This A-Level Biology synoptic reference brings together major ideas that connect across the whole course. Students need it because exam questions often combine biological molecules, cells, physiology, genetics, ecology, and data analysis in one problem. The sheet helps students recognize links between topics and choose the correct formula or concept quickly.
It is designed for revision, practical work, and exam preparation.
Key Facts
- Magnification is calculated using magnification = image size / actual size, with both sizes in the same units.
- Water potential controls osmosis, and water moves from higher water potential to lower water potential through a partially permeable membrane.
- Respiration transfers energy from glucose to ATP, and aerobic respiration can be summarized as glucose + oxygen -> carbon dioxide + water + ATP.
- The Hardy-Weinberg equations are p + q = 1 and p^2 + 2pq + q^2 = 1, where p and q are allele frequencies.
- Cardiac output is calculated using cardiac output = heart rate x stroke volume.
- Genetic diversity can be measured using index of diversity = N(N - 1) / sum n(n - 1), where N is total organisms and n is organisms of one species.
- Mean rate of reaction is calculated using rate = change in quantity / time taken.
- A statistical test is significant when the calculated value exceeds the critical value for chi-squared or Spearman's rank, but is significant when the calculated value is less than the critical value for a t-test at the chosen probability level.
Vocabulary
- Synoptic biology
- The linking of ideas from different biology topics to explain a larger biological process or solve an unfamiliar problem.
- Homeostasis
- The maintenance of a stable internal environment within narrow limits using negative feedback mechanisms.
- Allele frequency
- The proportion of all alleles in a population that are a particular form of a gene.
- ATP
- A nucleotide that acts as the immediate energy source for many cellular processes.
- Biodiversity
- The variety of living organisms in an area, including species diversity, genetic diversity, and habitat diversity.
- Statistical significance
- A result is statistically significant when it is unlikely to be due to chance at the chosen probability level.
Common Mistakes to Avoid
- Mixing units in magnification calculations is wrong because image size and actual size must be converted to the same unit before using magnification = image size / actual size.
- Writing that water moves from low water potential to high water potential is wrong because osmosis moves water down a water potential gradient, from higher to lower water potential.
- Assuming correlation proves causation is wrong because two variables can be associated without one directly causing the other.
- Using the Hardy-Weinberg equations without checking assumptions is wrong because the model requires conditions such as no selection, no mutation, random mating, and a large population.
- Confusing percentage change with percentage point change is wrong because percentage change = change / original value x 100, while percentage points compare two percentages directly.
Practice Questions
- 1 A mitochondrion measures 45 mm on a micrograph and its actual length is 3 micrometers. Calculate the magnification.
- 2 In a population, the frequency of the recessive allele q is 0.30. Use Hardy-Weinberg to calculate the expected frequency of heterozygotes.
- 3 A student's resting heart rate is 72 beats per minute and stroke volume is 70 cm3. Calculate cardiac output in cm3 per minute.
- 4 Explain why a question about exercise could require ideas from respiration, ventilation, circulation, homeostasis, and cell signaling.