AQA A2 Biology Essays Guide Paper 3
GUIDE TO WRITING ESSAYS
In Paper 3 there is a 25-mark essay question, where you need to link topics
based on the theme mentioned in the question, to fully test both your depth and
breadth of knowledge of the specification.
1. Choosing your question
You should choose the question you feel most confident about. One may seem
harder than the other but choose whichever you feel you can answer better.
Consider the topics you might include and how well you know them, how much
detail you can write and what you might know beyond the specification. Make
sure you understand the concept (if it’s about cycles, make sure you only name
examples of cycles) and are able to link your knowledge back to those concepts.
It might be an instant choice, or it might be better to do the rest of the paper and
come back.
2. Choosing your topics
Now that you have finished the rest of the paper, you can start choosing the
topics for the essay. This will depend on the question itself, but there are some
general guidelines you can follow when making your choices. Firstly, use a mix of
AS and A2 content, to show the breadth of your knowledge. 4-5 topics should
suffice with substantial enough detail. Always try to include a good amount of A2
content, because (generally) this is harder, has more detail, and can better show
your understanding.
Breadth of knowledge across fields of Biology can also be useful in answering
questions. Both AS and A2 content is generally split into biological molecules and
biochemistry, cell biology and physiology, DNA and genetics, and ecology. If you
can form a strong link between topics from these different areas that are
relevant to the question, this helps with cohesiveness and is sure to gain marks.
This is also true across organisms. If you can mention more than one of plants,
animals or bacteria (or other types of organisms) that shows great breadth of
knowledge too.
You will also find that the topics have been organised so that they link together,
e.g., genetics and DNA are covered in both Topic 4 and 7, and there is a heavy
emphasis on biological molecules in Topics 1 and 5. Choosing topics that links
will demonstrate that you really understand those topics, and how to interpret
the question.
Some good topics to include are photosynthesis and respiration (A2), for a few
reasons. They are vastly detailed and arguably some of the hardest on the
specification. They include an array of different organisms (photosynthesis in
plants, and respiration in plants, mammals, and bacteria). Try and include these
in your essay practice. However, don’t try and include these topics if they are not
relevant to the question.
One of the most important things is making sure the topics fit to the question. It
can be tempting to choose your strongest topics and just write as much as you
, AQA A2 Biology Essays Guide Paper 3
can about those. Whilst depth and detail are important for higher marks, you’re
going to lose marks if your content isn’t relevant enough.
To help, below is an example of an essay question with a vague list of
appropriate topics, in no particular order:
‘Discuss the significance of cycles in Biology’
A2 – Calvin cycle (the light independent reactions of photosynthesis). High level
of detail, involves plants, is one of the most obvious examples of a cycle in the
spec.
A2 – Citric acid (Krebs) cycle – respiration is another hard topic. Potential for high
level of detail, can be applied to many organisms, another obvious example.
AS – ATP cycle – ATP can be applied to a lot of other topics (good links to
photosynthesis and respiration). Simple and easy to remember.
A2 – Nutrient cycles – Bring in ecology, which is less commonly mentioned, can
include nitrogen or phosphorus. Needed for protein and DNA production.
AS – Cell cycle – interphase and mitosis. Applicable to all eukaryotes. Detailed
process, many key words.
(You won’t need more than 5, but to be exhaustive, I’ve included more)
AS – Metabolism – making polymers and breaking them down, condensation and
hydrolysis. Link polymers to function.
AS – Cardiac cycle – systole and diastole. Many key words, specific to mammals.
Significance is easily arguable. Can link to control of heart rate in A2 for detail.
A2 – Homeostasis and negative feedback cycles – kidneys and ultrafiltration or
glucose regulation. Detailed processes and key words
3. What to actually write!
Now you’ve chosen your topics, it’s time to write the essay in detail. This starts
with an introduction. This is where you need to start thinking about the wording
of the question. If we take the cycles example from before we can unpack it
here:
How important are these Discuss the significance of cycles in Biology
cycles? What is their
Link it back. Remember to
function? What might
identify how your examples are
happen without them?
cycles.
1. Significance determines the ‘angle’ of the essay. Aswell as just talking
about the different examples, we need to also mention how they are
important to organisms, cells, other processes etc. Why does it matter
that they are there? Every process, cell, molecule has a function and is
linked to something else. What is that link for your examples?
2. Don’t get lost in the examples, remember to point out how they all form
cycles. Follow them through to completion. i.e. with glucose concentration,
