Stage 5: Establishing Credibility

Lyme disease is one of the fastest-growing infectious diseases in the US, and has spread to more and more places. Although infections mainly occur in summer, now it is reported even in winter months. Lyme disease usually causes symptoms such as a rash, fever, headache, and fatigue. But if it is not treated early, the infection can spread to your joints, heart, and nervous system creating long-term and chronic health problems. 

As a vector-borne disease, Lyme disease is transmitted to humans through the bite of infected ticks that carry the Borrelia burgdorferi bacteria. One of the two main varieties of ticks, hard ticks, can also cause Rocky Mountain spotted fever, Colorado tick fever, and other diseases. In the eastern part of the US, ticks that carry Lyme disease – black-legged ticks, also known as deer ticks, Ixodes scapularis – can transmit at least six diseases. We now know that ticks originated in the southern US about a half a million years ago, with later expansion into the mid-Atlantic and northeastern US, roughly 50,000 years ago. Reading the map, we noticed that the range of ticks has expanded substantially in the upper Midwest, northeast and mid-Atlantic states over the past two decades, and they are now found in each state in the U.S. Increases of the geographic range of ticks and the number of Lyme disease cases may derive from climate change and land use. 

Ticks are ectotherms that cannot control their internal body temperature but instead adapt to the outside temperature, so they are sensitive to their environment. We know that the most important factors of ticks’ activity are temperature and moisture. Ticks prefer warmer temperatures and a moister environment, especially immature ticks – nymphs – through whose bites most humans are infected, because they are smaller and consequently less likely to be detected after a bite. Nowadays, global warming has extended the period of time that is warm enough for tick activity, thus lengthening the season that ticks actively seek new hosts in a year, creating more opportunity for more disease transmission, and leading to more cases of disease, even if the tick population remains the same. However, some states have reported larger tick populations than before. 

Previously, cold winter temperatures in the northern and higher altitude areas killed ticks. However, as a result of increasing global temperatures in connection to climate change, these areas have become warmer. We know this because we read the data of climate change in class. Global warming also contributes to increasing precipitation in the east and northeastern parts of the US increasing the range of places with suitable habitats for tick survival. 

Furthermore, sensitivity to temperature also impacts the life cycle of a tick. As global warming accelerates the developmental rates of ticks, it potentially shortens a three-year life cycle to a two-year life cycle, quickens reproduction for the bacteria-bearing ticks, and also leads to an increase of tick populations. In summary, recent climate changes stemming from global warming have influenced tick activity and increased the transmission of Lyme disease. 

In addition to global warming, human activity influences the wildlife populations that act as hosts for ticks, thus affecting the prevalence of Lyme disease in our forests. When there exists a variety of potential hosts, this reduces or dilutes the chance that a tick will feed on an infected animal which, in turn, reduces the chance that a tick bite will transmit Lyme disease. This is because not all hosts are able to carry the bacterial disease. For example, lizards and rabbits rarely harbor the bacterial disease while white-footed mice often do because they can carry the bacteria without becoming ill. In other words, the more potential hosts that exist in an ecosystem, the less likely the infected hosts are able to transmit the bacteria. 

Human activities including habitat fragmentation from roadways and suburban development has decreased the diversity of tick hosts. Forest fragmentation causes populations of predators like foxes, owls, hawks, and other predators who typically feed on small hosts like mice to decrease . This contributes to the possibility of white-footed mice numbers subsequently exploding while populations of other hosts declining, increasing the possibility of mice serving as tick hosts and infecting ticks with Lyme Disease. This in turn increases the risk of human exposure to Lyme disease. Finally, we know that human risk of exposure to disease is higher in more fragmented forest habitats than in more contiguous forest habitats, because people have more opportunities to interact with infected vectors (i.e., ticks) in fragmented forest. With more buildings (e.g., homes, shopping centers) built near fragmented forests, more people are living near the animals that carry ticks, thus increasing their exposure to Lyme disease. Additionally, humans are more likely to spend more time outdoors in warmer seasons, so the time of human exposure to tick bites and Lyme disease also increases. 

We also see differences in how some racial and ethnic groups experience Lyme Disease. There is evidence that the differences of their socioeconomic position including occupation, income, wealth, awareness, and healthcare access, as well as white-centered medical resources may account for this phenomenon. 

