Environments & Life

LAND & SEA

• Oceans are fundamentally different from continents as expressed by proportion of Earth's surface lying at various altitudes & depths (See Fig.2-1)
  • Results from differences in crustal thickness (see Isostasy in Chapter 1)

ECOLOGICAL TERMS

• Ecologic niche vs life habit
  • Ecologic niche
    • PARTICULAR ENVIRONMENTAL CONDITIONS (food/nutrients, physical/chemical conditions, relationships with other organisms)
    • these are LIMITING FACTORS
  • Life habit
    • the WAY an ORGANISM LIVES (finds food/nutrients, reproduces, locates within environment)
• Ecologic communities
  • Producers - plants that manufacture their own food from inorganic compounds
  • Consumers - animals that feed on other organisms
    • HERBIVORES - animals that feed on plants
    • CARNIVORES - animals that feed on animals
    • SCAVENGERS - animals that feed on dead animals
    • PARASITES - organisms that feed on other organisms without killing their hosts
    • DECOMPOSERS - bacteria that break organic matter into inorganic compounds
  • Food chains & food webs
    • FOOD CHAINS - single species at each level
    • FOOD WEB - several species at each level
  • Ecosystem
    • ORGANISMS of a COMMUNITY &
    • the PHYSICAL ENVIRONMENT they occupy
  • Biota
    • a FLORA (plants of an ecosystem) &
    • a FAUNA (animals of an ecosystem) living together
  • Diversity
    • the NUMBER OF SPECIES that LIVE TOGETHER WITHIN A COMMUNITY
• Biogeography
  • Distribution & abundance of organisms on a broad geographic scale, like continent-wide or ocean-wide
  • Temperature plays the largest role in determining the biogeographic distribution of organisms
    • Barriers also are important

THE ATMOSPHERE

• COMPOSITION
  • N2 - Nitrogen = 79%
  • O2 - Oxygen = 20%
  • Ar - Argon = ~1%
  • CO2 - Carbon Dioxide = ~365 ppm (parts per million){0.0365%}
  • H2O - Water = variable [CO2 & H2O are the major greenhouse gasses]
• CIRCULATION - (See Figs. 2-9 & 2-10)
  • Driven by Convection
    • Unequal heating of Earth's surface by solar radiation
    • Results in THERMAL GRADIENT
      • Also tied into the hydrologic cycle (See Fig. 2-7) and ocean circulation (See below)
    • Moist, heated air rises at Equator, cools & releases moisture, & moves poleward at high altitude
    • At the poles, dry, cool air sinks & returns to the Equator along the surface
      • Actually, this simple convection system breaks down into 3 separate convection cells in each hemisphere, with tropical cells from the Equator to 30 degrees North & South, temperate cells between 30 & 60 degrees North & South, and polar cells poleward from 60 degrees North & South
    • Rotation of the Earth causes Coriolis deflection of the winds
      • The surface winds in the tropical & polar cells blow from the east, while those in the temperate cells are westerlies

TERRESTRIAL ENVIRONMENTS- (See Fig. 2-11)

• CHARACTERIZED BY VEGETATION
  • Tropical
    • Forest
      • Includes both rain forest & seasonal forest
    • Grassland (savannah)
  • Desert
  • Temperate
    • Forest
    • Mediterranean vegetation
    • Grassland
  • Polar
    • Forest
    • Tundra
  • Species diversity decreases from the Tropics to the poles
  • Climate Indicators
    • SHAPE of LEAF MARGIN