O Level Biology

Describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications

Explain that the cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, resulting in diarrhoea, dehydration and loss of ions from the blood

Explain the importance of a clean water supply, hygienic food preparation, good personal hygiene, waste disposal and sewage treatment in controlling the spread of cholera (details of the stages of sewage treatment are not required)

Describe the role of the mosquito as a vector of disease

Describe that a pathogen may be transmitted: (a) through direct contact, including through blood or other body fluids (b) indirectly, including from contaminated surfaces or food, from animals, or from the air

Describe a pathogen as a disease-causing organism

List the components of blood as red blood cells, white blood cells, platelets and plasma

Describe the transfer of substances between blood in capillaries, tissue fluid and body cells

State the functions of the components of blood: (a) red blood cells – oxygen transport (b) white blood cells – antibody production by lymphocytes and engulfing pathogens by phagocytes (c) platelets – clotting by converting soluble fibrinogen to insoluble fibrin to prevent blood loss and the entry of pathogens (d) plasma – transport, limited to: … Read more

Explain how the structure of arteries, veins and capillaries is related to the pressure of the blood that they transport