Earth's biosphere is a complex web of life, intertwining ecosystems and biomes. From lush rainforests to barren deserts, each environment plays a crucial role in the planet's ecological balance. Understanding these systems is key to grasping Earth's physical geography.

Ecosystems and biomes showcase the intricate relationships between living organisms and their surroundings. By exploring their structure, function, and global distribution, we gain insights into how Earth's physical systems shape and are shaped by life on our planet.

Ecosystems and Biomes

Ecosystem Structure and Function

• Ecosystems form complex networks of living organisms interacting with their physical environment
• Key components include producers (autotrophs), consumers (heterotrophs), decomposers, and abiotic factors (soil, water, climate)
• Energy flows through trophic levels via food chains and food webs
  • Example: Grassland ecosystem - grass (producer) → grasshopper (primary consumer) → bird (secondary consumer)
• Nutrient cycling moves matter between biotic and abiotic components
  • Carbon cycle, nitrogen cycle, phosphorus cycle
• Ecological succession describes species composition changes over time
  • Primary succession (bare rock) → lichens → mosses → grasses → shrubs → trees
  • Secondary succession (disturbed area) → grasses → shrubs → pioneer tree species → climax forest

Biome Characteristics and Classification

• Biomes encompass large-scale ecological areas with distinct climate patterns and vegetation types
• Primarily defined by temperature, precipitation, and dominant plant life
• Terrestrial biomes include tundra, taiga, temperate forests, grasslands, tropical forests, deserts
• Aquatic biomes divided into freshwater (lakes, rivers) and marine (oceans, coral reefs) ecosystems
• Climate diagrams illustrate temperature and precipitation patterns for each biome
• Adaptations of organisms reflect the environmental conditions of their biome
  • Cacti in deserts have water-storing stems and reduced leaves
  • Deciduous trees in temperate forests shed leaves to conserve energy in winter

Terrestrial and Aquatic Biomes

Major Terrestrial Biomes

• Tundra characterized by extremely cold temperatures, low precipitation, permafrost
  • Vegetation includes mosses, lichens, sedges (Arctic tundra)
• Taiga (boreal forest) features long, cold winters and short, cool summers
  • Dominated by coniferous trees (spruce, fir, pine)
• Temperate deciduous forest experiences distinct seasons and moderate rainfall
  • Trees shed leaves annually (maple, oak, beech)
• Temperate grassland has hot summers, cold winters, and periodic drought
  • Grasses dominate, with few trees (prairies, steppes)
• Tropical rainforest maintains high temperatures and abundant rainfall year-round
  • Highest biodiversity of any terrestrial biome (Amazon, Congo Basin)
• Desert receives less than 25 cm of precipitation annually
  • Plants and animals adapted to water scarcity (cacti, camels)

Aquatic Biome Diversity

• Freshwater biomes include lakes, rivers, and wetlands
  • Lakes stratify into distinct thermal layers (epilimnion, thermocline, hypolimnion)
  • Rivers change characteristics from source to mouth (erosion, deposition)
• Marine biomes cover about 70% of Earth's surface
  • Influenced by salinity, temperature, light penetration, and ocean currents
  • Coral reefs support high biodiversity in warm, shallow waters
• Wetlands serve as transitional areas between terrestrial and aquatic ecosystems
  • Crucial for water filtration, flood control, and unique biodiversity
  • Types include marshes, swamps, and bogs

Biotic and Abiotic Interactions

Ecological Relationships and Niches

• Biotic factors encompass all living organisms in an ecosystem
• Abiotic factors include non-living components (temperature, soil, light)
• Ecological niche describes an organism's role and its response to resource distribution
  • Fundamental niche: potential range of conditions and resources an organism can use
  • Realized niche: actual conditions and resources used in the presence of competitors
• Limiting factors control organism growth, abundance, or distribution
  • Liebig's Law of the Minimum: growth is dictated by the scarcest resource
• Keystone species disproportionately affect ecosystem structure
  • Sea otters in kelp forests control sea urchin populations, protecting kelp

Environmental Influences on Ecosystems

• Biogeochemical cycles illustrate matter movement between ecosystem components
  • Water cycle: evaporation, condensation, precipitation, runoff, and transpiration
  • Carbon cycle: photosynthesis, respiration, decomposition, and fossil fuel combustion
• Climate shapes global biome distribution through temperature and precipitation patterns
  • Köppen climate classification system relates vegetation types to climate zones
• Soil composition and topography interact with biotic factors to determine vegetation
  • Soil pH affects nutrient availability for plants
  • Aspect (direction a slope faces) influences local temperature and moisture conditions

Human Impact on Ecosystems

Anthropogenic Threats to Biodiversity

• Habitat destruction fragments ecosystems, reducing species populations
  • Deforestation in the Amazon for agriculture and ranching
  • Urbanization destroys natural habitats and creates urban heat islands
• Climate change alters species distributions and phenology
  • Earlier spring blooming in temperate regions
  • Coral bleaching due to increased ocean temperatures
• Overexploitation depletes natural resources and disrupts ecosystem balance
  • Overfishing has led to collapse of cod populations in the North Atlantic
  • Illegal wildlife trade threatens endangered species (rhinos, elephants)

Conservation and Sustainable Management

• Protected areas preserve critical habitats and endangered species
  • National parks, marine protected areas, wildlife refuges
• Species recovery programs aim to restore populations of threatened organisms
  • California condor captive breeding and reintroduction
• Sustainable resource management balances human needs with ecosystem health
  • Forest Stewardship Council (FSC) certification for responsible forestry
  • Marine Stewardship Council (MSC) certification for sustainable fisheries
• Ecosystem-based approaches integrate conservation with human activities
  • Payment for ecosystem services incentivizes conservation on private lands
  • Agroforestry combines agriculture with tree cultivation to maintain biodiversity