Energy & Matter Exchange in the Biosphere
Ms. Terkper's Digital Classroom — Themes: Energy, Equilibrium, Matter & Systems
Focusing Questions
"How are carbon, oxygen, nitrogen and phosphorus cycled in the biosphere? How is the flow of energy balanced in the biosphere? How have human activities and technological advances affected the balance of energy and matter in the biosphere?"
General Outcomes
Key Concepts
Unit Overview
The constant flow of energy and cycling of matter in the biosphere leads to a balanced or steady state. This balance is achieved through biogeochemical cycles and the processes of photosynthesis and cellular respiration. The unit explores how various human activities have affected this balance.
Builds on Science 10 Unit D
This unit extends knowledge from Science 10's Energy Flow in Global Systems, diving deeper into the biochemical processes that drive energy transfer and matter cycling at the biosphere level.
Energy Flow Through the Biosphere
One-Way Energy Flow
Unlike matter, which is cycled continuously, energy flows in one direction through the biosphere. It enters as solar energy, is converted to chemical energy by producers, and is ultimately lost as heat at every trophic level. Energy is never recycled.
Chemosynthetic Ecosystems
Not all ecosystems depend on photosynthesis. Deep-sea hydrothermal vent ecosystems use chemosynthesis — bacteria oxidize inorganic compounds (H2S) to produce energy, supporting a complete food web without sunlight. This shows the biosphere can be powered by chemical energy too.
Photosynthesis & Respiration Equations
Prairie Food Web Explorer — Click an Organism
Grasses (Poaceae)
The foundation of the Alberta prairie ecosystem. Grasses capture solar energy through photosynthesis, converting CO2 and H2O into glucose. They are the primary energy entry point for the entire food web.
Why Does Energy Decrease?
At each trophic level, organisms use energy for metabolic processes (movement, growth, heat production, reproduction). Only the energy stored in new biomass is available to the next level. This is why food chains rarely exceed 4–5 levels.
Three Types of Ecological Pyramids
- Energy pyramid: Always decreases upward (kJ/m²/yr)
- Biomass pyramid: Usually decreases upward; exceptions in aquatic ecosystems (phytoplankton bloom)
- Numbers pyramid: Can invert (e.g., many parasites on one host; many insects on one tree)
Biogeochemical Cycles
Unlike energy, matter is continuously cycled through the biosphere. The same atoms have been used and reused for billions of years. The four major nutrient cycles are driven by biological, geological, and chemical processes, with water acting as the universal transport medium.
Water is essential to all biogeochemical cycles because of its unique chemical and physical properties.
- Universal solvent: Polar structure dissolves ions and organic molecules, allowing nutrients to be transported in solution through cells, soil, and water bodies
- Hydrogen bonding: Creates surface tension, capillary action (xylem), and high specific heat capacity; moderates climate
- Phase changes: Evaporation and condensation transfer enormous amounts of thermal energy globally
- Density anomaly: Ice is less dense than liquid water, so water bodies freeze from the top down, protecting aquatic life below
- Reactant in photosynthesis: H atoms from water are used to reduce CO2 to glucose
What Are Biogeochemical Cycles?
Biogeochemical cycles are the pathways through which chemical elements move between living (biotic) components and non-living (abiotic) components of the Earth. The "bio" refers to living organisms, "geo" refers to Earth's physical systems (atmosphere, hydrosphere, lithosphere), and "chemical" refers to the chemical transformations that occur.
There are two types: gaseous cycles (carbon, oxygen, nitrogen) where the atmosphere is the main reservoir, and sedimentary cycles (phosphorus) where the Earth's crust is the main reservoir.
Biosphere Equilibrium & Atmospheric Composition
The Biosphere as an Open System
The biosphere is an open system — it exchanges both energy and matter with space. Energy enters as solar radiation and leaves as infrared radiation. Matter cycles internally with minimal net loss or gain. This openness allows the biosphere to maintain a dynamic equilibrium.
Gas Exchange Equilibrium
Photosynthesis consumes CO2 and produces O2. Cellular respiration does the opposite. When these processes are in balance, atmospheric composition stays relatively stable. Human activities are disrupting this balance by adding CO2 faster than photosynthesis can remove it.
Current Atmosphere (~present day)
CO2 pre-industrial was ~0.028% (280 ppm). Now ~420 ppm due to fossil fuel combustion and deforestation.
