IB Biology Internal Assessment Guide

Internal Assessment Help Notes for the Teacher Design For this type of practical it is best to give the students an open-ended question, without providing them with instructions for methods or materials. The students should be supplied with the materials they ask for. If these are not available, the student would do some alteration in the plan in order to carry out the experiment within the available resources. Aim: the student must enlarge on the given question to make it more specific for the investigation planned. For example if the question is testing the factors affecting enzyme activity, the aim can be: effect of temperature on the rate of breakdown of starch by amylase. Other students might come up with other types of enzymes, other factors and different plans for measurement and collection of data. Hypothesis is what the student expects will happen during the experiment. This should be supported and explained scientifically from books and other resources. If a scientific explanation is not shown clearly and in sufficient detail, no marks are gained for this part of the criterion. Variables: there are three types of variables 1. Independent variable: this is the one changed during the experiment in order to test its effect. For example if temperature is changed to test its effect on enzyme activity, then temperature is the independent variable. In a graph, the independent variable is on the x-axis. 2. Dependent variable: this is the one affected by the independent. In the above example, enzyme activity is the dependent variable, which can be measured in the form of time, volume, mass, length etc. The independent factor is plotted on the yaxis 3. Constant variables: these are the factors which should be kept constant during the experiment. For example if we are changing the temperature to test its effect on enzyme activity, then concentration and pH should be kept constant.

Materials: this should preferably be written in points; amounts should be stated in mass or volume with appropriate units. Containers, graduated cylinders and syringes should be mentioned with the appropriate volume, e.g. 200cm3 beaker, or 5cm3 syringe. Method: this should be written clearly in steps, quantities such as volume, mass and time should also be stated. The method should allow for collection of sufficient data and the control of variables. For example, how the temperature was kept constant throughout the investigation. It is not acceptable to send samples to the moderator for Design with all the students having the same plan for an investigation. For sending samples for moderation, it is best to send a full lab report for moderation of Design, and not just the planning part. Suggestions for suitable investigations for Design •

Sensitivity of human skin

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Osmosis/diffusion

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Heart/breathing rate

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Enzyme activity

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Photosynthesis

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Transpiration

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Seed germination

Data collection and processing (DCP) To perform these aspects at best levels, teachers need to consider the following points: •

Students should present their data independently without any help from the teacher

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No tables should be given to students to help them fill in their data

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They should not be told to draw graphs or a tables

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They should not be told what axes to use for each variable in the graph

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They should not be given an equation to use (e.g. Lincoln formula) for data analysis

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An investigation where a table and a graph can be produced from the data should ideally be used for DCP.

Drawing and labeling a diagram is not appropriate for assessing DCP. These

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activities are excellent for teaching but not for IA. Teach the students that they need at least 8 points of readings in order to

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produce a good graph. The points of the independent factors should be well spread in order to give a good idea of the relation between the independent and the dependent factors. The students should be taught to establish different types of graphs such as the

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ones that appear in data analysis questions of paper 2 and 3. This will enable them to understand these graphs in exam questions and it widens their horizon in analysis and presentation of research data in future studies. The following is an example of a table of results established by a student: Distance of light from the pond weed

Distance traveled by bubble

100

3

80

9

60

38

40

89

What are the mistakes committed by the student in presenting this table for DC: 1. Units not shown. 2. Distance traveled by bubble, not clear what it means. 3. Uncertainties: the degree of precision is not clear from these readings. Each reading of distance should show fractions of a cm, or a millimeter depending on what units are used. 4. The figures on the left should be in increasing order. 5. In the lab report there should be a diagram to help the moderator understand the collected data. 6. A title should be provided for easy understanding of the information in the table. 7. The number of readings is too small and does not allow for the production of a good graph. 8. The intervals between the readings for distance of light are too large; there should be at least one more reading between each two readings in order to show clearly the relation between the two factors.

The following graph was produced from the above table and presented in the student’s lab report: x 80 60 40

x

20

x

0

20

40

60

80

100

 What are the mistakes in this graph (DPP)?

Conclusion and Evaluation This is a very important part of the lab report which is either completely ignored by some students or presented poorly. •

The conclusions should be valid based on the correct interpretation of the data.

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The results should be compared with literature values

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The procedure and the results should be evaluated. Errors, limitations, and weaknesses should be stated and discussed.

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Suggestions for improvement in order to avoid these weaknesses and limitations should also be discussed.

