Chapter 49

• Researchers work at 4 levels to understand distribution/abundance of organisms


  • Morphology
  • Physiology
  • Behavioral adaptations to live in area
  • Interactions (predation, parasitism, competition, fires, floods)

  
• Humans are impacting the distribution and abundance of organisms
• Can Earth support the life on it?
• Ecosystem


  Regional organisms + abiotic components
• Conservation efforts


  • Study, preserve/restore threatened populations & ecosystems
• Ecologists


  Study interactions between organisms and environments
• Conservation biologists


  Apply data to preserve species and restore environments
• Aquatic ecosystems


  • Physical (temperature, precipitation, wind, sunlight) and biological (various species) components
• 3 physical factors affecting aquatic organisms

  • Nutrient availability
  • Water depth
  • Water movement
• Nutrient availability


  Washed away in moving water vs. fall to bottom in still water, important because they limit photosynthesis and provide food
• Ocean upwelling and lake turnover

  Bring nutrients up to the surface
• Water depth


  Dictates amount of light reaching organisms, which influences productivity

  
• Wind effects on surface water

  Winds blow, moving surface water offshore, causing upwelling of nutrient-rich water from the bottom
• Lake turnover


  Spring and fall - dense 40°F water at bottom gets nutrient-rich, colder water at surface gets oxygen

  Winter and summer - temperature gradient (thermocline) with dense 40°F water at bottom getting nutrient-rich, warmer water at surface getting oxygen

  
• 5 water depth zones in freshwater environments

  • Shore (shallow, flowering plants rooted)
  • Lake (offshore, all regions with enough sunlight for photosynthesis)
  • Regions with no sunlight (detritus-feeders)
• Freshwater streams


  • Move constantly in one direction, shallow with sun reaching bottom (few organism types, mostly animals) vs. varied organisms (algae, plants, animals)
• Freshwater/marine estuaries


  • Very productive, where river meets ocean so fresh and salt water mix, salinity varies with proximity affecting osmosis, shallow with tides, nutrient-rich
• Marine environments - oceans


  • Beach (exposed to air at low tide, submerged at high), open ocean, very productive like coral reefs, each zone has distinct species adapted to physical conditions
• Biomes


  Major groups of plant and animal communities, dominant vegetation type depends on climate (temperature, moisture, sunlight, wind)
• 14 major biomes


  • Tropical rainforest
  • Arctic tundra
  • Subtropical desert
  • Boreal forest
  • etc.

  
• Net primary productivity (NPP)


  Total carbon fixed per year minus amount fixed carbon oxidized, equals organic matter available as food
• Factors affecting NPP


  Minimum at low temperature and drought, maximum under warm and wet conditions
• Tropical rainforest


  • Abundant plant growth, high aboveground biomass, in equatorial regions with ~77°F
• Tropical rainforest structure


  • Tree canopy intermingled with vines, epiphytes, shrubs, herbs, diverse habitat for animals, huge species and plant diversity
• Subtropical deserts


  • Very low productivity due to water scarcity, plants widely spaced due to water competition, species adapted to grow at low rate year-round or fast upon rain
• Arctic tundra


  • Growing season only 6-8 weeks, soil is permafrost, dominated by small woody shrubs and herbaceous plants, low plant and animal diversity, low productivity and biomass
• Biomes are defined by dominant vegetation type, which depends on climate
• Tropics are warm and the poles are cold


  Dictated by Earth's spherical shape and 90° angle of sunlight
• Hadley cell - global air circulation pattern

  Air heated by strong sunlight at equator expands/rises, cools and condenses water, pushes poleward, sinks and warms at 30°N and 30°S, creating wet tropics and dry subtropics
• Earth's 23.5° tilt on axis


  Causes seasons
• Regional climate effects - mountains and oceans

  • Mountains produce rain shadow effect, oceans moderate temperatures
• Tools for predicting climate change effects

  Simulation studies, observational studies, experiments simulating changed climate conditions
• Experimental temperature increase in arctic tundra

  Resulted in decreased species diversity and increased grasses and shrubs
• Global warming is expected to cause 6°C increase in global temperature in next 100 years, leading to arctic tundra giving way to boreal forests
• Global warming is causing increased precipitation and temperature variability, with more extreme climates and storms