Tagged: biology

IGCSE Biology 2017 paper 2 predictions

This post starts with a massive proviso of course.  Making predictions as to which topics might appear in a future exam is a very risky business.  The paper 2 you will all sit after half term can test material from the entire specification (including all the specification points in bold) and there is absolutely no guarantee that topics tested in paper 1 may not reappear in some form in paper 2.

So the proviso is this:  the only way to be fully prepared for paper 2 is to revise the entire specification so that you are prepared for whatever the examiners might throw at you.

But having said that, it seems sensible to focus your revision for paper 2 onto topic areas that were not examined in paper 1.  If I were in your position, these are the topic areas for which I would be doing most of my revision in the coming weeks:

  • Respiration 2.33 – 2.37
  • Gas exchange in Plants 2.38-2.43
  • Transport in Plants 2.49 – 2.56
  • Transport in Humans 2.57 – 2.66
  • Kidney 2.68 – 2.76
  • Reproduction 3.1 – 3.12
  • Food Chains and Energy Flow 4.4 – 4.7
  • Nitrogen and Water Cycles 4.8, 4.10
  • Human Influences on Environment 4.11 – 4.17
  • Food Production (including fish farming) 5.1 – 5.9
  • Selective Breeding and Genetic Modification 5.10 – 5.16

The bad news is that this list above still forms a large proportion of the extensive EdExcel IGCSE Biology specification but the good news is that there are PMGBiology blog posts on all the above.  So please use the search function on my homepage to find material to help you revise.

Practice papers and mark schemes are available online (and for my students on the school Firefly page)

Keep working hard – you are almost there and the summer to come will be long and restful….

IGCSE Biology paper 2 – predictions

I am always very wary of trying to “second guess” IGCSE examiners and predict what questions might come up as it can be a risky business.  But as all the Y11 students out there start a well-earned half term, I thought I would put up a short post with some suggestions as to areas of the specification that have not yet been tested.

Important Disclaimer:  Remember that the examiners can set questions on the entire specification in paper 2 (including all the bullet points in bold).  It seems more likely to me that the questions will be on areas of the specification not yet tested in paper 1 but you cannot guarantee it.  So please make sure you revise the entire specification and are as prepared as you can for any questions that might come up.

Topics not yet assessed on 2016 paper 1

  • Viruses 1.2
  • Enzymes and Biological Molecules 2.5, 2.6, 2.7, 2.8, 2.9, 2.10. 2.11
  • Movement across Membranes (Diffusion and Osmosis) 2.12, 2.13, 2.14, 2.15, 2.16
  • Photosynthesis 2.17, 2.18, 2.19. 2.20. 2.21, 2.22
  • Breathing 2.44, 2.45, 2.46, 2.47, 2.48
  • Respiration 2.32, 2.33, 2.34, 2.35, 2.36
  • Kidney and Excretion 2.68, 2.69, 2.70, 2.71, 2.72, 2.73, 2.74, 2.75, 2.76
  • Plant Responses 2.80, 2.81, 2.82
  • Reproduction in Plants 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7
  • Water/Carbon/Nitrogen Cycles 4.8, 4.9, 4.10
  • Food Production (crops) 5.1, 5.2, 5.3, 5.4
  • Food Production (microorganisms) 5.5, 5.6, 5.7, 5.8
  • Fish Farming 5.9
  • Genetic Modification 5.12, 5.13, 5.14, 5.15, 5.16

Remember that there are posts on almost all these topics on the blog so use the search function on the Home page and just type in the syllabus code.

Finally, keep working hard. It is easy to get too comfortable about your exams now that many have already been sat.  A little bit of fear is still a good thing, so remember that 33% of your GCSE marks are still up for grabs and this paper 2 will make all the difference in determining your final grade.  No short cuts now, keep being organised, methodical and diligent.  The summer holiday will give you plenty of opportunities to socialise, have fun and relax so try to keep the momentum up in this coming week.  Good luck!

Any questions, please ask by leaving a comment on this blog post.

F Revision for Michaelmas Trial 2015

You might like to make revision notes or cards to address the following questions…. If you managed this, you would be well prepared for your end of term exam.

1. Explain the difference in meaning between cell, organelle, organism, tissue and organ.

2. Understand the relative size of atoms, molecules, viruses, bacterial cells, animal cells, plant cells.

3. Draw two fully labelled diagrams one of an animal cell, one of a plant cell and describe clearly the differences in structure between the two.

4. Understand the structure and function of the following organelles: cell membrane, plant cell wall, nucleus, chloroplast, mitochondrion, sap vacuole, ribosome and also the function of the cytoplasm.

