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). Aspect 1 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 s
Pre-lab/skills:
A preliminary visit to make observations, identification of animals or
techniques.
Possible variables:
Height above low water mark, density of other organisms, exposure
temperature.
Investigate the behavioural responses of woodlice, or other small invertebrates, to an environme
Possible variables:
Light intensity, light wavelength, humidity, temperature, surface textu
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 p
Pre-lab/skills:
Observation of gas release by plant (analysis of gas produced by ph
produced by photosynthesis or hydrogencarbonate indicator colour
logging apparatus.
Possible variables:
Light intensity, light wavelength, temperature, species of plant, pH, s
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
Investigate the effect of a physical or chemical factor on variations in the heart rate of water flea
Pre-lab/skills:
Immobilization of animal, location and observations of the animal's h
Possible variables:
Temperature, light, pH, electrolytes, alcohol, tobacco extract, polluta
Investigate a factor affecting either the movement of chloroplasts in Elodea leaf cells by cytoplas
gills of mussels.
Pre-lab/skills:
Use of microscope and micrometer eyepiece, preparation of tempor
Possible variables:
Light, temperature, pH, salinity, electrolytes, pesticides, pollutants, t
Further suitable investigations
Investigate a factor affecting either heart rate, blood pressure, breathing rate, CO 2 production, s
Pre-lab/skills:
Taking a pulse correctly, use of sphygmomanometer and spiromete
absorb exhaled CO2, use of relevant probes with data-logging appar
Possible variables:
Exercise, age, fitness, gender, body mass/height, time of day, amou
Investigate a factor affecting fermentation rates of yeast.
Pre-lab/skills:
Measuring rates of respiration by CO2 production or indicator colour
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, sta
extraction by pectinase, protein digestion by bromelin in pineapples,
probes with data-logging apparatus.
Possible variables:
Substrate concentration, pH, temperature, inhibitor concentration, so
types of fruit, or on fruit of varying ripeness, catalase from different t
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 meth
Design an investigation on the hypothetical survival of caterpillars (using models made from woo
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 legibili
food types).
Design an investigation on variations in the fitness of individuals.
Pre-lab/skills:
Tests for fitness including muscle endurance, arm or shoulder powe
acceleration, body composition.
Possible variables:
Gender, height, mass, age, type of sport practised and intensity of p
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.