B4- rate of photosynthesis

• What does the graph on the right show regarding the rate of photosynthesis?

  It shows how the rate of photosynthesis is affected by light intensity and temperature.
• How does the rate of photosynthesis change with increasing light intensity?

  The rate of photosynthesis increases steadily as light intensity increases.
• What happens to the lines on the graph when light is no longer the limiting factor?

  The lines level off when light is no longer the limiting factor.
• What does the line at 25 °C indicate compared to the line at 15 °C?

  The line at 25 °C levels off at a higher point, indicating temperature was a limiting factor at 15 °C.
• What does the second graph show regarding the rate of photosynthesis?

  It shows how the rate of photosynthesis is affected by light intensity and CO₂ concentration.
• What happens to the lines on the second graph when light is no longer the limiting factor?

  The lines level off when light is no longer the limiting factor.
• What does the line at a higher CO₂ concentration of 0.4% indicate compared to 0.04%?

  The line at 0.4% levels off at a higher point, indicating CO₂ concentration was a limiting factor at 0.04%.
• What organism is used to measure the effect of light intensity on the rate of photosynthesis?

  Canadian pondweed.
• How does the experiment with Canadian pondweed measure the rate of photosynthesis?

  • The rate of oxygen production corresponds to the rate of photosynthesis.
  • A source of white light is placed at a specific distance from the pondweed.
  • Oxygen released collects in a capillary tube.
  • The length of the gas bubble is measured to determine O₂ volume.
• What is the purpose of controlling variables in the pondweed experiment?

  To ensure accurate results by minimizing the effects of other factors.
• How many times is the experiment repeated with the light source at the same distance?

  Twice.
• What is done after measuring the mean volume of O₂ produced?

  The experiment is repeated with the light source at different distances from the pondweed.
• How can the apparatus be altered to measure the effect of temperature or CO₂ on photosynthesis?

  • Use a water bath of a set temperature for the pondweed.
  • Dissolve a measured amount of sodium hydrogencarbonate in the water to provide CO₂.
  • Repeat the experiment with different temperatures or CO₂ concentrations.