5. Explain why respiration is an important process in all cells.

6. What kind of processes in cells require energy from respiration?

7. Learn the word and balanced chemical equation for aerobic respiration.

8. Learn the word equation for anaerobic respiration in animal cells and in plants/fungi.

9. Describe the differences between aerobic and anaerobic respiration.  What is an “oxygen debt” and how is it repaid?

10. Describe the structure of the thorax (ribs, lungs, intercostal muscles, trachea, bronchi, bronchioles, alveoli, pleural membranes, diaphragm).

11. Understand the mechanism of breathing – both in and out – using diaphragm and the two sets of intercostal muscles.

12. Understand how alveoli are adapted for efficient gas exchange.

13. Understand the process of diffusion and examples of diffusion in living things.

14. Understand how surface area:volume ratios affect the rate of diffusion and why this might be significant for living organisms.

15. Understand the consequences of smoking on the lungs and circulatory systems.

16. Understand how the processes of respiration and photosynthesis interact in the leaves of plants. What is a compensation point?

17. Know the tissue structure of the leaf and the role of stomata in gas exchange.

18. How a leaf is adapted both for photosynthesis and also for gas exchange.

19. Understand the hydrogencarbonate indicator practicals and why different results are obtained in the various set up tubes.

PMG revision quiz 2 – questions and answers

I am never sure how much information players can see about which are the correct answers.  Here is a pdf file that shows all 30 questions, the correct answer as well as all the distractor answers.

There was some good scoring in the quiz tonight – please read my blog post later for commentary on the questions, including the commonest mistakes and misconceptions.

PMG quiz 2 questions and answers

Commentary on Zondle GCSE Biology Revision challenge 1 questions

I hope that those of you who played the GCSE Biology revision challenge this afternoon enjoyed the process.  I would welcome comments on this blog post along the lines of www (what went well) and ebi (even better if)….

The questions were grouped into several topic areas.

Questions 1 to 4 were on thermoregulation.  Understanding vasoconstriction, vasodilation and sweating are the key things here and if you haven’e done already, I would read my blog post on this topic.

https://pmgbiology.wordpress.com/2014/05/29/skin-a-understanding-for-igcse-biology/

Questions 5 – 9 were on plant transport and these were well answered by almost all players.  Remember that phloem sieve tubes move sucrose and amino acids around the plant.  Water and minerals are transported in xylem vessels of course, but the other distractor answers included various polymers (starch and proteins) that are made in photosynthesis in the leaves but which are too large and insoluble molecules to be transported in phloem.

Questions 10-15 were all on the bacteria in the Nitrogen cycle.  This is a tricky topic but one that rewards patient work by candidates to master it. In reality the Nitrogen cycle is not difficult to understand but it is easy to muddle the names and roles of the four types of bacteria involved.  Again there are a couple of blog posts on Nitrogen cycle that I would encourage you to read….

https://pmgbiology.wordpress.com/2014/04/12/bacteria-of-the-nitrogen-cycle-a-understanding-for-gcse-biology/

https://pmgbiology.wordpress.com/2014/04/12/nitrogen-cycle-for-igcse-biology/

Questions 16-23 were on digestive systems.  These were generally well answered although many players didn’t appreciate that peristalsis doesn’t just happen in the oesophagus: it is the process that moves the food along the entire length of the gut tube from top of oesophagus to the end of the rectum.  The role of the lacteal in transporting fatty acids and glycerol away from the villi in the small intestine is also one of the trickier topics here.  Amino acids and sugars diffuse into the blood capillaries in the villus but fatty acids and glycerol (the products of digestion of lipids) don’t go into the capillaries but instead into a separate vessel called a lacteal. This forms part of the lymphatic system and the liquid formed ends up back in the blood but effectively bypasses the liver, preventing the cells in the liver being overloaded with fatty acids following a fatty meal.

Questions 24-29 were on the heart and circulation.  There were quite a few incorrect answers here but perhaps this was because enthusiasm levels were dropping….  The flow of blood through the heart is an important topic to appreciate – into RA through vena cava, then into RV through right AV valve, then into PA through semilunar valve, then to lungs, back from lungs in pulmonary veins, into LA, through Left AV valve into LV, then into aorta through the aortic semilunar valve…..

The heart strings in the heart (chordae tendinae) are commonly misunderstood.  They play no role at all in opening or closing the AV valves (this is done simply by the balance of blood pressures in atrium and ventricle) but do provide tension to stop the valve “blowing back” and thus opening when the ventricle contracts.  Have a look at pictures of a real heart dissection to see that these tendons attach to the valve flaps and ensure they cannot blow open when the pressure in the ventricles rise during ventricular contraction.  Ask me for more detail if this doesn’t make sense.

