Think Globally, Act LocallyThe lab activity described here was adapted by Erin Bardar of TERC for the EarthLabs project.
Summary and Learning Objectives
Students are introduced to four major components of the Earth system: the atmosphere, hydrosphere, biosphere, and pedosphere. They start to apply this knowledge as they visit the local study site to identify elements of these four spheres and infer connections among them. The investigation concludes with students making predictions about ways that a change in the characteristics of one component of their study site might affect the characteristics of other components.
After completing this investigation, students will be able to:
- identify the four major components of the Earth system (atmosphere, hydrosphere, biosphere, and pedosphere), and give examples from their local study site;
- infer connections among elements of the atmosphere, hydrosphere, biosphere, and pedosphere by describing connections at their local study site; and
- predict some ways that changes in one element of the study site might affect changes in other elements.
Activity Overview and Teaching Materials
In Part A: Students are introduced to four major components of the Earth system and some of the ways in which they shape the planet and its environment.
In Part B: Students visit the study site where they take photographs to document the site, identify components and elements of the Earth system, and then describe some of the ways in which the elements and components of the Earth system are interconnected. Bring a digital camera for documenting the study site. Also consider bringing gloves and/or hand-washing supplies for students who may wish to get their hands dirty while exploring the local study site.
In Part C: Students strengthen their developing sense of the interconnectedness of elements and components of the Earth system by predicting how changes in one element or component would affect others (e.g., How would a change in water level affect plants and animals at the site?).
For more information about the Earth system, read the section titled Background Information under Additional Resources below
Printable MaterialsTo download one of the PDF or Word files below, right-click (control-click on a Mac) the link and choose "Save File As" or "Save Link As."
- Local Study Site Work Sheet (Acrobat (PDF) 73kB Sep13 10)
- Stop and Think Questions (PDF (Acrobat (PDF) 37kB Jun11 10) and Word (Microsoft Word 2007 (.docx) 20kB Aug7 18)
Teaching Notes and Tips
In Part A:
- You may want to introduce the hydrosphere first, since it's likely that students have some level of understanding about the water cycle and may be able to identify most of the elements of the hydrosphere.
In Part B:
- Students visit the local study site to start to apply their new knowledge about the components of the Earth system and the way in which those components interact. Ask them to explain their reasoning for each statement they make. If it is not possible for students to complete all of their observations while at the study site, be sure they document the study site with photographs. Students can then continue their observations after they return to the classroom, using the photographs. Digital photos can be viewed on a computer or printed and distributed to students.
- As students describe the interconnections, have them do so using phrases or short sentences such as, "Water evaporates from the stream," or "Heat from the soil warms the air."
In Part C:
- A key point for students to understand is that while interactions between the elements are an essential part of maintaining an ecosystem, those same interactions can also lead to change in an ecosystem. For example, when one flux changes in any significant way, it will set off a chain reaction that changes reservoirs, fluxes, and interactions in the greater environment.
- Encourage students to consider changes that may occur that are two, three, or more steps past the original cause. (A change in "A" causes changes in "B", which causes changes in "C", which causes changes in "D". In each case, ask students to explain their reasoning behind their statements.
Review students' lists describing the interconnectedness between and among components of the Earth system. Have they explained their reasoning?
You can assess student understanding of topics addressed in this Investigation by grading their responses to the Stop and Think questions.
State and National Science Teaching Standards
The Earth System
What is a system? A system is generally described as a set of components that interact within a boundary. A clock is a good example of a system. Mechanical and often electrical components work together to display the time. In recent years, scientists have started to consider Earth, from the very top of the atmosphere to the core at its center, as a system with four major components or spheres that interact in very complex ways. Those spheres include:
- The geosphere (sometimes called the lithosphere) includes the solid part of Earth, the interior, and the pedosphere, which is the thin, outermost soil layer. NOTE: In this unit, we'll be concentrating only on the pedosphere.
- The hydrosphere is all of Earth's bodies of water, including groundwater and Earth's frozen water (the cryosphere).
- The biosphere is all living things, plants and animals, from microbes to humans.
- The atmosphere is the blanket of gas that surrounds Earth, and includes the precipitation, clouds, and aerosols (tiny suspended particles) that are found in air.
