(Essay question) How are cycles important in biology?

To obtain a top mark in an essay for A-level Biology it is vital that you mention areas covered under all the modules of the course- the questions that are asked are usually very broad and your answer should mirror that! Cycles occur all over biology and this is a good example of a question where you should be able to mention an extensive range of subjects. I would aim to include the following: 1. The cell cycle including G1 (in which some organelles are replicated), S phase (in which DNA is replicated) and G2 then mitosis. This should include detail on the stages of mitosis. 2. The Krebs cycle should also be mentioned as part of respiration which occurs in the mitochondrion. 3. The cardiac cycle is another important one to mention- the control of contraction and relaxation of cardiac muscle by an electrical impulse (Include an account of how the impulse is initiated and propagates through the atria and then the ventricles) 4.   The carbon cycle 5.   The Calvin cycle 6. The menstrual cycle 7.    PCR should be included as a key procedure commonly used in labs. Include a list of all the ‘ingredients’ required and a description of the procedure Top tips for those aiming for an A*: -Get creative in including links between your different subject areas and paragraphs -Ensure that everything you mention is relevant to the question being asked and explain why it is relevant