Question

In 1883, a researcher, named Theodor Engelmann, designed and completed an experiment to see which colors of light resulted in the highest production of oxygen from alga which indicates the highest rate of redox reactions during photosynthesis.

Study the graphics seen here and answer the following questions about the experimental design and the findings.



Experimental images adapted from AP Edition of Campbell Biology: 11th Edition (2018)

Question 1.

In Engelmann's experiment, what factor could be considered the "independent variable"?



(1 point)

Wavelength (color) of light shown on the alga

Amount of oxygen produced through photosynthesis

The amount of aerobic bacteria that collected along the alga

The type of alga used throughout the experiment
Question 2

Which pigment absorbed the most blue light (between 450-490 nm)?

(1 point)

Chlorophyll a

Chlorophyll b

Carotenoids

All pigments absorbed equal amounts of blue light.
How does frame (b) Action Spectrum best support the image seen here of how a chloroplast collects and emits light energy as photosynthesis progresses? This additional image may support your thinking.





(1 point)

Frame b shows that in a chloroplast the collection of pigments don't absorb as much green light as they do other colors (wavelengths).

Frame b shows that greenlight is absorbed more than other colors of light by pigments in chloroplasts.

Frame b shows that only green light is used in photosynthesis to produce oxygen.

Frame b shows that red and blue light are not absorbed as much as yellow light.
Question 3

In photosynthesis, oxygen is produced when water is split and electrons and hydrogens are attached to carbon dioxide through redox reactions. Which colors (wavelengths) of light show increased "action" of oxygen production through redox processes?

(1 point)

Blue and red light

Blue light only

Green light only

Yellow and green light
Question 4

Using the production of oxygen from redox reactions in photosynthesis as a measure, why did the experimenter most likely choose aerobic bacteria to show him which colors (wavelengths) of like are most productive?

(1 point)

Aerobic bacteria consumed the alga in the experiment.

Aerobic bacteria grow and reproduce where there is the most abundant source of oxygen.

Aerobic bacteria die in the presence of oxygen.

Aerobic bacteria avoid oxygen sources.
Question 5

Which statement best supports the correlation between frames b and c giving the experimenter the data that revealed which colors (wavelengths) of light best catalyze redox reactions in plant photosynthesis?

(1 point)

Aerobic bacteria congregated (gathered) along the alga where the most oxygen was produced connecting the action spectrum to the growth of bacteria AND the rate of redox.

Aerobic bacteria collected where there was the most green light illustrating how photosynthesis works.

Aerobic bacteria produced the oxygen needed by the alga for photosynthesis.
Question 6

What is the most logical next step in the movement of energy stored as electrons that have been transferred to sugars and other molecules through photosynthesis?

(1 point)

The plant itself or herbivores and omnivores can harvest the energy from sugar and convert it again into a different form of energy.

The energy flow of electrons will end with the formation of sugar.

The electrons will move back to oxygen independently and the plant will wilt.

The electrons will convert to protons and start a new nuclear process.

Answer 1

Question 1
- Wavelength (color) of light shown on the alga.
- (Independent variable = the light color applied.)

Question 2
- Chlorophyll b.
- (Chl b has its strong blue absorption peak in the 450–490 nm region.)

Question 3 (frame b support)
- Frame b shows that in a chloroplast the collection of pigments don't absorb as much green light as they do other colors (wavelengths).
- (Action spectrum and pigment absorption curves show low green absorption and low O2 production in green wavelengths.)

Question 4
- Blue and red light.
- (These wavelengths correspond to the peaks of photosynthetic activity and O2 production in the action spectrum.)

Question 5
- Aerobic bacteria grow and reproduce where there is the most abundant source of oxygen.
- (They were used as indicators because they accumulate where photosynthetic O2 production is highest.)

Question 6
- Aerobic bacteria congregated (gathered) along the alga where the most oxygen was produced connecting the action spectrum to the growth of bacteria AND the rate of redox.
- (This statement links the measured O2 production locations to the action spectrum.)

Question 7
- The plant itself or herbivores and omnivores can harvest the energy from sugar and convert it again into a different form of energy.
- (Sugars produced in photosynthesis are later used by the plant or consumers to release stored energy via respiration.)