Stromatolites — Evidence of Atmospheric Change
Closed System Comparison: Biosphere 2
In 1991, scientists sealed 8 people in Biosphere 2 in Arizona for 2 years, attempting to create a self-sustaining closed biosphere. CO2 unexpectedly rose and O2 fell due to decomposers in soil consuming oxygen faster than plants produced it — demonstrating how difficult it is to maintain gas exchange equilibrium in an artificial closed system. NASA uses this research for planning Mars habitats and space stations.
| Ecosystem | Net Primary Productivity (g C/m²/yr) | Total Global Contribution | Limiting Factor |
|---|---|---|---|
| Tropical Rain Forest | 900 | Highest; covers ~7% land area but contributes ~25% global NPP | Light in lower canopy |
| Temperate Deciduous Forest | 540 | Significant; seasonal growth limits annual output | Seasonality |
| Taiga (Boreal Forest) | 360 | Large area; lower intensity; Alberta's boreal forest is a major C sink | Cold temperature |
| Grassland / Savanna | 315 | Important globally; Alberta prairies | Water availability |
| Tundra | 65 | Very low; frozen soils and short growing season | Temperature, nutrients |
| Desert | 40 | Low; covers ~33% of land area but minimal NPP | Water |
| Open Ocean | 57 | Low intensity but enormous area; significant total contribution | Nutrients (N, P, Fe) |
| Coastal / Upwelling Zones | 360 | Highly productive due to nutrient upwelling | Nutrient cycling |
| Antarctic / Arctic Ocean | 55 | Nutrient-rich but cold; phytoplankton blooms in summer | Light, temperature |
Human Impacts on the Biosphere
- Fossil fuel combustion: Returns carbon stored for millions of years to the atmosphere as CO2 within decades
- Deforestation: Removes major CO2 sinks; releases stored carbon when forests are burned or decay
- Cement production: Releases CO2 from limestone (CaCO3 → CaO + CO2)
- Peatland drainage: Northern Alberta peatlands store millennia of carbon; drainage releases CH4 and CO2
- Synthetic fertilizers: Haber-Bosch process adds more fixed nitrogen to land than all natural biological fixation
- Feedlot operations: Concentrated animal waste overwhelms local nitrogen cycling capacity
- Vehicle emissions: NOx gases form acid deposition, disrupting soil and water N cycles
- Eutrophication: Excess N and P in runoff causes algal blooms, dead zones (e.g., Lac Ste. Anne, AB)
- Mining & processing: Sulfur released as SO2; forms sulfuric acid in atmosphere (acid rain)
- Sewage disposal: Phosphorus discharged to water bodies accelerates eutrophication
- Heavy metal bioaccumulation: Mercury, lead and cadmium accumulate through food chains (biomagnification) — 10× concentration at each level
- Persistent organic pollutants: PCBs, DDT bioaccumulate in fat tissue, most concentrated in top predators
- Ozone depletion: CFCs break down stratospheric O3, allowing UV-B radiation to increase surface levels
| Trophic Level | Example Organism | Approx. Mercury Concentration | Accumulation Factor |
|---|---|---|---|
| Water | H2O | 0.0001 ppm | Baseline |
| Producer | Phytoplankton | 0.001 ppm | 10× |
| Primary Consumer | Zooplankton | 0.01 ppm | 100× |
| Secondary Consumer | Small fish (perch) | 0.1 ppm | 1,000× |
| Tertiary Consumer | Large fish (pike, walleye) | 1 ppm | 10,000× |
| Quaternary Consumer | Bald eagle, osprey, humans | 10+ ppm | 100,000× |
Indigenous Knowledge & the Biosphere
Traditional Ecological Knowledge in Alberta
Alberta's First Nations, Métis and Inuit (FNMI) peoples have accumulated thousands of years of observation of ecological systems. Their Traditional Ecological Knowledge (TEK) reflects a deep, relational understanding of energy flow, matter cycling and ecosystem equilibrium — often reaching conclusions that parallel those of modern ecology.
Blackfoot Confederacy (Niitsitapi)
- The Blackfoot recognized the central role of the bison (iinnii) in structuring the prairie food web — a living understanding of trophic dynamics long before Western ecology formalized the concept.
- Controlled grassland burns were used to stimulate new plant growth, attract bison, and cycle nutrients back into the soil — a direct practical application of carbon and nutrient cycling principles.
