Photosynthesis

The grasslands of Africa are an example of an ecosystem.

Fig. 11.1 shows a food chain within this ecosystem.

Fig. 11.1

Name an example of each of the following in the food chain shown in Fig. 11.1.

A primary consumer.

An abiotic component.

Describe the role of grass as a producer in this food chain.

Organisms depend on each other for survival. This is called interdependence.

Fig. 11.2 shows a buffalo and some oxpeckers.

Fig. 11.2

Ticks are small organisms that feed on, live on and harm the buffalo.

Oxpeckers sit on the buffalo eating the harmful ticks. They also warn the buffalo if danger is nearby.

Identify the type of relationship between these organisms using ideas about interdependence.

Ticks and buffalo........

Oxpeckers and buffalo........

Photosynthesis is affected by many factors. The graph shows how the rate of photosynthesis in a plant is affected by varying light intensity.

Describe how light intensity affects the rate of photosynthesis.

Include how the graph changes from A–B, and B–C.

A student set up the apparatus below to measure how light intensity affects the rate of photosynthesis in a pond plant.

Suggest two variables they should have controlled in their investigation.

Describe how they could have done this.

This is controlled by........

This is controlled by........

Plants photosynthesise to produce food.

Oxygen is a product of photosynthesis.

What are the two reactants in photosynthesis?

Which statements about photosynthesis are true and which are false ?

Tick (✓) one box in each row.

The diagram shows apparatus used to investigate photosynthesis.

The number of oxygen bubbles released each minute indicate the rate of photosynthesis.

A student counts the number of oxygen bubbles released from the pondweed.

They count 23 bubbles in 3 minutes.

Calculate the rate of photosynthesis.

Give your answer to the nearest whole number.

Rate =........ bubbles per minute

The student develops their investigation to find the effect of light intensity on the rate of photosynthesis.

Describe how they should develop their investigation.

In your answer include:

• any additional apparatus they will need that is not shown in the diagram

• one variable they will need to control

• how they will change light intensity.

The diagram shows apparatus used to investigate photosynthesis.

The number of oxygen bubbles released each second indicates the rate of photosynthesis.

A student counts the number of oxygen bubbles released from the pondweed in 2 minutes.

They use their result to correctly calculate a rate of 0.525 bubbles per second.

How many bubbles did the student count in the 2 minutes?

* The student develops their investigation to find the effect of light intensity on the rate of photosynthesis.

Describe how they should develop their investigation. Explain how a change in light intensity will affect the rate of photosynthesis.

The picture shows the plant pathogen that causes powdery mildew.

Describe how powdery mildew is spread from one plant to another.

Powdery mildew reduces the efficiency of chloroplasts.

Explain how this might reduce the rate of respiration in a plant.

Plants resistant to powdery mildew are developed by genetic engineering.

Complete the sentences about genetic engineering.

The gene for resistance is cut out of DNA using a........ enzyme.

The gene is then joined to bacterial DNA using a........ enzyme.

To find out if the bacteria contain the gene, scientists use........

Explain why the process of cutting the DNA is prevented by high temperatures.

Use your knowledge of enzymes.

Powdery mildew can be controlled using chemicals.

Producing plants resistant to powdery mildew is better for biodiversity compared to using chemicals.

Suggest two reasons why.

Fig. 13.1 shows the apparatus used to prove that carbon dioxide is needed for photosynthesis. Fig. 13.1

Describe how this apparatus and iodine solution are used to prove that carbon dioxide is needed for photosynthesis.

What is the expected result for this experiment?

Result for Plant A........

Result for Plant B........

What is the dependent variable for this investigation?

Oxygen is one product of photosynthesis. The other product of photosynthesis is a monomer.

This monomer is then used to make a polymer. The polymer is then used as an energy store by the plant.

Name the monomer and polymer.

A student investigates the availability of carbon dioxide on the rate of photosynthesis. They use a measuring cylinder to measure the volume of gas collected in 20 minutes.

The diagram shows the apparatus they use.

Solution X contains a chemical that releases carbon dioxide.

