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Deck 6: Photosynthesis: Acquiring Energy From the Sun
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Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Applying Concepts
a. Variable. In the graph above, which is the dependent variable?
b. Index. What does the increase in levels of chlorophyll a say about numbers of phytoplankton?
c. Control. What substance is lacking in the waters sampled in the bluedot plots ?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Applying Concepts
a. Variable. In the graph above, which is the dependent variable?
b. Index. What does the increase in levels of chlorophyll a say about numbers of phytoplankton?
c. Control. What substance is lacking in the waters sampled in the bluedot plots ?
Question
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Interpreting Data
a. What happened to the levels of chlorophyll a in the test areas of the ocean (red dots)?
b. What happened to the levels of chlorophyll a in the control areas (blue dots)?
c. Comparing the red line to the blue line, about how many times more numerous are phytoplankton in iron-seeded waters on the three days of seeding?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Interpreting Data
a. What happened to the levels of chlorophyll a in the test areas of the ocean (red dots)?
b. What happened to the levels of chlorophyll a in the control areas (blue dots)?
c. Comparing the red line to the blue line, about how many times more numerous are phytoplankton in iron-seeded waters on the three days of seeding?
Question
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Making Inferences
a. What general statement can be made regarding the effect of seeding phytoplankton-poor regions of the ocean with iron?
b. Why did chlorophyll a levels drop by day 14?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Making Inferences
a. What general statement can be made regarding the effect of seeding phytoplankton-poor regions of the ocean with iron?
b. Why did chlorophyll a levels drop by day 14?
Question
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Drawing Conclusions Do these results support the claim that lack of iron is limiting the growth of phytoplankton, and thus of photosynthesis, in certain areas of the oceans?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Drawing Conclusions Do these results support the claim that lack of iron is limiting the growth of phytoplankton, and thus of photosynthesis, in certain areas of the oceans?
Question
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Further Analysis Based on this experiment, what would be a potential drawback of using this method of seeding with iron to increase levels of ocean photosynthesis?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Further Analysis Based on this experiment, what would be a potential drawback of using this method of seeding with iron to increase levels of ocean photosynthesis?
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Deck 6: Photosynthesis: Acquiring Energy From the Sun
1
The energy that is used by almost all living things on our planet comes from the sun. It is captured by plants, algae, and some bacteria through the process of
A) respiration.
B) the Krebs cycle.
C) photosynthesis.
D) fermentation.
The light-dependent reactions of photosynthesis are responsible for the production of
A) glucose.
B) CO2.
C) ATP and NADPH.
D) light energy.
Light encounters mesophyll cells of a leaf
A) outside the epidermis.
B) outside the cuticle.
C) beneath the epidermis.
D) within chloroplasts.
A) respiration.
B) the Krebs cycle.
C) photosynthesis.
D) fermentation.
The light-dependent reactions of photosynthesis are responsible for the production of
A) glucose.
B) CO2.
C) ATP and NADPH.
D) light energy.
Light encounters mesophyll cells of a leaf
A) outside the epidermis.
B) outside the cuticle.
C) beneath the epidermis.
D) within chloroplasts.
In this question, we discuss photosynthesis.
Nutrient acquisition is only one side of the equation. Those nutrients have to come from somewhere, and most organisms are not capable of producing their own; only autotrophs are capable of achieving this feat. Autotrophic organisms produce sugars from carbon dioxide and water through a process we call photosynthesis.
The generalized reaction of photosynthesis is as follows:
This reaction is the opposite of oxidative phosphorylation, where glucose is broken down into carbon dioxide and water to release energy. Photosynthesis occurs in two parts - the light-dependent reactions which generate electron carriers and ATP from sunlight and water, and the light-independent reactions which generate glucose from carbon dioxide using the electron carriers and ATP from the light-dependent reactions.
The energy captured from sunlight into glucose in this process serves as the basic level of energy for almost all life on Earth. Photosynthetic plants are the base of food webs for terrestrial animals, while photosynthetic algae are the base of aquatic food webs.
a) Option C is correct - this is the proper term.
Option A is incorrect - respiration is the process of breaking down sugars into energy.
Option B is incorrect - this is part of respiration.
Option D is incorrect - this is a simple breakdown process for sugar completed by many bacteria.
b) Option C is correct - this energy and the generated electrons will be used for the light-independent reactions.
Option A is incorrect - this is the end product of photosynthesis as a whole.
Option B is incorrect - carbon dioxide is a reactant in this system.
