🦉Intro to Ecology Unit 9 – Ecosystem Ecology

Key Concepts and Definitions

• Ecosystem consists of a community of organisms and their abiotic environment interacting as a functional unit
• Biotic factors include living organisms such as plants, animals, and microorganisms
• Abiotic factors encompass non-living components like sunlight, temperature, water, and soil
• Biogeochemical cycles involve the movement of essential nutrients through biotic and abiotic components of an ecosystem
• Trophic levels represent the position an organism occupies in a food chain based on its feeding relationships
  • Primary producers (autotrophs) convert solar energy into chemical energy through photosynthesis
  • Primary consumers (herbivores) feed on primary producers
  • Secondary consumers (carnivores) feed on primary consumers
  • Tertiary consumers (top predators) feed on secondary consumers
• Ecological efficiency measures the amount of energy transferred from one trophic level to the next

Ecosystem Components and Structure

• Ecosystems are composed of biotic and abiotic components that interact with each other
• Biotic components include producers (plants), consumers (animals), and decomposers (bacteria and fungi)
• Abiotic components consist of physical and chemical factors such as climate, soil, water, and nutrients
• Ecosystem structure refers to the arrangement and organization of biotic and abiotic components within an ecosystem
  • Vertical structure includes the layering of vegetation (canopy, understory, and forest floor in a forest ecosystem)
  • Horizontal structure encompasses the spatial distribution of organisms and resources across an ecosystem
• Habitat provides the necessary resources and conditions for an organism to survive and reproduce
• Niche refers to an organism's role and position within an ecosystem, including its interactions with other species and its use of resources

Energy Flow in Ecosystems

• Energy enters ecosystems through primary producers that capture solar energy via photosynthesis
• Energy is transferred from one trophic level to another through feeding relationships
• Only a small portion of energy (typically 10%) is transferred from one trophic level to the next due to energy loss through heat, respiration, and undigested material
• Gross primary productivity (GPP) represents the total amount of energy captured by primary producers through photosynthesis
• Net primary productivity (NPP) is the energy remaining in primary producers after accounting for their respiration ($NPP = GPP - Respiration$)
• Secondary productivity refers to the energy accumulated by consumers through feeding on other organisms
• Ecological efficiency decreases as energy moves up the trophic levels due to energy loss at each transfer

Nutrient Cycling

• Nutrient cycling involves the movement and exchange of essential nutrients between biotic and abiotic components of an ecosystem
• Carbon cycle encompasses the transfer of carbon through the atmosphere, oceans, and biosphere
  • Photosynthesis by primary producers removes carbon dioxide from the atmosphere and incorporates it into organic compounds
  • Respiration by organisms and decomposition release carbon dioxide back into the atmosphere
• Nitrogen cycle includes the processes of nitrogen fixation, nitrification, and denitrification
  • Nitrogen-fixing bacteria convert atmospheric nitrogen ($N_2$) into ammonia ($NH_3$), which plants can use
  • Nitrifying bacteria convert ammonia into nitrites ($NO_2^-$) and nitrates ($NO_3^-$)
  • Denitrifying bacteria convert nitrates back into atmospheric nitrogen
• Phosphorus cycle involves the weathering of rocks, uptake by organisms, and return to the environment through decomposition
• Water cycle (hydrologic cycle) encompasses the movement of water through evaporation, transpiration, precipitation, and runoff

Ecosystem Productivity

• Primary productivity refers to the rate at which primary producers convert solar energy into chemical energy through photosynthesis
• Gross primary productivity (GPP) represents the total amount of energy captured by primary producers
• Net primary productivity (NPP) is the energy remaining in primary producers after accounting for their respiration ($NPP = GPP - Respiration$)
• Secondary productivity refers to the rate at which consumers accumulate biomass through feeding on other organisms
• Ecosystem productivity is influenced by factors such as nutrient availability, water availability, temperature, and light intensity
• Ecosystems with high primary productivity (tropical rainforests, estuaries) support a greater diversity and biomass of organisms
• Ecosystems with low primary productivity (deserts, tundra) have lower species diversity and biomass

Trophic Levels and Food Webs

• Trophic levels represent the position an organism occupies in a food chain based on its feeding relationships
• Food chains depict the linear transfer of energy from primary producers to higher-level consumers
• Food webs illustrate the complex feeding relationships and energy flow among organisms in an ecosystem
• Autotrophs (primary producers) form the base of the trophic structure and convert solar energy into chemical energy
• Heterotrophs (consumers) obtain energy by feeding on other organisms
  • Herbivores (primary consumers) feed on plants
  • Carnivores (secondary and tertiary consumers) feed on other animals
  • Omnivores consume both plants and animals
• Decomposers (detritivores) break down dead organic matter and recycle nutrients back into the ecosystem
• Ecological pyramids represent the trophic structure and energy flow in an ecosystem
  • Pyramid of numbers shows the number of organisms at each trophic level
  • Pyramid of biomass illustrates the total biomass at each trophic level
  • Pyramid of energy depicts the energy flow through each trophic level

Human Impacts on Ecosystems

• Habitat destruction and fragmentation result from human activities such as deforestation, urbanization, and agriculture
• Pollution (air, water, soil) can disrupt ecosystem functions and harm organisms
  • Eutrophication occurs when excess nutrients (nitrogen and phosphorus) lead to algal blooms and oxygen depletion in aquatic ecosystems
  • Acid rain, caused by sulfur dioxide and nitrogen oxides emissions, can acidify soil and water bodies
• Overexploitation of natural resources (overfishing, overhunting) can lead to population declines and ecosystem imbalances
• Climate change, driven by anthropogenic greenhouse gas emissions, can alter temperature, precipitation patterns, and species distributions
• Invasive species, introduced by human activities, can outcompete native species and disrupt ecosystem balance
• Ecosystem restoration and conservation efforts aim to mitigate human impacts and protect biodiversity
  • Reforestation and afforestation involve planting trees to restore degraded forests
  • Marine protected areas (MPAs) safeguard marine ecosystems and their resources
  • Sustainable resource management practices balance human needs with ecosystem health

Practical Applications and Case Studies

• Bioremediation uses microorganisms to break down and remove pollutants from contaminated sites
  • Oil spills can be mitigated using oil-degrading bacteria
  • Phytoremediation employs plants to absorb and accumulate heavy metals from contaminated soils
• Agroecology applies ecological principles to design sustainable agricultural systems
  • Intercropping involves growing multiple crops together to enhance nutrient cycling and pest control
  • Agroforestry integrates trees with crops or livestock to improve soil fertility and biodiversity
• Ecosystem services are the benefits humans derive from ecosystems
  • Pollination by insects is crucial for crop production and food security
  • Wetlands provide water filtration, flood control, and habitat for diverse species
• Ecological restoration aims to restore degraded ecosystems to their natural state
  • Coral reef restoration involves transplanting coral fragments to damaged reefs
  • Prairie restoration requires planting native grasses and forbs and managing fire regimes
• Ecosystem-based management considers the entire ecosystem, including human activities, in decision-making processes
  • Marine spatial planning allocates ocean space for various uses while protecting important habitats
  • Integrated watershed management addresses land use, water quality, and ecosystem health at the watershed scale