When Moina micrura (microscopic aquatic crustaceans) are exposed to unfavorable environmental conditions, they produce ephippia (specialized eggs that each contain a dormant embryo). The embryos remain dormant until the ephippia are exposed to favorable environmental conditions that cause the ephippia to hatch. Two experiments examined how pH and light intensity affect the hatching of M. micrura ephippia.
Experiment 1
Each of 15 identical beakers received 50 mL of water and 120 freshly laid M. micrura ephippia. The beakers were then equally divided into 5 groups (Groups L-P). For each group of beakers, the water was maintained at 1 of 5 different pH values (see Table 1).
Each beaker was then incubated at 27°C and received 12 hr of light per day at a light intensity of 650 lux. At the end of 7 days, the number of ephippia that had hatched in each beaker was counted, and the average number of ephippia hatched in each group was calculated (see Figure I).
Experiment 2
Each of 20 identical beakers received 50 mL of water and 120 freshly laid M. micrura ephippia. The beakers were then equally divided into 5 groups (Groups Q-U). Each beaker was incubated at 25° C, and the water in each beaker was maintained at a pH of 7.0. Group Q was kept in the dark, and each of Groups R-U received 12 hr of light per day at 1 of 4 different light intensities (see Table 2).
At the end of 7 days, the average number of ephippia hatched in each group was determined as in Experiment 1 (see Figure 2).
17. Consider the statement “The number of ephippia that hatched, on average, was greater for the ephippia kept in the dark than it was for the ephippia exposed to light.” Do the results of Experiment 2 support this statement?
Answer and Explanation
Your Answer is
Correct Answer is C
Explanation
From figure 2, it can be seen that Group Q has the least amount of hatching;
By comparing table 2, it is found that Group Q has the weakest light intensity, so the darker it is, the less hatching , the statement in the title is wrong