Option D is incorrect - light energy is a reactant in this system.
c) Option C is correct - these cells are beneath the epidermis of the leaf.
Option A is incorrect - the epidermis is protective; the mesophyll cells are beneath it.
Option B is incorrect - the cuticle is a wax on top of the epidermis.
Option D is incorrect - chloroplasts are within the mesophyll.
Nutrient acquisition is only one side of the equation. Those nutrients have to come from somewhere, and most organisms are not capable of producing their own; only autotrophs are capable of achieving this feat. Autotrophic organisms produce sugars from carbon dioxide and water through a process we call photosynthesis.
The generalized reaction of photosynthesis is as follows:
This reaction is the opposite of oxidative phosphorylation, where glucose is broken down into carbon dioxide and water to release energy. Photosynthesis occurs in two parts - the light-dependent reactions which generate electron carriers and ATP from sunlight and water, and the light-independent reactions which generate glucose from carbon dioxide using the electron carriers and ATP from the light-dependent reactions.The energy captured from sunlight into glucose in this process serves as the basic level of energy for almost all life on Earth. Photosynthetic plants are the base of food webs for terrestrial animals, while photosynthetic algae are the base of aquatic food webs.
a) Option C is correct - this is the proper term.
Option A is incorrect - respiration is the process of breaking down sugars into energy.
Option B is incorrect - this is part of respiration.
Option D is incorrect - this is a simple breakdown process for sugar completed by many bacteria.
b) Option C is correct - this energy and the generated electrons will be used for the light-independent reactions.
Option A is incorrect - this is the end product of photosynthesis as a whole.
Option B is incorrect - carbon dioxide is a reactant in this system.
Option D is incorrect - light energy is a reactant in this system.
c) Option C is correct - these cells are beneath the epidermis of the leaf.
Option A is incorrect - the epidermis is protective; the mesophyll cells are beneath it.
Option B is incorrect - the cuticle is a wax on top of the epidermis.
Option D is incorrect - chloroplasts are within the mesophyll.
2
Plants capture sunlight
A) through photorespiration.
B) with molecules called pigments that absorb photons and use their energy.
C) with the light-independent reactions.
D) using ATP synthase and chemiosmosis.
A) through photorespiration.
B) with molecules called pigments that absorb photons and use their energy.
C) with the light-independent reactions.
D) using ATP synthase and chemiosmosis.
In this question, we discuss photosynthetic pigments.
To capture this energy, autotrophs use a series of pigments that react to light; when these molecules are exposed to photons of light of the correct wavelengths, they absorb those photons and start chain reactions within the plant that lead to the generation of electron carriers and ATP.
These pigments fall into three major categories:
• Chlorophylls, which are green in color
• Carotenoids, which can be red, orange, or yellow
• Phycobilins, which are green or blue.
The primary pigment of photosynthesis is chlorophyll, which promotes the energy of photons into electron-bound chemical energy in the form of NADPH. The other pigments are arranged around the primary chlorophyll promoter; they trap other colors of light and shuttle the energy to the chlorophyll promoter.
Option B is correct - these pigments are found within the photosystems of chloroplasts.
Option A is incorrect - photorespiration is a process used with the plant is losing too much water due to heat.
Option C is incorrect - the captured energy is transferred to these reactions, but not captured by them directly.
Option D is incorrect - this is part of respiration, and is also part of ATP synthesis in photosynthesis, but it is not the capture step for light energy.
To capture this energy, autotrophs use a series of pigments that react to light; when these molecules are exposed to photons of light of the correct wavelengths, they absorb those photons and start chain reactions within the plant that lead to the generation of electron carriers and ATP.
These pigments fall into three major categories:
• Chlorophylls, which are green in color
• Carotenoids, which can be red, orange, or yellow
• Phycobilins, which are green or blue.
The primary pigment of photosynthesis is chlorophyll, which promotes the energy of photons into electron-bound chemical energy in the form of NADPH. The other pigments are arranged around the primary chlorophyll promoter; they trap other colors of light and shuttle the energy to the chlorophyll promoter.
Option B is correct - these pigments are found within the photosystems of chloroplasts.
Option A is incorrect - photorespiration is a process used with the plant is losing too much water due to heat.
Option C is incorrect - the captured energy is transferred to these reactions, but not captured by them directly.
Option D is incorrect - this is part of respiration, and is also part of ATP synthesis in photosynthesis, but it is not the capture step for light energy.
