Intro to Environmental Science Unit 3 Review: Ecology and Ecosystem Dynamics

Key Concepts and Definitions

• Ecology studies the interactions between organisms and their environment, including both biotic (living) and abiotic (non-living) factors
• Ecosystems are communities of living organisms interacting with each other and their physical environment
• Biotic factors include all living components of an ecosystem (plants, animals, microorganisms)
• Abiotic factors encompass non-living components (temperature, water, sunlight, soil, nutrients)
• Biodiversity refers to the variety of life forms within an ecosystem, including genetic diversity, species diversity, and ecosystem diversity
• Trophic levels describe the feeding positions in a food chain (producers, primary consumers, secondary consumers, tertiary consumers)
• Ecological niche is the role and position a species has in its environment, considering factors such as food, habitat, and behavior
• Carrying capacity is the maximum population size an ecosystem can sustain given available resources

Ecosystem Components and Structure

• Ecosystems are composed of both biotic and abiotic components that interact with each other
• Producers (autotrophs) are organisms that convert light energy or chemical energy into organic compounds through photosynthesis or chemosynthesis
  • Examples of producers include plants, algae, and some bacteria
• Consumers (heterotrophs) are organisms that obtain energy by feeding on other organisms
  • Primary consumers (herbivores) feed on producers (rabbits, caterpillars)
  • Secondary consumers (carnivores) feed on primary consumers (snakes, birds)
  • Tertiary consumers (top predators) feed on secondary consumers (eagles, wolves)
• Decomposers break down dead organic matter, releasing nutrients back into the ecosystem (fungi, bacteria)
• Food chains represent the linear transfer of energy from producers to consumers
• Food webs illustrate the complex feeding relationships within an ecosystem, showing multiple food chains interconnected

Energy Flow and Nutrient Cycling

• Energy flows through ecosystems in a unidirectional manner, from the sun to producers, then to consumers and decomposers
• Only about 10% of energy is transferred from one trophic level to the next, with the remaining energy lost as heat or used for metabolic processes
• The amount of energy transferred decreases at each trophic level, resulting in an energy pyramid
• Nutrients cycle through ecosystems, being used and reused by different organisms
• The water cycle (hydrologic cycle) involves the continuous movement of water through evaporation, transpiration, condensation, precipitation, and runoff
• The carbon cycle includes the exchange of carbon among the atmosphere, oceans, and living organisms through processes like photosynthesis, respiration, and decomposition
• The nitrogen cycle involves the transformation of nitrogen through fixation, nitrification, denitrification, and ammonification

Population Dynamics and Interactions

• Populations are groups of individuals of the same species living in a particular area
• Population growth is influenced by factors such as birth rate, death rate, immigration, and emigration
• Exponential growth occurs when a population increases at a constant rate, resulting in a J-shaped curve
• Logistic growth occurs when a population's growth slows down as it approaches the carrying capacity, resulting in an S-shaped curve
• Intraspecific competition occurs between individuals of the same species for resources (food, space, mates)
• Interspecific competition occurs between individuals of different species for shared resources
• Predation is an interaction where one organism (predator) feeds on another organism (prey)
• Symbiosis is a close and long-term interaction between two different species
  • Mutualism is a symbiotic relationship in which both species benefit (bees pollinating flowers)
  • Commensalism is a symbiotic relationship in which one species benefits while the other is unaffected (barnacles on whales)
  • Parasitism is a symbiotic relationship in which one species (parasite) benefits at the expense of the other (host)

Biodiversity and Species Relationships

• Biodiversity is essential for ecosystem stability, resilience, and functioning
• Species richness refers to the number of different species present in an ecosystem
• Species evenness describes the relative abundance of each species within an ecosystem
• Keystone species have a disproportionately large impact on the ecosystem relative to their abundance (sea otters in kelp forests)
• Foundation species play a critical role in creating and maintaining habitats for other species (corals in coral reefs)
• Indicator species are sensitive to environmental changes and can be used to assess ecosystem health (lichens as indicators of air quality)
• Invasive species are non-native organisms that cause harm to ecosystems by outcompeting native species and altering habitats (kudzu in the southeastern United States)
• Endangered species are at risk of extinction due to factors such as habitat loss, overexploitation, or climate change (black rhinoceros)

Ecological Succession and Disturbances

• Ecological succession is the gradual process of change in species composition over time
• Primary succession occurs in areas where no soil or vegetation previously existed, such as newly formed volcanic islands or glacial moraines
  • Pioneer species are the first organisms to colonize a newly exposed area (lichens, mosses)
• Secondary succession occurs in areas where an existing ecosystem has been disturbed, such as after a wildfire or abandoned agricultural land
• Climax community is the final, relatively stable stage of succession, characterized by long-lived species and complex interactions
• Disturbances are events that disrupt ecosystems, such as fires, hurricanes, or human activities
• Intermediate disturbance hypothesis suggests that moderate levels of disturbance can promote higher biodiversity by creating a mosaic of habitats in different successional stages
• Resilience is the ability of an ecosystem to recover from disturbances and maintain its basic structure and function

Human Impacts on Ecosystems

• Habitat destruction is the primary cause of biodiversity loss, resulting from activities such as deforestation, urbanization, and agriculture
• Pollution affects ecosystems through the release of harmful substances into the air, water, or soil (pesticides, plastic waste)
• Overexploitation occurs when resources are harvested faster than they can be replenished (overfishing, poaching)
• Climate change, driven by human activities that increase greenhouse gas emissions, alters temperature, precipitation patterns, and sea levels, impacting species distributions and ecosystem functioning
• Invasive species, often introduced by human activities (ballast water, pet trade), can disrupt ecosystems by outcompeting native species and altering food webs
• Habitat fragmentation divides contiguous habitats into smaller, isolated patches, reducing connectivity and biodiversity
• Ecological restoration aims to assist the recovery of degraded or destroyed ecosystems (reforestation, wetland restoration)
• Sustainable resource management involves using resources in a way that meets current needs without compromising the ability of future generations to meet their needs (sustainable forestry, fisheries management)

Applications and Case Studies

• The Yellowstone wolf reintroduction in 1995 demonstrated the importance of keystone species in shaping ecosystems through trophic cascades
• The Great Barrier Reef is a prime example of a complex ecosystem with high biodiversity, facing threats from climate change, ocean acidification, and pollution
• The Hubbard Brook Experimental Forest has provided valuable insights into nutrient cycling and the effects of disturbances on forest ecosystems
• The Serengeti ecosystem in Tanzania illustrates the intricate relationships between species, such as the migration of wildebeest and the predator-prey dynamics with lions and hyenas
• The Chesapeake Bay watershed restoration efforts showcase the challenges and importance of managing ecosystems across multiple jurisdictions and stakeholders
• The Biosphere 2 project in Arizona aimed to create a self-sustaining closed ecosystem, providing lessons on the complexity of ecological interactions and the difficulties in replicating Earth's ecosystems
• The Mangrove restoration projects in Southeast Asia highlight the importance of these ecosystems for coastal protection, biodiversity, and carbon sequestration
• The Yellowstone to Yukon Conservation Initiative (Y2Y) is a transboundary effort to maintain ecological connectivity and protect biodiversity across the Rocky Mountains