What topics are the most important in A level Biology?
I’ve talked before about what makes A level Biology so difficult, and how the size of the syllabus causes so many issues for students and teachers alike, but there is a way in.
There are certain topics within A level Biology which you can hang the rest on. They make it all make sense. In this article I’ll talk about which topics are the most foundational, which are the trip-you-up topics - where students tend to get lower marks than they deserve, and which topics need the most study time. Often, knowing where to concentrate your efforts is half the battle.
Which are the foundational topics in A level Biology?
Without mastery of some foundational topics you may find it really hard to follow the lessons in some later topics. Your brain will be playing ‘catch-up’, struggling to remember the foundational understanding that the new topic is built on. In the language of educational psychology, the ‘cognitive load’ will be too high. I’ve listed the seven foundational topics below.
Protein structure
Many topics in A level come back to proteins. If you really get your head round how amino acid sequence (known as primary structure) leads to all the other levels of structure and therefore to protein function, then you're going to be a good place for:
Hormones
Transport across membranes
Enzymes
Effects of drugs
Cell regulation
How the immune system works
Synapses
Sliding muscle filaments
… the list goes on and on.
If you haven't mastered protein structure and function then it's going to add to the load in practically every other topic in the syllabus.
Here’s one I prepared earlier - protein structure.
2. Cell organelles
Cell organelles come back at you again and again and the really important one is membrane structure. You need to be 100% slick with membrane structure and components, as well as with transport across membranes. All cell to cell interaction happens via the cell surface membrane. This means if you understand that function, you’ll have no problem understanding:
The immune system
The detail of the function of parts of the nervous system
Selective reabsorption in the kidney
…and many others
3. The basics of sampling and ecology
These show up again in topics like Populations, Ecosystems and Conservation. A lot of students don't like this bit of the syllabus because it seems imprecise. Bad luck. You’re going to keep seeing it throughout the subject.
4. Chromosomes and sex
More specifically, the difference between a chromatid, a chromosome, a homologous pair, a bivalent, a gene, a locus and an allele. Or, when and how variation occurs during meiosis and sex. You can only make sense of the genetics stuff if you've got a good understanding of the fundamentals of chromosomes and sex.
5. How DNA structure leads to protein structure and function
All the details of transcription, translation and DNA replication. The way information is transformed from DNA to, for example, the shape of a receptor protein in the cell surface membrane in the post synaptic knob. The relationship between DNA nucleotide sequence and everything else in biology is called the central dogma for a reason. It is probably the single most important idea in Biology.
6. What Structure is
The idea that structure is atoms, bonds, and shapes, and that structures lead to properties, and that properties lead to functions. It's a way of thinking that is repeated again and again in biology. You need to be absolutely clear what the difference is between structure, property and function.
7. How precise you need to be when naming parts of living things
For example: The elastic fibres are in the wall of the artery, not the artery.
The reason why hydrostatic pressure is low in veins is that the diameter of the lumen of the veins is large, not that the width of the vein is large.
In translocation the sucrose molecules diffuse from the companion cells via plasmodesmata into the sieve tube elements at the source end of the sieve tubes, not into the phloem.
A good rule of thumb is to imagine it’s a postage address, it needs all its parts, not to Tim Dickinson or to North Devon you need all the address: Tim Dickinson, Flat 3, Happy Harry’s Home for the Bewildered, Bishop’s Tawton, Barnstaple, North Devon.
Those are my foundational seven, but this doesn't mean the other stuff is unimportant. The examiner can, and does, ask you about anything from all of the 2 years. However, with these fundamentals nailed, you’ll have a much easier time with the rest of the syllabus.
Which A level Biology topics do students usually underachieve in?
If you read the yearly examiners reports you’ll see there are some common factors which separate students who do really well in exams from those who don't get the grades the universities require.
Mostly, these are skills which apply equally to all areas of the syllabus. Skills like reading the question properly, using all the information in the question, being able to choose and use the appropriate maths to answer the question, and giving precise and concise answers.
The only syllabus content which regularly makes a big difference is students' knowledge and understanding of the practical work they have done. It’s often the case that the weaker students forget to revise this in the detail they need.
Another way of looking at this is; all the syllabus matters, don't forget the practicals, and make sure you've done as much past paper practice as possible because exam skills are really important.
Which topics are really hard and need lots of repeated time and effort?
In my 25+ years as an A level teacher, I’ve seen thousands of students work through A level Biology. The topics I see students struggle with most often are:
Carbohydrate structure
They just can't believe something can be this detailed and this abstract!
Protein structure
Same again - it’s so detailed and so abstract. They understand it, but don't put the time into fully integrating it into their ideas about molecules. You need to accept that it really is this much like chemistry.
Formation of tissue fluid
A masterclass in comparisons:
“The hydrostatic pressure in the blood plasma at the arterial end of the capillary is higher than the hydrostatic pressure in the tissue fluid at the arterial end of the capillary. This difference forces water and smaller solutes out of the plasma and into the tissue fluid at the arterial end of the capillary.”