Last minute advice: no cramming please

I hope the paper goes really well this morning and all the hard work you have done pays off. This is the culmination of three years of work and there is little to be gained from any last minute cramming this morning. So I would try to relax and summon up your concentration and will for this one last exam.

  • Have a proper breakfast.
  • Make sure you are properly hydrated – fruit juice this morning and water in the exam (if allowed)
  • Read the question carefullyevery word in every question. If there are data given in the question, take your time to make sure you understand what the data means before starting to answer any questions.

If there is a risk for you today, it is that it is easy to get too blasé and slapdash in the final exams in a set. You have sat many papers in the last few weeks and you can forget the importance of the exam technique and question-answering skills you had honed in the middle of May. Please don’t let that happen to you. Focus for the entire 60 minutes, think before writing and don’t waffle.

  • Any question with more than 3 marks should be answered with bullet points.

Enjoy this morning, enjoy showing the examiner your mastery of iGCSE Biology and then enjoy a long, well-deserved summer holiday.

Last week of work for Biology iGCSE students

This is the final week of work for all iGCSE year 11 Biologists.

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For the D block boys I teach, think back to those first few days at the start of F block when you had your new uniforms that didn’t fit and consider how much you have changed and learned in the intervening years.  Now with just one final week of Biology revision to go, this is the time to make those final steps in your journey to an A* grade.

It is so easy when the GCSE exams are almost done to relax, to ease up a little and not give of your best this week.  Please don’t do this – there is plenty of time for relaxing and easing up in late June, July and August.  You can still make a big difference to your chances next Monday if you can keep working hard for the final few days.

1) If you need more example of past paper 2s, please get in touch via email/Twitter or by commenting on the blog.

2) If you want to go through any past papers you have completed with me, contact me to fix up a time to meet up.

3) Why not have a go at one of my Zondle revision challenges this week?; next one is Monday 9pm – see Twitter feed for details of how to register.

4) Keep looking over your revision notes, keep practising questions and focus your revision now on the topics most likely to appear.  See my earlier post on question-spotting for paper 2 if you haven’t already.

2.62 Platelets and Blood Clotting – A* understanding for iGCSE Biology

There is a specification bullet point in bold (paper 2 only) about blood clotting and the role of platelets, and students are sometimes not sure to what level of detail is needed for a full GCSE understanding of this topic.  Well the good news is that the only questions I can recall are very straightforward indeed.  But in this post I will give you a little more detail than the minimum needed for A* answers so that you can be confident you are completely clear on this part of the specification.

Why does blood need to clot?

Capillaries have a very thin wall (one cell thick in fact) so can easily tear and get damaged.  This means that damage causes blood to leak into tissues forming a bruise and if the skin is broken, blood can be lost from the body entirely.  Blood clotting is the response in the blood that ensures that blood loss is minimised and also that the time micro-organisms have to get into the blood stream is kept as short as possible.  The surface of the skin is covered with millions of pathogenic organisms (mostly bacteria) all waiting for the chance to get into the blood stream through a cut or tear.

What are platelets?

Platelets are small fragments of cells found in bone marrow that then get into the blood and are carried round in the plasma. They are not entire cells as they lack a nucleus but they do play an essential role in blood clotting.

How does blood clotting work?

When the lining of a capillary is broken, platelets initially stick to the site of damage.  They then trigger a series of reactions in the blood plasma that causes a clot to form.  The details of how this works are too complicated to go into here but the basic idea is that in the blood plasma are a whole family of proteins called clotting factors. There is a cascade of reactions such that one clotting factor is activated and in turn, activates the next in the sequence.   The final reaction in the clotting cascade is that a soluble protein called fibrinogen is converted into an insoluble fibrous protein called fibrin.  Fibrin forms a mesh around the platelet cap covering the site of damage and this mesh traps red blood cells forming the final clot.

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The roman numerals on the diagram above refer to clotting factors and each in turn is activated.  You can see the final stage of the cascade is that soluble fibrin is converted into the fibrin clot.

Many of you will know of the disease where blood doesn’t clot called haemophilia.  The commonest type of haemophilia is a genetic disease where patients cannot produce clotting factor VIII.  This means one step in the clotting cascade does not work and so the blood cannot clot normally.

(Extension idea:  find out the link between Haemophilia, the British Royal family and the 20th century history of Russia)