Extended experimental investigation

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Although the syllabus suggests that the Year 12 Extended Experimental Investigation should be the choice of each student, it is also important that students gain experience in this style of assessment. Thus during Year 11 they should be given the opportunity to develop the skills of asking questions, formulating a hypothesis, designing and carrying out the experimental investigation, collecting data and presenting it in an appropriate format, interpreting and analysing the data and evaluating the validity of the results. Many teachers will prefer that the investigation be conducted on a topic related to the unit currently being studied. One approach could be to present the students with an observation or observations that could lead the student to specific questions that could then be investigated.

PRIOR to setting any practical assessment items the following questions should be asked:
1. What OBJECTIVES are to be assessed?

2. What are the best means of assessing these objectives?

3. What learning experiences are involved in the item?

4. Can students synthesise and evaluate the data obtained?

5. What is the best method of presenting the results and interpretation?

6. How will you ensure that the students interpret their results, discuss these interpretations in the light of theoretical knowledge and draw conclusions from their work?

7. What meaningful educational benefits will the students gain from this assessment?

8. What proportion of the work will be completed in the student's own time?

9. What means can be employed to ensure ownership of the submitted work if the student is performing the investigation predominantly away from school (e.g. an independent field investigation)?

10. What CRITERIA will be employed to assess the work?

11. If group tasks are involved, what criteria will be allocated for individual students?

Is cooperation assessed?

What do you do if one student is not, or is not perceived to be, effectively contributing?
E.g.: a project was set in which students:
a. Established and maintained a protozoan culture.

b. Sampled the culture at regular intervals by:

i. identifying the types of organisms in a specific volume,

ii. drawing and classifying (to Order) each of the protozoans present,

iii. recording the numbers of each type in the specific volume,

iv. recording the presence of other types of organisms in the sample,

v. measuring physical parameters such as pH, temperature, and opacity of the water in the culture tank, etc.

c. Undertook a library search for similar experiments.

d. Interpreted their data and evaluated it in the light of previous knowledge.

d. Proposed a hypothesis to explain their observations.

e. Presented their findings in the correct scientific format.
(Note: This investigation could be easily modified to become an investigation into the population dynamics of the Billabong Bug.)

The students were allowed class time in the library as well as some class periods for identification of organisms and general discussion of their results. Setting up of their experiment and sampling were undertaken in class time in the school laboratory with the teacher acting as a resource person. Students were expected to keep a logbook showing both library research and sampling progress which would be regularly checked by the teacher.

The general objectives being assessed included the ability to:


a. recall relevant facts, definitions and concepts

b. recall correct terminology and conventions of Biological Science

c. communicate information by presentation of a written report


  1. identify and formulate questions and hypotheses for investigation and research

  2. design, manage and carry out the investigation

c. collect information by observation, measurement and library research

d. organise information collected

e. analyse data collected

  1. evaluate data from experimental data and other sources to draw conclusions

g. evaluate the validity of the data


a. care for living organisms in a responsible and ethical manner

b. select, assemble, dismantle, clean and return materials and equipment

  1. maintain cultures

  2. make wet mount slides and use a microscope to observe specimens

  3. use appropriate methods and equipment to measure environmental factors

  4. draw biological specimens.


Students are given the opportunity

a. To understand that science is a human endeavour and has limitations.

b. To demonstrate collegiality and cooperation.

c. To retain a commitment to scientific reasoning, openness to new ideas, intellectual honesty, and respect for evidence.

d. To develop respect for living organisms.
Obviously the assessment of any specific part of the assignment would depend on such factors as:

  • The depth the teacher requires of the students.

  • The time allocated to the investigation.

  • The amount of help provided by the teacher, etc.

The handout to the students should show the objectives being assessed, the criteria and all deadlines.

Assessment Criteria could include the following:





Recall (UB1)

Discuss /

Apply / Link (UB3)

Questions / hypothesis (IB1)

Experimental design, management and performance (IB2)

Data collection / Organisation of data / interpretation (IB3)

Analysis of data (IB4)

Judge validity of the investigation (IB5)


Correct format (as stipulated)

Spelling and grammatical expression

Correct use of terminology

Effective use of library research

Correct citing of references


Showing questions asked and development of hypothesis


Design well described

Evidence of controls

Description of data collection

Description of sampling techniques

Management of the experiment

Performance of the experiment


Presentation – clear, easy to interpret inter-relationships between parameters

Drawings – Accurate representations following biological procedures Microscope and drawing magnification Labels Identification to Order


Interpretation of results

Analysis in light of previous research

Linkage to general concepts

Difficulties in sampling, identification etc.