3
Visible light occupies what part of the electromagnetic spectrum?
A) the entire spectrum
B) the upper half of the spectrum (with longer wavelengths)
C) a small portion in the middle of the spectrum
D) the lower half of the spectrum (with shorter wavelengths)
Why does light reflected by the pigment chlorophyll appear green?
A) the entire spectrum
B) the upper half of the spectrum (with longer wavelengths)
C) a small portion in the middle of the spectrum
D) the lower half of the spectrum (with shorter wavelengths)
Why does light reflected by the pigment chlorophyll appear green?
In this question, we discuss photosynthetic pigments.
To capture this energy, autotrophs use a series of pigments that react to light; when these molecules are exposed to photons of light of the correct wavelengths, they absorb those photons and start chain reactions within the plant that lead to the generation of electron carriers and ATP.
These pigments fall into three major categories:
• Chlorophylls, which are green in color
• Carotenoids, which can be red, orange, or yellow
• Phycobilins, which are green or blue.
The primary pigment of photosynthesis is chlorophyll, which promotes the energy of photons into electron-bound chemical energy in the form of NADPH. The other pigments are arranged around the primary chlorophyll promoter; they trap other colors of light and shuttle the energy to the chlorophyll promoter.
a) Option C is correct - the visible spectrum is a small portion of about 400nm of the electromagnetic spectrum that can be perceived by the human eye as colors.
Option A is incorrect - the entire spectrum is not visible without specialized equipment.
Option B is incorrect - the lower energy waves are not visible.
Option D is incorrect - the higher energy waves are not visible.
b) Chlorophyll absorbs a wide variety of electromagnetic light in the visible spectrum. The pigment appears green because chlorophyll reflects this wavelength of light instead of absorbing it.
To capture this energy, autotrophs use a series of pigments that react to light; when these molecules are exposed to photons of light of the correct wavelengths, they absorb those photons and start chain reactions within the plant that lead to the generation of electron carriers and ATP.
These pigments fall into three major categories:
• Chlorophylls, which are green in color
• Carotenoids, which can be red, orange, or yellow
• Phycobilins, which are green or blue.
The primary pigment of photosynthesis is chlorophyll, which promotes the energy of photons into electron-bound chemical energy in the form of NADPH. The other pigments are arranged around the primary chlorophyll promoter; they trap other colors of light and shuttle the energy to the chlorophyll promoter.
a) Option C is correct - the visible spectrum is a small portion of about 400nm of the electromagnetic spectrum that can be perceived by the human eye as colors.
Option A is incorrect - the entire spectrum is not visible without specialized equipment.
Option B is incorrect - the lower energy waves are not visible.
Option D is incorrect - the higher energy waves are not visible.
b) Chlorophyll absorbs a wide variety of electromagnetic light in the visible spectrum. The pigment appears green because chlorophyll reflects this wavelength of light instead of absorbing it.
4
The colors of light that are mostly strongly absorbed by chlorophyll are
A) red and blue.
B) green and yellow.
C) infrared and ultraviolet.
D) All colors are equally absorbed by chlorophyll.
A carotenoid pigment reflects ________ wavelengths of light.
A) green
B) blue
C) ultraviolet
D) orange
A) red and blue.
B) green and yellow.
C) infrared and ultraviolet.
D) All colors are equally absorbed by chlorophyll.
A carotenoid pigment reflects ________ wavelengths of light.
A) green
B) blue
C) ultraviolet
D) orange
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5
Once a plant has initially captured the energy of a photon,
A) a series of reactions occurs in thylakoid membranes of the cell.
B) the energy drives the synthesis of ATP.
C) a water molecule is broken down, releasing oxygen.
D) All of the above.
Where in a chloroplast would you find the highest concentration of protons?
A) in the stroma
B) in the thylakoid space
C) in the stomata
D) in the antenna complex
A) a series of reactions occurs in thylakoid membranes of the cell.
B) the energy drives the synthesis of ATP.
C) a water molecule is broken down, releasing oxygen.
D) All of the above.
Where in a chloroplast would you find the highest concentration of protons?
A) in the stroma
B) in the thylakoid space
C) in the stomata
D) in the antenna complex
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6
Plants use two photosystems to capture energy used to produce ATP and NADPH. The electrons used in these photosystems
A) recycle through the system constantly, with energy added from the photons.
B) recycle through the system several times and then are lost due to entropy.
C) go through the system only once; they are obtained by splitting a water molecule.
