Key term
Edexcel A-Level Biology B 9BI0
Biological Molecules
Topic overviewMonosaccharides, disaccharides and polysaccharidesGlycosidic bonds and condensation reactionsStarch, glycogen and cellulose structureTriglycerides and phospholipidsSaturated and unsaturated fats and lipid propertiesAmino acid structure and the peptide bondPrimary, secondary, tertiary and quaternary structureFibrous and globular proteinsThe structure of DNADNA replication and gene mutationsThe structure of RNATranscription and translationEnzymes as globular proteinsFactors affecting enzyme activityMeasuring the rate of enzyme activityUnits, uncertainty and experimental errorEnzyme inhibitionInorganic ionsThe properties of water
Cells, Viruses and Reproduction of Living Things
Topic overviewCell theory and eukaryotic cell structureProkaryotic cells and Gram stainingMicroscopy, magnification and resolutionSignificant figures, estimates and mathematical symbolsVirus structure and classificationThe lytic cycle and latencyTreating viral disease and the ethics of untested drugsThe cell cycle and its regulationMitosis and the behaviour of chromosomesMitosis in growth, repair and root tip squashesMeiosis, genetic variation and chromosome mutationsGametogenesis in mammalsFertilisation and early embryo developmentPollen and embryo sac formationDouble fertilisation in flowering plantsInvestigating pollen tube growth
Classification and Biodiversity
Exchange and Transport
Topic overviewSurface area to volume ratioThe fluid mosaic modelDiffusion, osmosis and facilitated diffusionActive transport, endocytosis and exocytosisGas exchange in insects, fish and mammalsDissecting the insect gas exchange systemGas exchange in flowering plantsThe structure of the heart and blood vesselsThe double circulatory systemThe cardiac cycleMyogenic stimulation and ECG tracesThe composition of bloodThe functions of blood and clottingAtherosclerosis and its risk factorsHaemoglobin and the Bohr effectOxygen dissociation curvesFormation of tissue fluidThe lymphatic systemXylem and phloem structureApoplastic and symplastic pathwaysThe cohesion-tension theoryMeasuring transpiration with a potometerTranslocation and the mass flow hypothesis
Energy for Biological Processes
Topic overviewAn overview of aerobic respirationGlycolysisThe link reaction and the Krebs cycleThe electron transport chainChemiosmosis and ATP yieldAnaerobic respiration and ATP yieldMeasuring respiration with a respirometerAbsorption and action spectraPhotosynthetic pigments and chromatographyChloroplast structure and the light-dependent stageThe Calvin cycleLimiting factors in photosynthesis
Microbiology and Pathogens
Topic overviewCulturing microorganisms and aseptic techniqueMeasuring bacterial growthThe bacterial growth curveBacteria as pathogensThe action of antibioticsAntibiotic resistanceOther pathogenic agentsControlling endemic diseasePhagocytosis and the humoral responseThe cell-mediated immune responseMemory cells and the secondary responseNatural and artificial immunityVaccination and herd immunity
Modern Genetics
Origins of Genetic Variation
Topic overviewMutation, meiosis and random fertilisationGenotype, phenotype and monohybrid inheritanceDihybrid crosses and pedigree diagramsAutosomal linkage and sex linkageThe chi-squared test in geneticsSelection pressures and allele frequencyGenetic drift and the founder effectThe Hardy-Weinberg equation
Control Systems
Topic overviewHomeostasis and negative feedbackChemical control in mammalsPlant growth substancesAuxins, cytokinins and apical dominancePhytochrome and photomorphogenesisThe organisation of the nervous systemBrain regions and divisions of the peripheral nervous systemThe autonomic nervous systemResting potential and the action potentialPropagation and saltatory conductionSynaptic transmissionEffects of drugs on the nervous systemThe structure of the retina and rhodopsinRods, cones and visual acuityControl of heart rateKidney structure and ultrafiltrationSelective reabsorption and the loop of HenleADH and osmoregulationThermoregulation in endotherms
Ecosystems
Topic overviewEcosystems, habitats and nichesPyramids of numbers, biomass and energyEcological techniques for measuring distributionChoosing the right ecological techniquePresenting data in tables and graphsStatistical tests in ecologyProductivity and energy transfer efficiencyDecomposers and nutrient cyclingSuccessionBiotic and abiotic factors in population changeHuman influences on ecosystemsSustainability, resource management and peer review
Ecosystems
- 12 subtopics
- 38 things to know
- Papers 2 and 3
What Ecosystems covers
How ecosystems are described and sampled, the statistics used to test ecological data, how energy passes between trophic levels and how nutrients are recycled, how communities change over time, and the human effects that make management necessary.
Where it is assessed
Papers 2 and 3
Advanced Physiology, Evolution and Ecology, then the general and practical principles paper.
Check the Pearson Edexcel specification ↗The 12 subtopics
Each one has its own page.
