🏝️Earth Science Unit 9 – Earth's Ecosystems and Biomes

Key Concepts and Definitions

• Ecosystem consists of all living organisms (biotic factors) in an area and their interactions with the non-living environment (abiotic factors)
• Biome refers to a large geographical area characterized by distinct plant and animal communities adapted to that particular environment
• Biodiversity encompasses the variety of life at all levels, from genes to ecosystems, and is essential for the health and resilience of ecosystems
  • Includes genetic diversity within species, species diversity within ecosystems, and ecosystem diversity across landscapes
• Habitat describes the natural environment where an organism lives and includes both biotic and abiotic factors that support its survival
• Niche refers to an organism's specific role within an ecosystem, including its habitat, interactions with other species, and resource requirements
• Trophic levels organize organisms based on their position in the food chain (producers, primary consumers, secondary consumers, tertiary consumers, and decomposers)
• Biogeochemical cycles (water, carbon, nitrogen) involve the exchange of nutrients between biotic and abiotic components of ecosystems

Earth's Major Biomes

• Tundra characterized by low temperatures, short growing seasons, and low-growing vegetation adapted to harsh conditions (lichens, mosses, sedges)
• Taiga (boreal forest) consists of coniferous forests (spruce, fir, pine) adapted to cold temperatures and long winters
• Temperate deciduous forests feature trees that shed their leaves seasonally (oak, maple, beech) and a diverse understory of plants and animals
• Temperate grasslands (prairies, steppes) dominated by grasses and herbaceous plants with few trees, supporting grazing animals and burrowing species
• Temperate rainforests characterized by high rainfall, cool temperatures, and tall, dense vegetation (redwoods, Douglas firs)
• Tropical rainforests known for high temperatures, abundant rainfall, and exceptional biodiversity, with complex layered structure (emergent, canopy, understory, forest floor)
  • Home to numerous endemic species and play a crucial role in global carbon storage and climate regulation
• Deserts defined by low precipitation, extreme temperatures, and adapted vegetation (cacti, succulents) and animals (reptiles, small mammals)
• Aquatic biomes include freshwater (lakes, rivers, wetlands) and marine (oceans, coral reefs, estuaries) ecosystems, each with distinct characteristics and species adaptations

Ecosystem Components and Interactions

• Producers (autotrophs) form the foundation of ecosystems by converting solar energy into organic compounds through photosynthesis (plants, algae, cyanobacteria)
• Consumers (heterotrophs) obtain energy by feeding on other organisms and can be classified as herbivores, carnivores, or omnivores
  • Primary consumers (herbivores) feed directly on producers (rabbits, zooplankton)
  • Secondary consumers (carnivores) feed on primary consumers (foxes, small fish)
  • Tertiary consumers (top predators) feed on secondary consumers (hawks, sharks)
• Decomposers (bacteria, fungi) break down dead organic matter, releasing nutrients back into the ecosystem for reuse by producers
• Food chains represent linear pathways of energy transfer from producers to consumers, while food webs illustrate the complex interconnections between multiple food chains in an ecosystem
• Symbiotic relationships involve close interactions between species, including mutualism (both benefit), commensalism (one benefits, one unaffected), and parasitism (one benefits, one harmed)
• Keystone species have a disproportionately large impact on ecosystem structure and function relative to their abundance (sea otters, wolves, beavers)
• Ecological succession describes the gradual process of change in species composition over time, from pioneer species to climax communities

Climate's Influence on Ecosystems

• Temperature and precipitation patterns are the primary determinants of biome distribution and characteristics
  • Warmer temperatures generally support higher biodiversity and productivity, while colder temperatures limit growth and species richness
  • Higher precipitation levels support more complex and diverse ecosystems (rainforests), while lower levels result in simpler, drought-adapted communities (deserts)
• Latitude affects the amount of solar radiation received, with higher latitudes experiencing lower temperatures and shorter growing seasons compared to lower latitudes
• Elevation influences temperature and precipitation, with higher elevations generally experiencing cooler temperatures and increased precipitation compared to lower elevations
• Ocean currents can moderate coastal climates by transferring heat from one region to another (Gulf Stream warming Europe)
• Atmospheric circulation patterns (Hadley cells, jet streams) redistribute heat and moisture across the globe, influencing regional climates and biome distribution
• Climate change, driven by human activities, is altering temperature and precipitation patterns worldwide, leading to shifts in species ranges, phenology, and ecosystem composition

