T. W. Engelmann did an experiment where he separated the wavelengths (colors) of light using a prism, and illuminated a chain of algae cells so that each cell received 1 color of light. He then added oxygen-loving bacteria to the mixture and saw that they preferentially went to the algae using red and blue light. He concluded (correctly) that red and blue light were the most efficiently used in photosynthesis (producing the most oxygen for the bacteria). Suppose that you did the same experiment, but did not use a prism to separate the wavelengths of light. Where will the bacteria go?

The bacteria will be evenly distributed on the chain of algae

Explanation:

If the component of white light is not separated by a prism, all the components will be evenly distributed in space and as such, equal amount of each component will go to the chain of algae.

The equal amount of each light component that goes to the chain of algae will ensure that there is equal rate of photosynthesis, and hence, oxygen production in each algae. Consequently, the oxygen-requiring bacteria will spread out evenly on the chain of algae without concentrating particularly on any algae.

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus