Kidney and osmoregulation 11.3 HL

This topic looks at the interesting concept of water balance in organisms. Insects control water balance using small malphigian tubules unlike mammals and other vertebrates who have a kidney. Even single celled animals like Amoeba can control the amount of water in their cells, but many other aquatic animals try to keep their body's osmotic potential as close a possible to their environment, this is why a shark stores urea in their bodies.

Key concepts

Learn and test your biological vocabulary using these 11.3 Kidney and osmoregulation flash cards

Essentials

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - great revision.

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Summary

Summary list for Kidney and osmoregulation 11.3

Control of water balances in different animals

  • Some animals are osmoconformers - their cells have solute concentration equal to their environment (eg. marine invertebrates)
  • Vertebrates and insects are osmoregulators. (so are some single cells, eg.Amoeba)
  • Insects have malphighian tubules but vertebrates have kidneys to carry out osmoregulation and remove nitrogenous wastes.
  • The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

Kidney structure & function

  • The differences in composition of blood in the renal artery & the renal vein.
  • Ultrafiltration helped by the ultrastructure of the glomerulus and Bowman’s capsule.
  • Selective reabsorption of useful substances by active transport in the proximal convoluted tubule.
  • The loop of Henle maintains hypertonic conditions in the medulla.
  • ADH controls reabsorption of water in the collecting duct.
  • The length of the loop of Henle is positively correlated with the need for water conservation in animals.

Skills & applications

  • To be able to draw and label a diagram of the human kidney.
  • To be able to annotate diagrams of the nephron. Including glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule; and the collecting duct
  • To have considered the consequences of dehydration and over-hydration.
  • To know about treatment of kidney failure by hemodialysis or kidney transplant.
  • To know about urinary test for Blood cells, glucose, proteins and drugs.

Mindmaps

These diagram summaries cover the main sections of topic 11.3 about osmoregulation and the kidney.
Study them and draw your own list or concept map from memory.

Exam style questions

Understanding the structure of the kidney nephron is not as important as understanding it's function in osmoregulation. Many students learn the names or all the parts of a nephron but few learn the details of it's function. This question will help to practise explaining these functions.

Answer this question on a piece of paper, then check your answer against the model answer below.

Describe the formation of glomerular filtrate in the kidney and how homeostasis of water balance is achieved using selective reabsorption and ADH secretion. [8]

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Extra exam question on nitrogenous waste excretion.    Click to open.

Nitrogenous wastes need to be excreted. Organisms have evolved methods to secrete these compounds depending upon their habitat and the availability of water.

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Discuss how the excretion of nitrogenous waste is related to the water availability of organisms.
(8 marks)
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Hint: Discuss give reasoned arguments.

Discuss type questions often have a generous mark scheme but keep to the question – here relating nitrogenous excretion to water economy.

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Extra exam question on drawing a diagram of the kidney.     Click to open.

A required skill is to draw a diagram of the kidney.

Answer this question on a piece of paper, then check your answer against the model answer below.

Draw a diagram of a cross-section of a mammalian kidney. (5 marks)






Hint: Draw a clear well defined drawing with accurate labels
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Extra exam question on the renal artery and vein.    Click to open.

The flow and composition of blood in arteries and veins varies, depending on the particular artery and vein.

Distinguish between the flow and composition of the blood in the renal artery and the renal vein. (6 marks).





Examiner hint - distinguish requires the differences. Include both flow of blood and composition as both are needed for full marks (6 differences in composition will only receive 4 marks)>

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Extra exam question on osmoregulators and osmoconformers       - - click to open.

Osmoregulators and osmoconformers have evolved different approaches to dealing with osmotic changes in their environment.

There is also a similar drag and drop question that you can use for practice before answering this question.

Answer this question on paper and then compare your answer to the model answer.

Distinguish between osmoconformers and osmoregulators. (3 marks)





Hint: Distinguish between asks for an account of the differences between two concepts.
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Test yourself

Multiple choice questions

This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding.


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Drag and drop activities

Test your ability to construct biological explanations using the drag and drop questions below.

Osmoconformers and osmoregulators.

Drag and drop the correct term into the gap to describe internal minaral and water concentrations in osmoconformers and osmoregulators.

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osmoconformers concentration functions water stable increases dilute Osmoregulators homeostatic energy fall

Some aquatic animals are . They do not control their internal salt and levels but allow them to rise and depending upon the outside aquatic medium. Their body size and body fluids become more in fresh water, the opposite occuring in a marine environment. This method saves energy but can cause bodily to be less efficient.

maintain control of their body mineral and water by balancing water and mineral gain and loss. They maintain internal conditions and bodily efficiency but the process is consuming.

 

Explanation: Homeostatic control is energy consuming but allows the body to work at high efficiency in varied environmental conditions.

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