Question

1. describe the experiment that proved the presence of vibrio fischeri is required for the maturation of the light organ. 7. 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:

1. Scientists likely used a gnotobiotic approach. They raised bobtail squid in a sterile environment. Some squid were exposed to Vibrio fischeri while others were not. The ones without the bacteria had under - developed light organs, while those with the bacteria had normal, mature light organs, proving the bacteria's necessity for light - organ maturation.

7a. Eliminating 95% of the bacteria during the day may be to conserve energy and resources. Since the squid hides in the sand during the day and doesn't need counter - illumination, it doesn't need a large bacterial population consuming resources. Also, it may prevent over - growth and potential negative impacts on the squid's health.
7b. The bacteria within the light organ can reproduce rapidly. Even though the squid doesn't take in new bacteria from the environment, the existing bacteria can divide and multiply, maintaining a sufficient population to produce light.

Answer:

1. Scientists raised bobtail squid in a sterile environment. Some were exposed to Vibrio fischeri and others were not. Squid without the bacteria had under - developed light organs, while those with it had normal ones, proving the bacteria's necessity for maturation.

7a. To conserve energy and resources as counter - illumination isn't needed during the day and to prevent over - growth and potential health issues.
7b. The bacteria within the light organ can reproduce rapidly to maintain a sufficient population for light production.