Students won’t accept how precise their language needs to be when talking about this stuff.
A difference always involves a quality (hydrostatic pressure), two places, a comparative statement of quantities (higher and lower), and a direction of difference.
The movement of blood in the cardiac cycle is another example, or the flow of air into and out of the lungs or the movement of assimilates through the phloem.
Cardiac cycle (including the pressure graph)
Not only does the language of differences need to be spot on, but you need to be able to relate events on the graph to events in the cardiac cycle. You REALLY need to understand what is shown on the two axes of the graph, and how to use a ruler to precisely compare pressures at particular times. It’s a skill and it needs practice.
Oxygen dissociation curves
Here the problem is being crystal clear about what is being shown on the axis. The key is understanding that the X axis shows free oxygen not bonded to haemoglobin but surrounding the haemoglobin molecule, while the Y axis shows oxygen bonded to the haemoglobin. It's hard and it gets worse before you have time to understand it you need to also cover the Bohr shift and foetal haemoglobin. Don't expect the lessons to be enough. Watch some good quality YouTube videos on it. How do you know what counts as good quality? - ask your teacher or tutor for recommendations. There's a LOT of rubbish out there. And, when you’re reading, note making and blurting from the textbook, make sure you work through it slowly and carefully.
Translocation of assimilates in phloem
Another nightmare of comparisons. You need to identify and name parts of plants so precisely that marks drop like flies.
“The cytoplasm of the sieve tube element at the source end of the sieve tube has a lower water potential than that of the surrounding tissues, so water moves from the surrounding tissues into the cytoplasm of the sieve tube elements at the source end of the sieve tube”.
Plant hormones
It's complicated, contradictory, and can seem SO dull that people zone out. I’d argue that plants are alien machines that build themselves; which makes them pretty cool. But, most students just aren’t that interested in plants and can name 50 brands before they could name 10 plants.
Respiration
Respiration is death by detail, and it's really quite abstract. Another classic example of where the tidal wave of more and more detail befuddles you before you get to grips with the fundamentals
Photosynthesis
This has the same sort of problems as respiration, AND it’s just so easy to mix the two up. They both have electron transport chains, they both have coenzymes, and it’s really easy to confuse NAD with NADP.
Resting and action potentials
It’s abstract, molecular, and you have to understand how molecular actions relate to a graph with volts on it for goodness sake. You left physics because it tried to sneak too much maths onto you… and now Biology’s at it too.
Answering the question they give you
…and not just writing about a related idea. Not a topic, I know, but so important.
You have to accept that it’s an exam set by apparently very unfriendly people. They want to see that you can think, and the first part of that is checking if you can understand the question. It’s important to get as much recent past paper practice as you can.
You won’t be able to get a good pass in A level Biology unless you know how to give the examiners what they are looking for - which isn’t just the ability to regurgitate the textbook. A level Biology is the Devil. You have to accept that and come out fighting.
The logic of the lac operon
Because it's all molecular and complicated again, and it's just a bit different from translation and transcription which you learnt in the first year. Very few Biology students also study computer science and so have no experience of formal logic. Actually, it's a lot easier than it first appears.
Interactions between gene loci
Epistasis and sex linkage. If you’re not 100% with the differences between a chromatid, a chromosome, a homologous pair, a bivalent, a gene, a locus and an allele, as well as when and how variation occurs during meiosis and sex, then you're always going to be struggling to understand this topic. Also, it's always an application rather than a recall question in the exam. You have to understand it to be able to answer the question. It's like maths.
Hardy Weinberg ratios
It’s maths and it’s abstract. If you like maths then it’s free marks for you! If you don’t like maths then it’s the devil's own work.
Plant hormones
See, they’re so boring you’d already forgotten that I’d covered them above.
Sliding filament theory
Molecules? Pfff. Applying understanding of molecular processes to explain why diagrams of muscles look like they do? Double pffff. AND vice versa? Triple pffff.
Maths questions in Biology
What! Make sure you do loads of recent past papers. Make sure you’re 100% practised in ratio, % change, converting between units, and standard form. Do a few examples of all the statistical tests. You cannot escape the maths - it’s a significant percentage of the marks. If maths is a weakness for you it’s important to accept that and do something to get better.
Which topics are going to be on this year’s exam?
If I knew that I'd finally be buying that 60ft yacht.
No-one else knows either, except the chief examiner.
Please don’t just revise the bits they didn't test last year. It’ll go horribly wrong.
My strategy as an A Level Biology tutor is to help you truly understand the seven fundamental topics that unlock the rest of the course. By mastering these topics you’ll create a solid base for understanding more complex concepts throughout the rest of the syllabus. We work through the areas where students often underachieve and make sure you have techniques in place for getting the highest possible marks in these areas.
For tailored help with your own study, book a free strategy call. During the call we’ll look at what’s holding you back, and make a clear plan to help you bring Biology back from the dead.
