Limiting factors in photosynthesis

Photosynthesis produces glucose (C₆H₁₂O₆).

Write a balanced symbol equation for photosynthesis.

A student investigated the effect of light intensity on the rate of photosynthesis in three species of aquatic plant.

Figure 7 shows the apparatus used.

This is the method used.

1. Place species A in water in a test tube.

2. Leave the test tube containing species A in a dark room for 10 minutes.

3. Put the test tube containing species A 20 cm away from the lamp.

4. Record the number of bubbles produced by species A in 5 minutes.

5. Repeat steps 2 to 4 at different distances from the lamp.

6. Repeat steps 1 to 5 using species B and species C.

The student repeated the investigation several times.

Explain how two other improvements to the method would ensure the results are more valid.

When the distance between the lamp and the plant is 20 cm, the light intensity is 0.0025 arbitrary units.

Calculate how many times greater the light intensity is at 20 cm compared with the light intensity at 60 cm.

Use the equation:

The student collected valid results.

Figure 8 shows the results.

Predict the number of bubbles that would be produced by species B at 10 cm from the lamp.

You should extend the line on Figure 8.

Species A, B and C grow at different depths in ponds.

Which species is most likely to be found growing near the surface of the pond?

Give the reason for your answer.

Tick () one box.

A B C

Global dimming is a decrease in the sunlight reaching the Earth’s surface due to particulates in the atmosphere.

Figure 12 shows equipment used to investigate how light intensity affects photosynthesis.

The light intensity can be changed by moving the pondweed to different distances from the lamp.

Describe a method to investigate the effect of light intensity on the rate of photosynthesis in pondweed.

Figure 2 shows equipment used to investigate how light intensity affects photosynthesis.

The light intensity can be changed by moving the pondweed to different distances from the lamp.

Describe a method to investigate the effect of light intensity on the rate of photosynthesis in pondweed.

The orca is a large animal that lives in the ocean.

Figure 4 shows an orca.

Figure 5 shows a food chain.

Draw one line from each organism to the description of that organism in the food chain.

Use information from Figure 5.

Figure 6 shows a food web.

Seaweed and microscopic algae photosynthesise.

Give two factors that affect the rate of photosynthesis.

The number of fish in the oceans has decreased since 1990.

Suggest one way that human activity has caused the decrease in the number of fish.

Explain how a decrease in the number of fish could affect the numbers of other organisms in the food web.

Use Figure 6.

Figure 3 shows a tomato plant.

A leaf is a plant organ.

Name one other plant organ shown in Figure 3.

A student investigated the effect of different colours of light on the growth of tomato plant seedlings.

Figure 4 shows the apparatus used.

This is the method used.

1. Place three tomato plant seedlings under each colour of light.

2. Water each seedling every day.

3. Measure the height of each seedling after 30 days.

Give two control variables the student should have used in their investigation.

The student repeated the investigation using a valid method.

Table 2 shows the results.

Give two conclusions from the results in Table 2.

Another student investigated the effect of light intensity on the rate of photosynthesis.

The student counted the number of bubbles of oxygen produced by pondweed at different light intensities.

Figure 5 shows some of the apparatus used.

Describe how the student could change the light intensity.

The pondweed did not produce many bubbles.

How could the student change the investigation to increase the number of bubbles produced?

Tick (✓) one box.

Add more water to the test tube.

Use a smaller piece of pondweed.

Use water at a higher temperature.

The student calculated the rate of photosynthesis.

Which equation is used to calculate the rate of photosynthesis?

Tick (✓) one box.

rate of photosynthesis = number of bubbles × time

Figure 6 shows the rate of photosynthesis at different light intensities.

Describe the pattern in Figure 6.

Use data from Figure 6.

Algal cells can photosynthesise.

A student investigated the effect of light intensity on photosynthesis in algal cells.

Figure 8 shows the apparatus used.

Describe the relationship between light intensity and distance, as the distance of the algal cells from the lamp is doubled.

You must include calculations of light intensity at 20 cm and 40 cm in your answer.

Use the equation:

The student recorded the pH of the water at the start and after one hour in each beaker.

Table 7 shows the results.

The method produced valid results.

Carbon dioxide is an acidic gas.

Explain the results in Table 7.

Corals are animals that live in the sea.

Corals: cannot move from one place to another place feed on tiny animals that float past in the water have algal cells living inside their own cells.

Figure 9 shows a coral and an enlarged coral cell.

Algal cells photosynthesise to produce glucose (C₆H₁₂O₆).

Write the balanced symbol equation for photosynthesis.

Explain one way the algal cells use glucose for growth.

Suggest one advantage to the algal cells of living inside the coral cells.

An increase in water temperature can cause coral to release the algal cells.

Releasing algal cells can result in the death of coral.

Suggest why coral may not survive without the algal cells.

Scientists investigated how the concentration of oxygen in the water around one coral changed during the day.

Figure 10 shows the results.

Explain the changes in oxygen concentration between A and B.

At C the rate at which oxygen is being produced equals the rate at which oxygen is being used.

Give the reason why.

Plants absorb light to photosynthesise.

Complete the word equation for photosynthesis.

Light intensity affects the rate of photosynthesis.

Figure 3 shows some of the equipment used to measure the rate of photosynthesis.

Describe a method to investigate the effect of light intensity on the rate of photosynthesis.

Use the equipment in Figure 3 and other laboratory equipment.

Algal cells photosynthesise.

Scientists investigated the effect of light intensity on algal cells.

The algal cells were placed in different light intensities.

Table 2 shows the number of extra algal cells after two days.

The initial number of algal cells was 200 000

Calculate the total number of algal cells after two days when the light intensity was 500 lux

Plot the data from Table 2 on Figure 4.

The first two points have been plotted.

Draw a line of best fit.

Give two conclusions from the results.

Use information from Table 2.

Explain how an increase in temperature from 20 °C to 25 °C would affect the number of algal cells.