First, racial and ethnic groups are exposed differently in outdoor environments. We know that in the areas where Lyme disease is most prevalent, almost half of outdoor workers (i.e., ground maintenance workers, farming, fishing, and forestry industries) are Hispanics, so they are at greater risk for Lyme disease infection from occupational exposures than the general population. The risk is even greater in the fall, the harvest season, due to an increase in migrant Hispanic farm workers and proportionately more time in outdoor spaces. Current and historical access and feelings of belonging in outdoor spaces also contributes to more exposure to Lyme Disease from tick bites compared to other racial and ethnic groups. Feelings of belonging in outdoor spaces can be traced back to restrictive codes from the era of Jim Crow laws where signs were posted declaring spaces to be “For Whites Only”. 

Second, members of racial and ethnic minority groups are more likely to encounter barriers to getting care because of lack of health insurance or not being paid when missing work to get care. Evidence shows that the rates of uninsured Hispanics and non-Hispanic Blacks are higher than non-Hispanic Whites. Further, if symptoms persist, patients need more high cost treatment, while many patients report that their doctors don’t accept insurance. When facing costly treatment, low income groups are more reluctant to get diagnosed. 

Third, we also see reports about how some racial and ethnic groups encounter medical racism when they see a doctor. For example, black patients are more likely to present with later complications of Lyme disease when they were first diagnosed compared to white patients. Reasons for the delay in early diagnosis may be that many medical practitioners haven’t been trained to recognize the characteristic “bulls-eye rash” on dark skin, since most medical training materials only focus on diagnoses on white skin. The rash appears differently on different skin types and tones, which, however, have historically been missing in medical training and in the medical literature. Further, fewer patients of color have a health-care provider of the same race or ethnicity that speaks the same language when compared to white patients. This can negatively affect patient-provider relationships, trust, and quality of healthcare. Some studies also revealed how healthcare providers appeared to have implicit bias in terms of positive attitudes toward white people and negative attitudes toward people of color. All of these differences in experiences connected to exposure, diagnosis, and treatment help account for the differences in how different racial and ethnic groups experience Lyme disease.

The Colorado Plateau is a formation that covers parts of Colorado, Utah, Arizona, and New Mexico. This area has been uplifted over a mile in elevation. Canyons were formed throughout the entire plateau through weathering and erosion by wind and water. This is how the canyons formed. The exposed walls of these canyons help us understand the history of the earth. Different layers of rock in the walls represent different eras in geologic and biologic history of the earth. The canyons Bryce, Zion, and the Grand Canyon represent “stair steps” of the Grand Staircase of the Colorado Plateau. In the geologic timeline activity, we saw that the Grand Staircase shows geological history from 1.77 billion years ago to the present. This covers the time multicellular life has been around. 

Starting at the bottom of the Grand Staircase places us at the very bottom of the Grand Canyon. In the Build a Canyon activity, we saw that the Grand Canyon allows us to see back in time because it uncovered rock layers from when the Colorado Plateau was still part of the ocean. The Grand Canyon was formed by erosion of the Colorado River. We know from the principle of superposition that the lower rock layers are older than the newer ones layed on top. We saw this in the Who’s on First activity. This helps us date the rock layers and is called relative dating. Example layers include the Vishnu Schist, Bright Angel Shale, Kaibab Limestone, and the Coconino Sandstone. 

The Build a Canyon activity showed us the ages, depositional environments, and common fossils of each layer. The oldest rock layer in the Grand Canyon is 1.7 billion years old. This is called the Vishnu Schist and it formed from cooling magma. No fossils are found in this layer because of the extreme heat and pressure during the rock formation. The Bright Angel Shale and the Kaibab Limestone layers are the next rock layers up. They were both formed at different times when the area was covered in a warm, shallow sea. The Bright Angel Shale is between 543 and 490 million years old and contains fossils of worm-like creatures and trilobites. The Kaibab Limestone is around 150 million years old and contains fossils of sponges, corals, fish and sharks. Next up is the Coconino Sandstone layer, which was formed during a period of desert landscape and is around 260 million years old. The fossils here include insects, spiders, and scorpions. 

The Grand Canyon has a lot of fossils in each layer. Some are index fossils that help us understand the geologic history of the Colorado Plateau because they are widespread, abundant, and limited in geologic time like we saw in the Who’s on First activity. There are different types of organisms found within the different rock layers. Some of these organisms were on land and some of them lived in water. This shows that there were different environments at different times that created these different rock layers. Since some fossils are different between the rock layers, we know that there must have been several extinctions throughout history. 

Further north is Zion Canyon. Zion Canyon was formed by river erosion. Zion shows the next few rock layers in geologic time. For example, the Moenkopi Formation is between 248 and 206 million years old. It contains layers of sandstone and limestone and has fossil footprints of reptiles and amphibians. This layer was formed by shallow seas. The Kayenta Formation is around 206 million years old and contains fossils of dinosaur tracks. The Kayenta Formation was formed by rivers and lakes. 

