How to Revise Excretion as an example of homeostatic control — OCR A-Level Biology
Excretion as an example of homeostatic control is a topic in the OCR A-Level Biology specification. This guide covers learning objectives, examiner tips, common mistakes, and key terminology to help you revise effectively.
Examiner Tips for Excretion as an example of homeostatic control
- Ensure you can draw and label the histology of the liver and nephron from microscope slides.
- Practice interpreting data related to glomerular filtration rate (GFR) and electrolyte balance.
- Be precise with terminology: use 'water potential' rather than 'concentration' when discussing osmosis.
- Understand the specific role of the ornithine cycle in converting ammonia to urea.
- Be prepared to explain how monoclonal antibodies work in diagnostic tests.
Common Mistakes in Excretion as an example of homeostatic control
- Confusing excretion with egestion (removal of undigested food).
- Failing to distinguish between the roles of the liver and the kidneys.
- Inaccurate description of the water potential gradient in the loop of Henle or collecting duct.
- Misunderstanding the role of ADH as a negative feedback mechanism.
- Confusing the processes of ultrafiltration and selective reabsorption.
Key Marking Points
- Definition of excretion as the removal of metabolic waste products from the body.
- Role of the liver in detoxification and the ornithine cycle for urea formation.
- Structure of the nephron and its role in ultrafiltration and selective reabsorption.
- Mechanism of osmoregulation involving osmoreceptors in the hypothalamus and the posterior pituitary gland.
- Action of ADH on the collecting ducts to alter water permeability.
- Consequences of kidney failure and the principles of renal dialysis.