G3 Program 7: Natural Selection

Even though “natural selection” is not necessarily a topic that leads us to create either gadgets, gizmos, or goo, this seemed like an appropriate theme given the approaching Earth Day on April 22nd. As scientists, it was time for us to focus on the world around us just a little bit and to observe the science that exists in nature itself.

Nicole started our discussion for the day by telling the story of the Peppered Moth. This story is one of the simplest and best representations of natural selection at work. Peppered Moths were originally ivory colored, with black specs – allowing them to blend in perfectly on the bark of trees covered with white lichen that were dominant in their environment. Around 1848, moths that were entirely black in color began to appear in the moth populations. Why was this happening? Well, scientists believed that the moths were adapting to their changing environment and as a species were selecting traits/characteristics that would help them to survive. As humans relied more and more on machines and large factories, the trees that were originally mostly white with dark specs were actually becoming completely black due to the soot and black smoke in the air. When the moths were still ivory with black specs, predators like birds were able to pick them off too easily from the trees. The only way for the moths to survive was to find a way to blend into the now mostly black trees…hence, the population started to create all black moths. By 1895 (less than 50 years from when the first black moths started to appear), the population of Peppered Moths was approximately 98% all black! Normally, it would take some species hundreds or thousands of years to make such an adaptation to their environment (which is why studying the Peppered Moths is so interesting for scientists). And in another fascinating turn of events, today, the populations of Peppered Moths are once again becoming mostly ivory with black specs. Why do you think that might happen? Well, scientists believe that now that humans are using cleaner burning fuels in factories, the trees are once again reverting to a cleaner, more natural state (once again mostly white)…and thus the Peppered Moth must once again change color to blend into its environment to avoid predators. It’s pretty tough to be a Peppered Moth, huh? 🙂

Galapagos Finches with different beaks
http://www.pbs.org

Next, our group watched a highlight from the BBC documentary entitled “Galapagos: The Islands that Changed the World (the video segment is available below via a youtube posting by user “DocumentariesForYou”).” In particular, we watched a 5-minute segment of episode 2 that highlighted the various finch species present on the Galapagos. The Galapagos are a unique environment because of the way they are isolated islands. The environment and the animals have essentially adapted to each others’ preferences and needs. For example, the most common honey bee on the island prefers yellow flowers, so most flowers are yellow. The most common bird species on the islands – by far – are finches, and each type of finch has adapted to their particular part of the island environment. You can see the differences most easily by looking at the different types of beaks each finch has and how they use that to obtain food. Some finches have narrow, pointy beaks, perfect for getting nectar out of flowers or bugs out of tiny crevices. Other finches have more rounded beaks best used for pounding on trees or logs to extract food. One type of woodpecker finch even creates a straw tool to help him pull worms and grubs out of holes that he creates in trees!

One important part of learning about how species adapt to their changing environment through natural selection is also understanding what happens when they are unable to adapt. According to the Yale Peabody Museum of Natural History (New Haven, CT), there have been 3 species of Connecticut birds in the past 100 years that have become extinct due to a variety of reasons: the Labrador Duck (extinct 1878), the Passenger Pigeon (extinct 1914), and the Heath Hen (extinct 1932). For each bird, the reasons for extinction were a little different. The Labrador Duck was unable to maintain its regular diet made up almost entirely of mollusks (which humans began to eat), and was not able to adapt and find another food source.  The Passenger Pigeon was, among other things, aggressively hunted for its meat (yes, we used to eat pigeon meat…). And the Heath Hen was heavily hunted, and then despite preservation efforts, was unable to survive due to a series of illnesses, etc. that hit the population. [Interestingly enough, the Heath Hen is the first species that our country ever tried to actively save with preservation efforts!].

The Tardigrade
Also known as "Moss Piglet" or "Water Bear"

Perhaps our most popular item for discussion of the day was the species that “cannot be killed”:  the Tardigrade. Such a weird, curious looking critter that at most will get to be 1.5 millimeters in length. All different kinds of Tardigrades are found near water, usually living on moss or lichen. Scientists have done their darnedest to see what kinds of environmental extremes the Tardigrade can endure. According to Nicola Davies in her book, Extreme Animals: The Toughest Creatures on Earth, scientists have frozen, boiled, squashed, zapped, and poisoned Tardigrades at extreme levels…and still they survive unharmed! [Though our G3 scientists thought that maybe knives, in combination with sniper rifles and acid might do the trick 🙂 ] And I bet you thought that Cockroaches were the toughest creatures around!

G3 scientists collecting "food" with their "beaks"

Now, for our activity of the day! Linking back to our discussion about the different finch species on the Galapagos, G3 scientists were provided with different tools that represented different types of bird beaks (see PBS’s Fetch program description for “Eat Like A Bird“). Our scientists were divided into 5 teams and each team was given one of the following tools to use: plastic spoons, plastic forks, tongs made from craft sticks, toothpicks, or clothespins. About twelve feet from the starting line was an 8-ft circular area that contained a variety of “food” items: marbles, crumpled paper, lima beans, kidney beans, rubber bands, and paper clips. When Nicole started the clock, each team ran a relay race for 5 min. One person from each team would rush to the food circle, use their tool (no hands allowed!), and grab a single item of food to carry back to their team cup. As soon as one person was back, another person from the team could go to the circle. When time was up, each team tallied the food items in their cups so we could see what items they were able to collect with their particular tool (in other words, their “beak”). We were able to complete 3 rounds of relays, giving each team of scientists the chance to test out 3 different “beaks.” When all was done, our G3 crew found that the most difficult to use tools/beaks were the toothpicks, followed closely by clothespins and then forks. Both tongs and spoons were able to collect a wide variety of “food” items.

Our thoughts? Well, a bird that has a narrow/pointy beak similar to our toothpicks probably has a limited selection of food for their regular diet. And if that food item were to disappear from their environment (like the mollusks disappeared for the Labrador Duck), the species could very well have a difficult time adapting and might become extinct. Birds that have beaks shaped like tongs or spoons have a greater selection of food sources and thus could adapt better to changes in their environments.

After a well-deserved bottle of water, our G3 scientists headed home. I wonder what is planned next for our G3 scientists! I’ll give you a hint: I think we’re finally going to investigate some “goo”…

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Categories: Natural Selection/Adaptation | Tags: , , , , , , , , | Leave a comment

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