Validity of results

Critique of method


Relationship to the hypothesis


Using the task given:
1. To raise questions about the observation / problem.

2. To undertake library research related to the task.

3. To maintain the chosen organism(s) for sufficient time to allow observation and experimentation.

4. To develop some the questions into specific hypotheses, expressed in operational terms.

5. To design simple experiments to test the hypotheses raised.

6. To control as far as possible all significant extraneous variables.

7. To carry out the experiments designed.

8. To collect and record data from the experiments.

9. To present the data as tables and/or graphs where appropriate.

10. To interpret the data/results in the light of the hypotheses raised.

11. To decide when you have sufficient observations to make valid interpretations.

12. To make links between the experimental data, and data and/or observations from similar research and theoretical concepts.

13. To critically analyse the experimental procedure to form a conclusion on the validity of the results.

14. To communicate your questions, hypotheses, experimentation interpretations and conclusions in the form of a scientific paper.


  1. Have a standard or control as well as a manipulated (experimental) condition.

  1. Test only one variable at a time.

  1. Design simple experiments. Complex apparatus is no guarantee of sophisticated research.

  1. More organisms and more trials will increase the confidence of an interpretation. How many trials is enough can only be determined in retrospect. However, there should be approximately 25 subjects for each experimental variable.

  1. The most efficient experiment is one which yields clear cut interpretations with a minimum of effort.

  1. Before doing the actual experiment, work out exactly what you are going to record, particularly if these results are to be quantitative. Also record any other unexpected or unusual observations – these may help in your interpretation, or suggest further tests which could help solve the problem.

  1. Statistical tests, when used appropriately, are tools which increase the precision of interpretation.


  • Use A4 paper.

  • No photocopied material is acceptable.

  • If handwritten the report must be legible. Computer printouts are acceptable.

  • Include all your raw data as an appendix.

  • Clearly state the organisms used.

  • Diagram, photograph or describe the procedure and apparatus in sufficient detail so that one of your classmates could repeat the experiment exactly from your description.

  • Justify your experimental method, identifying possible extraneous variables and how they are eliminated.

  • State the problem under investigation and specific hypothesis for each experiment if a series of variables is being examined.

  • Present your results (i.e. summaries of your raw data) in the form of graphs and tables where appropriate.

  • Distinguish between actual observations/measurements you made, observations made by others (if any) and inferences and deductions made from the results.

  • Be logical and objective.

  • Be clear and concise.

  • Write in the third person* (It was observed rather than I observed, etc.).

  • Avoid anthropomorphism.

  • Make interpretations that are based on actual results, not on what you thought should happen.

  • Draw a conclusion which relates to your hypothesis.

  • Remember to look at journals, such as New Scientist and Scientific American, as well as reference books and the internet for background information.

* The school may determine if they wish this method of presentation or not.

Note: The school must ensure that all Workplace Health and Safety requirements are met. For those topics below marked with an asterisk, the school would need to check with the Bioethics Committee for permission to conduct the investigation.

1. Germination of Australian native plants
The ‘recent’ history of many Australian ecosystems has been associated with fairly regular bush fires. It has been observed that germination of seeds of many species does not occur without these fires. Several ideas have been proposed to explain this observation, e.g.:

  1. Tannins in eucalypt leaf litter inhibit seedling development, thus reducing competition for scarce resources by established plants. The fires destroy these tannins, thus allowing seed germination.

  1. The seed coats and/or pods of many species are very hard and need the heat of the fire to crack them and so allow germination. Again this would be an adaptation in a harsh environment to prevent competition for resources.

  1. Quick burning fires release valuable minerals to the soil so that they are available to the young germinating plants.

  1. Burning decreases build up of slowly decomposing litter and removes the canopy of shrubs and small trees, thus allowing adequate light for growth of young plants.

Each of these ideas may apply to different species.

Scientists in south Western Australia have recently found that, for the species they have studied, it is not the actual fire that promotes germination but the smoke from the fire. When they bubble smoke through water and then, in artificial conditions, apply this water to pots containing indigenous plant seeds, the rate of germination is higher than with normal water or with heat-treated seeds. The soils in this area are sandy, with low mineral content and poor water retention. Design an experiment to test the following question:
Do the seeds of plants from the SE Queensland area (e.g. Banksia from wallum areas, Acacia fimbriata from forest areas, Eucalyptus curtisii from the Ipswich sandstone areas) have a higher germination rate if they are treated with smoky water than with heat-treatment or no treatment?

