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Core Practicals
Core Practicals for Biology
| Question | Answer |
|---|---|
| Describe how the effect of caffeine on heart rate in Daphnia can be investigated practically, and discuss whether there are ethical issues in the use of invertebrates | 1.Place Daphnia on cavity slide with caffeine 2.Idea of heart rate determined before treatment ; 3.Idea that daphnia need to be put into Caffeine and allowed to acclimatise ; 4.Use microscope; to check heartbeat |
| Describe how the effect of caffeine on heart rate in Daphnia can be investigated [2] | 5.Range of caffeine concentrations; 6.Repeats; 7.Water as control / zero caffeine concentration}; 8.Control temperature; 9.Similar organisms used; 10.Accurate measurement of DV; 11.Plot results on graph |
| Describe how to investigate the vitamin content of food and drink | 1.DCPIP ; 2.Use of juice ; 3.Idea of titrating juice with DCPIP 4.Colour change e.g. from blue to colourless 5.Use of calibration curve to determine vitamin C concentration / comparison with standard |
| Describe how to investigate the vitamin content of food and drink [2] | 6.Vitamin C ; 7.Repeated at time intervals 8.Replication ; 9.One controlled variable ; 10.Drawing graph of both sets of results ; |
| Describe how membrane structure can be investigated practically, eg by the effect of alcohol concentration or temperature on membrane permeability | 1.Tissue named e.g. beetroot ; 2.Washing/soaking beetroot thoroughly 3.Waterbath to maintain change temperature 4.Range at least 5{temperatures / alcohol concentrations} 5.Controlled variable named e.g. length of time, size of beetroot |
| Describe how membrane structure can be investigated practically, eg by the effect of alcohol concentration or temperature on membrane permeability [2] | 6.Indication of what is being used to judge permeability colour of solution, absorbance, transmission ; 7.Permeability can be assessed e.g. use of colorimeter, standard solutions ; 8.Repeats / replicates 9.Plot results onto a graph |
| Describe how enzyme concentrations can affect the rates of reactions and how this can be investigated practically by measuring the initial rate of reaction | Mesure of vol. of oxygen. volume of oxygen 3.Measure the initial rate of reaction 4.CV e.g. age, part of mussel mass,surface area,Vol of hydrogen peroxide, temperature, concentration, pH 6.Repeats |
| Describe the stages of mitosis and how to prepare and stain a root tip squash in order to observe them practically | 1.Use of root tip; 2.Add acid or acetic alcohol 3.Add stain e.g. Toluidine blue 4.Break open tip with (mounted) needle/eq}; 5.Mount in stain /acid / water 6.Squash under coverslip; 7.Warm to intensify staining |
| Describe how totipotency can be demonstrated practically using plant tissue culture techniques | 1.Sample/explants from both(tissues) 2.Aseptic cond. 3.Grow cells in a callus 4.Growth reg. 5.Cells / tissue can differentiate / cells can become whole plants 6.Procedure e.g. agar; leave for a suitable length of time / suitable controlled variable |
| Describe how to determine the tensile strength of plant fibres practically. | 1.Suspending fibres with weights,pulling them with forcemeter 2.Fibres of same diameter,different diameters accounted 3.Fibres of initial length 4.How weights added/forcemeter pulled 5.Measurable endpoint, breaking point stretched to standard length |
| Describe how to determine the tensile strength of plant fibres practically.[2] | 5.Measurable endpoint eg breaking point / stretched to standard length 6.Repeated readings taken at each {weight / forcemeter reading} 7.Safety procedure eg goggles;fibre snaps/precaution against weights}; 8.Control of {temperature / humidity |
| Describe how to investigate plant mineral deficiencies practically. | 1.3+ range of ion concentrations 2.Repeats(at each concentration) 3. Uniformity of seedlings (e.g. all from same parent plant, same age, same original root length) 4.Solution used should contain other mineral ions / named mineral ions |
| Describe how to investigate plant mineral deficiencies practically. [2] | 5. One other variable maintained / kept constant (e.g. temp, all run for same length of time, light intensity, volume of mineral solution) 6.Mechanism of judging root {growth /eq} (to measure optimum concentration) |
| Describe how to investigate the antimicrobial properties of plants. | 1.Filter paper soaked in extract placed on agar plate 2.Bacterial {lawn] 3.Sterile/aseptic e.g.sealing 4.Incubation-24 hours 1 week 5.Incubate temperature 25°C X 37°C human body temp 6.Clear area/inhibition zone 7.Shows no bacteria 8.Suitable con |
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