Biology Unit 4 AOS 3 - Lecture notes 1-3 PDF

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Experimental Variables Independent Variable is the only variable deliberately manipulated in an experiment. The purpose of an experiment is to test the effect of the independent variable on the dependent variable. Dependent Variable is being tested and measured in a scientific experiment. Values of the dependent variable depends on the independent variable or control. Controlled Variables are variables that must stay constant throughout the experiment. Controls show that experimental conditions are appropriate, and no unexpected independent variables are influencing the results. •

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Negative Control is a condition in which no independent variable are altered. Little to no change in the dependent variable is expected. o If substantial change is observed in the negative control, it may indicate that an additional variable is acting in the study. o This variable needs to be identified and controlled in a repeat experiment. o Using an example in a fertiliser experiment, the group with no fertiliser is a negative control for the experiment. Positive Control is a condition in which an effect is expected, demonstrating that the mechanism of measurement will respond to experimental conditions. o Positive Controls are valuable in assessing reliability of data generated o Using an experiment in a fertiliser experiment, the use of a standard fertiliser is a positive control as it can be expected that it will enhance root growth.

Extraneous Variables are all variables, except the independent variable, that could affect the results of the experiment. All extraneous variables must be controlled if possible. • • •

Situational Variables in the environment can affect results of an experiment such as changes in lighting conditions or changes in temperature. Investigator Variables may impact the experiment if the scientist unconsciously conducts the experiment in a way in which results may be more favourable. This is experimental bias. Participant Variables refer to how individual participants vary from each other. This can include health status or prior knowledge if humans are involved in the experiment.

Confounding Variables are uncontrolled extraneous variables that affect both the independent variable and dependent variable, causing a spurious association. They can muddle with results, as results may depict a cause and effect pattern when that doesn’t exist. In Psychological experiments, this can include age. •

Confounding variables can be controlled by random sampling.

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Scientific Concepts and Measurements Theory is a scientific explanation of aspects of the natural world that can be repeatedly tested and verified in accordance with the scientific method, using accepted protocols of observation, measurement and evaluation of results. Model is a representation of an idea, an object or a process that is used to describe and explain phenomena that cannot be expressed directly. Eg lock and key model of enzyme-substrate. Law is a generalised rule to explain a body of observations in the form of a verbal or mathematical statement. Scientific Laws imply a cause and effect between the observed elements and must always apply under the same conditions. Eg law of conservation of mass. Hypothesis is a testable prediction or explanation for a phenomena, fact or scientific inquiry which may be tested or not supported by a methodological experiment. Aim is the main purpose of designing the experiment. Accuracy is the degree of similarity between a measurement value and a reference ‘true’ value ➢ Impacted by systematic errors ➢ Measurement values with greater level of exactitude are considered more accurate as they are more likely to be closer to the ‘true’ value. ➢ Improved by ensuring devices are calibrated using known standards before testing for unknown values. Precision refers to the degree of similarity between multiple measurement values. ➢ Impacted by random errors, which cannot be avoided. ➢ Improved by controlling all possible extraneous variables to ensure experimental conditions are consistent. ➢ Improved using correct measurement tools to minimise the effect of error Reliability refers to being able to yield the same results upon repeated trials of the experiment. ➢ Objective data is more reliable than subjective data ➢ Improved by increasing the size of the data set via repetitions or reproductions. o Repeatability refers to multiple trials conducted concurrently using the same stock of equipment. Same operator, same apparatus and/or same lab. o Reproducibility refers to trials conducted asynchronously using different stocks of equipment. Different operators, different apparatus and/or different lab ➢ Increasing the size of a data set does not automatically increase reliability. The results must be consistent. Measures of central tendency identify most representative value of data sets Fairness refers to only changing and measuring a single condition when attempting to answer a scientific question. Relevant extraneous variables must be controlled for an experiment to be fair. Validity describes the extent to which results achieve the aim and/or conclusions represent the actual experimental outcomes. ➢ Correlations describe connections between two variables, whereas causations describe relationships between variables, where one variable directly impacts the other variable. ➢ Improving accuracy, precision, validity and fairness will improve validity.