2. Dust Mites
Dust mites are considered to be a major cause of asthma and other related allergic responses to the respiratory tract. It has also been suggested that these small organisms may be a contributory factor in Sudden Infant Death Syndrome. Dust mites are believed to feed on human skin flakes and other organic debris.
Design experiments to:

a. Determine the areas in the house that are most prone to dust mite congregation by:

i. Working out a method to collect a set sample size from each area.

ii. Collecting samples from various areas (the mites can be preserved in methylated spirits in a bottle for transport to school for microscopic examination).

b. Test practical means of controlling the mites in high population areas.

3. Vinegar as an antibiotic
Proponents of the use of vinegar as a natural therapy have even suggested that this versatile solution could be used to effectively sterilise hospitals against bacteria. Bacteria are ubiquitous. They are found on the surface of all matter. Many can withstand a wide range of environmental conditions, e.g. freezing.
Design and carry out experiments to determine:

a. If vinegar is effective in preventing bacterial decay of frozen peas which have been defrosted under controlled conditions.

b. If it is the actual chemical acetic acid, or other chemicals found in some types of vinegar, that act as a sterilising agent.

c. The most effective concentration of vinegar in the control of bacterial decay of these frozen peas.

d. The range of bacterial colonies developed on frozen peas.
NB These experiments must be performed at school under strict aseptic conditions in order to minimise spread of bacteria. Discuss the methods you propose to use with your teacher or the laboratory technician. Disposal of plates (which must never be opened) must be done by the teaching staff following correct procedures.

4. Mosquito control in pot plants
Mosquitos are vectors for a number of human diseases, e.g. Ross River Fever, Dengue Fever and Bahma Forest Disease. It is recommended that during the breeding season (summer) all open containers, e.g. pot plant saucers, be prevented from holding water. Many modern pot plants, however, are self-watering. They have a water well at the base which is filled with water. The plants therefore have a supply of water as they require it. In order to overcome the problem of mosquito breeding, one enterprising person suggested that bleach placed in the well would kill any mosquito larvae.
Design and carry out experiments to:

a. Test if bleach (the common active constituent is sodium hypochlorite) kills mosquito larvae.

b. Determine the most effective concentration (the original concentration may vary from brand to brand) for killing mosquitos.

c. Determine if the common fish-bone fern is affected by this concentration of bleach in its soil water. (You will need to establish approximately 25 ferns in pots at the start of your experimentation to allow them to stabilise after transplanting and before testing.)

5. Factors affecting metamorphosis in tadpoles*
It has been observed that frog tadpoles reared in captivity do not grow and develop at the same rate even though they may hatch from the egg at the same time. As the first tadpole develops legs, the development of the rest of the tadpoles is suppressed until the metamorphosis is completed. Once this frog has left the water another tadpole develops legs and so on.
Design and carry out experiments to determine:

a. If population density was a factor in the suppressed development.

b. If amount of food available was a factor in the suppressed development.

6. Growth of wattles after a fire
In a mature eucalypt forests there are very few wattle trees yet after a bush fire these become very prolific.
Design and carry out experiments to determine factors associated with bush fires that influence germination and growth of a specific species of wattle common in your area.
7. Germination of the blackbean
The Moreton Bay Chestnut (or blackbean) tree normally grows along creek banks. They produce numerous large woody pods containing three to four seeds. Very few of these seeds germinate in the vicinity of a mature tree but will readily germinate downstream when washed up on a bank.
Design and carry out experiments to determine factors associated with this observation.

8. The effect of music on human emotions
It has been observed that different human emotions are often triggered by particular styles of music.
Design and carry out experiments to investigate this observation to determine if this is a general statement or determined by specific variables.

9. Site selection by ant lion larvae
Conical pits constructed by ant lion larvae are often found in dry, sandy soil. The larvae buries itself in the soil at the bottom of the pit with only its sharp mandibles exposed. When prey, such as ants, fall into the pit they are seized by the mandibles and devoured.
Design and carry out experiments to investigate factors influencing the choice of site for pit construction by ant lions.

10. Human body language
Human body language often sends a stronger message than verbal communication.
Design and carry out experiments to determine variables that influence the effectiveness of one human body language signal.

