Advanced Higher Biology Course Specification PDF

Investigative biology Key area Depth of knowledge required Suggested learning activities 1 Scientific principles and process (a) Scientific method Scientific cycle — observation; construction In science, refinement of id...

Investigative biology Key area Depth of knowledge required Suggested learning activities 1 Scientific principles and process (a) Scientific method Scientific cycle — observation; construction In science, refinement of ideas is the norm, Research Karl Popper’s concept of of a testable hypothesis; experimental and scientific knowledge can be thought of as falsifiability as the basis for scientific thinking. design; gathering, recording, and analysis of the current best explanation, which may then data; evaluation of results and conclusions; be updated after evaluation of further the formation of a revised hypothesis where experimental evidence. necessary The null hypothesis proposes that there will Failure to find an effect (a negative result) is Research recent examples of scientific be no statistically significant effect as a result a valid finding, as long as an experiment is breakthroughs to identify any examples of of the experiment treatment well designed. Conflicting data or conclusions unexpected results, conflicting data, or can be resolved through careful evaluation or creative experimentation. can lead to further experimentation. If there is evidence for an effect, unlikely due to chance, then the null hypothesis is rejected Scientific ideas only become accepted once Effects must be reproducible; one-off results they have been checked independently are treated with caution. (b) Scientific literature and communication The importance of publication of methods, Common methods of sharing original data, analysis, and conclusions in scientific scientific findings include seminars, talks and reports so that others are able to repeat an posters at conferences, and publishing in experiment academic journals. Version 4.1 109  Investigative biology Key area Depth of knowledge required Suggested learning activities The importance of peer review and critical Most scientific publications use peer review. Compare the dispassionate approach taken evaluation by specialists with expertise in the Specialists with expertise in the relevant field in presenting scientific results with the relevant field assess the scientific quality of a submitted passionate reality of scientific investigation, manuscript and make recommendations described in Frederick Grinnell’s book, regarding its suitability for publication. The Everyday Practice of Science: Where Intuition and Passion Meet Objectivity and Logic. The use of review articles, which summarise [Grinnell F. (2008), The Everyday Practice of current knowledge and recent findings in a Science: Where Intuition and Passion Meet particular field Objectivity and Logic, Oxford: Oxford University Press] Critical evaluation of science coverage in the wider media Increasing the public understanding of science, and the issue of misrepresentation of science (c) Scientific ethics Importance of integrity and honesty — While judgements and interpretations of Discuss excerpts from Ben Goldacre’s book, unbiased presentation of results, citing and scientific evidence may be disputed, integrity Bad Science providing references, avoiding plagiarism and honesty are of key importance in Goldacre B. (2008), Bad Science, London: science. The replication of experiments by Fourth Estate others reduces the opportunity for dishonesty or the deliberate misuse of science. Use a standard system, such as Harvard or Vancouver, to make appropriate citations in a piece of scientific writing and to construct a Version 4.1 110  Investigative biology Key area Depth of knowledge required Suggested learning activities reference list that allows another investigator to locate your source material. In animal studies, the concepts of replacement, reduction, and refinement are used to avoid, reduce or minimise the harm to animals Informed consent, the right to withdraw, and Discuss the implications of the British confidentiality in human studies Psychological Society’s ethical guidelines on school-based investigations on humans. The justification for scientific research and The value or quality of science investigations the assessment of any risks must be justifiable in terms of the benefits of its outcome, including the pursuit of scientific knowledge. As a result of the risks involved, many areas of scientific research are highly regulated and licensed by governments. The risk to and safety of subject species, individuals, investigators and the environment must be taken into account Legislation, regulation, policy and funding Legislation limits the potential for the misuse can all influence scientific research of studies and data. Version 4.1 111  Investigative biology Key area Depth of knowledge required Suggested learning activities 2 Experimentation Validity, reliability, accuracy and precision Validity: variables controlled so that any measured effect is likely to be due to the independent variable. Reliability: consistent values in repeats and independent replicates. Accuracy: data, or means of data sets, are close to the true value. Precision: measured values are close to each other. (a) Pilot study Integral to the development of an Follow a multi-step protocol, such as protein investigation, a pilot study is used to help electrophoresis, mitotic index, or cell cycle plan procedures, assess validity and check mutation in yeast, to appreciate the need to techniques practise difficult techniques. This allows evaluation and modification of experimental design The use of a pilot study can ensure an Use a pilot study to establish ranges for appropriate range of values for the variables in an investigation, such as enzyme independent variable activity or Daphnia heart rate. Version 4.1 112  Investigative biology Key area Depth of knowledge required Suggested learning activities In addition, it allows the investigator to establish the number of repeat measurements required to give a representative