Tagged: revision
Never forget the pathway to success……
PMG Zondle Zero 3 challenge
Just confirming the playing regulations for my two iGCSE Y11 groups with Zondle. Create an account using the classcode I have given you. Play the games I set for you as many times as you like, collecting “zollars” for high scores but also for repeated attempts.
At the start of next half the student in each class with the most “zollars” will be taken out for lunch at Zero 3 on the High Street and I will pay. If you want to set your own revision quizzes on Zondle, do please have a go. You can see the other games from people in the class under the “games set by my friends” drop down list.
Enjoy – I think this will be a great way to make revision a little more interesting…..
Holiday revision: some PMG tips for Y11 students to maximise the effectiveness of their work
The Easter holidays will be the critical period for all Y11 students preparing for the summer iGCSE exams. The main paper for Biology is so early in May that you need to make good use of time of the holidays. Indeed the majority of your Biology revision should be accomplished before you come back to school in April
Here are some tips in no particular order that might help.
1) Revision is not measured in hours. It is not how many hours you do that matters, it is the benefit you gain from your work. Don’t worry about people who tell you they are doing 10 hours a day – most of their effort will be wasted….
2) What do you need for revision? I suggest you make sure you have all of the following ready for Biology revision this holidays.
- Textbook (absolutely essential as it should now be your main source of information)
- Specification booklet (either the printed version I give you or one downloaded from Firefly)
- Blank paper/cards and coloured pens and pencils (for making summary notes and diagrams)
- Past Paper 1B booklet
- Past Paper 1B mark schemes
3) Active Revision: You all know that reading is a very poor way to revise. The more active and multi-sensory you can be in revision, the more you will learn. Make flash cards that summarise each topic. Use a dictation app to record yourself speaking about the three key ideas in a topic. Make revision videos that you can post to a YouTube channel. Do some of the Zondle revision activities I will set up during the holidays. Leave replies to my blog posts with anything that doesn’t make sense or with any questions you may have. Past papers are best used sparingly in the early stages of revision – your task this holidays is to try to learn as much of the specification as you can. We will look at many past papers and mark schemes next term.
4) Do not revise any one topic for more than 35 minutes. Take a 5-10 minute break and then start something new.
5) Have a plan. I suggest you should aim to work a maximum of 5 hours a day and I think it is best to split the day into three periods of work. 9.15am – 12pm; 2pm – 4.45pm; 7.30pm – 10.15pm. The idea is that every day you always work in the morning slot plus either the afternoon or the evening slot as you prefer.
The plan is good because you want to know that when you are not working, you can relax and enjoy yourself properly. Each revision session is divided into three or four topics, each lasting about half an hour.
Do not ever work late in the evening. Always get up at your normal time and always start work at 9.15am.
6) Do some fun things in the holidays as well as work, but put them into the plan. Exercise is good, spending time with friends is good, eating healthily is good, getting plenty of sleep (8 hours at least a night) is essential.
Basically for this one holiday, you want to trick your body and mind into sticking in “school mode”. Early to bed, early to rise, keep active each day and work hard! The summer term will fly by and you can do a great deal of sleeping and proper relaxing in the months of June, July and August.
Good luck – and keep checking the blog and/or Twitter for new posts and Zondle quizzes
New IGCSE Biology posts on their way….
I am getting quite close to having a comprehensive coverage of the EdExcel iGCSE specification in the various posts on my blog. Here are some of the topics that have yet to be covered. All will be appearing in the next few weeks…..
- Viruses
- Cell Structure
- Mineral Ions in Plants
- Human diet
- The Digestive System in Mammals
- Small Intestine
- Respiration
- Comparison between Sexual and Asexual reproduction
- Cell Division and Chromosomes
- Use of Quadrats
- Air pollution and Climate Change
- Deforestation
- Microorganisms and Food Production
- Growing Crop plants
- Fish farming
- Cloning in Plants
- Cloning in Animals
Please add comments or tweet me with any further topics you would like to see in this blog.
