Ecology Unit 3: The Biosphere as a Closed System

The Biosphere as a Closed System

• The biosphere is a closed system that contains life, surrounded by the lithosphere (land), hydrosphere (water), and atmosphere (air).
• The Earth is in a state of dynamic equilibrium, constantly changing but maintaining a steady state.

Biological Levels of Organization

• Biological levels of organization:
  1. Cell: the smallest functional unit of life
  2. Tissue: groups of cells with similar functions
  3. Organ: groups of tissues with similar functions
  4. Organ system: groups of organs with similar functions
  5. Organism: groups of organ systems that make up an organism
  6. Population: groups of organisms of the same species living in the same area
  7. Community: groups of different species living in the same area
  8. Ecosystem: a community and its physical and chemical components
  9. Biome: a large area with specific climate and organisms
  10. Biosphere: the narrow zone around the Earth with life

Biotic and Abiotic Relationships

• Types of relationships:
  1. Abiotic-abiotic: two non-living components
  2. Abiotic-biotic: one living, one non-living component
  3. Biotic-biotic: two living components (symbiotic relationships)
     • Parasitism (+/-): one benefits, one is harmed
     • Mutualism (+/+): both benefit
     • Commensalism (+/o): one benefits, one unaffected

Energy Flow in the Biosphere

• Solar radiation is the ultimate source of energy for the biosphere
• Energy flows from one trophic level to the next, with approximately 10% of energy transferred from one level to the next
• Trophic levels:
  1. Autotrophs (producers): obtain energy from sunlight or inorganic sources
  2. Heterotrophs (consumers): obtain energy by consuming other organisms
• Ecosystem structure:
  1. Producers (autotrophs)
  2. Primary consumers (herbivores)
  3. Secondary consumers (carnivores)
  4. Tertiary consumers (carnivores that eat other carnivores)

Ecological Pyramids

• Types of ecological pyramids:
  1. Pyramid of numbers: shows the number of organisms at each trophic level
  2. Pyramid of biomass: shows the total dry mass of organisms at each trophic level
  3. Pyramid of energy: shows the energy available at each trophic level
• Only 10% of energy is transferred from one trophic level to the next, resulting in a decrease in energy available at each level.

Human Interference with Energy Flow in Ecosystems

• Examples of human interference:
  1. Hunting and fishing: overhunting and overfishing can disrupt ecosystems
  2. Monocultures: cultivating single species can lead to ecosystem collapse
  3. Species reintroduction: reintroducing species can have unintended consequences
  4. Chemical use: pesticides and other chemicals can harm ecosystems

Practice Problems

• Answers to practice problems on topics such as trophic levels, food chains, energy flow, and ecological pyramids.### Energy Flow in Ecosystems
• Only 10% of energy available in a plant is transferred to a primary consumer, as the plant uses the rest for photosynthesis, growth, and reproduction.
• Using a pyramid of numbers to show energy flow has limitations, as it doesn't account for the varying sizes of organisms.

Omnivores and Energy Sources

• An omnivore would obtain more energy by consuming plants rather than animal tissue, as only 10% of energy is passed on to the next trophic level.

Cycling of Matter

• Biogeochemical cycles involve both biotic and abiotic components.
• The cycling of matter consists of two processes: digestion and decay.
• Decomposers break down organic matter, releasing nutrients back into the environment.

Properties of Water

• Water is essential for organisms due to its unique properties:
  • Absorbs and releases thermal energy, moderating temperature fluctuations.
  • Acts as a solvent, facilitating metabolic reactions.
  • Supplies hydrogen atoms to producers during photosynthesis and oxygen atoms to organisms during cellular respiration.

The Water Cycle

• Evaporation, condensation, precipitation, and groundwater flow are the main processes involved in the water cycle.
• Percolation, leaching, and transpiration also play important roles in the water cycle.

Carbon, Oxygen, and Nitrogen Cycles

• The carbon cycle involves the balance between photosynthesis and cellular respiration.
• Carbon is stored in the lithosphere (sedimentary rocks, fossil fuels), hydrosphere (dissolved in water), and atmosphere.
• Human activities, such as combustion of fossil fuels, deforestation, and livestock farming, contribute to an enhanced greenhouse effect.
• The nitrogen cycle involves nitrogen fixation, ammonification, nitrification, and denitrification.