Suggest how solution X could be used to change the availability of carbon dioxide.

What is the dependent variable for this investigation?

Plants are important for life on Earth as they photosynthesise and provide oxygen.

Describe one other reason why plants are important to life on Earth.

A scientist investigates the effect of temperature on the rate of photosynthesis.

The diagram shows the apparatus they use.

The scientist counts the number of bubbles released by the water plant in 10 minutes.

They repeat this method with different temperatures of water.

The table shows their results.

The scientist decides to repeat the investigation for 20 °C. Suggest why.

When the scientist repeats the investigation at 20 °C the result is 26 bubbles.

Use this result and the results in the table to describe the effect of temperature on the rate of photosynthesis.

The scientist decides to use the apparatus to investigate the effect of light intensity on photosynthesis.

Describe how they could use the apparatus to change light intensity.

A student investigates the rate of photosynthesis.

The diagram shows the apparatus they use.

The bubbles of gas are made during photosynthesis.

Which is the main gas in the bubbles?

The student counts the number of bubbles made by the pondweed for 5 minutes.

They repeat this three more times.

The table shows their results.

Calculate the mean number of bubbles.

Give your answer to the nearest whole number.

Write your answer in the table.

There is one anomaly in the results.

Identify the anomaly and suggest one reason other than human error that may have caused it.

Anomaly........

Reason........

*(c) Describe how the student could develop their investigation to show how light intensity affects the number of bubbles made.

In your answer include ideas about variables, what the student should measure and the expected results.

Fig. 16.1 shows a single-celled organism called an alga.

The alga cell is a eukaryotic cell.

Describe two differences in structure between eukaryotic and prokaryotic cells.

Explain why chloroplasts are needed for photosynthesis.

Fig. 16.2 shows algae growing on the surface of a lake.

In the summer the area covered by the algae increases.

Other plants growing at the bottom of the lake receive less light.

Explain how this could affect the growth of the plants at the bottom of the lake.

Compare the process of photosynthesis with the process of aerobic respiration.

A student investigates photosynthesis.

The student uses small organisms called algae, trapped inside beads.

The algae beads are put inside a jar containing hydrogen carbonate indicator solution.

A lid is placed on the jar to stop any air getting in.

At the start of the investigation the hydrogen carbonate indicator solution is red showing the presence of carbon dioxide. This changes to purple when there is no carbon dioxide present.

The student times how long it takes the indicator solution to turn purple.

She repeats the investigation using different numbers of algae beads.

The table shows her results.

Calculate the mean for 40 beads.

Give your answer to the nearest whole number.

Look at the mean for 30 beads.

Explain why the student did not use the result for trial 2 when calculating the mean.

Look at the results for 10, 20 and 40 beads.

Which set of data is the most precise ?

Explain your answer.

Explain why the student sets up a bottle with zero algae beads in.

Use ideas about photosynthesis to explain the pattern in the results.

The student wants to investigate the effect of temperature on the rate of photosynthesis.

The student uses a stop watch and a bottle of hydrogen carbonate indicator solution containing 20 algae beads.

The student also uses a large beaker and a kettle of hot water.

Explain why the student uses the beaker and kettle of hot water.

Describe how the student could develop her method to find the best temperature for photosynthesis.

Which of these statements about photosynthesis is correct?

A Single stage endothermic reaction

B Single stage exothermic reaction

C Two stage endothermic reaction

D Two stage exothermic reaction

The picture shows plant cells as they are seen using a light microscope.

The actual length of plant cell X is 75 m.

You can use this fact to calculate the magnification of the image.

Explain how.

The same cells can be observed using an electron microscope.

Magnification of the cells can be increased using an electron microscope.

Explain how and why the image may also look different.

A student investigates different conditions that affect photosynthesis.

He sets up four different sets of apparatus, A, B, C and D.

The plants used are all of a similar age and size. Each plant is left under cover at room temperature.

After three days one leaf from each plant is tested for the presence of starch.

Describe all the stages required to test the leaves for the presence of starch.

What are the expected results of the starch test on each plant?

Write down reasons for your answers.