A-Level Biology Specification

OCR A H420

Section 5.1.2: Excretion as an example of homeostatic control

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#5.1.2a

the term excretion and its importance in maintaining metabolism and homeostasis

To include reference to the importance of removing metabolic wastes, including carbon dioxide and nitrogenous waste, from the body.

#5.1.2b

(i) the structure and functions of the mammalian liver

(ii) the examination and drawing of stained sections to show the histology of liver tissue

To include the gross structure and histology of the liver AND the roles of the liver in storage of glycogen, detoxification and the formation of urea (the ornithine cycle covered in outline only).
PAG1

#5.1.2c

(i) the structure, mechanisms of action and functions of the mammalian kidney

(ii) the dissection, examination and drawing of the external and internal structure of the kidney

(iii) the examination and drawing of stained sections to show the histology of nephrons

To include the gross structure and histology of the kidney including the detailed structure of a nephron and its associated blood vessels AND the processes of ultrafiltration, selective reabsorption and the production of urine.
PAG1, PAG2

#5.1.2d

the control of the water potential of the blood

To include the role of osmoreceptors in the hypothalamus, the posterior pituitary gland, ADH and its effect on the walls of the collecting ducts.

#5.1.2e

the effects of kidney failure and its potential treatments

To include the problems that arise from kidney failure including the effect on glomerular filtration rate (GFR) and electrolyte balance AND the use of renal dialysis (both haemodialysis and peritoneal dialysis) and transplants for the treatment of kidney failure.

#5.1.2f

how excretory products can be used in medical diagnosis

To include the use of urine samples in diagnostic tests, with reference to the use of monoclonal antibodies in pregnancy testing and testing for anabolic steroids and drugs.
PAG9