How to answer IB Biology Paper 2 extended response questions
Your IB Biology Paper 2 exam will consist of short answer and extended response questions. Knowing how to properly answer both will help you maximise marks. In this article our author, Ashby Merson-Davies, provides examples of how to successfully answer your IB Biology extended response questions for the command terms Outline, Describe, and Explain. Additional examples can be found in both our Standard Level and Higher Level study guides for IB Biology. The guides also feature comprehensive syllabus review, easy-to-reproduce diagrams, and helpful hints for exam success.
IB Biology Paper 2 extended response questions – Maximising your marks
The following extended response prompts are typical of those in IB Biology Paper 2. Each of these is marked out of 15. There is 1 additional mark if:
- your answers are clear enough to be understood without re-reading.
- you have answered the question succinctly with little or no repetition or irrelevant material.
Each question is in three parts, (a), (b) and (c). You do not need to answer them in this order but you MUST indicate clearly which part you are answering.
Read each sub-section carefully and look at the marks allocated. Each relevant fact gains a mark so 5 marks means you have included 5 facts.
Ensure you follow the command term precisely.
I would suggest spending at least 5 minutes planning time and then 25 minutes writing time for each question.
In the examples below, I have picked out the key words from the question and then listed the key vocabulary. In the exam I would suggest you scribble down the vocab and then, if desirable, produce a mind map from the vocab.
Another point to remember is that you do not have to answer in an essay format as you would for say History or Psychology. An answer could be an annotated diagram or a table.
Notice how in some of them I have broken each answer up into paragraphs, each paragraph dealing with a different component of the question. This helps to produce a clear and well-structured answer, and also, which is VERY important, helps the examiner to mark it.
Notice also how the first sentence is often an introduction stating the meaning of the key word in the question.
I have not included drawings in these answers. However, answers can be greatly enhanced by drawings and they also help you to structure your answer.
Example 1: Outline how plants use the nitrates and phosphates that they absorb from the soil to make organic compounds [3]
Key words
Nitrates; phosphates; organic compounds
Key vocabulary
Solution; Xylem; Amino acids / nucleotide bases; Calvin cycle; ATP / DNA/ RNA; Carbon compounds / triose phosphate; Photosynthesis
When a plant photosynthesises it makes triose phosphate in the Calvin cycle, a simple carbon compound. This is then used to make all the other organic compounds the plant needs. These include ATP, DNA and RNA which all require phosphate, and amino acids and nucleic acid bases which all require nitrogen from nitrates. The phosphates and nitrates are absorbed from the soil and transported to cells in solution in the xylem.
Example 2: Describe what takes place in the alveoli. [4]
Key words
Alveoli
Key vocabulary
Type I and type II pneumocytes; Oxygen / carbon dioxide; Diffusion; Capillaries; Haemoglobin; Ventilation; Blood flow
Alveoli are composed of type I and type II pneumocytes. Type I are very thin and allow rapid gas exchnage and type II secrete a sufactant that prevents the alveolar walls from sticking together. Oxygen diffuses from the alveolar air into the blood and binds to haemoglobin in the red blood cells whereas carbon dioxide diffuses from the plasma into the alveolar air. The gases can do this as concentration gradients are maintained by ventilation changing the alveolar air and blood flowing through the capillaries covering the alveoli.
Example 3: Explain DNA replication in prokaryotes. [8]
Key vocabulary
Gyrase; Helicase; DNA primase; DNA polymerase I; DNA polymerase III; Ligase; RNA nucleotides; DNA nucleotides; Template strand; Replication fork, RNA primer; Complentary base pairing; Leading / lagging strands; Okazaki fragments; Semi-conservative; 5' - 3'; Single strand binding proteins
All you need to do is take each enzyme and explain what it does. The other terms should be included with the relevant enzyme. Four of them are below to illustrate this. Note how a blank line is left between each one to make it clearer and therefore easier to mark.
Helicase unwinds the double helix and breaks the hydrogen bonds between the strands at the replication fork. Single strand binding proteins then keep the strands apart.
DNA primase adds a short RNA primer strand in a 5' - 3' direction to the lagging strand using RNA nucleotides and complementary base pairing (CBP) to the template strand.
DNA polymerase I replaces the RNA nucleotides of the primer with DNA nucleotides using CBP to the template strand.
DNA polymerase III adds DNA nucelotides in a 5' - 3' direction using CBP to the template strand at the replication fork on the leading strand and to the primer on the lagging strand.
Becoming exam ready
Whether you are in your first or your final year of your IBDP studies, the IB exams will be on your mind. If you are a DP1 student, you have plenty of time to prepare and a crucial part of that preparation will be building your exam revision structure. Start early and revise often. Going over things little by little as you work your way through the syllabus will pay dividends in the end. A good place to start is by becoming familiar with the command terms you need to know and how to properly answer them, this article should help with that and your teacher is an obvious source of further support.
If you are a DP2 student, your approach will vary depending on how close your exams are. If you are early in your academic year, the advice for DP1 students applies to you too and you can really help yourself by not leaving your revision too late. If your exams are swiftly approaching, then take the time to identify what the gaps in your knowledge are and begin to fill these with concentrated study. While doing so, be sure to keep your command terms in mind and practice crafting answers to questions. The more you practice the more comfortable you will become with what will be expected of you on exam day. There are many resources out there to help you organise and focus your IB Biology exam revision, more of which can be found on our IB Biology subject resource page.