The following is a procedure for testing the effect of substrate concentration on enzyme activity: 1. Prepare a yeast suspension by adding 5g of yeast to 100cm3 of water and stirring for 2 minutes. 2. Add 1.5 g of sugar to the suspension to activate the yeast. 3. Leave the solution in the container for about 10 minutes.

4. Stir the yeast suspension thoroughly, and then take 5cm3 of the suspension into a test tube. 5. Close the test tube with a cork that has a delivery tube coming out through a tight hole in the rubber stopper. 6. Insert a needle into the rubber stopper. 7. Take 1cm3 of a 10cm3 suspension into a 1cm3 syringe. 8. Insert the syringe into the needle. 9. Push the hydrogen peroxide solution through the needle into the test tube and at the same time stat the stopwatch. 10. Observe the bubbles of oxygen escaping from the test tube through the delivery tube into the burette. 11. When no more bubbles come out, stop the stopwatch and record its reading. 12. Record the reading of oxygen volume in the burette. 13. Repeat the above steps with different concentrations of hydrogen peroxide. 14. Remember to wash the test tube between readings.

Errors involved in the above method 1. The yeast suspension for each test is not the same, since yeast is a living organism carrying out respiration and reproduction. These two processes change the conditions for the experiment. For example respiration increases the temperature which interferes with the rate of reaction. Reproduction increases the number of yeast cells and this affects the amount of the enzyme catalase involved in this experiment. 2. No thermometer was used to ensure that the temperature is staying constant. 3. No water bath was used to ensure that the temperature is kept constant 4. Hydrogen peroxide breaks slowly into water and oxygen without the presence of catalase, and so the trials carried out later have weaker concentration of hydrogen peroxide.

5. When the tube is washed between trials, there will be some drops of water inside it which cause dilution of the yeast suspension. This is different from the condition at the start of the experiment when the tube was dry. 6. As the solution is pushed into the syringe, some of it drips out at the connection between the syringe and the needle. 7. The hole through which the needle penetrates allows the leakage of oxygen 8. Oxygen can also leak from the tube if the stopper is not perfectly airtight. 9. At the end point of each trial it is difficult to take the readings of volume and time simultaneously. 10. It is difficult to decide the end point since some air bubbles might come out later or small bubbles that cannot be noticed might be still evolving after the reading is taken. 11. With higher concentrations, the burette might empty completely before the reaction is complete. 12. The yeast suspension in the test tube is not stirred, and so the yeast might start settling in the bottom of the tube while the experimenter is getting the syringe of hydrogen peroxide ready. This varies in the different trials making the conditions different. The above account can aware the students of how careful they should be in planning an investigation and carrying out the procedure. Also it helps them discuss the errors and improvements involved in their investigations.

Manipulative skills •

These skills are assessed throughout the course for each student and not from one single occasion.

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Students should learn to carry out the procedure safely without causing any harm or damage to people or property.

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Students should learn to follow the instructions accurately and to modify the method according to certain situations and limitations.

Group 4 project (The following account shows an example of how it can be done)

Brainstorming session: 1- 2 hours 1. All IB science students and teachers meet and the meeting is chaired by the IB Head of Science. 2. A brief introduction about the role and importance of the project in the science curriculum is presented. 3. The previous themes of group 4 are presented to the students, so that the theme is not repeated and that the students get an idea of what is required. 4. A brain storming session is carried out, through which the students come up with the general theme ideas 5. The ideas are all listed on the board. Students and science teachers are asked about the feasibility of the themes and the possibility of a wide range of topics that can be worked under each theme. 6. Some themes are deleted in response to the above action. For example if the physics teacher refuses “Respiration” because she/he cannot see good physics topics that can be investigated under this theme, then the theme is deleted. Short listing continues by consulting students and teachers until in the end one theme is decided. Separate subjects: 1 hour • In each class the subject teacher and the students start discussing different ideas and forming groups of 2 or 3 students for each subject topic. For example a group decides to work on the effect of different fertilizers on the growth of wide beans plants, another on the action of pectinase in different fruit species. Practical work: 8-10 hours 1. 2 weeks of teaching are used for the actual practical work by the students. 2. The work is supervised and observed by the subject teacher. 3. Students record their results and at the end of the two weeks they are supposed to submit a rough report on the whole project. 4. In the first month of the second IB year students get ready to present their work in the form of: • Presentations • Posters Presentations: 2 hours At the end of September in the afternoon, students, parents, principal, IB coordinators and other guests are invited to the school theater to attend the presentations by the students. The groups from the different disciplines present their work to the audience, using computer data show, each group is given 10 minutes. Posters can be exhibited for the guests to visit after the presentations.