General review
WELL, IT is that time again; we have come to the end of another series. I have enjoyed the time that I have spent getting your lessons together and I hope that you have enjoyed reading them. I also hope that you have benefited in some way from our interaction over the years. I wish for you a sense of calm and peace as you read your examination paper, because these two states will set the foundation for you to do your best in your examination.
This week, we will be reviewing osmoregulation in animals and plants. Remember that you may be asked to draw a diagram of the organ that is responsible for osmoregulation. What organ is this? It is the kidney! Can you reproduce a diagram of the kidney? Yes, you probably can, that’s not so hard, is it? Can you take that one step further and reproduce one of a kidney tubule? That is a bit more challenging, isn’t it? Well, you need to be able to do this, so practise, practise and practise, and then practise some more! You can make the diagram of the kidney tubule annotated and use this to describe it. Together, let us list below some of the annotated labels that can be attached to your diagram.
LABELS OF ANNOTATION
Glomerulus – Network of capillaries used for ultrafiltration due to differences in the diameter of efferent and afferent arterioles.
Bowman’s capsule – Cup-shaped structure holding glomerulus.
Convoluted tubules – Used for the reabsorption of glucose and minerals.
Capillary network around the tubules – Used for reabsorption and transport.
Loop of Henle – The length of the loop is associated with the quantity of water to be absorbed.
Collecting tubules – Reabsorbs solutes and water from filtrate.
Pelvis – Used for the collection of urine from the tubules.
The functioning of the tubule is affected by ADH (anti-diuretic hormone) in the following manner:
When there is a high concentration of solute in the tubule, more ADH is secreted.
The increased ADH causes the convoluted tubules and the collecting ducts to be more permeable to water, so more water is reabsorbed into the blood vessels.
The reverse happens when the solute concentration is low. Less ADH is secreted, the distal convoluted tubules and the collecting ducts are less permeable and less water is reabsorbed into the capillaries, more copious urine is produced.
Does osmoregulation take place in plants? Yes, it does! Why do plants need osmoregulation?
Osmoregulation provides water for cell metabolism. It provides water to prevent wilting. It provides water to maintain turgor.
It helps to keep the water level of the plant’s cells constant.
Planting crops with deeply penetrating roots and leaves with thick cuticles aid farmers in cultivating certain areas of land. These characteristics would confer the following advantages to the farmer:
Deep roots – These would improve the plant’s chances of survival in a drought, since the roots would be able to draw water from the water table.
Thick cuticle – This would reduce the amount of water lost by evaporation from the leaves.
These plants would require less water, less irrigation.
This would help to reduce production costs.
Let us talk a little bit about the exam. Remember the set-up of your exam? There are three papers: Paper 03 represents the school-based assessment which is now history, and there is nothing you can do at this time to alter the mark that you got, so we will not spend any time talking about it. Paper 01 is the multiple-choice paper. This consists of 60 multiple-choice items which cover the entire syllabus.
Despite what you may think or what you may have practised, Paper 01 does not provide items for a guessing game; nor is it a contest providing prizes for the candidate who finishes in the shortest possible time! Each question requires serious analysis and thought before you decide on an answer and attempt to shade. Take careful note of the words that are in capitals and in bold, as these are the key words and they are important in helping you to understand the questions and, hence, give correct answers. Read the lead for each question carefully!
Paper 02 is the paper that deals with structured questions (Section A) and extended essays (Section B). This is the paper that most students tend to dread. It consists of three structured and three extended essay questions, each worth 15 marks. There is a difference, however; the 15 marks are much harder to earn from Section A than from Section B. Why is this so? This is so because Section A requires precise, wellreasoned answers and few students are very good at giving these! How, then, can you manipulate this paper to get maximum marks? Do not spend time answering all of the questions in Section A before you attempt Section B. If you do this, you will find that you will spend too much time on Section A and not enough time will be left for you to do justice to Section B, where you are likely to gain more marks. What should you do then? Do Question 1 in Section A and then go to Question 4 in Section B, and continue like this until you get to the end. This way, all the questions will be given equal attention.
Remember to spend the first five minutes reading through the entire paper before you begin to write. All the best for your exams. Remember: read, think, then write.
Blessings!