Biology for Non-STEM Majors Unit 20 ReviewEcosystems and Earth's Biosphere

Key Concepts

• Biosphere encompasses all life on Earth and the environments in which it exists
• Ecosystems are communities of living organisms interacting with each other and their physical environment
• Biomes are large regions of Earth characterized by distinct climate, flora, and fauna (tundra, rainforest, desert)
• Energy flows through ecosystems via trophic levels, starting with primary producers and moving to consumers
• Nutrients cycle through ecosystems, being used and reused by different organisms (carbon cycle, nitrogen cycle)
• Biodiversity refers to the variety of life within an ecosystem, including genetic diversity, species diversity, and ecosystem diversity
• Human activities, such as habitat destruction, pollution, and climate change, can have significant impacts on ecosystems
• Conservation and sustainability practices aim to protect and maintain healthy ecosystems for future generations

Earth's Major Biomes

• Tundra biome characterized by extremely cold temperatures, low precipitation, and limited vegetation (mosses, lichens, sedges)
  • Permafrost, a layer of permanently frozen soil, is a key feature of tundra ecosystems
• Taiga (boreal forest) biome features cold temperatures, coniferous forests, and acidic soils
• Temperate forest biome has moderate temperatures, deciduous trees, and distinct seasonal changes
  • Temperate rainforests, a subtype of temperate forests, receive high amounts of rainfall and support diverse plant and animal life
• Temperate grassland biome characterized by grasses, herbaceous plants, and occasional trees
• Desert biome defined by low precipitation, extreme temperatures, and adapted flora and fauna (cacti, succulent plants)
• Tropical rainforest biome features high temperatures, abundant rainfall, and incredible biodiversity
• Aquatic biomes include freshwater (lakes, rivers, wetlands) and marine (oceans, coral reefs, estuaries) ecosystems

Ecosystem Components

• Abiotic factors are non-living components of an ecosystem (temperature, water, sunlight, soil)
• Biotic factors are living components of an ecosystem, including producers, consumers, and decomposers
• Producers, such as plants and algae, convert solar energy into chemical energy through photosynthesis
  • Chemosynthetic producers, found in deep-sea hydrothermal vents, use chemical energy to produce organic compounds
• Consumers are organisms that obtain energy by feeding on other organisms (herbivores, carnivores, omnivores)
• Decomposers, such as bacteria and fungi, break down dead organic matter, releasing nutrients back into the ecosystem
• Ecological niche refers to an organism's role within an ecosystem, including its habitat, diet, and interactions with other species
• Habitat is the physical environment in which an organism lives and includes both biotic and abiotic factors

Energy Flow in Ecosystems

• Primary producers convert solar energy into chemical energy through photosynthesis, forming the base of the food chain
• Primary consumers (herbivores) obtain energy by consuming producers
• Secondary consumers (carnivores) feed on primary consumers
• Tertiary consumers (top predators) feed on secondary consumers
• Decomposers break down dead organic matter, releasing nutrients back into the ecosystem
  • Detritivores, such as earthworms and millipedes, feed on dead organic matter and aid in decomposition
• Trophic levels represent the position of an organism in the food chain (producers, primary consumers, secondary consumers)
• Energy is lost at each trophic level through heat, respiration, and undigested matter, limiting the number of trophic levels in an ecosystem

Nutrient Cycles

• Carbon cycle involves the exchange of carbon among the atmosphere, living organisms, and Earth's crust
  • Photosynthesis, respiration, decomposition, and combustion are key processes in the carbon cycle
• Nitrogen cycle encompasses the transformation of nitrogen between the atmosphere, living organisms, and soil
  • Nitrogen fixation, nitrification, denitrification, and ammonification are essential processes in the nitrogen cycle
• Phosphorus cycle involves the movement of phosphorus through the environment, including rocks, soil, and living organisms
• Water cycle (hydrologic cycle) describes the continuous movement of water on, above, and below Earth's surface (evaporation, transpiration, precipitation)
• Nutrient cycling is essential for maintaining the health and productivity of ecosystems
• Human activities, such as fossil fuel combustion and deforestation, can disrupt natural nutrient cycles

Biodiversity and Ecosystem Health

• Genetic diversity refers to the variety of genes within a species, enabling adaptation to changing environments
• Species diversity is the number of different species within an ecosystem
• Ecosystem diversity encompasses the variety of ecosystems within a given area
• Biodiversity enhances ecosystem resilience, the ability to recover from disturbances
  • Keystone species, such as sea otters and wolves, have a disproportionately large impact on ecosystem health and biodiversity
• Ecosystem services are benefits provided by healthy ecosystems (clean air and water, pollination, climate regulation)
• Habitat fragmentation, invasive species, and overexploitation can lead to biodiversity loss and ecosystem degradation

Human Impact on Ecosystems

• Habitat destruction, such as deforestation and wetland drainage, is a major threat to biodiversity
• Pollution, including air, water, and soil contamination, can disrupt ecosystem functions and harm living organisms
  • Bioaccumulation is the accumulation of toxins in an organism over time, often magnified at higher trophic levels
• Climate change, driven by human activities like fossil fuel combustion, affects ecosystems through rising temperatures, altered precipitation patterns, and sea-level rise
• Overexploitation of natural resources, such as overfishing and poaching, can lead to species decline and ecosystem imbalance
• Invasive species, introduced by human activities, can outcompete native species and alter ecosystem dynamics
• Urbanization and agricultural expansion contribute to habitat loss and ecosystem fragmentation

Conservation and Sustainability

• Habitat conservation involves protecting and restoring natural habitats to maintain biodiversity
  • Protected areas, such as national parks and wildlife reserves, are essential for conserving ecosystems and species
• Sustainable resource management aims to use natural resources in a way that meets current needs without compromising future generations
• Ecosystem restoration involves actively repairing degraded or destroyed ecosystems (reforestation, wetland restoration)
• Reducing greenhouse gas emissions is crucial for mitigating climate change and its impacts on ecosystems
• Sustainable agriculture practices, such as crop rotation and integrated pest management, can minimize environmental damage
• Environmental education and public awareness are essential for promoting conservation and sustainability efforts
• International cooperation and policies, such as the Convention on Biological Diversity, aim to address global environmental challenges