Exploring in Biology (DP IB Biology): Revision Note
Exploring in Biology
This is the creative start of the process, where you act like a true scientist
It involves using your curiosity and existing biological knowledge to formulate a focused research question and a testable hypothesis
It requires independent thinking and consulting a variety of sources to understand the scientific context behind your idea and to make a clear, scientifically-justified prediction
Developing your investigation
Demonstrate independent thinking, initiative, and insight
The best investigations often start with a simple question or statement about a standard experiment
For example, "measuring the effect of temperature on enzyme activity."
You can show insight by framing it as a comparative investigation:
"To what extent does the source of the enzyme (e.g. fungal amylase vs. bacterial amylase) affect its optimal temperature?"
This shows you are thinking about the links between an organism's environment and its molecular function
A common mistake is trying to investigate too many variables at once
A strong investigation explores the relationship between one independent variable and one dependent variable in depth
Avoid questions like "How do light intensity and CO₂ concentration affect the rate of photosynthesis?"
Choose just one factor and investigate it thoroughly
Consult a variety of sources
Before you can formulate a high-quality question, you need background information
This is a crucial research step
Good research helps you to:
understand the underlying biological theory
find established scientific values for comparison
identify a suitable method for collecting data
You can use various resources, including:
This research provides the scientific context for your investigation, showing that you understand the biology behind your question
Formulate research questions and hypotheses
A research question must:
be focused
be specific
clearly state the link between the independent variable and the dependent variable
A question like "How do abiotic factors affect plants?" is too general
A focused research question specifies the relationship or biological process being investigated:
"What is the effect of soil pH (from pH 5.0 to pH 8.0) on the rate of germination of garden cress (Lepidium sativum) seeds?"
A hypothesis is not a guess, it is a clear, testable statement that predicts the outcome and includes a scientific justification
The best hypotheses follow an "If..., then..., because..." structure
State and explain predictions using scientific understanding
The "because" part of your hypothesis is where you explain your prediction
This explanation must be based on established biological principles, such as enzyme function, osmosis, or ecological interactions
A hypothesis like "If temperature increases, enzyme activity will increase" is just a prediction
To make it a valid scientific hypothesis, you must add the justification:
"...because according to collision theory, higher kinetic energy increases the frequency of effective collisions between the enzyme's active site and substrate molecules, up to the optimal temperature."
Worked Example
Exploring enzyme activity investigation
Broad idea:
I am interested in how environmental factors affect how well enzymes work
Consulting sources and gaining insight:
My textbook states that every enzyme has an optimal pH at which it functions most efficiently
Deviations from this pH can alter the bonding in the enzyme active site, disrupting the tertiary structure and reducing its activity
Extreme pH changes cause irreversible denaturation
Research shows that pepsin (a stomach enzyme) has an optimal pH of ~2, while trypsin (found in the small intestine) has an optimal pH of ~8
This shows enzymes are adapted to their specific environments
Formulating the research question:
"What is the effect of pH (from pH 4 to pH 10) on the rate of activity of the enzyme trypsin in breaking down casein protein?"
Formulating the hypothesis:
If the pH is increased from 4 towards 10...
then the rate of trypsin activity will increase to an optimum at around pH 8 and then decrease...
because trypsin is found in the alkaline conditions of the small intestine and its active site is specifically shaped to function optimally at this pH. pH values far from the optimum will cause the enzyme to denature
Worked Example
Exploring an osmosis investigation
Broad idea:
I want to investigate how plant cells react to being in sugary or salty water
Consulting sources and gaining insight:
Textbooks explain osmosis as the net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane
Placing plant tissue in a solution with a lower water potential (hypertonic) will cause it to lose water and decrease in mass
Placing it in a solution with a higher water potential (hypotonic) will cause it to gain water and increase in mass
The point at which there is no net movement of water is the isotonic point, where the water potential of the tissue matches the water potential of the solution
Formulating the research question:
"What is the effect of sucrose concentration (from 0.0 M to 1.0 M) on the percentage change in mass of potato (Solanum tuberosum) cylinders after 24 hours?"
Formulating the hypothesis:
If the concentration of the sucrose solution is increased...
then the percentage change in mass of the potato cylinders will become more negative...
because as the external sucrose concentration increases, the water potential of the solution decreases, leading to a steeper water potential gradient and causing more water to move out of the potato tissue via osmosis
Worked Example
Exploring germination
Broad idea:
I want to see how salt affects seed germination. This is relevant to farming in coastal areas
Consulting sources and gaining insight:
The syllabus explains that water is required for the metabolic processes of germination to begin
High concentrations of salt (solute) in the soil create a low water potential. This can prevent seeds from absorbing the water they need for germination through osmosis, a condition known as water stress
Some plants, known as halophytes, are specifically adapted to grow in saline conditions
Formulating the research question:
"What is the effect of sodium chloride concentration (from 0% to 2.0% w/v) on the final percentage germination of radish (Raphanus sativus) seeds over 7 days?"
Formulating the hypothesis:
If the concentration of sodium chloride is increased...
then the final percentage germination of the radish seeds will decrease...
because the high salt concentration will lower the water potential of the surrounding environment, inhibiting the seeds' ability to absorb water by osmosis, which is essential for activating the metabolic pathways for germination
Examiner Tips and Tricks
Struggling for an idea is normal
Good starting points include:
A surprising or unexplained result from a class experiment
Investigating a different aspect of a standard lab, such as using a different enzyme or organism
Applying a biological concept to a real-world problem, like the effect of an abiotic factor (e.g., salt, pH) on seed germination
Check the feasibility first
Always consider if you have the right equipment, organisms, and time to actually carry out your investigation. Remember that experiments on plants can take days or weeks
A great idea is not useful if it's not practical in a school lab
Be prepared to refine your idea
Your initial research might show that your first idea is not possible or practical
Don't be afraid to change your research question based on what you learn
This is part of the scientific process
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