Question

use the passage and graph to answer the following questions.
two biology students, noah and mateo, conducted an experiment testing the effects of
intense light vs darkness on the amount of dissolved oxygen in an aquatic ecosystem.
they placed two aquatic plants (java moss) in a tank filled with freshwater. they
exposed the tank to each condition for 30 minutes, and recorded the percent dissolved
oxygen using a sensor. before each experiment, they allowed the tank to sit
undisturbed in normal conditions for 6 hours. a graph of their data is shown below.
unfortunately, the students forgot to label their data files, so they dont know which
plant was exposed to which condition.

1. noah claims the \a\ trial was exposed to the intense light, while mateo thinks \a\

was in the darkness. which students claim and reasoning is correct?
a mateo is correct. plants store light to photosynthesize; in the dark, oxygen
use would increase.
b mateo is incorrect. plants substitute oxygen for energy in the dark; this
would decrease the oxygen in the water.
c noah is correct. oxygen is a product of photosynthesis; intense light would
increase the amount of oxygen in the water.
d noah is incorrect. plants use oxygen during photosynthesis; intense light
would decrease the amount of oxygen in the water.

1. which conclusion below is best supported by the data in the graph?

a plants can only use cellular respiration if they are in the dark.
b plants can only carry out photosynthesis if there is sunlight all the time.
c plants can either use photosynthesis or cellular respiration but not both at
the same time.
d plants can switch between cellular respiration and photosynthesis in
changing conditions.

1. what should mateo and noah do next to improve their investigation?

a change the intensity of the light.
b conduct the same experiment several more times.
c have another group follow their procedures with different plants.
d change the length of time the plants are exposed to light or darkness.

Explanation:

Question 20

Plants perform photosynthesis in light, producing oxygen. In the graph, Java moss (A) shows an increase in dissolved oxygen over time, which aligns with photosynthesis (a light - dependent process). Oxygen is a product of photosynthesis, so intense light (which would enhance photosynthesis) would increase oxygen levels.

Plants can carry out both photosynthesis (in light, producing oxygen) and cellular respiration (in light and dark, consuming oxygen). The graph shows changes in oxygen levels over time. For example, when there are changes in oxygen levels (increase and decrease), it implies that plants can switch between processes depending on conditions (like light availability).

To improve the reliability of an experiment, conducting the same experiment multiple times (replication) helps to account for any random errors or variations. Changing light intensity (A) or time of exposure (D) would change the independent variable. Using different plants (C) would introduce another variable. Replication (B) is a standard way to improve experimental validity.

Answer:

C. Noah is correct. Oxygen is a product of photosynthesis; intense light would increase the amount of oxygen in the water.

Question 21