In this curriculum unit, the focus is on spheres that are most accessible to most students: the portion of the geosphere called the pedosphere; the hydrosphere; the biosphere; and the atmosphere.
NOTE: The terms we will use as we describe the earth system are as follows:
- Each of the spheres (e.g., the biosphere) is a component of the Earth system. Sphere and component (of the Earth system) are used synonymously.
- Each sphere or component is made up of elements (e.g., a bird is an element of the biosphere; a pond is an element of the hydrosphere).
- The term chemical element is used whenever referring to an element in the periodic table (e.g., carbon)
The pedosphere (soil) covers approximately 10%* of Earth's surface and deeply affects every other part of the ecosystem. Soil holds air, water, heat, and nutrients and is the medium in which we grow food and fiber. Soil supports billions of plants, animals, and microorganisms, it filters water, and it facilitates the decomposition of wastes. *Some scientists also consider the sediments that lie below Earth's bodies of water as part of the pedosphere, so there is some debate over the exact figure for soil coverage.
The hydrosphere covers about 75% of Earth's surface, and includes all bodies of water (oceans, lakes, rivers, streams, groundwater) liquid and frozen, fresh and salt. The oceans help regulate climate by absorbing large amounts of solar energy, particularly near the equator, and circulating heat towards the poles. Water constantly circulates between the hydrosphere, the pedosphere, the biosphere, and the atmosphere.
The biosphere is intimately connected with and dependent on the other spheres. Through processes such as photosynthesis, respiration, decay, and human activity such as burning forests or fossil fuels, the biosphere continuously exchanges gases with the atmosphere. Human activities can also cause changes in land and water use. To the extent that the biosphere modifies the other components of the Earth system, it can also modify Earth's climate.
The atmosphere distributes rain and traps some of the heat radiated by Earth to help keep us warm. It also protects us from harmful solar radiation, and plays a role in driving ocean currents that redistribute Earth's heat. Atmospheric aerosols from both natural causes (sea salt, pollen) and human activity change the composition of the atmosphere.
At any moment in time, all matter and energy on Earth is part of one or more of these spheres, and across time, all of Earth's matter cycles through two or more of these spheres.
Interconnections and Processes
At the local level, there are many simple examples of the interconnections between components and elements of the Earth system. The roots of plants (biosphere) draw water and nutrients from the pedosphere, exchange oxygen and carbon dioxide with the atmosphere through the process of photosynthesis, and send water into the atmosphere through the process of transpiration. Plants also die and decompose to become part of the pedosphere. Water evaporates from rivers (hydrosphere) and the soil (pedosphere) to become part of the atmosphere. Oxygen in the atmosphere dissolves in a river (hydrosphere). Fish (biosphere) draw dissolved oxygen into their bodies from the hydrosphere.
There are also connections between elements within a component of the earth system. Birds eat plant seeds; flowers attract insects; rivers flow into lakes or oceans.
In addition to the exchanges of matter, the transfer of energy is a key process of the Earth system. The sun warms the pedosphere, which transfers its heat to the atmosphere; warmed air transfers heat to cooler land surfaces; evaporation from a lake (hydrosphere) transfers heat to the atmosphere; rivers and ocean currents redistribute heat energy; precipitation can warm or cool the pedosphere on which it falls.
Change Leads to Change
Because of the interconnectedness, changes in one sphere bring about changes in the others. Sometimes these changes are dramatic. Droughts (atmosphere) can cause severe changes in the hydrosphere, the biosphere, and the pedosphere. Frequently these changes are more subtle. Every rain changes the soil moisture and the amount of water in lakes and rivers. Increased water level in a lake has an impact on the plants and animals that inhabit the shoreline. An increase in air temperature decreases the amount of moisture in the pedosphere by increasing the rate of evaporation and the rate at which vegetation loses water (transpiration) to the atmosphere.
Much of this curriculum unit is drawn from the GLOBE program's "Earth as a System" unit. The 40-page Introduction to that unit provides extensive background information about the Earth system and can be downloaded using the link below.
To download the file, right-click (control-click on a Mac) the link and choose "Save File As" or "Save Link As."