value for each independent datum point (b) Experimental design (i) Independent and dependent variables An independent variable is the variable that is changed in a scientific experiment. A dependent variable is the variable being measured in a scientific experiment. Independent and dependent variables can be continuous or discrete Experiments involve the manipulation of the independent variable by the investigator The experimental treatment group is compared to a control group The use and limitations of simple (one The control of laboratory conditions allows independent variable) and multifactorial simple experiments to be conducted more (more than one independent variable) easily than in the field. However, a drawback experimental designs of a simple experiment is that its findings may not be applicable to a wider setting. Version 4.1 113  Investigative biology Key area Depth of knowledge required Suggested learning activities A multifactorial experiment involves a combination of more than one independent variable or combination of treatments. Investigators may use groups that already exist, so there is no truly independent variable Observational studies are good at detecting In observational studies the independent Carry out an observational study in which the correlation, but since they do not directly test variable is not directly controlled by the investigator groups the independent variable, a hypothesis, they are less useful for investigator, for ethical or logistical reasons. such as a study of the effect of gender in a determining causation human study. (ii) Confounding variables Due to the complexities of biological systems, Design and carry out a simple laboratory true other variables besides the independent experiment, such as an enzyme experiment, variable may affect the dependent variable where confounding variables are tightly controlled. These confounding variables must be held Design and carry out a field observational constant if possible, or at least monitored so study, such as an environmental transect, that their effect on the results can be where the independent variable is not under accounted for in the analysis direct control and where confounding variables cannot be tightly controlled. Version 4.1 114  Investigative biology Key area Depth of knowledge required Suggested learning activities In cases where confounding variables cannot Randomised blocks of treatment and control easily be controlled, a randomised block groups can be distributed in such a way that design could be used the influence of any confounding variable is likely to be the same across the treatment and control groups. (iii) Controls Control results are used for comparison with the results of treatment groups Negative and positive controls may be used The negative control provides results in the Design an experiment with positive and absence of a treatment. A positive control is negative controls, such as a laboratory a treatment that is included to check that the investigation using an enzyme. system can detect a positive result when it occurs. Use of placebos and the placebo effect Placebos can be included as a treatment without the presence of the independent variable being investigated. Placebo effect is a measurable change in the dependent variable as a result of a patient’s expectations, rather than changes in the independent variable. Version 4.1 115  Investigative biology Key area Depth of knowledge required Suggested learning activities (iv) In vivo and in vitro studies In vitro refers to the technique of performing Examples of in vitro experiments: cells a given procedure in a controlled growing in culture medium, proteins in environment outside of a living organism solution, purified organelles. In vivo refers to experimentation using a whole, living organism Advantages and disadvantages of in vivo and in vitro studies (c) Sampling Where it is impractical to measure every individual, a representative sample of the population is selected The extent of the natural variation within a population determines the appropriate sample size More variable populations require a larger sample size A representative sample should share the same mean and the same degree of variation about the mean as the population as a whole Version 4.1 116  Investigative biology Key area Depth of knowledge required Suggested learning activities Random, systematic and stratified sampling In random sampling, members of the In ecological studies, use random numbers to population have an equal chance of being select quadrats for sampling. selected. In systematic sampling, members of a population are selected at regular Establish sample size by determining a intervals. In stratified sampling, the travelling mean or the cumulative total of population is divided into categories that are species in quadrats. then sampled proportionally. Use line or belt transects to systematically sample an environment. Use stratified sampling to sample habitats that are not uniform, using a standard formula to calculate the number of samples from each area. (d) Reliability Variation in experimental results may be due to the reliability of measurement methods and/or inherent variation in the specimens The precision and accuracy of repeated The reliability of measuring instruments or Determine the precision of a measuring measurements procedures can be determined by repeated procedure by repeated measurements, and measurements or readings of an individual the accuracy of a measuring procedure by datum point. The variation observed indicates calibration against a known standard. the precision of the measurement instrument or procedure but not necessarily its accuracy. Version 4.1 117  Investigative biology Key area Depth of knowledge required Suggested learning activities The natural variation in the biological material being used can be determined by measuring a sample of individuals from the population The mean of these repeated measurements will give an indication of the true value being measured The range of values is a measure of the extent of variation in the results If there is a narrow range then the variation is