🪺Environmental Biology Unit 1 – Ecosystems and biomes

What's This Unit About?

• Explores the interconnectedness of living organisms and their environments
• Examines the flow of energy and cycling of nutrients within ecosystems
• Investigates the characteristics and distribution of various biomes across the globe
• Analyzes the complex interactions between species in ecological relationships
• Assesses the impact of human activities on the health and stability of ecosystems
• Emphasizes the importance of understanding and preserving Earth's biodiversity
• Provides practical applications and case studies 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, distinct ecological community characterized by specific plant and animal species adapted to the prevailing climate and soil conditions
• Biodiversity: the variety of life forms within a given ecosystem, biome, or the entire Earth
• Trophic levels: the hierarchical stages of energy transfer in an ecosystem, typically from producers to primary, secondary, and tertiary consumers
• Producers: organisms that convert light energy or chemical energy into organic compounds through photosynthesis or chemosynthesis (plants, algae, some bacteria)
• Consumers: organisms that obtain energy by feeding on other organisms
  • Primary consumers: herbivores that feed on producers
  • Secondary consumers: carnivores that feed on primary consumers
  • Tertiary consumers: carnivores that feed on secondary consumers
• Decomposers: organisms that break down dead organic matter, releasing nutrients back into the ecosystem (bacteria, fungi)
• Nutrient cycling: the continuous movement of essential elements (carbon, nitrogen, phosphorus) through an ecosystem

Types of Ecosystems

• Terrestrial ecosystems: land-based ecosystems characterized by the predominant vegetation and climate
  • Forests: ecosystems dominated by trees and other woody vegetation (tropical rainforests, temperate forests, boreal forests)
  • Grasslands: ecosystems characterized by grasses and herbaceous plants (prairies, savannas, steppes)
  • Deserts: ecosystems with low precipitation and sparse vegetation (hot deserts, cold deserts)
  • Tundra: cold, treeless ecosystems with low-growing plants (arctic tundra, alpine tundra)
• Aquatic ecosystems: water-based ecosystems categorized by salinity, depth, and water flow
  • Freshwater ecosystems: ecosystems with low salt concentration (rivers, lakes, wetlands)
  • Marine ecosystems: saltwater ecosystems (oceans, coral reefs, estuaries)
• Transitional ecosystems: ecosystems that occur at the boundaries between two distinct ecosystems (ecotones)
  • Riparian zones: areas along the banks of rivers and streams
  • Intertidal zones: areas where the ocean meets the land

Biomes Around the World

• Tropical rainforests: characterized by high rainfall, warm temperatures, and high biodiversity (Amazon, Congo Basin, Southeast Asia)
• Temperate forests: characterized by moderate climates, distinct seasons, and a mix of deciduous and coniferous trees (eastern United States, Europe, eastern Asia)
• Boreal forests (taiga): characterized by cold climates, coniferous trees, and long winters (Canada, Russia, Scandinavia)
• Grasslands: characterized by grasses, herbaceous plants, and varying levels of precipitation (North American prairies, African savannas, Eurasian steppes)
• Deserts: characterized by low precipitation, extreme temperatures, and adapted plant and animal life (Sahara, Mojave, Gobi)
• Tundra: characterized by cold temperatures, short growing seasons, and low-growing vegetation (Arctic tundra, Alpine tundra)
• Aquatic biomes: characterized by the presence of water and adapted aquatic organisms
  • Freshwater biomes: rivers, lakes, wetlands
  • Marine biomes: oceans, coral reefs, estuaries

Energy Flow and Nutrient Cycles

• Energy flow: the transfer of energy through an ecosystem, typically from the sun to producers, then to consumers and decomposers
  • Only about 10% of energy is transferred from one trophic level to the next (ecological efficiency)
  • Energy is lost at each trophic level through heat, respiration, and incomplete digestion
• Carbon cycle: the movement of carbon through the ecosystem
  • Carbon is absorbed by producers during photosynthesis
  • Carbon is released through respiration, decomposition, and combustion
• Nitrogen cycle: the movement of nitrogen through the ecosystem
  • Nitrogen fixation: conversion of atmospheric nitrogen (N2) into usable forms by bacteria and lightning
  • Nitrification: conversion of ammonium (NH4+) to nitrate (NO3-) by bacteria
  • Denitrification: conversion of nitrate back to atmospheric nitrogen by bacteria
• Phosphorus cycle: the movement of phosphorus through the ecosystem
  • Phosphorus is released from rocks through weathering and is taken up by plants
  • Phosphorus is returned to the environment through decomposition and excretion

Ecological Relationships

• Competition: interaction between organisms that require the same limited resources
  • Intraspecific competition: competition between individuals of the same species
  • Interspecific competition: competition between individuals of different species
• Predation: interaction where one organism (predator) hunts and consumes another organism (prey)
  • Predators can help regulate prey populations and maintain ecosystem balance
• Symbiosis: close and long-term interactions between two different species
  • Mutualism: both species benefit from the interaction (pollination, nitrogen fixation in legumes)
  • Commensalism: one species benefits while the other is unaffected (epiphytes growing on trees)
  • Parasitism: one species (parasite) benefits at the expense of the other (host)
• Keystone species: species that have a disproportionately large impact on their ecosystem relative to their abundance (sea otters, wolves, beavers)

Human Impact on Ecosystems

• Habitat destruction: loss of natural habitats due to human activities (deforestation, urbanization, agriculture)
  • Habitat fragmentation: division of continuous habitats into smaller, isolated patches
• Overexploitation: unsustainable harvesting of natural resources (overfishing, poaching, logging)
• Pollution: introduction of harmful substances into the environment (air pollution, water pollution, plastic waste)
  • Bioaccumulation: accumulation of pollutants in the tissues of organisms over time
  • Biomagnification: increasing concentration of pollutants in organisms at higher trophic levels
• Climate change: long-term changes in global weather patterns due to human activities (greenhouse gas emissions)
  • Rising temperatures, sea levels, and ocean acidification
  • Shifts in species distributions and phenology (timing of biological events)
• Invasive species: non-native species that cause ecological or economic harm in a new environment
  • Introduced intentionally or accidentally by human activities (ballast water, pet trade, horticulture)
  • Lack of natural predators and competitors allows for rapid spread and dominance

Practical Applications and Case Studies

• Ecosystem services: benefits that humans derive from ecosystems (clean air and water, pollination, recreation)
  • Valuing ecosystem services can help inform conservation and management decisions
• Ecological restoration: the process of assisting the recovery of degraded or destroyed ecosystems
  • Examples: reforestation, wetland restoration, coral reef restoration
• Sustainable resource management: balancing the use of natural resources with the need to preserve ecosystems
  • Examples: sustainable forestry, fisheries management, ecotourism
• Biodiversity conservation: protecting and preserving the variety of life on Earth
  • Establishing protected areas (national parks, wildlife reserves)
  • Implementing endangered species recovery plans
  • Promoting sustainable land use practices
• Case studies:
  • Yellowstone wolf reintroduction: the return of wolves to Yellowstone National Park and its impact on the ecosystem
  • Great Barrier Reef conservation: efforts to protect and restore the world's largest coral reef system
  • Costa Rican ecotourism: a model for sustainable economic development and biodiversity conservation