Practice Pakistan questions with answers and explanations.
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The small intestine has villi that greatly increase surface area.
Most digested nutrients enter blood or lymph there.
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The heart contracts rhythmically to circulate blood.
It supplies tissues with oxygen and nutrients.
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The heart has two atria and two ventricles.
The chambers separate oxygenated and deoxygenated blood.
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Arteries carry blood away from the heart under pressure.
Most carry oxygenated blood, with pulmonary arteries as an exception.
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Veins return blood to the heart.
Many contain valves that help prevent backflow.
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Capillary walls are only one cell thick.
This allows diffusion of gases, nutrients, and wastes.
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Photosynthesis stores light energy in glucose.
Oxygen is released as a by-product.
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Red blood cells contain hemoglobin.
Hemoglobin binds and transports oxygen.
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Carbon dioxide supplies carbon for glucose formation.
It enters leaves mainly through stomata.
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White blood cells identify and attack pathogens.
Different types act through phagocytosis or immune responses.
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Splitting water during photosynthesis releases oxygen.
The gas diffuses out through stomata.
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Platelets gather at damaged vessels and activate clotting.
This limits blood loss.