Last week of work for Biology IGCSE students
This is the final week of work for all iGCSE year 11 Biologists.
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.
Feedback on Zondle Biology revision challenge part 2
The questions in this revision test were more challenging than last time. I hope that players found them interesting and useful.
The plant transport questions at the start were well answered overall. Osmosis is the only way water can ever cross a cell membrane and although active transport does occur in the root hair cells (pumping mineral ions such as nitrates into the cell against the concentration gradient), water cannot be directly pumped against its concentration gradient using energy from respiration.
The cloning questions were difficult but I think the low scores here were perhaps more to do with problems with my school wifi than with your abilities to answer them! Micropropagation is the way that you learned when a small part of a plant is cut out, sterilised, washed and then added to a culture medium that triggers cell differentiation. You probably did this experiment with explants from a cauliflower. The aim was to produce whole new plants from these small explants. This technique could not work with animals simply because animal’s bodies contain many more types of tissue and have a more complex internal architecture that requires a much more sophisticated genetic programme of development.
I want to talk about a few questions in the latter stages of the test that were not well answered. I am sure there is plenty you can all learn from these.
The first was the one that asked you what was meant by a “diploid cell”. More than half of you thought that diploid meant having 46 chromosomes. This is almost a trick question because of course in humans, diploid cells will have 46 chromosomes. But diploid can be applied to any cell that has chromosomes found in homologous pairs. The number 23 is only important to humans as for our species it is the number of homologous pairs of chromosomes found in our diploid cells. Different species have differing numbers of pairs of chromosomes, some less than the number in humans but in many species they have more.
The second big idea question was the true or false question on whether energy is recycled in the ecosystem like carbon atoms. It is vital you understand that there is absolutely no recycling of energy ever in an ecosystem. Energy enters in the form of light energy being trapped by plants in photosynthesis and all this energy ultimately ends up as heat energy in the atmosphere. To find out the details of how it gets there, please read the relevant sections on my blog. Try the tag energy from the Tag cloud on the right of the screen.
There was one question in the quiz which not a single player answered correctly and it is the one about which type of cells produce antibodies. Antibodies are made from a cell called a plasma cell. Plasma cells secrete antibodies in large numbers to combat an infection. Plasma cells are descended from B lymphocytes that have been activated by the presence of antigen. This clonal selection theory is one of the most complicated bits in iGCSE Biology so make sure you have looked carefully at it. The final question was about active v passive immunity. This is not specifically mentioned in the specification so perhaps is a bit mean to include but if you can understand it properly, you understand how immunity works. Passive immunity is the name for when antibodies are transferred, perhaps across the placenta for a foetus or in an injection as an adult. Antibodies are made of protein and so do not exist for long in the blood – after a month or two they will all have been broken down and cleared from the blood. So passive immunity cannot give long-lasting protection. Active immunity is when memory cells are produced via a clonal selection response. These memory cells can survive for an entire lifetime and so do provide long lasting protection.
By far the biggest thing you can learn from this quiz however was about virus structure. I asked you whether “viruses are made from a different kind of cell not found in animals or plants – true or false.” Almost everyone went for false but remember this can’t be correct: viruses are definitely not made of cells! They are much simpler than even the simplest cell and just consist of a protein coat with some genetic material (DNA or RNA) inside. No cell membrane, no cytoplasm, no metabolism – just two chemicals associated into one simple particle.
Anyway I hope you enjoyed the quiz – look out for the next one on my Twitter feed and please use the comment facility on this blog to get in touch if you have any questions or want more explanations.
Understanding the Eye to Grade 9 at GCSE Biology (part 2) 2.91 2.92
In the first blog post on this series, I described the pupil reflex in the eye. If you remember this involved the circular and radial muscles in the iris contracting and relaxing in an antagonistic fashion to alter the size of the pupil. You should understand why the pupil size needs to altered and what state the two sets of muscles are in varying light intensities.
