ENVISCI-MIDTERM-LESSONS

TERRESTRIAL ECOSYSTEMS

A terrestrial ecosystem is defined as an ecosystem located on land rather than in aquatic environments. These ecosystems provide a variety of habitats for many species and are characterized by distinct flora and fauna. Five major types of terrestrial ecosystems exist:

TUNDRA

Two subcategories of tundra exist:

  • Arctic Tundra: Located in the Arctic Circle, this environment is characterized by extreme cold, strong winds, and a short growing season. It features a stark landscape with few trees, relying instead on hardy vegetation.

  • Alpine Tundra: Found on mountain tops, it experiences similar cold conditions but can have a more varied topography.

  • Climate: The tundra has consistently cold temperatures year-round, with only the top layer of soil thawing during summer due to permafrost. This limits the types of plants that can grow.

  • Flora: The primary plant life consists of lichens, low shrubs, mosses, and small flowering plants due to harsh climatic conditions. The root systems are shallow because of the frozen subsoil.

  • Fauna: The fauna varies; many animals such as caribou and migratory birds extensively depend on the tundra's seasonal changes. Most animals migrate south or descend to lower altitudes to escape winter conditions.

TAIGA

  • Definition: Also known as northern coniferous forest or boreal forest, the taiga is characterized by its cold climate and coniferous vegetation.

  • Geography: This biome exists primarily in the northern hemisphere, covering significant areas in Canada, Alaska, Russia, and Scandinavia. It serves as a crucial source of timber.

  • Biodiversity: The taiga has low species diversity, primarily consisting of evergreen conifers such as pines, spruces, and firs. This limited diversity makes the ecosystem vulnerable to threats.

  • Climate: It features long winters and short summers with poor, acidic soil due to needle litter decay. Rainfall is moderate.

  • Animals: Notable species include lynx, moose, gray wolves, bears, and various bird species that adapt to the cold seasons.

FOREST

Forests cover approximately one-third of Earth's land area and are vital for biodiversity and ecological balance.

  • Classification of Forests: They are categorized based on tree types and precipitation levels:

    • Temperate Deciduous Forests: Characterized by four distinct seasons with trees that lose leaves seasonally.

    • Temperate Rainforests: Found in coastal areas, these forests are lush and receive high annual rainfall.

    • Tropical Rainforests: Located near the equator, these forests have high biodiversity and dense canopies.

    • Tropical Dry Forests: These forests are marked by wet and dry seasons but rely on less rainfall than rainforests.

    • Coniferous Forests: These consist mainly of conifers and are adapted to cooler climates.

  • Human Impact: Deforestation caused by agriculture, logging, and urban development threatens forest biodiversity and contributes to climate change. Conservation efforts are vital to preserve these ecosystems.

GRASSLAND

  • Types: Grasslands can be temperate (such as prairies and steppes) or tropical (savannas).

  • Characteristics: Grasslands exist where there is not enough rain to support large forests; they experience seasonal changes that affect flora and fauna.

  • Flora and Fauna: The ecosystem supports grazing animals like gazelles, antelopes, and migratory birds. Many species are specially adapted to the environment, such as prairie dogs and bison.

  • Human Encroachment: Increased agricultural activities have led to habitat loss, significantly impacting the biodiversity within grassland ecosystems.

DESERT

  • Definition: Deserts are defined by significantly low precipitation levels, typically receiving less than 25 cm (10 inches) of rain annually.

  • Temperature Variability: Deserts experience extreme temperature fluctuations, with hot days and cold nights.

  • Flora: Plant life includes succulents such as cacti and drought-resistant plants like the creosote shrub; these species have adapted to minimize water loss.

  • Fauna: The desert is home to a variety of animals, including scorpions, snakes, and several mammals, all uniquely adapted to survive in harsh conditions. Their behavior includes nocturnal activity to avoid daytime heat.

  • Notable Deserts: Examples include the Sahara Desert in Africa and the Sonora Desert in North America.

BIODIVERSITY HOTSPOTS

  • Definition: Biodiversity hotspots are regions that are rich in endemic species but are highly threatened by human activities. They are critical for global biodiversity.

  • Criteria for Hotspots:

    • Must contain at least 1,500 species of vascular plants as endemics.

    • Must have lost at least 70% of its original habitat.

  • Examples: Notable biodiversity hotspots include the Tropical Andes, Mesoamerican forests, the Philippines, and the Western Ghats in India.

  • Threats: Key threats include habitat loss due to agriculture, urbanization, invasive species, poaching, and climate change, requiring urgent conservation actions.

ECOLOGICAL SUCCESSION

  • Definition: Ecological succession refers to a series of changes in species structure and ecosystem functioning over time within an ecological community.

  • Types:

    • Primary Succession: Occurs in previously lifeless areas, such as after a volcanic eruption, where soil has yet to form.

    • Secondary Succession: Follows a disturbance (like a fire) that alters an existing community but leaves the soil intact, allowing for a quicker recovery of vegetation.

  • Pioneer Species: In primary succession, lichens and mosses are the first organisms to colonize bare rock, leading to soil formation. Grasses and shrubs prevail in secondary succession as the ecosystem recovers.

AQUATIC ECOSYSTEMS

  • Definition: Aquatic ecosystems occur in water and are divided into freshwater and marine environments, including oceans, rivers, lakes, and wetlands.

  • Abiotic Factors: Important abiotic factors include water salinity, temperature, light availability, dissolved oxygen levels, nutrient availability, and water flow.

  • Biotic Factors:

    • Producers: Phytoplankton and aquatic plants form the foundation of most aquatic food webs, facilitating energy transfer in ecosystems.

    • Consumers: Various herbivores, carnivores, and decomposers play critical roles in sustaining ecosystem balance and nutrient cycling.

MARINE ECOSYSTEMS

  • Overview: Marine ecosystems cover approximately 71% of Earth's surface and include oceans, coral reefs, and estuaries.

  • Significance: These ecosystems play crucial roles in oxygen production through photosynthesis and CO2 absorption, impacting global climate. They are home to an immense variety of species, many of which are unstudied and unidentified.

  • Challenges: Marine environments face threats such as overfishing, pollution, and climate change, impacting biodiversity and ecosystem health.

HUMAN POPULATION AND DEMOGRAPHY

  • Definition: Demography is the study of populations, encompassing size, density, distribution, and changes due to birth rates, death rates, and migration.

  • Population Dynamics: These dynamics are influenced by various factors, including healthcare access, living conditions, and economic stability, which can boost or decline population figures.

  • Malthusian Theory: This theory posits that population growth can outpace resource availability, potentially leading to starvation and conflict over scarce resources.

  • Demographic Transition: It describes the transition from high birth and death rates to lower rates as societies develop economically and socially.

ENVIRONMENT AND HUMAN HEALTH

  • Interrelation: Human health is closely linked to environmental quality, where factors such as pollution can adversely affect health outcomes.

  • Pollution Types: Air, water, and soil pollution are significant threats to health, resulting in illnesses and reduced quality of life.

  • Environmental Factors: Challenges such as overpopulation, urbanization, and resource degradation not only threaten biodiversity but also impact human health and quality of life through increased diseases and inadequate living conditions.