Photosynthesis ( Populations In Ecosystems ) Flashcards
Scientists studied the rate of carbon dioxide uptake by grape plant leaves.
Grape leaves have stomata on the lower surface but no stomata on the upper surface.
The scientists recorded the carbon dioxide uptake by grape leaves with three different
treatments:
Treatment 1 − No air-sealing grease was applied to either surface of the leaf.
Treatment 2 − The lower surface of the leaf was covered in air-sealing grease that
prevents gas exchange.
Treatment 3 − Both the lower surface and the upper surface of the leaf were covered in
air–sealing grease that prevents gas exchange.
The scientists measured the rate of carbon dioxide uptake by each leaf for 60 minutes in
light and then for 20 minutes in the dark.
The scientists’ results are shown in the diagram below.
( Diagram shows treatment 1 starting from 4.5 and staying constant until the light is turned off, when turned off the graph directs towards 0 instantly )
( Treatment 2 starts at 0.5 and stays constant, when light is turned off it directs to 0 )
( Treatment 3 remains at 0 )
( Mean rate of carbon dioxide uptake against time )
Suggest the purpose of each of the three leaf treatments.
- Treatment 1 - Stomata are open
- Treatment 2 - Seals stomata
- Treatment 3 - Stops all CO2 uptake
Describe the results shown for Treatment 1.
( Scientists studied the rate of carbon dioxide uptake by grape plant leaves.
Grape leaves have stomata on the lower surface but no stomata on the upper surface.
The scientists recorded the carbon dioxide uptake by grape leaves with three different
treatments:
Treatment 1 − No air-sealing grease was applied to either surface of the leaf.
Treatment 2 − The lower surface of the leaf was covered in air-sealing grease that
prevents gas exchange.
Treatment 3 − Both the lower surface and the upper surface of the leaf were covered in
air–sealing grease that prevents gas exchange.
The scientists measured the rate of carbon dioxide uptake by each leaf for 60 minutes in
light and then for 20 minutes in the dark.
The scientists’ results are shown in the diagram below.
( Diagram shows treatment 1 starting from 4.5 and staying constant until the light is turned off, when turned off the graph directs towards 0 instantly )
( Treatment 2 starts at 0.5 and stays constant, when light is turned off it directs to 0 )
( Treatment 3 remains at 0 )
( Mean rate of carbon dioxide uptake against time ) )
- CO2 uptake was constant and fell after the light was turned off
- Uptake fell from 4.5 to 0
The stomata close when the light is turned off.
Explain the advantage of this to the plant.
( Scientists studied the rate of carbon dioxide uptake by grape plant leaves.
Grape leaves have stomata on the lower surface but no stomata on the upper surface.
The scientists recorded the carbon dioxide uptake by grape leaves with three different
treatments:
Treatment 1 − No air-sealing grease was applied to either surface of the leaf.
Treatment 2 − The lower surface of the leaf was covered in air-sealing grease that
prevents gas exchange.
Treatment 3 − Both the lower surface and the upper surface of the leaf were covered in
air–sealing grease that prevents gas exchange.
The scientists measured the rate of carbon dioxide uptake by each leaf for 60 minutes in
light and then for 20 minutes in the dark.
The scientists’ results are shown in the diagram below.
( Diagram shows treatment 1 starting from 4.5 and staying constant until the light is turned off, when turned off the graph directs towards 0 instantly )
( Treatment 2 starts at 0.5 and stays constant, when light is turned off it directs to 0 )
( Treatment 3 remains at 0 )
( Mean rate of carbon dioxide uptake against time ) )
- Water is loss through stomata
- Prevents water loss when closed
Treatment 2 shows that even when the lower surface of the leaf is sealed there is still some uptake of carbon dioxide.
Suggest how this uptake of carbon dioxide continues.
( Scientists studied the rate of carbon dioxide uptake by grape plant leaves.
Grape leaves have stomata on the lower surface but no stomata on the upper surface.
The scientists recorded the carbon dioxide uptake by grape leaves with three different
treatments:
Treatment 1 − No air-sealing grease was applied to either surface of the leaf.
