The Design Criterion in Biology Internal Assessment

The design criterion in biology internal assessment

Deciding upon the most suitable strategy for assessing the design criterion is one of the most important decisions for the teacher of IB biology. The questions to be considered when implementing a design strategy are as follows.

How much lesson time is to be allocated to the task?

How many students are in the teaching group?

What resources are available for use by the students?

Will the task stimulate a spirit of inquiry in the students and promote thinking skills in addressing a complex problem?

Do the students have the prerequisite skills and knowledge base to address the task in a meaningful manner?

Can the teacher ensure that, when completing the written phase of the investigation outside the classroom, the students work independently?

The answers to these questions will differ according to each school’s environment, but some common principles remain.

Students are more likely to work independently if their design task is unique to them.

Students are more likely to work independently if they have confidence in their own ability to complete the design task successfully.

Therefore, designing a scientific investigation is not done in a vacuum. For productive designs to be developed, students will need to have:

acquired some theoretical background

made observations in the relevant field

experience in certain manipulative skills specific to the investigation

an understanding of the scientific method (the importance of hypothesis testing where relevant, replicates, independent and dependent variables, controls, and sampling techniques).

Students will need to have their limits set, and counselling will be necessary in feasibility (time and cost), safety and ethics. For the sake of assessment, the students should design their investigations individually. However, it is possible that an initial brainstorming exercise would be useful to generate ideas that could then be further developed by individuals. It is also possible for students to work in groups on their proposed investigations after their individual designs have been assessed.

To increase the students’ self-confidence in their ability to accomplish the task independently, it is important for the design setting strategy to recognize that they need to have some familiarity with the concepts and techniques involved. Some suggested approaches are as follows.

Set tasks that are an advance on prior work. However, it is unethical to set students essentially the same task as previously. Similarly, teachers should avoid setting a task that is already covered completely in readily available literature such as the class’s laboratory manual. It is not uncommon to find whole classes responding in an identical manner to such a design task, which is not good practice. It is better to restrict such an investigation to assessment of data collection and processing (DCP) and conclusion and evaluation (CE).

Give students a practical session to familiarize themselves with the techniques required prior to the writing up of their design. They can use this session to try out materials, to develop a workable procedure, and to see if their proposed independent variable has any measurable effect. If the teacher takes the opportunity during this session to ask the students to explain their thinking behind what they are planning to do, then it is subsequently easier to ascertain whether the student has produced the final written design independently. Also, at this stage, students can be encouraged to think more deeply if they are considering undertaking an over-simplistic investigation.

Once a teacher has decided on a strategy for assessing design, acceptable instructions then need to be given to the students. Normally this takes the form of a brief description of the general problem(s). Aspect1 of the design criterion requires students to formulate the focused problem or research question themselves, as well as to identify independent and dependent variables, and relevant controlled variables. It is essential that the teacher gives the students only an open-ended prompt, and the topic must allow for a variety of different approaches.

Most commonly, there are two types of appropriate teacher prompts.

Firstly, where neither the dependent nor independent variables are given but the system to be investigated is identified. An example of an open-ended teacher prompt would be “Investigate an aspect of a pond ecosystem”.

The second type of prompt is where the dependent variable is given by the teacher and the student must select the independent variable as well as appreciate the controlled variables. An example here is when the teacher tells the student to investigate one factor that affects the rate of photosynthesis in an aquatic plant.

It is wise to set a common task for all students only when the task potentially has many different independent/control variables. For large class sizes, it can be difficult to ensure a wide enough range of different approaches.

If a teacher is confronting the problem of many students simply reciting designs from web-based sources or internal assessment (lA) manuals, it may be necessary to allocate supervised class time to the task of writing up designs.

Inappropriate research questions often occur when the teacher prompts give both the dependent and the independent variables, for example, “Investigate the relationship between wind speed and the rate of transpiration of a leafy shoot”.

Investigations suitable for design

Students would be given only the titles of the following investigations. The titles are general to give students a sense of direction, but they are not sufficiently specific to serve as a research question. Students will have to modify the title to make it more specific and focused. In most cases, this will involve indicating the variable(s) chosen for investigation and the species used or the source of the biological material.

