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The blood in the capillary has just returned to the lungs from the rest of the body, so contains a low concentration of oxygen. The alveolus contains air that has just been breathed in by ventilation, so ...

Aorta --> systemic circulation [branches in order: coronary artery (to supply the heart), carotid artery (to supply the head), hepatic artery (to supply the liver), mesenteric artery (to supply the gut...

• Thin alveolar walls for O2 and CO2 to travel through - To travel across the membrane, gases have to be dissolved, so the alveolar walls are moist - Large surface area to volume ratio allows for maxi...

There are three key factors affecting rate of photosynthesis at GCSE level. They are light intensity, CO2 concentration, and temperature. These factors are best visualised by drawing graphs with rate of p...

Eutrophication occurs when nitrate fertilisers are carried by ground water into lakes and ponds. The fertliser encourages algal growth in the water, which in turn blocks out sunlight. This causes submerge...