3(h) Transport
19 specification points in sub-topic 3(h).
Specification points
3.1: Diffusion in unicellular organisms
Why single-celled organisms can rely on diffusion alone: large surface area to volume ratio, short distances.
3.2: Need for a transport system
Why larger organisms need exchange surfaces and a transport system, not diffusion alone.
3.3: Phloem
Phloem carries sucrose and amino acids around a plant, from where they are made to where they are used.
3.4: Xylem
Xylem carries water and mineral ions up from the roots to the stem and leaves.
3.5B: Water absorption by root hair cells
How root hair cells take in water by osmosis and mineral ions from the soil.
3.6B: Transpiration
Transpiration: water evaporates inside leaves and escapes as vapour through the stomata.
3.7B: Factors affecting the transpiration rate
How light, temperature, humidity and wind speed change the rate of transpiration.
3.8B: Environmental factors and transpiration
Practical: using a potometer to see how conditions affect water uptake by a shoot.
3.9: Composition of the blood
What blood is made of: plasma, red blood cells, white blood cells and platelets.
3.10: Role of plasma
What plasma carries: carbon dioxide, digested food, urea, hormones and heat.
3.11: Red blood cells and oxygen transport
How the shape, lack of nucleus and haemoglobin of red blood cells suit them to carry oxygen.
3.12: White blood cells and the immune response
How white blood cells defend the body by phagocytosis and by making antibodies.
3.13B: Vaccination and memory cells
How vaccination leaves memory cells for a faster, larger response to the real pathogen.
3.14B: Platelets and blood clotting
How platelets start a blood clot that stops bleeding and keeps pathogens out.
3.15: Structure and function of the heart
The structure of the heart and how blood flows through it as a double pump.
3.16: Heart rate, exercise and adrenaline
Why heart rate rises during exercise and with adrenaline.
3.17: Risk factors for coronary heart disease
Factors that raise the risk of coronary heart disease, and which ones people can change.
3.18: Arteries, veins and capillaries
How the structures of arteries, veins and capillaries match their jobs.
3.19: The circulation system
The main blood vessels to and from the heart, lungs, liver and kidneys.