Ecosystem Energy and Matter Flow c4.2

Ecosystems as open systems

Systems where both energy and matter can enter and exit

Closed systems

Systems that only exchange energy across their boundary

Sunlight

Principal source of energy for most ecosystems

Photoautotrophic organisms

Organisms like green plants and some bacteria that use sunlight as an energy source

Chemoautotrophic bacteria

Bacteria in ecosystems like caves and hydrothermal vents that use energy from chemical processes

Trophic levels

Positions in a feeding sequence within an ecosystem

Food chains

Linear feeding relationships between species in a community

Food webs

Diagram showing complex feeding relationships in an ecosystem

Decomposers

Organisms essential for recycling matter in ecosystems

Autotrophs

Organisms that synthesize carbon compounds from inorganic substances using external energy sources

Heterotrophs

Organisms that obtain carbon compounds from other organisms for synthesis

Cell respiration

Process where energy is released by the oxidation of carbon compounds

Classification of organisms into trophic levels

Positioning organisms at their highest trophic level when constructing food webs to maintain arrow direction

Construction of energy pyramids

Graphical representation of energy at each trophic level in a food chain, expressed in energy per area per time units

Pyramid of energy

Graphical representation of energy at each trophic level in a food chain, measured in units like kJ m-2 year-1

Energy loss in food chains

Energy transformations are ~10% efficient, with about 90% of available energy lost between trophic levels

Biomass

Total mass of organisms, consisting of carbon compounds in cells and tissues, used to measure energy added to organisms

Heat loss in cell respiration

Heat loss to the environment in autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration

Energy losses in ecosystems

Energy and biomass decrease between trophic levels, limiting the number of trophic levels in ecosystems.

Higher trophic levels

Levels in a food chain that receive less energy and biomass, requiring larger quantities of food to obtain sufficient amounts.

Unviable trophic level

Occurs when the energy needed to hunt food surpasses the energy available from the food eaten.

Fossil Fuels

Organic compounds compacted underground for millions of years, resulting in coal, oil, and natural gas as non-renewable energy sources.

Keeling Curve

Continuous measurement of atmospheric CO2 concentrations since 1958 at Mauna Loa Observatory, showing annual fluctuations, increasing trends, and highest levels recorded.

Cell Respiration

Process involving breakdown of organic molecules to produce ATP, releasing carbon dioxide as a by-product, with removal facilitated by passive diffusion.

Compensation Point

Balance point in autotrophs where CO2 uptake by photosynthesis equals CO2 production by respiration, resulting in zero net carbon dioxide assimilation.

Nutrient Recycling

Constant recycling of chemical elements required by organisms like carbon, nitrogen, and phosphorus through autotrophs, heterotrophs, and saprotrophs in ecosystems.

Biogeochemical Cycle

Pathway of a chemical substance through Earth's biotic and abiotic spheres, such as the carbon cycle and other essential nutrient cycles.