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Biology 20

Biology 20 · Worksheets

Mixed review · Human systems

Ten questions of mixed difficulty, covering Circulation, Digestion, Excretion and movement. Print it, or work through it on screen — the answer key starts on its own page.

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Mixed review · Human systems

Biology 20 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. The functional unit of the kidney is the

    1. a) nephron
    2. b) glomerulus
    3. c) alveolus
    4. d) villus

  2. In the pulmonary circuit, blood travels

    1. a) from the left ventricle to the body and back to the right atrium
    2. b) from the lungs to the body and back
    3. c) from the right atrium to the lungs and back to the right ventricle
    4. d) from the right ventricle to the lungs and back to the left atrium

  3. Bile helps fat digestion even though it contains no enzymes, because it

    1. a) emulsifies fat into small droplets that lipase can work on
    2. b) lowers the pH so lipase can work
    3. c) chemically breaks fat into fatty acids
    4. d) absorbs fat directly into the blood

  4. Valves in the heart and veins

    1. a) produce blood cells
    2. b) increase blood pressure
    3. c) prevent blood from flowing backwards
    4. d) filter the blood

  5. Bile is produced by the

    1. a) gall bladder
    2. b) pancreas
    3. c) liver
    4. d) stomach

  6. The loop of Henle makes concentrated urine possible because it

    1. a) actively pumps water out of the filtrate
    2. b) creates a salt concentration gradient in the medulla that water can be drawn into
    3. c) adds urea to the filtrate
    4. d) filters the blood a second time

  7. The heartbeat is initiated by the

    1. a) sinoatrial node
    2. b) brain
    3. c) atrioventricular node
    4. d) aorta

  8. Arteries are defined as vessels that

    1. a) carry blood away from the heart
    2. b) carry blood towards the heart
    3. c) exchange gases with tissues
    4. d) carry oxygenated blood

  9. Starch digestion begins in the

    1. a) stomach, with pepsin
    2. b) mouth, with salivary amylase
    3. c) large intestine, with bacteria
    4. d) small intestine, with lipase

  10. Filtration at the glomerulus forces out of the blood

    1. a) only urea and water
    2. b) only wastes
    3. c) water, glucose, salts and urea, but not proteins or blood cells
    4. d) everything, including blood cells

Answer key · Mixed review · Human systems

Biology 20 · maddyhelps.com

  1. a) nephron — Each kidney holds about a million nephrons, and each one does the whole job in miniature: filter, reabsorb, secrete. The glomerulus is only the filtering part of a nephron.
  2. d) from the right ventricle to the lungs and back to the left atrium — The pulmonary circuit is the short loop to the lungs; the systemic circuit is the long loop to everything else. Blood passes through the heart twice per complete journey.
  3. a) emulsifies fat into small droplets that lipase can work on — Fat clumps together in water, so enzymes can only reach the outside of a globule. Breaking it into droplets multiplies the surface area — a mechanical effect that makes the chemical step far faster.
  4. c) prevent blood from flowing backwards — They are one-way flaps that close when pressure would push blood the wrong way. In veins, where pressure is low, they are what lets blood in the legs return upwards at all.
  5. c) liver — The liver makes it continuously; the gall bladder only stores and concentrates it between meals. Knowing which organ makes what is worth being precise about here.
  6. b) creates a salt concentration gradient in the medulla that water can be drawn into — Water is never pumped directly. The loop builds a salty medulla, and when the collecting duct passes through it under the influence of ADH, water leaves by osmosis. Mammals with long loops can make very concentrated urine.
  7. a) sinoatrial node — The SA node in the right atrium fires on its own and sets the pace, which is why a heart continues beating when removed from the body. Nerves and hormones adjust that rate but do not create it.
  8. a) carry blood away from the heart — The definition is direction, not oxygen content. The pulmonary artery carries deoxygenated blood, and the pulmonary vein carries oxygenated blood — both exceptions to the usual pattern.
  9. b) mouth, with salivary amylase — Amylase in saliva starts breaking starch into maltose while you chew, which is why bread begins to taste sweet if you hold it in your mouth. Stomach acid then halts it until pancreatic amylase takes over.
  10. c) water, glucose, salts and urea, but not proteins or blood cells — Filtration is driven by pressure and sorted by size, so small molecules go through whether the body wants to lose them or not. That is why useful substances have to be reclaimed further along.