But there is a second reflex in the eye totally separate from the pupil reflex and it is to do with focusing. This reflex is sometimes called accommodation but as this is a word I can’t spell, I prefer to call it focusing…. The retina at the back of the eye contains the photoreceptors. There are two types of photoreceptor in the retina (rods and cones) and these are individual cells that can detect the light and then send a nerve impulse in the optic nerve that goes to the brain.
Focusing in the Eye (this is quite complicated and needs careful, slow reading)
When the eye views objects from differing distances away, the degree the light has to be bent to produce a focused image will vary. Light coming from near objects will be diverging (the rays will be moving away from each other) and so to focus the light onto the retina, a large amount of bending (or better still refraction) will be needed. Light rays coming from far away objects are almost parallel when they hit the eye so the degree of refraction required is much less.
How can varying degrees of refraction be achieved in the eye?
Well as the diagram above shows, this is brought about by changing the shape of the lens. A short fat lens will refract (or bend) the light more than a long thin one. (If you want an explanation for why this is, you need to ask a Physics teacher – it is to do with the angle of curvature of the lens and the refractive indices of the liquids in the eye compared to the lens…….)
The lens in its default state is short and fat. This means that with no tension pulling it out of shape it will adopt the short fat shape suitable for viewing near objects.
How can the lens be pulled out of its default short fat shape?
Now this is the bit where people get confused. Read this section really carefully, check with your own notes and revision notes and make sure you have got this all the right way round! Here goes…..
There is a ring of muscle that surrounds the lens in the eye called the ciliary muscle. (Please make sure you don’t confuse this with the circular muscles in the iris) The ciliary muscle doesn’t attach to the lens directly but is attached to the lens via some strong and inelastic ligaments called the suspensory ligaments. Tension in the suspensory ligaments can pull the lens from its default short, fat shape into the long this shape needed to view far away objects.
When the ciliary muscle contracts, it shortens. This effectively moves it closer to the lens and so any tension in the suspensory ligaments is released as the ligaments go slack. Slack ligaments mean the lens adopts its short fat shape.
When the ciliary muscle relaxes, this changes its position to increase the tension in the suspensory ligaments. Taut suspensory ligaments (caused by the relaxed muscle) will pull the lens into a long thin shape.
You can easily see why people get confused here: a contracted ciliary muscle leads to slack suspensory ligaments and vice versa.
One way you can improve your understanding is to be really precise with your use of language. The ciliary muscle is a muscle (no honestly it is) and as you know, muscles can either contract or relax. Suspensory ligaments cannot contract or relax but their tension can be altered from taut (loads of tension) to slack.
So to summarise this complex sequence of events:
Looking at a far object
- Lens needs to be long and thin
- as light rays are almost parallel as they hit the eye
- and so require little bending.
- To pull the lens long and thin requires
- suspensory ligaments to be taut
- and this is achieved by the ciliary muscle relaxing.
Looking at a near object
- Lens needs to be short and fat
- as light rays are diverging as they hit the eye
- and so require a lot of bending.
- The lens will adopt a short, fat shape with
- no tension in the suspensory ligaments (the ligaments are slack)
- and this is achieved by contracting the ciliary muscle.
You can easily check your understanding here because it is much more tiring on the eye to look at a near object. If you sit on a sunny beach after all your GCSEs are finished, staring out to sea in a contemplative manner wondering how you managed to work so hard through the revision period, you could continue like this for hours. But if you try staring at your finger a few centimetres from your face for even a few seconds, your eye starts to tire. In the former scenario the ciliary muscle is relaxed and so not expending any energy but in the latter, the ciliary muscle is contracted, using energy from respiration and so can get tired.
Please comment me on this blog post with any questions – I will do my best to respond to anyone who gets in touch.
Good luck and keep working hard!
