Chapter 52: The Physical Environment Study Notes

52. The Physical Environment

1. Introduction to Ecology

• Ecology defined: Study of the interaction between organisms and their environment, encompassing both biotic (living) and abiotic (non-living) components.   

• Levels of Ecological Organization:
    - Individual: Focus on survival and reproduction, the unit of natural selection.
    - Population: Population dynamics, the unit of evolution.
    - Community: Interactions among various species in a specific area.
    - Ecosystem: Flow of energy and cycling of matter among organisms and their environment.
    - Landscape: Interactions among multiple ecosystems.

2. Global Climate

• Key Differences:
    - Weather:
      - Short-term meteorological conditions (temperature, precipitation).
      - Geographically limited scale.   - Climate:
      - Large-scale (continental or greater) trends.
      - Trends that occur over long periods of time.

• Main Climates:
    - Tropical
    - Arid
    - Temperate
    - Continental
    - Polar

• Influence of Climate:   - Climates shape environments where populations evolve and diversify.   - Solar radiation is the ultimate driver of Earth’s climates, impacting the atmosphere, oceans, and geography.

• Greenhouse Effect:
    - Results from absorption of solar radiation by the Earth and its atmosphere.
    - Breakdown of solar radiation absorption:
      - Water vapor (30%)
      - Reflected solar radiation
      - Absorbed by atmosphere
      - Absorbed by surface (50%)
      - Infrared surface radiation.

• Latitudinal Variation:
    - Earth’s spherical shape leads to varying solar radiation intensity:
      - Near equator: sunlight travels through less atmosphere, concentrated over a smaller area.
      - At high latitudes: sunlight experiences more atmospheric absorption and spreads over a larger area.

• Temperature Gradient:
    - Global temperature decreases from the equator to the poles (approximately $0.8^ ext{º} C$per degree latitude).

• Seasonal Changes Due to Tilt:
    - The tilt of the Earth causes seasonal variations in solar radiation.

• Global Air Circulation:
    - Driven by unequal solar heating, linking warm air that holds more moisture to precipitation patterns.
    - The equator receives the most solar energy, causing warm, moist air to rise and create heavy rainfall, with dry conditions at $30^ ext{º}$ latitudes.   

• Precipitation Patterns:
    - Highest global precipitation occurs near the equator (tropical climates).
    - Subtropical deserts form around $30^ ext{N}$ and $30^ ext{S}$ latitude (arid climates).

• Ocean Gyres:
    - Created by Earth’s rotation and unequal heating, they redistribute heat and shape regional climates.

3. Regional and Local Climate

• Regional and local climate patterns are affected by:
    - Topography: Physical features such as mountains and plains.
    - Proximity to Water: Affects temperature and precipitation.
    - Vegetation: Influences local climate conditions.
    - Human Activity: Impacts local climates significantly.

• Impact of Mountains:
    - Mountain ranges alter elevation, affecting temperature and precipitation, resulting in rain shadows and distinct climate zones on each side.
    - Wet climates on one side and dry climates (major deserts) on the other outside $30^ ext{N}$ and $30^ ext{S}$ latitude.

• Upwellings:
    - Produced by ocean topography and wind patterns, where cold, nutrient-rich water rises along continental coasts.

• Climate Moderation by Water Bodies:
    - Large bodies of water absorb and release heat slowly, moderating local climates and reducing seasonal temperature extremes.

• Human Impacts on Climate:
    - Deforestation leads to increased local temperatures and reduced precipitation.
    - Development of urban heat islands where buildings and pavement absorb heat, causing cities to be warmer than surrounding rural areas.

4. Biogeography

• Biogeography defined: Scientific study of distribution and diversity of life on Earth.

• Global Climate Influence:
    - Temperature and precipitation patterns determine the distribution of terrestrial biomes, which are regions where organisms are adapted to specific climates.

• Species Distribution Influences:
    - Reflects both evolutionary history and evolutionary isolation, influenced by continental drift (e.g., Pangaea, Laurasia, Gondwana).

• Global Species Diversity Patterns:
    - Highest species diversity occurs in the tropics, decreasing as one moves north or south from the equator.

• Processes Affecting Tropical Diversity:
    - High Speciation Rates and Low Extinction Rates: Contribute to higher biodiversity in tropics.   - Time for Diversification: Tropics have experienced fewer ice ages, allowing more time for species to diversify.   - Higher Environmental Energy: Availability of environmental energy is positively correlated with species diversity.