1. The following article from the August 2003 Discover Magazine (p. 12) tells of a scientist who was studying communication between butterflies. She made an interesting observation that iridescent markings on some butterfly wings create polarized patterns. She was also struck by the colors in the wings. Using the previous examples as a guide, determine the best theory for the communication between butterflies. Do they communicate with color or with polarized light? Hand in a page similar to the answer to the practice exercise previously given. For this homework you do not need to explicitly show that the theories have scientific merit, just state that we assume that they do have merit as shown in the answer to the practice exercise.
"Butterflies Like Mates With a Twist"
"Alison Sweeney, a biologist at Duke University, was studying deep-forest butterflies in South America when she realized that color alone is not the key to their beauty. To other butterflies, iridescence-the way light rays align when they reflect off the wing-is at least as fetching as the fancy colors. Sweeney knew that butterflies have an excellent ability to detect polarization, the direction in which the waves in a beam of light are oscillating. Then she discovered that iridescent markings on some butterfly wings create polarized patterns. 'It struck me as odd that with all the colors, they would have taken the energy to evolve iridescence as well, so I assumed it must have a significant purpose,' Sweeney says."
"Sweeney gathered a group of male Heliconius butterflies, a highly polarized genus, and showed them two sets of wings from Heliconius females. One set was displayed normally; the other was shown through a filter that blotted out the polarization effects. The males swarmed toward the normal wings and largely ignored the filtered ones. When the insects could not see the polarization patterns, they were not interested. Sweeney claims this is the first known instance of a terrestrial species using polarized light for anything other than navigation. 'I wouldn't be surprised if there were other insect species using this type of thing for communication,' she says. 'It's just hard to explore what you can't really see.' -Jocelyn Selim [Author]"
2. Using the previous examples as a guide, determine the best theory for the high bacteria count in the following story from Dr. Lloyd Carr. Dr. Carr had his water system serviced and the serviceman told the following story. Hand in a page similar to the answer to the practice exercise previously given. For this homework you do not need to explicitly show that the theories have scientific merit, just state that we assume that they do have merit as shown in the answer the practice exercise.
"A few weeks ago I got a call from a MacDonald's. They were in a panic. They wanted to know if I could install a filtration system for bacteria right away. These systems are big bucks, not to mention my labor! I asked why they needed it. It seems that the state water inspector came by for one of the random water tests for bacteria that restaurants and fast-food places have to get. Well, this MacDonald's tested as having a bad bacteria contamination in their water. That means they only have to the end of the week to fix it. If they fail the test on a Monday it's not too bad, but if they fail toward the end of the week they still must fix the situation by the end of the week or be closed down. They called me on a Wednesday or a Thursday, I forgot which."This situation seemed odd to me, because I service several well-water systems in that area and I could not remember a single case where bacteria were a problem. Also, in my experience these fast-food places have all kinds of sources for bacteria - they are real breeding grounds! So it didn't add up. The well might be the source, but I suspected the bacteria were coming from somewhere else. I asked the guy who called me where the state inspector drew the water sample from, and he got upset saying what difference did it make, their well is contaminated. See, he was assuming the well was the source of the bacteria and so couldn't see where I was coming from. I was thinking the bacteria were coming from the kitchen area where they handle all the food - they wash it and work with it and it gets all over the place. So I insisted he tell me, if he wanted me to help them out. He said - the kitchen sink. That's just what I thought! I told him to call the state inspector back and tell him he made a mistake, the well is not contaminated. Tell him to do another test drawing the water sample from the bathroom sink not the kitchen sink. I figured if the well was the source of the bacteria, the bathroom sink sample should fail the test because all their water comes from the same well, but if the source was somewhere in the kitchen you would expect the kitchen water sample to have bacteria but it would be very strange for the bathroom sample to be contaminated too.
"I told the guy - just do it; he couldn't see what I was up to, but I told him I was the expert and I deal with these things all the time, and I might save him a lot of money. Next day he calls back all happy and thanking me. He said the bathroom sink passed the bacteria test. So then I knew that the well was ok and that they didn't need any filtration system for bacteria. I could have sold them a very fancy system, and they would never have known!
"But I still wanted to be sure it wasn't the well, because bacteria are nothing to fool with. So I stopped at the MacDonald's to see if I could find the source of the bacteria. I used bleach. If I washed the kitchen sink area with bleach, and especially up a few inches into the inside of the faucet where food splashes and no one ever cleans, I expected I would get no bacteria contamination, if the sink was the source. But if the well was the source, then I should get a contaminated sample even if I cleaned with bleach. I tested the water out of that faucet and it had a pretty high bacteria count. Then I bleached it all and made sure I got up into the faucet. I let it run to wash all the bleach out, and tested it. No more bacteria!
"Their well water was fine. But I had to give the guy a lesson on how to use bleach."