Biodiversity and Adaptation

• Genetic diversity within populations allows for adaptation to changing environmental conditions through natural selection
• Species richness refers to the number of different species present in an ecosystem, while species evenness describes the relative abundance of each species
• Endemism occurs when species are unique to a particular geographic location, often due to isolation or specialized habitat requirements (Madagascar, Galapagos Islands)
• Adaptive radiation is the process by which a single ancestral species gives rise to multiple descendant species adapted to different ecological niches (Darwin's finches)
• Convergent evolution occurs when unrelated species independently evolve similar traits in response to similar environmental pressures (cacti and euphorbs in deserts)
• Coevolution involves the reciprocal adaptation of two or more species in close ecological relationships (flowers and pollinators, predators and prey)
• Ecosystem resilience is the ability of an ecosystem to withstand and recover from disturbances, often enhanced by higher levels of biodiversity

Human Impact on Ecosystems

• Habitat destruction, fragmentation, and degradation are major threats to biodiversity, caused by land-use changes (deforestation, urbanization, agriculture)
  • Leads to loss of species, reduced ecosystem services, and increased vulnerability to invasive species and disease
• Overexploitation of natural resources (overfishing, poaching, logging) can disrupt food webs and cause population declines or extinctions
• Pollution (air, water, soil) can have detrimental effects on ecosystem health, including eutrophication, acid rain, and bioaccumulation of toxins
• Introduction of invasive species, often through human activities (shipping, pet trade), can outcompete native species and alter ecosystem dynamics
• Climate change, driven by anthropogenic greenhouse gas emissions, is causing rising temperatures, altered precipitation patterns, and more frequent extreme weather events
  • Impacts include species range shifts, phenological mismatches, coral bleaching, and ecosystem disruption
• Human population growth and resource consumption place increasing pressure on ecosystems, leading to land-use conflicts and resource depletion

Conservation and Sustainability

• Protected areas (national parks, wildlife reserves) aim to safeguard habitats and species by limiting human activities and development
• Habitat restoration involves the active recovery of degraded ecosystems through planting native species, removing invasive species, and restoring natural processes
• Sustainable resource management practices (selective logging, catch limits, renewable energy) seek to balance human needs with the long-term health of ecosystems
• International agreements (Convention on Biological Diversity, CITES) promote global cooperation in conservation efforts and regulate trade in endangered species
• Community-based conservation engages local communities in the management and protection of their natural resources, often combining traditional knowledge with scientific approaches
• Ecosystem-based management considers the complex interactions within ecosystems and aims to maintain their structure, function, and services
• Environmental education and awareness are crucial for fostering public understanding and support for conservation and sustainability initiatives

Case Studies and Real-World Examples

• The Yellowstone Wolf Reintroduction (1995) demonstrated the importance of keystone species in shaping ecosystem dynamics and trophic cascades
• The Great Barrier Reef, the world's largest coral reef system, is under threat from climate change, ocean acidification, and coastal development
• The Amazon Rainforest, a global biodiversity hotspot, is experiencing rapid deforestation due to logging, agriculture, and infrastructure development
  • Deforestation contributes to climate change, habitat loss, and the displacement of indigenous communities
• The Serengeti Ecosystem in East Africa is renowned for its large mammal migrations and serves as a model for studying predator-prey dynamics and grassland ecology
• The Chesapeake Bay, the largest estuary in the United States, has been impacted by nutrient pollution, overfishing, and invasive species, leading to efforts to restore water quality and habitat
• The Mojave Desert in the southwestern United States is home to diverse plant and animal species adapted to extreme heat and aridity, including the iconic Joshua tree
• The Galapagos Islands, an archipelago in the Pacific Ocean, are famous for their high levels of endemism and their role in inspiring Charles Darwin's theory of evolution by natural selection