Limiting factors in photosynthesis

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........

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.

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 measures the effect of light intensity on photosynthesis. They place a lamp at different distances from pondweed in a beaker of water.

The student uses the inverse square law to calculate the relative light intensity.

What is the distance of the lamp from the beaker when the relative light intensity is 4.00?

A 0.2 m

B 0.3 m

C 0.4 m

D 0.5 m

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.

Complete these sentences about different factors that affect the ecosystem.

Use the words or phrases in the list.

abiotic biotic carbon dioxide food oxygen

pH in soil predators temperature

Living organisms affecting the ecosystem are known as........ factors.

Physical factors that affect living organisms are described as........ factors.

Physical factors that can directly affect the rate of photosynthesis include

........ and........ concentration.

A student investigates the relationship between bean plants and the bacteria that live in the roots of the bean.

They think the bacteria live inside root nodules.

Fig. 12.1 shows root nodules on a bean plant.

Fig. 12.1

The student takes a thin section of the nodule and looks at it under a light microscope.

Fig. 12.2 shows bacteria inside the root nodule.

Fig. 12.2

Describe how to take a thin section of the nodule and prepare it to view under a light microscope.

The bacteria were not visible clearly using a light microscope.

The student found an image taken using a different type of microscope.

Fig. 12.3 shows this image.

Fig. 12.3

The maximum resolution of a light microscope is 200 nm.

What type of microscope is used to take this image?

The bacteria live inside the bean plant cells in root nodules. The bacteria are able to take nitrogen gas from the air and turn it into nitrates. The plants use nitrates to make amino acids.

Explain the relationship between the bacteria and the bean plant. Include ideas about photosynthesis in your answer.

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.

The flowchart in Fig. 12.1 shows bacteria involved in cycling nitrogen.

Identify which of the bacteria in Fig. 12.1, if present in large amounts, would make the soil poor for plant growth.

Tick (✓) one box.

Explain why large amounts of these bacteria would make the soil poor for plant growth.

Abiotic and biotic factors can affect the bacterial communities.

Which is a biotic factor?

Tick (✓) one box.

Plants are an important part of any community.

Fig. 12.2 shows the effect of abiotic factors on the rate of photosynthesis by plants.

Explain why lines X, Y and Z level out at different rates of photosynthesis.

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.

Algae can photosynthesise and grow rapidly in lakes during the summer.

The growth of algae is affected by abiotic factors.

An experiment measured the dry mass of algae at different temperatures for 25 days. Light intensity was kept constant.

Table 13.1 shows the results for 25 °C and 35 °C.

Describe the trends shown in the graph.

Table 13.2 shows the dry mass of algae on day 25 for all the temperatures measured in the experiment.

In some lakes, algae are the main producers.

One year, water temperatures in a lake did not rise above 20 °C.

Use data from Table 13.2 to explain how this might affect the community of organisms living in the lake.

The algae produce a toxin. High levels of toxins can kill fish in the water.

Suggest why scientists are concerned about the effects of global warming on algae growth.

The rate of photosynthesis is affected by light intensity.

When you increase distance between a light source and a plant, light intensity decreases.

The relative light intensity can be calculated using the inverse square law:

The relative light intensity is 6.25.

Calculate the distance from the light source.

A 0.08 m

B 0.16 m

C 0.32 m

D 0.40 m

The graph shows how one limiting factor affects the rate of photosynthesis.

Which limiting factor is having the effect shown in the graph?

A Carbon dioxide concentration

B Humidity

C Light intensity

D Temperature