Investigations into abiotic factors and their effects

Investigate the effect of an abiotic factor on the distribution of an organism on a rocky shore or stream.
Pre-lab/skills: / A preliminary visit to make observations, identification of animals or plants, measurement of variables, sampling techniques.
Possible variables: / Height above low water mark, density of other organisms, exposure to sea, current speed, light intensity, temperature.
Investigate the behavioural responses of woodlice, or other small invertebrates, to an environmental factor.
Possible variables: / Light intensity, light wavelength, humidity, temperature, surface texture, density of animals.
Investigate the effect of an environmental variable on the transpiration rate of a plant.
Pre-lab/skills: / Use of potometer, mass changes in leaf as it dehydrates.
Possible variables: / Wind speed, leaf area, species of plant, light, humidity.
Design an investigation on the effect of an abiotic factor on the rate of photosynthesis in water plants.
Pre-lab/skills: / Observation of gas release by plant (analysis of gas produced by photosynthesis), method for collecting gas produced by photosynthesis or hydrogencarbonate indicator colour change, use of relevant probes with data logging apparatus.
Possible variables: / Light intensity, light wavelength, temperature, species of plant, pH, salinity.
Investigate a factor affecting germination or seedling growth of a plant.
Pre-lab/skills: / Testing for seed viability.
Possible variables: / Temperature, light, oxygen, pollutants, herbicides, salinity, seed age, species, pH, nutrients.
Investigate the effect of a physical or chemical factor on variations in the heart rate of water fleas or annelid worms.
Pre-lab/skills: / Immobilization of animal, location and observations of the animal's heart.
Possible variables: / Temperature, light, pH, electrolytes, alcohol, tobacco extract, pollutants, pesticides.
Investigate a factor affecting either the movement of chloroplasts in Elodea leaf cells by cytoplasmic streaming, or the beating of cilia on the gills of mussels.
Pre-lab/skills: / Use of microscope and micrometer eyepiece, preparation of temporary mounts.
Possible variables: / Light, temperature, pH, salinity, electrolytes, pesticides, pollutants, tobacco extract.

Further suitable investigations

Investigate a factor affecting either heart rate, blood pressure, breathing rate, CO2 production, skin temperature or rate of sweat production.
Pre-lab/skills: / Taking a pulse correctly, use of sphygmomanometer and spirometer, titrating the acidity of NaOH solutions that absorb exhaled CO2, use of relevant probes with data-logging apparatus.
Possible variables: / Exercise, age, fitness, gender, body mass/height, time of day, amount of clothing.
Investigate a factor affecting fermentation rates of yeast.
Pre-lab/skills: / Measuring rates of respiration by CO2 production or indicator colour change, use of relevant probes with data-logging apparatus.
Possible variables: / Concentration of sugar, type of sugar, temperature, pH, inhibitors.
Investigate a factor affecting enzyme activity.
Pre-lab/skills: / Measurement of enzyme activity (oxygen production by catalase, starch digestion by amylase, fruit juice extraction by pectinase, protein digestion by bromelin in pineapples, invertase activity in yeast), use of relevant probes with data-logging apparatus.
Possible variables: / Substrate concentration, pH, temperature, inhibitor concentration, sources of substrate (pectinase on different types of fruit, or on fruit of varying ripeness, catalase from different tissues).
Investigate a factor affecting the amount of vitamin C activity in foods.
Pre-lab/skills: / Introduction to a test for the amount of vitamin C in a food.
Possible variables: / Sources (fruit juices, vegetables, milks), the effects of different methods of food processing.
Design an investigation on the hypothetical survival of caterpillars (using models made from wool, pasta or modelling clay).
Possible variables: / Background colour, light intensity, collecting tools.
Investigate the effect of colour on human choice.
Pre-lab/skills: / Unbiased testing methods.
Possible variables: / Background colour, intensity of colour, age, gender, effect on legibility, learned associations (for example, with food types).
Design an investigation on variations in the fitness of individuals.
Pre-lab/skills: / Tests for fitness including muscle endurance, arm or shoulder power, leg power, flexibility, speed and acceleration, body composition.
Possible variables: / Gender, height, mass, age, type of sport practised and intensity of practice.

Note: In addition to the student work, samples submitted for moderation must include the instructions, written or oral, given to the student by the teacher. This vital information is used by moderators to assess whether the experiment as given was suitable for assessing the criteria.