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Year 8 Science — Life processes in plants

Say what photosynthesis needs and what it gives back, read the experiment that proves each ingredient, and name the tubes that carry water up and food out.

Name: ________________________

Before you start

The parts of a plant, and what each one does with water and with food.

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  1. 1. Leaf
  2. 2. Stem
  3. 3. Roots

The leaf is where the food is made. Water and minerals go up from the roots through tubes called xylem, inside the stem. Food made in the leaves goes out through a second set of tubes called phloem, to wherever the plant needs it or stores it. Tiny pores in the leaf surface, the stomata, let gases in and out.

  1. 1.Put the steps of the starch test on a leaf in order, starting from softening the leaf in boiling water.

    • Decolourise it in alcohol standing in a beaker of boiling water
    • A blue-black colour means starch is present
    • Soften the leaf in boiling water
    • Put a few drops of dilute iodine solution on it
    • Lay the pale leaf out on a plate

  2. 2.What is the name of the process by which a plant prepares its food in the presence of sunlight and chlorophyll?

  3. 3.Tiny pores on the surface of a leaf, seen under a microscope in a peel of its underside, let gases in and out. What are they called?

  4. 4.Why does the chapter call leaves the food factories of a plant?

    • a) They are the primary site of photosynthesis, where the food is made
    • b) They store most of the plant's food until it is needed
    • c) They are the part of the plant that animals eat most often
    • d) They take in the water and minerals the plant lives on

  5. 5.A potato slice turns blue-black with iodine, so it holds starch. Where was that starch made?

    • a) In the potato itself, which photosynthesises underground
    • b) In the stem, from water carried up by the xylem
    • c) In the leaves, and carried down to the potato through the phloem
    • d) In the roots, from minerals taken out of the soil

  6. 6.Which pair of ingredients does a plant draw from its surroundings to make food?

    • a) Starch from the soil and sunlight from the sky
    • b) Oxygen from the air and glucose from the soil
    • c) Carbon dioxide from the soil and oxygen from the air
    • d) Carbon dioxide from the air and water from the soil

  7. 7.Why is a leaf boiled in alcohol until it loses its colour before the iodine test?

    • a) So that the starch dissolves out of it into the alcohol
    • b) So that the chlorophyll starts making starch again
    • c) So that any colour change from the iodine is easy to see
    • d) So that the iodine can soak through the waxy surface

  8. 8.Three identical saplings are grown for two weeks: A in sunlight with water, B in sunlight without water, C in the dark with water. What do their fates show?

    • a) A plant needs water and can manage without sunlight
    • b) A plant needs both sunlight and water to grow
    • c) A plant needs sunlight and can manage without water
    • d) Neither sunlight nor water makes much difference over two weeks

Answer key — Year 8 Science — Life processes in plants

  1. 1. 1. Soften the leaf in boiling water 2. Decolourise it in alcohol standing in a beaker of boiling water 3. Lay the pale leaf out on a plate 4. Put a few drops of dilute iodine solution on it 5. A blue-black colour means starch is present
  2. 2. photosynthesis
  3. 3.
    • stomata
    • stoma
  4. 4. a) They are the primary site of photosynthesis, where the food is made
  5. 5. c) In the leaves, and carried down to the potato through the phloem
  6. 6. d) Carbon dioxide from the air and water from the soil
  7. 7. c) So that any colour change from the iodine is easy to see
  8. 8. b) A plant needs both sunlight and water to grow