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Biology 20

Biology 20 · Worksheets

Cumulative review

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

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Biology 20 · maddyhelps.com

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

  1. Bile is produced by the

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

  2. Gas exchange in the alveoli happens by

    1. a) bulk flow through valves
    2. b) osmosis
    3. c) active transport using ATP
    4. d) diffusion down partial pressure gradients

  3. Aldosterone acts on the nephron to

    1. a) reduce blood volume
    2. b) increase sodium excretion
    3. c) increase glucose reabsorption
    4. d) increase sodium reabsorption, with water following

  4. The Calvin cycle consumes

    1. a) CO₂ and light
    2. b) CO₂, ATP and NADPH
    3. c) O₂, ATP and NADPH
    4. d) glucose and O₂

  5. The ultimate source of energy for almost every ecosystem on Earth is

    1. a) heat from Earth's interior
    2. b) sunlight captured by producers
    3. c) oxygen in the atmosphere
    4. d) organic matter in soil

  6. Decomposers are essential to nutrient cycles because they

    1. a) fix nitrogen from the atmosphere
    2. b) store carbon permanently in the soil
    3. c) break organic matter down into inorganic forms producers can take up again
    4. d) produce oxygen for consumers

  7. The biosphere is

    1. a) all the water on Earth
    2. b) the solid outer layer of Earth
    3. c) the zone of Earth where living things are found
    4. d) the layer of gases surrounding Earth

  8. In a predator–prey cycle, the predator population peaks

    1. a) shortly after the prey population peaks
    2. b) independently of the prey
    3. c) at exactly the same time
    4. d) shortly before the prey population peaks

  9. The enzyme rubisco is responsible for

    1. a) making ATP in the stroma
    2. b) breaking glucose down for energy
    3. c) attaching CO₂ to RuBP at the start of the Calvin cycle
    4. d) splitting water in the thylakoid

  10. Most absorption of nutrients happens in the

    1. a) large intestine
    2. b) oesophagus
    3. c) small intestine
    4. d) stomach

Answer key · Cumulative review

Biology 20 · maddyhelps.com

  1. a) 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.
  2. d) diffusion down partial pressure gradients — Oxygen is at higher partial pressure in the alveolus than in the blood, and carbon dioxide the other way round, so each moves down its own gradient. No energy is spent on the exchange itself.
  3. d) increase sodium reabsorption, with water following — Water follows salt by osmosis, so reclaiming sodium reclaims water and raises blood pressure. ADH and aldosterone both conserve water, but by different routes — one moves water directly and one moves salt.
  4. b) CO₂, ATP and NADPH — Carbon dioxide provides the carbon; ATP and NADPH provide the energy and electrons needed to reduce it. The cycle needs no light directly, which is why calling it the dark reactions is misleading — it stops when the light stops because the supplies do.
  5. b) sunlight captured by producers — Producers convert light energy into chemical energy, and everything else in the food web is living off that conversion. The rare exceptions are deep-sea vent communities, which run on chemical energy instead.
  6. c) break organic matter down into inorganic forms producers can take up again — Without decomposition, nutrients would stay locked in dead tissue and the cycles would stop. Decomposers are heterotrophs, but they are the step that returns matter to the abiotic pool.
  7. c) the zone of Earth where living things are found — The biosphere is the thin shell where the atmosphere, hydrosphere and lithosphere overlap enough to support life. It is defined by the presence of life, not by a particular substance.
  8. a) shortly after the prey population peaks — Predators need time to convert abundant prey into offspring, so their peak lags behind. The lag is what makes the two populations oscillate instead of settling at a fixed pair of numbers.
  9. c) attaching CO₂ to RuBP at the start of the Calvin cycle — Carbon fixation — joining inorganic CO₂ to a five-carbon sugar — is the cycle's first and defining step. Rubisco is thought to be the most abundant protein on Earth, and it is also famously slow.
  10. c) small intestine — The small intestine is long, folded, and lined with villi and microvilli, giving it an enormous surface area. The stomach absorbs almost nothing; the large intestine mainly takes back water.