Ecology and Biosphere Notes

Biological Levels

  • The most fundamental biological unit is debatable, with options including individuals, cells, and species, depending on the context.
  • Biological levels, in order of increasing inclusiveness, include:
    • Atoms
    • Molecules
    • Organelles
    • Cells
    • Tissues
    • Organs
    • Organ Systems
    • Individuals
    • Populations
    • Communities
    • Ecosystems
  • Individuals interact with the external world.

Introduction to Ecology & the Biosphere (Chapter 52: Part 1)

  • Ecology is the study of interactions between organisms and the living (biotic) and nonliving (abiotic) components of their environment.
  • Organismal ecology studies how an organism’s structure, physiology, and behavior meet environmental challenges.
  • Key definitions:
    • Population: A group of individuals of the same species in an area.
    • Community: A group of populations of different species in an area.
    • Ecosystem: A community of organisms in an area and the physical factors with which they interact.
    • Landscape: A mosaic of connected ecosystems.
    • Biosphere: The global ecosystem.

Climate

  • Earth’s climate varies by latitude and season and is changing rapidly.
  • Four major physical components of climate: temperature, precipitation, sunlight, and wind.
  • Global climate patterns are influenced by latitudinal variation.

Latitude and Longitude

  • Equatorial: On or near the equator.
  • Tropical: Within the tropics of Capricorn and Cancer (23.5 degrees latitude north & south).
  • Temperate: Middle latitudes.
  • Subequatorial: Near the equator.
  • Subtropical: Near the tropics.

Weather vs. Climate

  • Weather: Current conditions of temperature, precipitation, humidity, cloud cover.
  • Climate: Long-term weather trends based on averages and variation measured over decades, including daily, seasonal, yearly, and decadal cycles.

Influence of Solar Energy on Climate

  • Solar radiation, temperature, and air movement are key factors.
  • Toward the poles, the sun’s rays are spread over a larger area and take a longer path through the atmosphere.
  • Near the equator, the sun’s rays strike Earth perpendicularly.
  • This establishes latitudinal gradients in temperature, which drive climate dynamics.
  • Heating in equatorial regions causes air near the surface to warm.
  • Warm air is less dense than cool air, leading to uplift.
  • Warm air rises until it reaches the stratosphere.
  • Continued rising of air causes north and south movement of air.
  • As air approaches the poles, it cools and descends, filling the void of warm air and moving south.

Global Air Circulation and Precipitation Patterns

  • Global air circulation and precipitation patterns are influenced by latitude.
  • Descending dry air absorbs moisture, creating arid zones around 30° N and S.
  • Ascending moist air releases moisture, leading to precipitation in other regions.
  • Wind patterns drive ocean currents, which influence regional climate.

Seasons

  • Seasons are caused by Earth's constant tilt of 23.5∘23.5^{\circ} and its orbit around the sun.
  • Key points in the year:
    • June solstice
    • March equinox
    • December solstice
    • September equinox

Mountains and Climate

  • Mountains increase precipitation on the windward side and decrease it on the leeward side, creating a rain shadow.

Global Climate Change

  • Climate change is a directional change to the global climate lasting three decades or more.

Terrestrial Biomes (Chapter 52.2)

  • Biomes are major life zones characterized by vegetation type (terrestrial biomes) or physical environment (aquatic biomes).

Biome Distribution

  • Annual mean temperature and precipitation influence biome distribution.
  • Example: Nacogdoches, TX has an average annual temperature of 19∘C19^{\circ}C and average annual precipitation of 125cm125 cm.

Ecotones and Convergent Evolution

  • Ecotones: Areas of transition between biomes.
  • Similar characteristics often arise in distant biomes through convergent evolution, which is the evolution of similar traits in distantly related organisms.
  • Disturbance: An event such as a storm, fire, or human activity that changes a community, playing a large role in maintaining some biomes.

Specific Biomes

  • Tropical Forest
    • Equatorial and subequatorial regions.
    • Rainfall is relatively constant in tropical rain forests but highly seasonal in tropical dry forests.
    • Temperature is high year-round (25−29∘C25-29^{\circ}C) with little seasonal variation.
  • Desert
    • Occurs in bands near 30∘30^{\circ} north and south of the equator and in the interiors of continents.
    • Precipitation is low overall and highly variable.
    • Temperature is variable seasonally and daily, and may be hot or cold.
  • Savanna
    • Equatorial and subequatorial regions.
    • Precipitation is seasonal with long dry seasons.
    • Temperature averages 24−29∘C24-29^{\circ}C.
    • Dominant plant species are fire-adapted and drought-tolerant. Grasses and forbs make up most of the ground cover.
  • Temperate Grassland
    • Precipitation is highly seasonal.
    • Cold winters are dry, and summers are hot and wet.
    • Dominated by grasses and forbs; fire-adapted plants.
  • Chaparral
    • Midlatitude coastal regions.
    • Precipitation is high in winters and low in summers.
    • Shrubs are prevalent.
  • Temperate Broadleaf Forest
    • High precipitation (including snow).
    • Cold winters, and summers are hot and humid.
    • The dominant plants are deciduous trees in the Northern Hemisphere and evergreen eucalyptus in Australia.
  • Northern Coniferous Forest/Taiga
    • Precipitation varies.
    • Cold winters; summers often hot.
    • Conifers dominate.
  • Tundra
    • Covers expansive areas of the Arctic; alpine tundra exists on high mountaintops at all latitudes.
    • Precipitation is lower in arctic tundra.
    • Cold winters, cool summers.
    • Vegetation is herbaceous.
    • Permafrost, a permanently frozen layer of soil, restricts the growth of plant roots.