low Independent replication should be carried out Overall results can only be considered to produce independent data sets reliable if they can be achieved consistently. These independent data sets should be compared to determine the reliability of the results (e) Presentation of data Discrete and continuous variables give rise to Qualitative data is subjective and descriptive. qualitative, quantitative, or ranked data Quantitative data can be measured objectively, usually with a numerical value. Version 4.1 118  Investigative biology Key area Depth of knowledge required Suggested learning activities Ranked data refers to the data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest. The type of variable being investigated has consequences for any graphical display or statistical tests that may be used Identification and calculation of mean, median and mode Use of box plots to show variation within and Median, lower quartile, upper quartile and between data sets inter-quartile range. Interpret error bars on graphical data Correlation exists if there is a relationship Correlation is an association and does not between two variables imply causation. Causation exists if the changes in the values of the independent variable are known to cause changes to the value of the dependent variable Positive and negative correlations A positive correlation exists when an increase in one variable is accompanied by an increase in the other variable. Version 4.1 119  Investigative biology Key area Depth of knowledge required Suggested learning activities A negative correlation exists when an increase in one variable is accompanied by a decrease in the other variable. Strong and weak correlations Strength of correlation is proportional to spread of values from line of best fit. Correlation values are not required. 3 Reporting and critical evaluation of biological research (a) Background information Scientific reports should contain an Background information should be clear, explanatory title, an abstract including aims relevant and unambiguous. A title should and findings, an introduction explaining the provide a succinct explanation of the study. purpose and context of the study including An abstract should outline the aims and the use of several sources, supporting findings of the study. statements, citations, and references An aim must link the independent and dependent variables. The introduction should provide any information required to support: choices of method, results, and discussion. An introduction should explain why the study has been carried out and place the study in the context of existing understanding. Key points should be summarised and supporting and Version 4.1 120  Investigative biology Key area Depth of knowledge required Suggested learning activities contradictory information identified. Several sources should be selected to support statements, and citations and references should be in a standard form. Decisions regarding basic selection of study methods and organisms should be covered, as should the aims and hypotheses. (b) Reporting and evaluating experimental design A method section should contain sufficient information to allow another investigator to repeat the work Experimental design should address the The validity and reliability of the experimental intended aim and test the hypothesis design should be evaluated. An experimental design that does not address the intended aim or test the hypothesis is invalid. Treatment effects should be compared to controls Any confounding variables should be taken into account or standardised across treatments Version 4.1 121  Investigative biology Key area Depth of knowledge required Suggested learning activities The validity of an experiment may be compromised when factors other than the independent variable influence the value of the dependent variable The effect of selection bias and sample size Selection bias is the selection of a sample in on representative sampling a non-random way, so that the sample is not representative of the whole population. Selection bias may have prevented a representative sample being selected. Sample size may not be sufficient to decide without bias whether the change to the independent variable has caused an effect in the dependent variable. (c) Data analysis The appropriate use of graphs, mean, In results, data should be presented in a median, mode, standard deviation and range clear, logical manner suitable for analysis. in interpreting data Consideration should be given to the validity of outliers and anomalous results. Statistical tests are used to determine Knowledge of specific statistical tests is not Explore error bars showing standard whether the differences between the means required. deviation, standard errors, or range. These are likely or unlikely to have occurred by could be used in project work, where chance appropriate. Version 4.1 122  Investigative biology Key area Depth of knowledge required Suggested learning activities A statistically significant result is one that is unlikely to be due to chance alone Error bars indicate the variability of data around a mean If the treatment mean differs from the control mean sufficiently for their error bars not to overlap, this indicates that the difference may be significant (d) Evaluating results and conclusions Conclusions should refer to the aim, the results and the hypothesis The validity and reliability of the experimental design should be taken into account Consideration should be given as to whether the results can be attributed to correlation or causation Evaluation of conclusions should also refer to Meaningful scientific discussion would existing knowledge and the results of other include consideration of findings in the investigations context of existing knowledge and the results of other investigations. Scientific writing should reveal an awareness of the contribution of scientific research to Version 4.1 123  Investigative biology Key area Depth of knowledge required Suggested learning activities increasing scientific knowledge, and to the social, economic and industrial life of the community. Version 4.1 124