🦉Intro to Ecology Unit 1 – Introduction to Ecology and the Biosphere

Key Concepts and Definitions

• Ecology studies the interactions between organisms and their environment at various levels of organization
• Biosphere encompasses all living organisms on Earth and the environments they inhabit
• Ecosystems consist of communities of organisms interacting with each other and their physical environment
• Habitat refers to the specific environment where an organism lives and obtains resources for survival
• Niche describes an organism's role within an ecosystem, including its interactions with other species and its use of resources
  • Fundamental niche represents the full range of environmental conditions an organism can potentially occupy
  • Realized niche is the actual niche an organism occupies due to biotic interactions and resource limitations
• Biodiversity measures the variety of life at different levels, including genetic diversity, species diversity, and ecosystem diversity

Levels of Ecological Organization

• Ecology can be studied at various levels of organization, from individual organisms to the entire biosphere
• Organisms are individual living entities that belong to a particular species
• Populations consist of individuals of the same species living in a specific area at a given time
• Communities are assemblages of different populations that interact with each other within a shared environment
• Ecosystems encompass both the biotic communities and the abiotic components of an environment, such as soil, water, and climate
• Biomes are large-scale ecosystems characterized by distinct plant and animal communities adapted to specific climatic conditions (tropical rainforests, deserts)
• The biosphere is the global sum of all ecosystems on Earth, including all living organisms and their environments

Biotic and Abiotic Factors

• Biotic factors are the living components of an ecosystem, including all organisms and their interactions
  • Producers (plants) convert solar energy into chemical energy through photosynthesis
  • Consumers (animals) obtain energy by feeding on other organisms
  • Decomposers (bacteria, fungi) break down dead organic matter and recycle nutrients back into the ecosystem
• Abiotic factors are the non-living components of an ecosystem that influence the distribution and abundance of organisms
  • Climate factors include temperature, precipitation, humidity, and wind patterns
  • Soil properties such as texture, pH, and nutrient content affect plant growth and ecosystem productivity
  • Water availability and quality are critical for sustaining life in aquatic and terrestrial ecosystems
  • Topography and elevation influence microclimates and species distribution
• Biotic and abiotic factors interact to shape the structure and function of ecosystems

Energy Flow and Nutrient Cycling

• Energy flows through ecosystems in a unidirectional manner, from producers to consumers and eventually dissipating as heat
• Trophic levels describe the position of organisms within a food chain or food web based on their energy source
  • Primary producers (plants) form the base of the trophic pyramid
  • Primary consumers (herbivores) feed on producers
  • Secondary consumers (carnivores) feed on primary consumers
  • Tertiary consumers (top predators) feed on secondary consumers
• Energy transfer between trophic levels is inefficient, with only about 10% of energy passed on to the next level
• Nutrients cycle through ecosystems in biogeochemical cycles, moving between biotic and abiotic components
  • Carbon cycle involves the exchange of carbon between the atmosphere, oceans, and living organisms through processes like photosynthesis and respiration
  • Nitrogen cycle includes nitrogen fixation, nitrification, and denitrification, which convert atmospheric nitrogen into forms usable by plants and animals
  • Phosphorus cycle is a sedimentary cycle, with phosphorus moving from rocks to soil to living organisms and back to sediments

Ecosystems and Biomes

• Ecosystems are dynamic systems that exhibit spatial and temporal variability in their structure and function
• Ecosystem boundaries are often defined by physical features (watersheds, mountain ranges) or by the extent of biotic interactions
• Ecosystem services are the benefits that humans derive from ecosystems, such as food production, water purification, and climate regulation
• Biomes are large-scale ecosystems characterized by distinct plant and animal communities adapted to specific climatic conditions
  • Terrestrial biomes include tundra, boreal forest, temperate forest, tropical rainforest, grassland, desert, and savanna
  • Aquatic biomes include freshwater (lakes, rivers, wetlands) and marine (oceans, coral reefs, estuaries) ecosystems
• Biome distribution is primarily determined by temperature and precipitation patterns, which influence the dominant vegetation types
• Ecotones are transitional zones between adjacent biomes or ecosystems, often exhibiting high species diversity

Ecological Interactions

• Species interactions shape the structure and dynamics of ecological communities
• Competition occurs when two or more species vie for limited resources, leading to reduced fitness for one or both species
  • Intraspecific competition involves individuals of the same species competing for resources
  • Interspecific competition involves different species competing for shared resources
• Predation is an interaction where one species (predator) feeds on another species (prey), affecting population dynamics and community structure
• Herbivory is a type of predation where animals feed on plants, influencing plant growth, reproduction, and evolution
• Mutualism is a symbiotic relationship in which both species benefit from the interaction (pollination, nitrogen fixation in legume-rhizobia associations)
• Commensalism is an interaction where one species benefits while the other is unaffected (epiphytes growing on trees)
• Parasitism involves one species (parasite) living on or within another species (host), causing harm to the host

Human Impact on Ecosystems

• Human activities have significant impacts on ecosystems at local, regional, and global scales
• Habitat loss and fragmentation due to land-use change (deforestation, urbanization) are major threats to biodiversity
• Overexploitation of natural resources (overfishing, overhunting) can lead to population declines and ecosystem imbalances
• Pollution (air, water, soil) can disrupt ecosystem processes and harm living organisms
  • Eutrophication is the excessive growth of algae in aquatic ecosystems due to nutrient pollution, leading to oxygen depletion and fish kills
• Invasive species introduced by humans can outcompete native species and alter ecosystem dynamics (kudzu in the southeastern United States)
• Climate change driven by anthropogenic greenhouse gas emissions is causing shifts in species distributions, phenology, and ecosystem functioning
• Ecosystem management and conservation efforts aim to mitigate human impacts and promote sustainable use of natural resources

Research Methods in Ecology

• Observational studies involve collecting data on organisms and their environment without manipulating variables
  • Field surveys and inventories provide baseline data on species presence, abundance, and distribution
  • Long-term ecological monitoring tracks changes in ecosystems over time
• Experimental studies involve manipulating one or more variables to test hypotheses about ecological processes
  • Field experiments are conducted in natural settings to investigate species interactions, ecosystem functions, or responses to environmental changes
  • Mesocosm experiments use enclosed outdoor systems to simulate natural conditions under controlled settings
  • Laboratory experiments allow for precise control of variables but may have limited applicability to real-world ecosystems
• Modeling is used to simulate ecological processes, predict outcomes, and guide management decisions
  • Mathematical models use equations to describe relationships between variables and project future scenarios
  • Spatial models incorporate geographic information to analyze patterns and processes across landscapes
• Stable isotope analysis can trace the flow of energy and nutrients through food webs by measuring the ratios of isotopes in tissues
• Remote sensing techniques (satellite imagery, aerial photography) provide large-scale data on land cover, vegetation dynamics, and ecosystem health