D) go through the system only once; they are obtained from the photon.
In plants,
A) photosystem I acts before photosystem II.
B) photosystem II acts before photosystem I.
C) photosystems I and II act simultaneously.
D) only photosystem II is present.
A) recycle through the system constantly, with energy added from the photons.
B) recycle through the system several times and then are lost due to entropy.
C) go through the system only once; they are obtained by splitting a water molecule.
D) go through the system only once; they are obtained from the photon.
In plants,
A) photosystem I acts before photosystem II.
B) photosystem II acts before photosystem I.
C) photosystems I and II act simultaneously.
D) only photosystem II is present.
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7
During photosynthesis, ATP molecules are generated by
A) the Calvin cycle.
B) chemiosmosis.
C) the splitting of a water molecule.
D) photons of light being absorbed by ATP synthase molecules.
NADPH is recycled during photosynthesis. It is produced during the ________ and used in the_________.
A) electron transport system of photosystem I, Calvin cycle
B) process of chemiosmosis, Calvin cycle
C) electron transport system of photosystem II, electron transport system of photosystem I
D) light-independent reactions, light-dependent reactions
Could a plant cell produce ATP through chemiosmosis if the thylakoid membranes of its chloroplasts were "leaky" with regard to protons? Explain.
To reduce six molecules of carbon dioxide to one molecule of glucose via photosynthesis, how many molecules of NADPH and ATP are required?
A) the Calvin cycle.
B) chemiosmosis.
C) the splitting of a water molecule.
D) photons of light being absorbed by ATP synthase molecules.
NADPH is recycled during photosynthesis. It is produced during the ________ and used in the_________.
A) electron transport system of photosystem I, Calvin cycle
B) process of chemiosmosis, Calvin cycle
C) electron transport system of photosystem II, electron transport system of photosystem I
D) light-independent reactions, light-dependent reactions
Could a plant cell produce ATP through chemiosmosis if the thylakoid membranes of its chloroplasts were "leaky" with regard to protons? Explain.
To reduce six molecules of carbon dioxide to one molecule of glucose via photosynthesis, how many molecules of NADPH and ATP are required?
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8
The overall purpose of the Calvin cycle is to
A) generate molecules of ATP.
B) generate NADPH.
C) build sugar molecules.
D) produce oxygen.
If the Calvin cycle runs through six turns,
A) all of the fixed carbon will end up in two molecules of glucose.
B) 12 carbons will be fixed by the process.
C) enough carbon will be fixed to make one glucose, but they will not all be in the same molecule.
D) one glucose will be converted into six CO2.
Why do plants employ NADPH in photosynthesis? Why do they not use NADH to transport energetic electrons, as the Krebs cycle does?
A) generate molecules of ATP.
B) generate NADPH.
C) build sugar molecules.
D) produce oxygen.
If the Calvin cycle runs through six turns,
A) all of the fixed carbon will end up in two molecules of glucose.
B) 12 carbons will be fixed by the process.
C) enough carbon will be fixed to make one glucose, but they will not all be in the same molecule.
D) one glucose will be converted into six CO2.
Why do plants employ NADPH in photosynthesis? Why do they not use NADH to transport energetic electrons, as the Krebs cycle does?
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9
In theory, a plant kept in total darkness could still manufacture glucose, if it were supplied with which molecules?
The overall flow of electrons in the light-dependent reactions is from
A) antenna pigments to the reaction center.
B) H2 O to CO2.
C) photosystem I to photosystem II.
D) reaction center to NADPH.
The products of the light-dependent reactions feed into
A) the Calvin cycle.
B) photosystem I.
C) glycolysis.
D) the Krebs cycle.
The overall flow of electrons in the light-dependent reactions is from
A) antenna pigments to the reaction center.
B) H2 O to CO2.
C) photosystem I to photosystem II.
D) reaction center to NADPH.
The products of the light-dependent reactions feed into
A) the Calvin cycle.
B) photosystem I.
C) glycolysis.
D) the Krebs cycle.
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10
Many plants cannot carry out the typical C 3 photosynthesis in hot weather, so some plants
A) use the ATP cycle.
B) use C 4 photosynthesis or CAM.
C) shut down photosynthesis completely.
D) All of these are true for different plants.
Why are plants that consume 30 ATP molecules to produce one molecule of glucose (rather than the usual 18 molecules of ATP per glucose molecule) favored in hot climates but not in cold climates? What role does temperature play?
