Biochemical Systems
About this free Biochemical Systems course
Biochemical Systems is a free Earth science course on biogeochemical cycles, the ways Earth recycles vital elements like water, carbon, nitrogen, phosphorus, and sulfur through the atmosphere, land, oceans, and living things.
You'll explore how these cycles sustain ecosystems, power life processes, and connect all parts of the planet. You'll also learn how energy flows through food webs and how natural cycles stay in balance. Finally, you'll see how human activities such as farming, industry, and fossil fuel use can disrupt these systems and affect climate, biodiversity, and environmental health. Each lesson ends with key takeaways for quick review.
Who this course is for
The course is designed for students in grades 7 through 10 studying Earth science, environmental science, or biology. No prior coursework is required.
Course outline
- Earth as a system. The atmosphere, hydrosphere, geosphere, and biosphere, open vs. closed systems, feedback, and the law of conservation of mass.
- The water cycle. Phase changes and energy, infiltration, groundwater, and human impact on water supplies.
- The carbon cycle. Carbon reservoirs, sources and sinks, sequestration, and human impact on climate.
- The nitrogen cycle. Nitrogen fixation, the organisms that drive it, and the effects of fertilizers.
- The phosphorus and sulfur cycles. How these elements move through rock, soil, and water, and how humans affect them.
- Energy in ecosystems. Energy transfer, trophic levels, pollutants, and their solutions.
- Climate change and systems thinking. Causes and consequences of climate change, feedback loops, and human impact solutions.
What you'll learn
- Describe Earth's four spheres and how they interact
- Trace water, carbon, nitrogen, phosphorus, and sulfur through their cycles
- Explain carbon sources, sinks, and sequestration
- Explain why energy decreases at each trophic level
- Evaluate how human activities disrupt cycles and propose solutions
How long it takes
Plan on about 10 hours, or roughly 90 minutes per module, including the key takeaways review at the end of each lesson.
Frequently asked questions about Biochemical Systems
Is Biochemical Systems really free?
Yes. Biochemical Systems is completely free, with no fees, subscriptions, or account required. STEM for Others is a 501(c)(3) nonprofit, and every course in our curriculum library is free for students, families, and teachers.
What is a biogeochemical cycle?
A biogeochemical cycle is the path an element or compound takes as it moves between living things (bio), rocks and soil (geo), and the air and water (chemical). The water, carbon, and nitrogen cycles are the best-known examples.
How do I start the course?
Click Begin Course at the top of this page to open the full slide deck in a new tab. You can also flip through the slides embedded above. Work through one unit at a time and try the practice questions before moving on.
Do I get a certificate?
The self-paced Biochemical Systems materials don't include an official certificate. If you're taking the course through a STEM for Others chapter program, ask your chapter leader about recognizing your completion.
Can teachers and clubs use this curriculum?
Yes. Teachers, homeschool families, libraries, and after-school clubs are welcome to use the Biochemical Systems materials with their students at no cost. STEM for Others volunteers also teach our curriculum in partner schools and libraries. You can find a chapter near you or start one at your school.
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