11. Learning in cane toads*
Examination of the gut contents of the cane toad has shown that cane toads eat a large variety of food – insects, small birds and mammals, dog food, etc.
Design and carry out an experiment to determine if cane toads can lean to ignore unsuitable food.

12. Flower responses of the morning glory (Ipomea purpurea)
The morning glory is a vigorous annual climber with large purple flowers that occurs along the coast from the New South Wales border and the Darling Downs. It has been reported as a weed of cultivation from Kingaroy and the Lockyer Valley.
As its name suggests, the flower is normally only open between dawn and midday, after which it closes.
Design and carry out experiments to determine factors that may be responsible in this plant response.
13. Human reaction rates
The speed at which individuals can physically respond to stimuli is age dependent.
Design and carry out an experiment to determine the validity of the observation.

14. Plant Responses
Choose a particular plant response and design and carry out experiments to determine factors that may be responsible for the response.

15. Animal Behaviour*
Choose a topic related to Animal Behaviour that is suitable for experimental investigation. Design and carry out an experiment to determine factors that might influence this behaviour pattern.

16. Water Quality
Water quality in streams and rivers is affected by the surrounding land use. You are to design and carry out an investigation that links land use and water quality (as measured by such factors as water colour, odour, flow rate, turbidity, temperature, pH, dissolved solids, oxygen and carbon dioxide levels, oil and grease, ammonia, chlorides, sulfur, bacteria etc.) at three different sites along a permanent waterway.

17. Poisonous plants
Many angiosperms have evolved mechanisms to deter herbivores, such as prickles, thorns, unpleasant taste or smell and various poisons in parts or all of the plant. Some plant poisons, such as saponins and cyanogenic glucosides, can be detected using simple chemical tests. Design and carry out an experiment to determine the relative amounts of these chemicals in various parts of a known poisonous plant.
18 Plant Associations
This investigation could be carried out as a Field Study in a Natural Environment. Students could be given a field guide to a particular plant group, e.g. the eucalypts (Brisbane City Council has produced very good illustrated guides to both the local gums and wattles), and after learning to identify the major species students could be set the following task:
Design and carry out an investigation to determine if there are distinct associations between particular species of ………. at ………….. and the factors that might be associated with the associations.

This task could be modified for anemones/ molluscs / crustaceans /algae on a rocky shore.


In Year 12 the students could be given an opportunity to investigate a topic that is of interest to them. This should, however, be carefully monitored by the teacher since many questions posed may not be readily investigated, may not yield easily interpreted results, or may require more time than can be allocated or specialised equipment. The students should be made aware of the legal requirements for working with animals


and science safety requirements: (http://education.qld.gov.au/corporate/doem/healthsa/hs-10000/hs-10000.html).

The students would be expected to:

  • Gather information (this could include personal observations or a literature search) on a topic of their choice.

  • Formulate a researchable question related to the selected phenomenon.

  • Develop a hypothesis for the question.

  • Determine the data needed to test the hypothesis. This also involves how the data will be collected, the equipment required, the process involved in collecting the data and the time needed to provide adequate data.

  • Write a clear, easy to follow method. In an experimental investigation the method needs to explicitly state how all variables, other than the experimental variable, will be controlled; what is being measured and how it will be measured and recorded.

  • Where possible trial the method.

  • Present the collected data in a suitable format that is easy to interpret and clearly shows any trends observed.

  • Interpret the raw data.

  • Analyse the data by comparing it with second-hand data, relating the data to theoretical concepts. Explain the findings.

  • Analyse possible error (human, systemic and random) and propose improvements in methodology where necessary.

  • Propose further hypotheses / investigations to support the investigation.

  • Draw a conclusion that states the purpose of the experiment, the major findings, relationship to the hypothesis and brief explanation of the findings.

  • Produce a scientific report on the investigation, ensuring a correctly annotated reference list, or another form of presentation (e.g. PowerPoint).

Some students may find it difficult to come up with a topic. Teachers can provide a stimulus list of material in which the title of a possible topic only is given, e.g. Conditioned learning in earthworms. This list can be developed from a number of sources such as titles from practicals listed in a text. Some useful resources include:

Roberts MBV (1974), Biology: A Functional Approach, Student’s Manual, Nelson & Sons Inc.

Keeton WT (1972), Biological Science: Practical Manual, WW Norton & Company, Inc.

The International Baccalaureate web site www.ibid.com.au
Mary Rafter from the Queensland Studies Authority has developed a large list of stimulus topics from a variety of sources. (Mary.Rafter@qsa.qld.edu.au)

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