Treatment 2 − The lower surface of the leaf was covered in air-sealing grease that
prevents gas exchange.
Treatment 3 − Both the lower surface and the upper surface of the leaf were covered in
air–sealing grease that prevents gas exchange.
The scientists measured the rate of carbon dioxide uptake by each leaf for 60 minutes in
light and then for 20 minutes in the dark.
The scientists’ results are shown in the diagram below.
( Diagram shows treatment 1 starting from 4.5 and staying constant until the light is turned off, when turned off the graph directs towards 0 instantly )
( Treatment 2 starts at 0.5 and stays constant, when light is turned off it directs to 0 )
( Treatment 3 remains at 0 )
( Mean rate of carbon dioxide uptake against time ) )
- Through the upper surface
In both Treatment 1 and Treatment 2, the uptake of carbon dioxide falls to zero when the light is turned off.
Explain why.
( Scientists studied the rate of carbon dioxide uptake by grape plant leaves.
Grape leaves have stomata on the lower surface but no stomata on the upper surface.
The scientists recorded the carbon dioxide uptake by grape leaves with three different
treatments:
Treatment 1 − No air-sealing grease was applied to either surface of the leaf.
Treatment 2 − The lower surface of the leaf was covered in air-sealing grease that
prevents gas exchange.
Treatment 3 − Both the lower surface and the upper surface of the leaf were covered in
air–sealing grease that prevents gas exchange.
The scientists measured the rate of carbon dioxide uptake by each leaf for 60 minutes in
light and then for 20 minutes in the dark.
The scientists’ results are shown in the diagram below.
( Diagram shows treatment 1 starting from 4.5 and staying constant until the light is turned off, when turned off the graph directs towards 0 instantly )
( Treatment 2 starts at 0.5 and stays constant, when light is turned off it directs to 0 )
( Treatment 3 remains at 0 )
( Mean rate of carbon dioxide uptake against time ) )
- No use of CO2 in photosynthesis
- No diffusion gradient maintained for CO2 to come into the leaf
A student investigated the effect of different wavelengths of light on the rate of photosynthesis.
She used the apparatus shown in Figure 1.
( Image shows a container with algae in it and a oxygen meter. )
( Light with a particular wavelength hits the container )
What measurements should the student have taken to determine the rate of photosynthesis?
- Oxygen production and time
Other than temperature and pH, give two factors which should be kept constant during this investigation.
( A student investigated the effect of different wavelengths of light on the rate of photosynthesis.
She used the apparatus shown in Figure 1.
( Image shows a container with algae in it and a oxygen meter. )
( Light with a particular wavelength hits the container ) )
- Intensity of light
- CO2 concentration
The student did not use a buffer to maintain the pH of the solution.
Explain what would happen to the pH of the solution during this investigation.
( A student investigated the effect of different wavelengths of light on the rate of photosynthesis.
She used the apparatus shown in Figure 1.
( Image shows a container with algae in it and a oxygen meter. )
( Light with a particular wavelength hits the container ) )
- pH increases
- As more CO2 is removed
Figure 2 shows the student’s results.
( Image shows a fluctuating line graph, looking like a “ U “, kind of showing that the rate of photosynthesis has an optimal wavelength of light )
( Graph is rate of photosynthesis against wavelength of light )
Suggest and explain why the rate of photosynthesis was low between 525 nm and 575 nm wavelengths of light.
( A student investigated the effect of different wavelengths of light on the rate of photosynthesis.
She used the apparatus shown in Figure 1.
( Image shows a container with algae in it and a oxygen meter. )
( Light with a particular wavelength hits the container ) )
- Less absorption
- Light is required for light dependent reaction
Chloroplasts contain chlorophyll a and chlorophyll b.
Scientists found tobacco plants with a
mutation that caused them to make more chlorophyll b than normal tobacco plants.
They investigated the effect of this mutation on the rate of photosynthesis.
The scientists carried out the following investigation.
• They grew normal and mutant tobacco plants.
