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Practical Investigation Students are to carry out a guided investigation on an organism Practical Investigation • Students are to investigate an aspect of the ecological niche of the organism. • It is essential that they develop an understanding of the ecological niche of the organism before the investigation is carried out Practical Investigation • The investigation is to be done individually • The investigation and report writing must be at a NCEA level 3 • This standard is worth 4 credits Planning an Investigation • There is great information in your “Continuing Biology” text book by Meg Bayley. Log books - 1B5 • Ideas such as rough notes, brainstorming, possible investigations, collection of data and observations, research and planning, failures, successes and tentative conclusions. • Is a working document - neatness is not important. • Purpose is to show investigative skills, and to record checking of milestones for Task 2. Planning an Investigation COPY Step 1) Knowing the Organism. • Investigate the ecological niche. – An understanding of the normal way of life so an experiment can be designed to yield meaningful results. • The introduction must briefly refer to relevant aspects of the ecological niche. • And in detail when discussing the significance of he results in the discussion section of the report What is an Ecological Niche? COPY • “The opportunities provided by the habitat and the adaptations of the organism to make the most of those opportunities” • Aspects that should be focused on are: – The usual habitat of the organism and what the organism gains from this habitat. – Adaptations of the organism that allow it to exploit its ecological niche – Important relationships the organism has with others in the habitat, such as feeding, predation, competition. What is an Ecological Niche? COPY 1) For the habitat use quantitative or qualitative data for the factors (abiotic and biotic) 2) For adaptations consider structural, physiological, behaviour and life cycle as factors Planning an Investigation COPY Step 2: The Statement of Purpose • Needs to be very specific • Both independent and dependent variables should be clearly identifiable • Enable a quality method to be written that tests it • Must be related to an aspect of the ecological niche • Must not be a guess Planning an Investigation COPY Step 3: The Method • The independent variable must be clearly specified and it must have a range of values – At least 4 for Achieved. – No more than 6. – Light and dark do not constitute as a range - a range of at least four different specific intensities I.e. 0% light, 25% light, 50% light, 75% light, 100% light Planning an Investigation COPY • The dependent variable must be clearly specified – Activity/Growth is not specific enough – Measurement of the dependent variable must also be described. – I.e. ‘the time taken for 10 slaters to clump together’ Planning an Investigation COPY • How other key variables were controlled must be described. – These can affect the investigation if not controlled – Think abiotic! • Describing how the data will be collected – Use units where appropriate. – Try to write it for someone who has no background in biology. Clear and specific Planning an Investigation COPY • Ensure that when planning your method: – The range for the independent variable doesn’t go beyond the tolerance limits of the organism. – Its appropriate to the organism’s niche – The increments between the values of the range have been established in a valid way (trialing maybe done. Planning an Investigation COPY – The measurement of the dependent variable has been done in a valid way – How the data will be collected. – How the other variables or factors that may affect the investigation are controlled Planning an Investigation COPY Step 4: The Data The data collected can either be quantitative or qualitative….. What is the difference? • Quantitative: o Numerical data obtained through some type of measurement. oIt is relatively straightforward to analyse for reliability using some method of processing. oE.g. the water temperature is 25C Planning an Investigation COPY • Quantitative: • Descriptive rather than numerical. • Can be more variable as they are difficult to • measure objectively and can be difficult to establish the reliability • E.g. the water in the beaker is warmer than the water in the sink Planning an Investigation COPY • Collecting and recording data – Raw data measured and/or collected must be recorded and sufficient data must be collected so a trend or pattern can be seen (requirement for M or E) – The method should include ways in which sufficient data can be collected. – Several measurements for each independent value (repeats) and/or having a suitable range for the independent variable allows for a fair test. COPY – Data must be relevant. – Ensure your data is recorded clearly and accurately, flow on errors from mistakes can effect your grade. Planning an Investigation COPY • Data is normally recorded in tables or charts; features that allow any trends or patterns in the data to be clearly seen include: – A full title that includes descriptions of the independent and dependent variables – Full headings and appropriate units for each column and/or row. – Ruled lines around the sets of data – The data are ordered in a logical way – Raw and processed data are clearly identifiable from each other The effect of temperature on the heart rate of Daphnia magna (n=20) Full, descriptive title Independent variable Temperature(C) Avearge heart rate(beats min-1) 5 10 15 22 27 49 20 25 30 35 80 152 200 50 No units in body of table Full, descriptive headings Dependent variable Values vertically aligned and to same number of significant figures and/or decimal points. Planning an Investigation COPY • Transforming raw data in someway so that they can be used to show a pattern or trend. • Data should initially be processed (where appropriate) into the form that is stated in the hypothesis (e.g. rate, speed, density, percentage, frequency). • Correct number of significant figures needs to be used. Planning an Investigation COPY • Mean - the average of a set of data, calculated by adding the individual data values and dividing by the number of values. A consideration when calculating the mean is that outliers (values very different to other data points) skew the mean. Repeating an investigation several times can lead to outliers being rejected or ignored • Median - the middle value the same number of values are above the median as below. COPY the missing notes • Standard deviation – (S) represents the spread or variability of the data. A high standard deviation means that the data are widely scattered around the mean; the best way to reduce the standard deviation is for more data to be collected by repeating the investigation. •The standard deviation is usually calculated at the same time as the mean using the formula: S= QuickTime™ and a decompressor are needed to see this picture. Planning an Investigation • Standard Error - is a measure of how close your calculated sample mean is to the true population mean, i.e. the reliability of your sample mean. Standard error is calculated using the formula: – Confidence intervals shows the range in which a parameter such as the true mean is estimated to lie. They are usually shown on graphs as a line equidistant above and below each plotted parameter – 95% confidence range represents 2 standard deviations above and below, 99% represents 3 standard deviations above and below Planning an Investigation • Data can be processed into a graph (See Meg Bayley). – Line graphs – continuous data that have been obtained from an investigation into how the manipulation of one factor affects another – Histograms – continuous data recorded in categories or ranges, but the dependent variable is frequency rather than a measurement. – Bar graphs – used when data are discontinuous or cannot be quantified – Kite diagrams – used to show abundance of organisms, usually along a transect line in a field of study – Scatter graphs – drawn to show trends between two variables that correlate, but there is no manipulation of one of the variables. Your Data Is it grouped in separate divisions or in class size intervals Is it in a group Was one variable altered during the experiment Use a line graph Use a scatter graph Separate divisions Use a bar graph, kite graph or pie graph Class size intervals Use a histogram • Step 6: Statistical Analysis – Refer to Handout. • Step 7: Conclusion – Refer to Handout. • Step 8: The Report – Refer to Handout.