Phosphorus Cycle

• Phosphorus is essential for ATP, bones, cell membranes, and DNA.
• Most phosphorus is stored in rocks, and it can take one of two paths: the fast track (dissolved phosphates in soil) or the slow track (phosphorus in ocean sediment).

Agriculture and Nutrient Cycles

• Harvesting crops removes nitrogen and phosphorus from the soil, interrupting natural cycles.
• Fertilizing soil with nitrogen and phosphorus can restore nutrients and increase food production.
• Excess fertilizers can contribute to eutrophication and algal blooms in freshwater ecosystems.

Additional Notes

• Climate change is enhanced by human activities, leading to an increase in global temperatures.
• The rate of global warming is concerning, and it requires collective efforts to slow it down.
• The albedo effect is affected by the Earth's surface, with white surfaces having a high albedo and black surfaces having a low albedo.
• Permafrost thawing in Alaska and changes in the Earth's atmosphere are related to global warming.
• Stromatolites, layered rocks containing fossils of ocean bacteria, have helped change the gases in our atmosphere, shifting from methane to oxygen over time.Here are the study notes in detailed bullet points:

Importance of Aerating Lawns

• Aerating lawns exposes denitrifying bacteria to oxygen, reducing the breakdown of nitrates to nitrogen
• This helps the soil retain nitrates that would otherwise be lost

Nitrogen and Phosphorus Cycling

• Nitrogen and phosphorus are essential nutrients for plants and animals
• Nitrogen and phosphorus cycles are linked to the water cycle
• Both are water-soluble, allowing them to be taken up by plant roots and enter the food chain
• Water also plays a role in leaching and dissolving phosphates out of rocks

Terrestrial Ecosystems in Alberta

• Four main biomes: tundra, taiga, temperate deciduous forest, and grassland
• Taiga (boreal forest) ecosystems:
  • Found in northern and central Alberta
  • Characterized by coniferous trees, cold winters, and short growing seasons
  • Canopy, forest floor, and understory habitats support different species
• Muskeg ecosystems:
  • Found in northern Alberta, characterized by permafrost and acidic soil
  • Slow decomposition, poor drainage, and low tree growth
• Grassland ecosystems:
  • Found in southern Alberta, characterized by nutrient-rich soil and diverse species
  • Limited biodiversity, dominated by grasses and grazers
• Deciduous forest ecosystems:
  • Found in central Alberta, characterized by mixed deciduous and coniferous trees
  • Rich soil, diverse species, and a mix of canopy, understory, and forest floor habitats

Changes to Terrestrial Ecosystems

• Human activities alter ecosystems:
  • Clear-cutting, prescribed burns, and succession
  • Changes to nutrient cycling, decomposition, and species diversity
• Forestry practices:
  • Slash and burn: clearing and burning to create agricultural land
  • Clear-cutting: removing all trees for timber, followed by replanting
  • Prescribed burns: controlled fires to promote grasslands and biodiversity
  • Succession: natural changes to ecosystems over time

Aquatic Ecosystems in Alberta

• Freshwater ecosystems: lakes, rivers, and wetlands
• Littoral zone: shallow water, plants, and high productivity
• Limnetic zone: open water, plankton, and photosynthesis
• Profundal zone: deep water, low oxygen, and decomposers
• Benthic zone: sediment and detritus, supporting decomposers and bottom-dwellers
• Eutrophication: nutrient-rich lakes with high productivity and low oxygen
• Pollution: sources include sewage, disease-causing organisms, dissolved minerals, and thermal energy

Indicators of Water Quality

• Bacteria count: measures water quality and potential health risks
• Dissolved oxygen: measures water quality and suitability for aquatic life
• Biological oxygen demand (BOD): measures oxygen consumed by decomposers

Key Terms

• Biotic potential: the maximum number of offspring a species can produce
• Limiting factors: abiotic or biotic factors that prevent population growth
• Density-independent limiting factors: factors that affect populations regardless of size
• Density-dependent limiting factors: factors that affect populations due to their size