A) use the ATP cycle.
B) use C 4 photosynthesis or CAM.
C) shut down photosynthesis completely.
D) All of these are true for different plants.
Why are plants that consume 30 ATP molecules to produce one molecule of glucose (rather than the usual 18 molecules of ATP per glucose molecule) favored in hot climates but not in cold climates? What role does temperature play?
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11
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Applying Concepts
a. Variable. In the graph above, which is the dependent variable?
b. Index. What does the increase in levels of chlorophyll a say about numbers of phytoplankton?
c. Control. What substance is lacking in the waters sampled in the bluedot plots ?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Applying Concepts
a. Variable. In the graph above, which is the dependent variable?
b. Index. What does the increase in levels of chlorophyll a say about numbers of phytoplankton?
c. Control. What substance is lacking in the waters sampled in the bluedot plots ?
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12
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Interpreting Data
a. What happened to the levels of chlorophyll a in the test areas of the ocean (red dots)?
b. What happened to the levels of chlorophyll a in the control areas (blue dots)?
c. Comparing the red line to the blue line, about how many times more numerous are phytoplankton in iron-seeded waters on the three days of seeding?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Interpreting Data
a. What happened to the levels of chlorophyll a in the test areas of the ocean (red dots)?
b. What happened to the levels of chlorophyll a in the control areas (blue dots)?
c. Comparing the red line to the blue line, about how many times more numerous are phytoplankton in iron-seeded waters on the three days of seeding?
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13
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Making Inferences
a. What general statement can be made regarding the effect of seeding phytoplankton-poor regions of the ocean with iron?
b. Why did chlorophyll a levels drop by day 14?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Making Inferences
a. What general statement can be made regarding the effect of seeding phytoplankton-poor regions of the ocean with iron?
b. Why did chlorophyll a levels drop by day 14?
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14
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Drawing Conclusions Do these results support the claim that lack of iron is limiting the growth of phytoplankton, and thus of photosynthesis, in certain areas of the oceans?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that Phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplankton-poor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Drawing Conclusions Do these results support the claim that lack of iron is limiting the growth of phytoplankton, and thus of photosynthesis, in certain areas of the oceans?
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15
Does Iron Limit the Growth of Ocean Phytoplankton?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Further Analysis Based on this experiment, what would be a potential drawback of using this method of seeding with iron to increase levels of ocean photosynthesis?
Phytoplankton are microscopic organisms that live in the oceans, carrying out much of the earth's photosynthesis. The photo below is of Chaetoceros, a phytoplankton. Decades ago, scientists noticed "dead zones" in the ocean where little photosynthesis occurred. Looking more closely, they found that phytoplankton collected from these waters are not able to efficiently fix CO2 into carbohydrates. In an attempt to understand why not, the scientists hypothesized that lack of iron (needed by the ETS) was the problem, and predicted that fertilizing these ocean waters with iron could trigger an explosively rapid growth of phytoplankton.
To test this idea, they carried out a field experiment, seeding large areas of phytoplankton-poor ocean waters with iron crystals to see if this triggered phytoplankton growth. Other similarly phytoplanktonpoor areas of ocean were not seeded with iron and served as controls.
In one such experiment, the results of which are presented in the graph to the right, a 72-km 2 grid of phytoplankton-deficient ocean water was seeded with iron crystals and a tracer substance in three successive treatments, indicated with arrows on the x axis of the graph (on days 0, 3, and 7). The multiple seedings were carried out to reduce the effect of the iron crystals dissipating over time. A smaller control grid, 24 km 2 , was seeded with just the tracer substance.
To assess the numbers of phytoplankton organisms carrying out photosynthesis in the ocean water, investigators did not actually count organisms. Instead, they estimated the amount of chlorophyll a in water samples as an easier-to-measure index. An index is a parameter that accurately reflects the quantity of another less-easily-measured parameter. In this instance, the level of chlorophyll a , easily measured by monitoring the wavelengths of light absorbed by a liquid sample, is a suitable index of phytoplankton, as this pigment is found nowhere else in the ocean other than within phytoplankton.
Chlorophyll a measurements were made periodically on both test and control grids for 14 days. The results are plotted on the graph. Red points indicate chlorophyll a concentrations in iron-seeded waters; blue points indicate chlorophyll a levels in the control grid waters that were not seeded.
Further Analysis Based on this experiment, what would be a potential drawback of using this method of seeding with iron to increase levels of ocean photosynthesis?
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