversity in the water body.

Accuracy versus precision

Accuracy is closeness of a measurement to the true value; precision is closeness of repeated measurements to each other; random errors reduce precision, systematic errors reduce accuracy.

Standard deviation

A measure of the spread of data around the mean; a large standard deviation indicates high variability, and it is often shown as error bars on a graph.

Interpolation versus extrapolation

Interpolation estimates a value within the measured range of data; extrapolation predicts outside it and is less reliable because the trend may not continue.

Informed consent

Voluntary agreement to participate or be treated after receiving understandable information about purpose, procedures, risks, benefits and the right to withdraw, central to research ethics.

Precautionary principle

When evidence suggests a serious or irreversible threat, lack of full scientific certainty is not grounds to postpone cost-effective measures to prevent harm.

Recombinant DNA technology

A gene is inserted into a vector such as a plasmid and expressed in a host organism, used to produce human insulin, vaccines and other therapeutic proteins.

Titration

A solution of known concentration is added from a burette to a measured volume of analyte until an indicator changes colour, allowing calculation of the unknown concentration.

Chromatography

A separation technique in which components move at different rates between a stationary phase and a mobile phase according to their differing affinities, used for pigments and mixtures.

Microscope magnification

Total magnification equals eyepiece magnification multiplied by objective magnification; the field of view narrows as magnification increases, so specimens are located at low power first.

Cellular respiration

The controlled oxidation of glucose, C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O, releasing energy stored as ATP; it links biochemistry, gas exchange and energy transfer across systems.

Trophic energy transfer

Only about ten percent of energy at one trophic level passes to the next, the rest being lost as heat through respiration, which limits food chain length and pyramid shape.

Environmental impact assessment

A structured evaluation of the likely environmental effects of a project, combining measurement, modelling and statistical analysis, and reporting uncertainty before decisions are approved.