11.3 The kidney and osmoregulation

Essential idea: All animals excrete nitrogenous waste products and some animals also balance water and solute concentrations.

The form in which nitrogenous waste is excreted reflects evolution and ecological niche occupied, by the animal.

Understandings, applications and skills

11.3.U1	Animals are either osmoregulators or osmoconformers.
11.3.U2	The Malpighian tubule system in insects and the kidney carry out osmoregulation and removal of nitrogenous wastes.
11.3.U3	The composition of blood in the renal artery is different from that in the renal vein.
11.3.U4	The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.
11.3.U5	The proximal convoluted tubule selectively reabsorbs useful substances by active transport.
11.3.U6	The loop of Henle maintains hypertonic conditions in the medulla.
11.3.U7	ADH controls reabsorption of water in the collecting duct. [ADH will be used in preference to vasopressin. ]
11.3.U8	The length of the loop of Henle is positively correlated with the need for water conservation in animals.
11.3.U9	The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.
11.3.A1	Consequences of dehydration and overhydration.
11.3.A2	Treatment of kidney failure by hemodialysis or kidney transplant.
11.3.A3	Blood cells, glucose, proteins and drugs are detected in urinary tests.
11.3.S1	Drawing and labelling a diagram of the human kidney.
11.3.S2	Annotation of diagrams of the nephron. [The diagram of the nephron should include glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule; the relationship between the nephron and the collecting duct should be included. ]

[Text in square brackets indicates guidance notes]

Presentation and notes

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Nature of science

Curiosity about particular phenomena—investigations were carried out to determine how desert animals prevent water loss in their wastes. (1.5)

For this point simply being able to state the point of understanding should be sufficient.