- Ecosystems, habitats and nichesRecall questions on the biotic and abiotic components of an ecosystem, examples of small and large ecosystems, how the components interact, and trophic levels from producers to tertiary consumers.Open →
- Pyramids of numbers, biomass and energyRecall questions on pyramids of numbers, biomass and energy, what each shows, their advantages and disadvantages, and why pyramids of numbers and biomass can be inverted while pyramids of energy cannot.Open →
- Ecological techniques for measuring distributionRecall questions on random placement of point, frame and gridded quadrats, line and belt transects, the ACFOR scale and its limits, and when percentage cover or individual counts suit a species.Open →
- Choosing the right ecological techniqueRecall questions on transects and interrupted belt transects, random and systematic sampling, choosing quadrat size, comparing the reliability of methods, estimating population size, and the safe and ethical use of organisms and risk assessment in fieldwork.Open →
- Presenting data in tables and graphsRecall questions on laying out a results table with consistent decimal places, frequency tables and modal classes, and when to choose a bar chart, histogram, line graph or scattergram, with how to draw and label the axes.Open →
- Statistical tests in ecologyRecall questions on when and how to use the t-test and Spearman's rank correlation coefficient, degrees of freedom and critical values, and calculating the mean, median, mode, range and standard deviation of ecological data.Open →
- Productivity and energy transfer efficiencyRecall questions on gross and net primary productivity, calculating the efficiency of transfer, and why energy is lost at each level.Open →
- Decomposers and nutrient cyclingRecall questions on the role of microorganisms in decay, and on the recycling of nitrogen and carbon within an ecosystem.Open →
- SuccessionRecall questions on colonisation, primary and secondary succession, pioneer species and how they change abiotic conditions, and the climax community, climatic climax and plagioclimax.Open →
- Biotic and abiotic factors in population changeRecall questions on biotic factors such as predation, competition, disease and food supply, abiotic factors such as temperature, light, water, pH and mineral ions, and investigating how an abiotic factor affects distribution or morphology along a transect.Open →
- Human influences on ecosystemsRecall questions on overfishing and its effects on breeding populations and food webs, CITES, balancing use against conservation, the effects of climate change on species ranges, timing, coral, ocean pH and pests, and interpreting carbon dioxide, ice core and flowering data.Open →
- Sustainability, resource management and peer reviewRecall questions on sustainable resource use, catch quotas, closed seasons, mesh sizes and marine protected areas, approaches to reducing climate change, and how peer review, journals and conferences validate evidence.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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What is a transect, and how do line and belt transects differ?
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After ranking both variables for Spearman's rank correlation, what values are calculated for each data pair?
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In the energy transfer efficiency formula, what do the numerator and denominator represent?
Numbers
Define 'energy transferred' and 'energy available', and state the formula for energy transfer efficiency between trophic levels.
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Explain why the equation NPP = GPP − R is used to determine energy available to consumers.
Process
What happens to pioneer species as succession progresses?
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Define a climax community.
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When investigating the effect of an abiotic factor on species distribution, how should the transect be positioned and what should be recorded?
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Why is statistical analysis important when investigating relationships between abiotic factors and species, and what should the conclusions establish?
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What do pyramids of biomass show?
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What conclusion is drawn if the calculated t-value exceeds the critical value?
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After ranking data, what is calculated next for Spearman's correlation?
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In a calculation of NPP, what information do you need about respiratory losses?
Process
What is the potential long-term consequence of continued overfishing for an entire ecosystem?
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What is the biotic component of an ecosystem?
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What constitutes the abiotic component of an ecosystem?
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What is a quadrat?
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Describe how a line transect is carried out.
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What is meant by depletion of biological resources?
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Explain how mesh size regulations contribute to fish stock conservation.
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Define peer review in the context of scientific research.
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Give an example of a very small ecosystem.
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What do pyramids of numbers represent?
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What is a belt transect?
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How does an interrupted belt transect differ from a continuous belt transect?
Process
When is a bar chart the appropriate way to present data?
Process
When should data be plotted as a line graph?
Process
When should a scattergram be used to present ecological data?
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What is the purpose of a t-test?
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What is gross primary productivity (GPP)?
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In the equation NPP = GPP − R, what does the term R represent?
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What are decomposers and which organisms are the main examples?
Process
What would happen to nutrient cycling in an ecosystem without decomposers?
Process
Why are decomposers essential for the continued productivity of an ecosystem?
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What is colonisation in an ecological context?
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Why can new species establish after pioneer species have modified the environment?
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Define overfishing.
Take Ecosystems further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Gross primary productivity vs Net primary productivity
Gross primary productivity: total chemical energy fixed by producers. Net primary productivity: chemical energy remaining after producer respiration.
Primary succession vs Secondary succession
Primary succession: community development beginning where soil is absent. Secondary succession: community redevelopment where soil remains.
Biomass vs Productivity
Biomass: mass of living material in a defined area. Productivity: rate of living-material or energy production.
Questions from this topic
Each one with the model answer underneath.
- 1
What is the biotic component of an ecosystem?
Model answer
The community of living organisms present in the ecosystem.
- 2
What constitutes the abiotic component of an ecosystem?
Model answer
The non-living physical environment, including factors such as temperature, light, water, and soil.
- 3
Give an example of a very small ecosystem.
Model answer
A rock pool or a rotting log.
- 4
Give an example of a very large ecosystem.
Model answer
An ocean or a tropical rainforest.
- 5
What is a trophic level?
Model answer
The position an organism occupies in a food chain, determined by how many energy transfers separate it from the original energy source.
- 6
Which organisms occupy the first trophic level (T1)?
Model answer
Producers.
What is inside Levo
Six ways to work the same material.
Ecosystems revision questions
- What does Ecosystems cover in Edexcel A-Level Biology B?
- 12 subtopics: ecosystems, habitats and niches, pyramids of numbers, biomass and energy, ecological techniques for measuring distribution, choosing the right ecological technique, presenting data in tables and graphs, statistical tests in ecology, productivity and energy transfer efficiency, decomposers and nutrient cycling, succession, biotic and abiotic factors in population change, human influences on ecosystems and sustainability, resource management and peer review. Each one has its own page with questions and model answers.
- How is Ecosystems organised?
- By the Edexcel 9BI0 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Ecosystems, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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