Rationale
Environmental Science Class
We are nearing the end of our unit on population: I have displayed a slide with a graph of the world’s population growth from the late 18th century to the present. I point to the exponential curve and the projected 7 billion people and warn the class, “We are placing great stresses on the earth’s ecosystem… the world’s nations have too many people”. The next graph shows the relative contributions of developed and developing nations to our growing population. Poorer developing nations are experiencing rapid growth, while higher income developed countries have little growth while the population in a few countries is actually contracting. Some students immediately object to the inequity. Is it fair that countries with more resources have less people, while those with more people have to survive with less? Why can some countries control their population while others cannot? Is this why poorer countries have so many diseases and wars? What does economics have to do with this? A great debate ensues. As students propose answers, other questions arise. Malala Yousafzai, the young Nobel laureate, had recently met with girls from our school. They remember that she told them that not all women in her culture have access to education: the conversation moves to issues of women’s rights in developing countries. Do they want to have so many children? Do women have a voice in the matter? Do some countries force people NOT to have children? Do people’s culture or religion influence them? The discussion goes on for almost an hour: we are still “arguing” when the bell rings signaling the end of the period.
This was an excellent science class: not only did my students understand the data presented to them, but they were able to formulate and answer a series of highly provocative questions about the social, cultural, and political implications hidden in the data. Their insights and perspectives were critical, informed, and complex. The nature of the discussion allowed them to engage in their learning in ways that were meaningful, personally relevant, and educative.
I begin my curriculum unit with this vignette from my environmental science class as it exemplifies the kind of learning environment that allows students to maximize their learning potential. It is the kind of atmosphere I hope to create for this unit.
I teach at the Philadelphia High School for Girls, an all girls’ public high school in the northeast section of Philadelphia. Our students are selected from all of Philadelphia’s neighborhoods thus we have a relatively diverse student body. The total population is nearly 1300, of which 66% are African American, 17% Asian; 10% Latino; 5% White with an approximately 2% mixture of African, and Caribbean. Students attending our school must have a minimum of a 3.5 GPA, and have advanced or proficient scores in state standardized assessments.
While most students can perform well on assessments that rely on the recall of content knowledge, many struggle with academic tasks that require them to analyze data, criticize an opinion, or form an argument supported by evidence. Although test scores suggest that they “know” the science content many do not connect the classroom content to larger societal issues that affect their everyday lives. Neither do they use their science knowledge to inform perspectives and decisions that affect their health and well-being.
The Common Core Science Literacy Standards (Common Core Initiative), that inform this unit suggest that teachers regularly provide opportunities for students to evaluate the science that informs topical social and cultural issues, engage in substantive discussions that explore the impact of science on society, and take critical stances on the science - technology that informs and continually transforms their lives (Bucher and Manning). Engaging in these discursive practices fosters a deep understanding of science content, as it requires students to use their knowledge in ways that are personally relevant, meaningful, and educative. The vignette that opens this unit exemplifies this kind of learning.
The guiding principle of my environmental science curriculum is the belief that we all have a responsibility to engage in and promote practices that protect the viability of ecosystems throughout the world: all life on our planet is interconnected and interdependent. An underlying theme in our curriculum is that human activities that pollute our environment threaten the viability of organisms living in various ecosystems. In the past, as we explored the effects of pollutants on living organisms, I realized that although I knew the general effects of environmental toxins on other species, my understanding of how pollution affects human health was limited. This deficiency in my content knowledge limited my ability to engage my students in the kinds of critical discussions I feel are important in my science classrooms. As I struggled with the content, I came to the realization that in order to fully challenge my students, I needed to learn more about the processes that affect human health.
Our health depends on an array of chemical reactions, physiological systems, and cellular processes that help maintain a relatively constant internal environment. These internal processes are primarily dependent on our genetic makeup (our genotype) as all of the requisite information for the proper functioning of our bodily systems is encoded in our DNA. Our health is however not solely dependant on our genetic makeup as there are countless pathogens and toxic substances in our environment that can occasion serious disease. Thus our health depends on the interaction of our genotype with the environments in which we live.
The study of one’s personal health however requires a global perspective as our local environments are interconnected with ecosystems throughout the world. Recent climatic changes, the outbreaks and transmission of lethal diseases, and the continuing evolution of new pathogens that emerge anywhere on the planet, provide evidence for the interdependent nature of our health today. Thus, in order to fully understand our personal health; we must analyze it from a global perspective.
Global Determinants of Health
Analysis of the global burden of disease data (Sepulveda and Murray) revealed that the effect of the environment on human health differs according to a nation’s degree of economic development. Data from the 194 member states that comprise the World Health Organization showed that communicable (neo-natal, maternal, and childhood) diseases were the primary causes of death in lower income developing nations, while in higher income developed nations, non-communicable diseases occasioned the most deaths (World Health Organization-a; World Health Organization).
The high rates of communicable diseases in developing nations results from the lack of infrastructures that provide clean water and sanitation. The poverty of these nations also limits their ability to provide adequate health care for its citizens: thus pathogens in the environment occasion most deaths. Such is not the case in developed nations with robust economies that can provide advanced health care and a “relatively” pathogen free environment. In these economies, ischemic heart disease and cancers, (which are diseases that arise later in life, but are also linked to environmental causes), are the predominant causes of death.
Unit Goals
This unit will provide students the opportunity to analyze the effects of environmental toxins and pathogens on human health. We will analyze these effects at the cellular level because that is where diseases ultimately originate (Robbins & Coltran). Cancer, for example, results from the complex interaction of cancer genes and aberrant cells; obligate pathogens (either DNA or RNA viruses) rely on the cell’s genetic processes to replicate themselves. Pathogens will often alter their genetic code to mask their appearance, or change their surface proteins in order to evade host’s immune responses. Thus a central goal of this unit will be to analyze the genetic and cellular components of health and disease
Data on global disease burdens show a strong correlation between a nation’s degree of economic development and the health of its citizens (World Health Organization). I will engage the class in the analysis of health statistics from the World Health Organization’s 2015 report on global health (WHOb). The intent of these lessons is to encourage a critical debate as to why some countries have such poor infrastructures and why health varies with demographic variables such as race, gender, and degree of economic development. It is my hope that these investigations will foster a critical awareness of how the environment affects human health.
Context of Unit within the Environmental Science Curriculum
My units on air, water, and soil contamination end with a study of population dynamics as increased human population exacerbates the effects of pollutants on our ecosystems.
We use the demographic transition model (Scruggs), to evaluate how population growth varies with degree of economic development. Developed nations (with more progressive social perspectives) have stable or declining birth rates: developing nations (with more rigid beliefs) have exponentially increasing populations. Central to this analysis is the discussion of a society’s social, cultural, and religious perspectives since these beliefs affect how a society modulates its birth rate and hence its population. Economic development also determines a nation’s ability to provide adequate health care, clean water, and a pathogen / toxin free environment. These differing realities provide a perfect forum in which to explore how environmental factors affect health and disease burdens in developing and developed nations.
Although students in my environmental science class have already completed a year of biology, I will review the concepts of DNA, RNA, the genetic code and protein synthesis as these topics are central to understanding the ways in which pathogenic microbes, and cancer cells proliferate and cause disease. The unit will unfold in two distinct phases.
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