Understanding the functioning of the Eye to Grade 9 for Biology IGCSE (part 1) 2.91, 2.92
There are two reflex responses in the eye that you need to fully understand for A* levels at iGCSE. It is really easy to get them confused but I am going to put on consecutive blog posts so you can see the similarities and differences easily.
The first is a reflex called the “Pupil Reflex” which is to ensure an appropriate amount of light enters the eye in both bright and dim light. The only structure in the eye involved in the Pupil Reflex is the Iris. The second reflex explained in part 2 is the “Focusing Reflex” (or sometimes Accommodation) which makes sure that light entering the eye from objects at different distances away is focused correctly onto the retina. The structures involving in Focusing are the Lens, Ciliary Muscle and Suspensory Ligaments.
The Pupil Reflex
1) Why do we need a pupil reflex?
The eye has evolved a mechanism to ensure that the amount of light entering the eye can be adjusted. In bright light you need to limit the amount of light to prevent the light damaging the light-sensitive cells in the retina (a process called “bleaching”) and this is done by making the pupil at the front of the eye small. A small pupil would be useless for vision in low light intensities as then not enough light would get to the retina and vision would be very poor. So in dim light (low light intensities) the pupil is enlarged to allow a maximal amount of light into the eye.
2) What is the Pupil?
The pupil isn’t really a structure at all as it is simply a circular hole in the iris. The iris is a coloured muscular disc at the front of the eye.
The iris has two sets of antagonistic muscles in it that can contract or relax to change the diameter of the pupil. There are radial muscles arranged like the spokes of a bicycle tyre and also circular muscles in the iris as shown in the diagram below.
3) How do the muscles in the iris bring about the pupil reflex?
Remember muscles can only contract or relax. When the radial muscles contract (shorten) they will pull the iris into a narrower shape so the pupil gets much wider. When the circular muscles contract, they will squeeze the pupil smaller so the pupil will narrow.
So you need to basic understand the state of these two sets of antagonistic muscles in both bright and dim light.
Bright light – circular muscles contracted, radial muscles relaxed, pupil small
Dim light – circular muscles relaxed, radial muscles contracted, pupil large
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/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.
Question spotting for IGCSE Biology paper 2
Trying to guess what might come up in paper 2 of public exams is a dangerous business…… But I think it is sensible for Y11 students sitting IGCSE Biology to now focus their remaining revision on topics that have yet to be tested. You are now two thirds of the way through your exams and a final push to paper 2 might just get you across the A-A* boundary. Every mark is vital in any exam so keep working hard!
Here are some PMG tips for topic areas that seem a better than average bet for coming up in paper 2:
- Variety of Living Organisms (5 Kingdom Classification, Viruses)
- Biological Molecules, especially Enzymes – (graph interpretation question?, effect of temperature and pH on rates of reaction?)
- Photosynthesis and Respiration (perhaps a question testing bullet points 2.40 and 2.43 on gas exchange in plants over 24 hour period?)
- Role of White Blood cells in Immunity (perhaps linked in with viruses above, vaccination, memory cells etc.?)
- Coordination in Humans (nerves, reflex arcs, the eye, homeostasis in the skin, hormones)
- Reproduction in Flowering Plants (asexual mechanisms plus insect/wind pollination)
- DNA structure (including mutations), Chromosomes and Cell Division
- Carbon, Nitrogen and Water Cycles
- Pollution (atmospheric, water pollution and climate change)
- Fish Farming (surely they can’t leave this out?…..)
I will post some blog entries on some or all of these topics in the week or two after half term so keep your eyes posted on Twitter or follow this blog.
I am not suggesting that these are the only topics you revise in preparation for paper 2. That would be very foolish as the examiners can ask questions on anything at all. I am merely suggesting that you focus your remaining revision time on the topics most likely to come up and the list above might help you to decide what best to do.
Good luck and keep working hard! Not long to go now……
PMG Biology 