- Detailed knowledge of seasonal plant phenology (which plants emerged when, and in which soil conditions) reflects deep understanding of nutrient availability in the carbon and nitrogen cycles.
- The concept of napi (the creative life force) reflects recognition of the interconnectedness of all biosphere components — energy and matter as part of a single living system.
- Bison pounds and cliff drives were managed to minimize waste — every part of the animal was used, reflecting an understanding of energy efficiency and matter recycling.
Cree Nation (nehiyawak)
- The Cree concept of miyo wîcêhtowin (good relations / interconnectedness) describes the web of relationships between all living and non-living components of the boreal ecosystem.
- Detailed knowledge of the beaver (amisk) as a keystone ecosystem engineer — beaver dams create wetlands that serve as major nitrogen and phosphorus cycling hubs, supporting biodiversity.
- Cree trappers maintained detailed oral records of population cycles (lynx-hare cycles, marten populations) spanning many generations — a form of long-term ecological monitoring equivalent to modern population biology data.
- Knowledge of medicinal plants linked ecosystem productivity (soil type, water availability, light conditions) to the chemical composition of plants — an understanding of nutrient cycling effects on biomass quality.
- Sacred water protocols: Water was treated as a living relative, with community responsibilities to maintain watershed health — reflecting understanding of water's role in all biogeochemical cycles.
Métis Nation of Alberta
- Deep knowledge of ecotones (forest-prairie transition zones) where ecological exchange is most active and biodiversity highest — areas where multiple biogeochemical cycles intersect.
- Traditional harvesting practices (game, fish, berries, medicines) were guided by observed carrying capacity and seasonal availability — demonstrating intuitive understanding of sustainable energy yield from ecosystems.
- Knowledge of indicator species: changes in the distribution or abundance of particular plants or animals were used to assess ecosystem health — functioning as informal ecological monitoring of cycle disruptions.
- Winter gardens and traditional food preservation (pemmican, dried fish) reflected understanding of energy storage and transfer in biological systems.
Athabasca Chipewyan & Dene Nations
- Multi-generational knowledge of Athabasca River and lake systems tracked water quality, fish populations and ice conditions — creating a continuous record of hydrologic cycle changes over centuries.
- Concerns about changes to the Athabasca watershed downstream of the oil sands represent community-based ecological monitoring grounded in TEK — reporting disruptions in the water, carbon and sulfur cycles.
- Caribou migration knowledge tracked herd movements linked to lichen availability (slow-growing N-fixing organisms critical to taiga nutrient cycling) — connecting energy flow to matter cycling at the ecosystem scale.
- Understanding of permafrost dynamics in northern Alberta — knowledge passed through generations about which areas remained frozen and when, now being validated by climate science as permafrost thaws.
Principles of Traditional Ecological Knowledge (TEK) and Their Connections to Biology 20 Unit A
TEK is grounded in long-term observation, relational thinking, and reciprocity with the natural world. These principles parallel the scientific methods and ecological concepts developed in this unit.
Controlled burns (Blackfoot, Cree, Anishinaabe) returned carbon and nutrients to soil, stimulating new growth — a practical application of the carbon cycle and carbon-nitrogen balance in soils.
The "Three Sisters" companion planting (corn, beans, squash) used by Plains peoples demonstrates knowledge of nitrogen fixation — beans fix atmospheric N2; corn and squash use it. An organic nitrogen management system.
Placing fish in garden beds (common among Plains and woodland peoples) returned phosphorus from aquatic ecosystems to terrestrial soils — deliberately connecting two ecosystem nutrient cycles.
Sacred water teachings emphasize water as the connector of all living things. Beaver dam protection practices maintained wetland systems that filter, cycle and store water — watershed stewardship grounded in observed water cycle dynamics.
Bison as a keystone species: Blackfoot management of bison herds maintained healthy grasslands that supported the full trophic cascade from producers through decomposers — an intuitive understanding of energy pyramid stability.
The principle of miyo wîcêhtowin (good relations) and the practice of taking only what is needed reflects understanding of sustainable yield and ecosystem equilibrium — avoiding overharvesting that disrupts population balance.
Interactive Practice & Review
Knowledge Check Quiz
Test your understanding of energy flow, matter cycling and biosphere equilibrium.
Bio 20 — Unit A
Cycle Process Match
Match each process on the left with the biogeochemical cycle it belongs to on the right.
Vocabulary Flashcards
Click card to flip. Navigate all 20 terms.