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.4-1)
  • Results from differences in crustal thickness (see Fig. 1-16)

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. 4-8 & 4-9)
  • Driven by Convection
    • Unequal heating of Earth's surface by solar radiation
    • Results in THERMAL GRADIENT
      • Also tied into the hydrologic cycle (See Fig. 1-21) 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. 4-10)

• 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

MARINE ENVIRONMENTS

• CHARACTERIZED BY TEMPERATURE & SALINITY - controlled by wind driven ocean circulation (See Figs. 4-21, 4-22 & 4-27)
  • Tropical
  • Subtropical ( = Desert on land)
  • Transitional ( = Temperate on land)
  • Subpolar
  • Polar
• WAVES & TIDES
  • Waves base - no motion of water below a depth equal to one half of the wave length
  • Tides - unequal gravitational attraction of Moon (& Sun) of ocean water
    • At shore
    • Subtidal = seafloor generally water covered except during lowest tides
    • Intertidal = beach face that is alternately exposed during low tide & covered during high tide
    • Supratidal = shore area generally exposed except during highest tides & storms
• WATER DEPTH
  • Plankton - Floaters
    • Phytoplankton - marine algae = producers using phothosynthesis
      • LIVE in PHOTIC ZONE = sunlit upper 100 meter of water column
    • Zooplankton - marine protozoans & larval stages of multicellular animals = consumers (dominantly herbivorous, but can be carnivorous)
  • Nekton - Swimmers
    • Fish, whales, squids
  • Benthos - Bottom dwellers
    • Many different groups - plants (algae & seaweed), protozoans, sponges, corals, bryozoans, brachipods, mollusks, annelids, arthropods, & fish
    • Some live on top of seafloor (epifauna), some within sediments (infauna)
  • Pelagic = open ocean beyond continental shelf
    • Continental slope, continental rise, deep sea trenches, abyssal plains, seamounts, Mid-Ocean Ridge
• MARINE FOOD WEBS - (See Fig. 4-26)

Study Questions

1. How do continents differ from oceans?

2. What is an ecologic niche?

3. How do consumers & producers in ecologic communities differ?

4. What are the various types of consumers?

5. What is the difference between a food chain & a food web?

6. What are the main constituents of the Earth's atmosphere?

7. What is the main cause of atmospheric circulation on Earth?

8. Briefly describe the main attributes of the Earth's atmospheric circulation.

9. What are the major terrestrial & marine envrionments?

10. What are basic causes for these major terrestrial & marine envrionments?

11. How can plants be used to reconstruct past climatic conditions?

12. What is wave base?

13. What are the 3 shore areas based on tidal characteristics?

14. What are the differences among plankton, nekton, & benthos?

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