Question

1. describe the experiment that proved the presence of vibrio fischeri is required for the maturation of the light organ.
2. within the light organ, bacteria are protected and nourished, and rapidly increase in number. at night, they provide the light needed for counterillumination. but by dawn, as the squid prepares to hide in the sand for the day, it ejects about 95% of the bacteria from the light organ.

a) write a possible explanation for why eliminating 95% of the bacteria present in the light organ is necessary.
b) once the light organ is colonized, the squid no longer takes in vibrio fischeri or other bacteria from the environment. explain how a sufficiently large population of bacteria can be maintained in the light organ to produce light.

Explanation:

Question 6:

Scientists raised squid in a bacteria - free environment. Squid in this environment had under - developed light organs. When exposed to Vibrio fischeri, the light organs matured, proving the bacteria's necessity.

Question 7a:

During the day, the squid hides in the sand and doesn't need counterillumination. Maintaining a large bacterial population would be energetically costly and unnecessary, so ejecting 95% helps conserve resources.

Question 7b:

The remaining 5% of bacteria can rapidly reproduce due to the favorable conditions (protection and nourishment) within the light organ, replenishing the population to produce light.

Answer:

Question 6:

Squid were raised in a bacteria - free environment. Their light organs remained under - developed. When exposed to Vibrio fischeri, the light organs matured, showing the bacteria is required for maturation.

Question 7a:

During the day, the squid doesn't need counterillumination as it hides in the sand. A large bacterial population is energetically costly, so ejecting 95% conserves resources.

Question 7b:

The 5% of remaining bacteria can multiply rapidly in the favorable conditions of the light organ to maintain a sufficient population for light production.