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Scientific Method for Investigations Section Title Introduction Method

Results Discussion

Conclusion

References and Acknowledgements

Content and Activities The main idea and purpose of the experiment posed as a testable and concise question. Explanation or reason for undertaking the investigation. This includes the aim and the hypothesis and relevant background biological concepts. • Summary that outlines the process used in the investigation and is authenticated by logbook entries • Identification and management of relevant risks, including relevant health, safety and ethical guidelines followed in the investigation. • Designed to minimise errors with justification • IV and DV clearly identified. Attempt to control as many extraneous variables • Allows for the production of reliable results that relate to the title. Repeat the experiment should always be the last step of the method. Presentation of collected data/evidence in an appropriate format to illustrate trends, patterns and relationships. All results/observations need to be in logbook. • Analysis and evaluation of the data. Explanation of usefulness of data • Critical evaluation of reproducibility and repeatability • Appropriate level of manipulations to the data obtained • References to correlations between IV and DV • Identification of outliers and their subsequent treatment • Discussion of Accuracy, Precision, Reliability and Validity • Identification of limitations in data and methods • Practical suggestions for improvement to the experiment • Fully developed use of scientific conventions and language • Accurate explanations of the link between experimental results and relevant scientific concepts, relationships and principles. • Provides a reasoned response to the question posed in the title • Communicates valid reflections to the aim and hypothesis • Conclusion must be reasonably inferred from the data and explain the difference between expected and unexpected results if applicable • Suggestions for improving or extending the investigation. Referencing and acknowledging of all quotations and sourced content as they appear in the report or poster. The referencing must be consistent. Logbook authentication acknowledgement must be provided.

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Fields of Study Biochemistry is the study of chemical processes in living organisms. Methods of studying Biochemistry include: •

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Studying DNA o DNA Hybridisation Technique is used to establish evolutionary relationships between two different species. o Polymerase Chain Reaction (PCR) is used to amplify small DNA fragments. o Gel Electrophoresis is used to separate fragments of DNA based on their size. o DNA sequencing using Sanga method used to sequence the whole human genome. o DNA Profiling is a technique used to identify individuals based or to determine the degree of relatedness between individuals. DNA fingerprints establish DNAS banding patterns at multiple loci using STRs. o Gene Cloning involves locating a gene of interest then cloning it to produce multiple exact copies of the same gene. o Genetic Screening involves testing a population to identify individuals at risk of developing genetic diseases or passing on alleles associated with genetic disorders. Studying Enzymes o Plant hormones are commercially available to experiment with o Animal enzymes are also commercially available, such as catalase, amylase and trypsin. The activity of these enzymes can be measured by their product formation. Eg measuring rate of O2 production in catalase experiments. Biochemical Assays o Bicinchoninic Acid (BCA) Assay determines protein concentration in a solution o Enzyme-Linked Immunosorbent Assay (ELISA) uses monoclonal antibodies to test for the concentration of a specific molecule, such as a virus in a blood sample. o Liquid Chromatography separates components of a solution. o Luminol tests for the detection of blood, copper or iron in cellular assays.

Cytology is the study of living cells, including their anatomy and behaviour. Methods of studying cytology include: •

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Immunohistochemistry tests for molecules on cells or tissue on a microscope slide. This uses antibodies with fluorescent markers or enzymes that convert a particular substrate to a product. The antibodies are specific to epitopes of the molecule being scanned for. o Differs from ELISA as it is testing for molecules on cells, not fluids. Elodea plants are common sources of plant for cytological studies. Beetroots are useful sources of fruits for cytological studies.

Immunology is the study of immune systems of various organisms. •

ELISA is most common immunological testing method. It has three purposes: o Used for detection of pathogen amount in a sample o Presence of antibodies against a specific antigen in a fluid sample. o Testing for allergies in food.

Geomorphology

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