They grew some of each in low light
intensity and grew others in high light intensity.
• They isolated samples of chloroplasts from mature plants of both types.
• Finally, they measured oxygen production by the chloroplasts they had isolated from
the plants.
The figure below shows the scientists’ results.
( Graph with rate of reaction curves that don’t level off, all the graphs are at different levels and mutant plants always have a higher oxygen production then normal plants )
( Graph is oxygen production against light intensity )
Explain why the scientists measured the rate of production of oxygen in this investigation.
- Oxygen is produced in the light - dependent reaction
- Faster the O2 production, the faster the light - dependent reaction
In each trial, the scientists collected oxygen for 15 minutes.
Calculate the difference in the oxygen produced by the chloroplasts from mutant plants grown in low and high light intensities at a light intensity of 500 μmol photons m^-2 s^-1.
Show your working.
( Chloroplasts contain chlorophyll a and chlorophyll b.
Scientists found tobacco plants with a
mutation that caused them to make more chlorophyll b than normal tobacco plants.
They investigated the effect of this mutation on the rate of photosynthesis.
The scientists carried out the following investigation.
• They grew normal and mutant tobacco plants.
They grew some of each in low light
intensity and grew others in high light intensity.
• They isolated samples of chloroplasts from mature plants of both types.
• Finally, they measured oxygen production by the chloroplasts they had isolated from
the plants.
The figure below shows the scientists’ results.
( Graph with rate of reaction curves that don’t level off, all the graphs are at different levels and mutant plants always have a higher oxygen production then normal plants )
( Graph is oxygen production against light intensity ) )
- 200 - 60 = 140 ( Oxygen production at 500 for both graphs, minused from each other )
- 15 / 60 = 0.25 ( 15 mins converted in hours )
- 140 x 0.25 = 35
The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities.
Explain how these data support this suggestion.
( Chloroplasts contain chlorophyll a and chlorophyll b.
Scientists found tobacco plants with a
mutation that caused them to make more chlorophyll b than normal tobacco plants.
They investigated the effect of this mutation on the rate of photosynthesis.
The scientists carried out the following investigation.
• They grew normal and mutant tobacco plants.
They grew some of each in low light
intensity and grew others in high light intensity.
• They isolated samples of chloroplasts from mature plants of both types.
• Finally, they measured oxygen production by the chloroplasts they had isolated from
the plants.
The figure below shows the scientists’ results.
( Graph with rate of reaction curves that don’t level off, all the graphs are at different levels and mutant plants always have a higher oxygen production then normal plants )
( Graph is oxygen production against light intensity ) )
At all light intensities, chloroplast from mutant plants:
- Have a faster production of ATP and reduced NADP
- So more light independent reaction
- So produce more sugars that can be used in respiration
- Therefore more energy for growth
Farmland previously used for growing crops was left for 30 years and developed into woodland.
During this period, ecologists recorded an increase in the diversity of birds in the area.
Name the process that resulted in the development of woodland from farmland.
- Succession
Explain the increase in the diversity of birds as the woodland developed.
( Farmland previously used for growing crops was left for 30 years and developed into woodland.
During this period, ecologists recorded an increase in the diversity of birds in the area. )
- Greater variety of plants
- More food sources
- Greater variety of niches
The ecologists also investigated photosynthesis in two species of plant found in the woodland.
One of the species was adapted to growing in bright sunlight ( sun plant ) and the other was adapted to growing in the shade ( shade plant ).
The ecologists’ results are shown in the figure below.
( Graph shows a scale from -10 to 20 on the y - axis and two rate of reaction graphs, sun plant starts from a lower value and levels off at a high value, whereas shade plant starts from a higher value but levels off at a lower value )
( Graph is rate of uptake or release of CO2 by leaves against light intensity )
Give two factors which could be limiting the rate of photosynthesis in the sun plant between points A and B on the figure.
( Farmland previously used for growing crops was left for 30 years and developed into woodland.
During this period, ecologists recorded an increase in the diversity of birds in the area. )
- Temperature
- CO2 concentration