Continuing north we get to Bryce Canyon. Bryce Canyon was formed by weathering from water and ice. Bryce Canyon has the Claron Formation of rocks which is between 65 and 1.8 million years old, the youngest layer on the Colorado Plateau. This layer was carved out by erosion and weathering. Mammal fossils are found here in Bryce Canyon. 

Taken together, the canyons of the Colorado Plateau give us a glimpse of 1.7 billion years of Earth’s history because they let us see the many rock layers that are normally hidden beneath our feet. We understand what the Earth used to be like because certain rock layers mean that they were laid down in certain environments. We also know how old they are because of relative dating techniques.

(This is optional for 3-5 grade students. They can do oral presentations with their models  instead) 

There are constant struggles that a species must overcome in order to survive in an  ecosystem. An adaptation is a characteristic that helps an organism survive in its environment. Over  time these adaptations will allow a species to survive more frequently then those who do not adapt.  Future generations of an organism that has adapted to its environment may inherit those adaptations.  

Adjustments to internal or external physical structures are called structural adaptations.  Examples of structural adaptations include the ability to run fast, fur, and even jaw size. Structural  adaptations help an organism survive in its environment. For example, a giraffe’s long neck or a  snake’s flexible jaw.  

Other structural adaptations protect animals in extreme temperatures. An emperor penguin  has a thick coat of fat under their skin called blubber to trap heat from leaving their bodies. In  addition to having blubber, penguins have other adaptations that prevent their bodies from losing too  much heat. This helps the penguin keep a normal body temperature. Humans also have a normal  body temperature. A normal body temperature for humans is 98.6℉ or 37℃. This is necessary for  survival, just like penguins. Their normal body temperature is 40℃. Since their feet are exposed to  the elements quite often, they cannot be covered with blubber or feathers to help them stay warm.  

A penguin’s feet also help walk around icy surfaces without slipping and when swimming. In  addition to having thick, windproof, or waterproof coats, emperor penguins have special nasal  passages that can recover heat loss through breathing in addition to their closely aligned veins and  arteries. All of these adaptations help emperor penguins retain heat in order to survive.  

Why don’t penguin’s feet freeze? Penguins’ feet can keep heat by not allowing blood to flow in  really cold weather. Their feet work like a heat exchange system; their blood vessels to and from their  feet are very thin and are twisted together. The blood is cooled that is moving away from their bodies  on the way to their feet and heated as it returns to their bodies. With this structural adaptation, their  feet get cool blood so they lose less heat allowing their bodies to stay warm. This special ability helps  penguins to keep their eggs warm until they are ready to hatch.  

Emperor penguins also have short stiff tails that allow them to learn backwards and balance  on their heels and their tail. This also helps the penguin reduce heat loss from their feet when on the  ground. Another physical adaptation that emperor penguins have is the color of their bodies. This  helps them camouflage when swimming because from above their dark backs blend in with the ocean  and from below, blending in with the sky. 

Behavioral adaptations are adjustments to an organism's behavior. For example, gray wolves  hunt in groups in order to take down prey much larger than if they traveled alone. Within a group  gray wolves come together for protection and they will always benefit from collaborating with one  another which helps form loyalty to one another in the pack. Some behavioral adaptations can help  animals survive seasonal climate changes.  

Emperor penguins also adapt behaviorally to their environment. Penguins in Antarctica form  large huddles to share body warmth, and as a shelter against the harsh winds. When in a huddle  emperor penguins will constantly move so that all the penguins can have a turn in the middle. This  behavioral adaptation can reduce heat loss by up to 50%. Emperor penguins also breed in the winter  so that their offspring can be independent during the summer when there is more food to catch.  

Another behavioral adaptation of the emperor penguin is their migration patterns. They make  yearly travels which bring them inland to breed in March. When summer begins the emperor penguin  and their young return to the sea to feed.

• Ask each student to provide specific feedback to peers. 

• Provide explanation rubrics for each peer review and describe how to evaluate an explanation using it. 

• Coordinate students sharing written explanations and feedback. Pair students, provide 15 minutes to read and provide feedback, and meet to discuss each other’s work. Then move to the second pairing if time. 

• Provide time for students to evaluate peer feedback and choose what to change in their second draft. 

• Prompt: Three things I plan to change are… 

• Students will have all of the public records to reference and will have the remainder of class period to work on a second draft of written explanation to turn in.