Key term
Eduqas A-Level Biology A400QS
Biological Molecules
Cell Structure and Organisation
Cell Membranes and Transport
Enzymes
Nucleic Acids and Their Functions
Importance of ATP
Photosynthesis
Respiration
Microbiology
Population Size and Ecosystems
Topic overviewPopulation growth and its measurementThe population growth curve and carrying capacityDensity dependent and density independent factorsSampling abundance and distributionEcosystems, habitats and communitiesEnergy transfer and pyramids of biomassSuccessionDecomposition and the carbon cycleThe nitrogen cycle and human interventionEutrophication and the effects of drainage
Human Impact on the Environment
Classification and Biodiversity
Topic overviewThe need for classification and the taxonomic hierarchyThe three domain and five kingdom systemsCharacteristic features of the five kingdomsAssessing relatedness by physical features and biochemistryThe species concept and the binomial systemBiodiversity, adaptation and natural selectionMeasuring biodiversity in a habitatGenetic and molecular measures of biodiversity
Mitosis and Meiosis
Sexual Reproduction in Humans
Sexual Reproduction in Plants
Inheritance
Variation and Evolution
Application of Reproduction and Genetics
Topic overviewThe Human Genome Project, other sequenced genomes and genomics in healthcareScreening embryos, stem cells and the ethical issuesGenetic fingerprinting, PCR and electrophoresis in forensic workRecombinant DNA and the production of human insulinGenetically modified crops and gene therapy
Adaptations for Gas Exchange
Topic overviewSurface area to volume ratio and gas exchange in small organismsSpecialised respiratory surfaces and the need for ventilationGills and counter current flow in bony fishThe human breathing system and its histologyVentilation and gas exchange in humansThe insect tracheal systemThe angiosperm leaf, stomata and gas exchange
Adaptations for Transport
Topic overviewVascular systems compared across animal groupsThe mammalian heart and blood vesselsThe cardiac cycle and its controlBlood, haemoglobin and dissociation curvesThe Bohr effect, chloride shift and tissue fluidThe root and the uptake of waterThe endodermis and the entry to the xylemXylem, transpiration and cohesion-tensionThe potometer and xerophytes and hydrophytesPhloem and translocation
Adaptations for Nutrition
Homeostasis and the Kidney
The Nervous System
Immunology and Disease: Disease and Its TransmissionImmunology
Immunology and Disease: AntibioticsImmunology
Immunology and Disease: The Immune ResponseImmunology
Human Musculoskeletal Anatomy: Skeletal TissuesMusculoskeletal
Topic overviewCartilage and its three typesThe composition and functions of compact boneBone remodelling and the Haversian systemRickets, osteomalacia, osteoporosis and brittle bone diseaseThe structure of skeletal muscleThe sliding filament theoryFast and slow twitch fibres, and energy for contraction
Human Musculoskeletal Anatomy: Structure and Function of the SkeletonMusculoskeletal
Human Musculoskeletal Anatomy: JointsMusculoskeletal
Neurobiology and Behaviour: The BrainNeurobiology
Neurobiology and Behaviour: NeuroscienceNeurobiology
Microbiology
Monitoring population growth and the milk investigation
- 3 things to know
- Component 1
Overview
Recall questions on total against viable counts, serial dilution and the calculation of colony-forming units, the haemocytometer, turbidity as an indirect measure, and the resazurin or methylene blue milk test with its controls.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe how the numbers of bacteria in fresh and stale milk are compared.
Key term
Distinguish a total count from a viable count.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Distinguish a total count from a viable count.
Model answer
A total count includes every cell present whether alive or dead, while a viable count includes only those cells able to grow and divide.
- 2
Give one method of making a total count.
Model answer
A sample is placed in a counting chamber of known depth and the cells in a measured area are counted under the microscope.
- 3
Why can a total count give a misleading picture of a culture?
Model answer
It counts dead cells along with living ones, so a dying culture may appear as populous as a healthy one.
- 4
How is a viable count obtained?
Model answer
A known volume of a diluted sample is spread on nutrient agar and incubated, and the colonies that appear are counted.
- 5
Why is each colony taken to represent one living cell in the sample?
Model answer
A colony can only arise where a cell able to divide landed, and the cells were spread far enough apart for each to grow separately.
- 6
Why is a viable count reported in colony-forming units rather than cells?
Model answer
A colony may have grown from a clump or chain of cells rather than a single one, so the count is of units capable of forming a colony.
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