Ch. 1 - A Practical Investigation

AS91601 (B3.1): “Carry out a practical investigation in a biological context with guidance”

Goal:

• Develop a sound practical investigation

• Present a report with a comprehensive discussion of the investigation

The investigation can involve:

• The manipulation of variables - isolating a variable to investigate, and controlling the rest

  eg. the effect of nutrient levels on plant growth

• Investigation of a pattern or relationship

• Use of models to predict or explain what might happen in a certain situation, drawing from current knowledge

  eg. Predicting the spread of a new strain of COVID-19 based on knowledge on known strains

DEVELOPING + CARRYING OUT INVESTIGATION

1. Select organism

*Strict guidelines for using certain bacteria due to potential pathogenic effect

**Except those found on skin - these can be used but must remain sealed

2. Become familiar with the study organism(s)

You will need to find out the organism(s)’s

• Usual habitat/Lifestyle/ecological niche

  • This will allow you to look after the organism correctly so the responses/behaviours are a result of investigation and NOT because of physiological stress

• How the organism should behave or respond to your investigation and what responses you should keep an eye out for

  • Doing pre-reading on typical behaviours of your organism will allow you to identify the causal relationship between the organism response & the factor you are investigating

  • If the behaviour is out of the ordinary, you can identify it, and then discuss potential reasons why the organism exhibited such behaviour

Sources of information you can use:

1. Books or textbooks

2. Websites

3. Your experimental observations and/or other students’ experimental observation

4. Peer-reviewed studies

Aspects to guide your research

*Independent variable

3. Formulating a purpose

Purpose → hypothesis = prediction statement (if xyz happens, then abc will happen)

Checklist for a good hypothesis

• Is the hypothesis easily testable by experimentation?

• Has it specified both the independent and dependent variables (IV & DV)?

Examples

• Increasing the intensity of light (independent variable) will increase the intensity of the kinesis response (dependent variable) exhibited by the woodlice

NOTE: When gathering data, you should be gathering data that either supports or rejects the hypothesis, not prove/disprove

• It is important to have a precise and well-written hypothesis to develop an experimental plan

4. Designing a method

Rule of thumb - Keep it simple but precise

A good method will:

• Be able to be replicated by someone else

  → This could mean adding diagrams so they know how to use

• Use readily available equipment

• Yield straightforward results to be analysed and interpret

• Be clear about what is being measured - the dependent variable

  → What the DV is

  → How it is going to be measured or sampled

• Be clear about what is being manipulated - the independent variable

  → Must be 1 variable only

  → The IV must have a range of values that are to be investigated

• Indicate variables that need to be controlled to ensure an unbiased and valid experiment

  → How the CV will be controlled

• Outline assumptions that need to be made with this study

  → These are variables outside your control despite your best efforts to control them

• Have precise instructions on collection of data

  → What data will be collected?

  → When will it be measured?

  → What is the unit of measurement?

  → How will it be measured? ie. with what equipment?

  → How the raw data will be processed? ie. will it be averaged?

NOTE: Be prepared to trial and adjust your method. This can ensure that

• Sufficient data can be collected from this method

• The range for the IV is able to be worked with

• Variables that need to be constant are adequately controlled

COLLECTING, RECORDING AND PROCESSING DATA

1. Collecting

• Data should be collected the moment you start studying your organism

→ this could be general observations of its behaviour as well as other factors ie. abiotic or biotic, that are present

2. Recording

Raw data

• Unprocessed data

• Must still be recorded in a retrievable way

• Usually presented in a table/chart format that has

  → A full and informative title

  → Each column or row has a full and informative heading with units where applicable

Process data

• To process raw data you either calculate the averages and/or standard deviations

• These are recorded and discussed in the results and discussion section of the report

• After processing, data is used to draw a graph to identify a relationship between the IV and the DV - or the lack of

• Examples: Averages, means, graphs drawn to illustrate patterns or trends, results of any statistical analysis

• Two kinds of data

  1. continuous data → measurements where each piece of data can take on any value between the smallest and the largest value in the range

  2. discrete data → counts - ie. no intermediates between adjacent values. “You can’t have 2.5 people!!“

3. Formats of data presentation

For every graph make sure

• Title

• Labels

• Units

REPORT STRUCTURE

1. Purpose

   • Hypothesis linked to a biological concept/idea & meets above requirements

2. Method

   • Final and refined method

   • Clearly structured, and as precise & concise as possible without losing essential steps

3. Results

   • Should only contain your processed data - raw data → appendix and logbook

   • Should include an interpretation of processed data

     → What does the data presented indicate?

4. Conclusion: short paragraph

   • State outcome of investigation

   • Identify the relationship between DV and IV

   • Must refer back to hypothesis

   • DO NOT restate/describe results, or discuss the results in terms of the biology of organism

5. Discussion

   • Explain biological ideas or concepts relevant to investigation

   • Here is where you can synthesise all the information you have learnt together. Including

     • Your findings

     • Other studies and their findings*

     • Key biological concepts relevant to your organism

       *try not to spend too much time describing their study, instead, use their studies to support your findings

   • Must explain the significance of the results in terms of the biology, not just reiterate/describe

6. Justification - justify choices you made during the investigation

   • Justify your choice of control variables and how they were maintained

   • Justify your range of values for the independent variable

   • Justify the changes you made to your method

   • A good thing to consider is how all of these affect the validity of your study ie. do these affect the amount of error and bias in your study?

7. Appendix

   • Raw data

   • Logbook that was used to record all the observations, changes, and refinement of the investigation process to show the ongoing nature of the investigation

8. Referencing

   • Correctly use in-text citations or footnotes, and the correct format for the list

   • Reference list = only sources of information actually cited in the report

   • APA 7 is a common style