🧭Physical Geography Unit 16 – Ecosystem Dynamics and Biomes

What's This Unit All About?

• Explores the complex interactions and processes within ecosystems
• Examines the flow of energy and cycling of nutrients through ecosystems
• Investigates the major biomes of the world and their characteristics
• Analyzes the factors influencing the distribution of ecosystems across the globe
  • Includes climate, topography, and soil type
• Assesses the impact of human activities on ecosystems and their functioning
• Provides case studies and real-world examples to illustrate key concepts

Key Concepts and Definitions

• Ecosystem: a community of living organisms interacting with each other and their physical environment
• Biome: a large-scale ecosystem characterized by distinct plant and animal communities adapted to specific environmental conditions
• Biodiversity: the variety of life forms within an ecosystem, including genetic diversity, species diversity, and ecosystem diversity
• Trophic levels: the position an organism occupies in a food chain or food web
  • Consists of producers (plants), primary consumers (herbivores), secondary consumers (carnivores), and decomposers
• Biogeochemical cycles: the movement of essential nutrients (such as carbon, nitrogen, and water) through ecosystems
• Ecological succession: the gradual process of change in an ecosystem's species composition over time
  • Can be primary succession (on newly exposed surfaces) or secondary succession (following a disturbance)

Ecosystem Components and Interactions

• Abiotic components: the non-living physical and chemical factors in an ecosystem (temperature, light, water, soil)
• Biotic components: the living organisms in an ecosystem, including producers, consumers, and decomposers
• Food chains: a linear sequence of organisms, each dependent on the previous as a source of food
  • Example: grass (producer) → grasshopper (primary consumer) → bird (secondary consumer) → hawk (tertiary consumer)
• Food webs: a complex network of interconnected food chains within an ecosystem
• Symbiotic relationships: close and long-term interactions between two or more species
  • Includes mutualism (both species benefit), commensalism (one benefits, the other is unaffected), and parasitism (one benefits, the other is harmed)

Energy Flow and Nutrient Cycling

• Primary production: the process by which producers (mainly plants) convert solar energy into chemical energy through photosynthesis
• Energy transfer: the movement of energy from one trophic level to another, with some energy lost as heat at each level
• Ecological efficiency: the percentage of energy transferred from one trophic level to the next
  • Typically around 10%, meaning 90% of energy is lost at each level
• Carbon cycle: the movement of carbon through the ecosystem, involving photosynthesis, respiration, and decomposition
• Nitrogen cycle: the circulation of nitrogen through the ecosystem, including nitrogen fixation, nitrification, and denitrification
• Water cycle: the continuous movement of water through the ecosystem and the Earth's surface, atmosphere, and underground

Major Biomes of the World

• Tundra: cold, treeless biome with low-growing plants adapted to harsh conditions (Arctic tundra, Alpine tundra)
• Boreal forest (taiga): coniferous forest biome with long, cold winters and short, cool summers (Canada, Russia)
• Temperate deciduous forest: biome characterized by trees that lose their leaves seasonally (eastern United States, Europe)
• Temperate grassland: biome with grasses as the dominant vegetation and occasional trees (prairies, steppes)
• Tropical rainforest: biome with high rainfall, high biodiversity, and tall, dense vegetation (Amazon, Congo)
• Desert: biome with low precipitation, extreme temperatures, and sparse vegetation (Sahara, Mojave)

Factors Influencing Ecosystem Distribution

• Climate: the long-term average weather conditions of an area, primarily determined by temperature and precipitation
  • Influences the type and distribution of vegetation and animal communities
• Topography: the physical features of an area, such as elevation, slope, and aspect
  • Affects local climate, soil development, and water availability
• Soil type: the composition and characteristics of the soil, influenced by parent material, climate, and biotic factors
  • Determines the nutrients and water available for plant growth
• Latitude: the distance north or south of the equator, influencing the amount of solar radiation received
• Ocean currents: the movement of water in the oceans, affecting the climate of nearby landmasses
  • Example: the Gulf Stream warms the climate of northwestern Europe

Human Impact on Ecosystems

• Habitat destruction: the alteration or elimination of natural habitats through human activities (deforestation, urbanization)
• Pollution: the introduction of harmful substances into the environment (air, water, soil)
  • Can disrupt ecosystem functions and cause biodiversity loss
• Overexploitation: the unsustainable use of natural resources (overfishing, poaching)
• Climate change: the long-term alteration of global climate patterns, largely driven by human activities (greenhouse gas emissions)
  • Affects the distribution and functioning of ecosystems worldwide
• Invasive species: non-native species that can outcompete native species and alter ecosystem dynamics
  • Often introduced by human activities (international trade, pet trade)

Case Studies and Real-World Examples

• Yellowstone National Park: a classic example of the reintroduction of a keystone species (gray wolves) and its impact on the ecosystem
• The Great Barrier Reef: a marine ecosystem threatened by climate change, ocean acidification, and coastal development
• The Amazon rainforest: a biodiversity hotspot facing deforestation, fragmentation, and climate change
  • Plays a crucial role in global carbon cycling and climate regulation
• The Sahel: a region in Africa experiencing desertification due to overgrazing, deforestation, and climate change
• The Aral Sea: an endorheic lake that has shrunk dramatically due to water diversion for irrigation, leading to ecological and socio-economic consequences
• The Chernobyl Exclusion Zone: an area demonstrating the long-term effects of radioactive contamination on ecosystems and wildlife