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Chapter 52

Chapter 52. An Introduction to Ecology and the Biosphere. Interactions between organisms and the environment limit the distribution of species. Ecologists have long recognized global and regional patterns of distribution of organisms within the biosphere.

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Chapter 52

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  1. Chapter 52 An Introduction to Ecology and the Biosphere

  2. Interactions between organisms and the environment limit the distribution of species • Ecologists have long recognized global and regional patterns of distribution of organisms within the biosphere. • Biogeography is a good starting point for understanding what limits geographic distribution of species. • Ecologists recognize two kinds of factors that determine distribution: biotic = living factors, and abiotic = nonliving factors / physical environment.

  3. Distribution and Abundance of the red kangaroo in Australia Kangaroos/km2 0–0.1 0.1–1 1–5 5–10 10–20 > 20 Limits of distribution

  4. Ecologists consider multiple factors when attempting to explain the distribution of species.Flowchart of Factors Limiting Geographic Distribution Why is species X absent from an area? Yes Area inaccessible or insufficient time Yes Habitat selection Does dispersal limit its distribution? Yes Predation, parasitism, competition, disease Chemical factors Does behavior limit its distribution? Do biotic factors (other species) limit its distribution? No Water Oxygen Salinity pH Soil nutrients, etc. No Do abiotic factors limit its distribution? No Temperature Light Soil structure Fire Moisture, etc. Physical factors

  5. Dispersal and Distribution • Dispersalismovement of individuals away from centers of high population density or from their area of origin. • Natural range expansions show the influence of dispersal on distribution. • Species transplants include organisms that are intentionally or accidentally relocated from their original distribution. • Species transplants can disrupt the communities or ecosystems to which they have been introduced.

  6. Biotic Factors • Biotic factors that affect the distribution of organisms may include: • Interactions with other species • Predation • Competition

  7. Does feeding by sea urchins limit seaweed distribution? RESULTS 100 Both limpets and urchins removed 80 Sea urchin Only urchins removed 60 Seaweed cover (%) Limpet 40 Only limpets removed 20 Control (both urchins and limpets present) 0 August 1982 February 1983 August 1983 February 1984

  8. Abiotic Factors • Abiotic factors affecting distribution of organisms include: • Temperature • Water • Sunlight • Wind • Rocks and soil • pH

  9. Temperature • Environmental temperature is an important factor in distribution of organisms because of its effects on biological processes. • Cells may freeze and rupture below 0°C, while most proteins denature above 45°C. • Mammals and birds expend energy to regulate their internal temperature.

  10. Water & Salinity • Water availability in habitats is another important factor in species distribution. • Desert organisms exhibit adaptations for water conservation. • Salt concentration affects water balance of organisms through osmosis. • Few terrestrial organisms are adapted to high-salinity habitats.

  11. Sunlight • Light intensity and quality affect photosynthesis. • Water absorbs light, thus in aquatic environments most photosynthesis occurs near the surface. • In deserts, high light levels increase temperature and can stress plants and animals.

  12. Rocks and Soil • Many characteristics of soil limit distribution of plants and thus the animals that feed upon them: • Physical structure • pH • Mineral composition

  13. Climate: temperature, water, sunlight, and wind • Four major abiotic components of climate are temperature, water, sunlight, and wind. • The long-term prevailing weather conditions in an area constitute its climate. • Macroclimate consists of patterns on the global, regional, and local level. • Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log.

  14. Global Climate Patterns • Global climate patterns are determined largely by solar energy and the planet’s movement in space. • Sunlight intensity plays a major part in determining the Earth’s climate patterns. • More heat and light per unit of surface area reach the tropics than the high latitudes.

  15. Global climate patterns:How direct or slanted - the sun’s rays …Impacts Climate.The Strength of Sun’s Rays in an area varies seasonally as Earth Orbits Sun. Latitudinal Variation in Sunlight Intensity 90ºN (North Pole) 60ºN Low angle of incoming sunlight 30ºN 23.5ºN (Tropic of Cancer) Sun directly overhead at equinoxes 0º (equator) 23.5ºS (Tropic of Capricorn) 30ºS Low angle of incoming sunlight 60ºS 90ºS (South Pole) Atmosphere Seasonal Variation in Sunlight Intensity 60ºN 30ºN March equinox 0º (equator) June solstice 30ºS December solstice Constant tilt of 23.5º September equinox

  16. Seasonal variations of light and temperature increase steadily toward the poles. • Global air circulation and precipitation patterns play major roles in determining climate patterns. • Warm wet air flows from the tropics toward the poles.

  17. Global climate patterns Global Air Circulation and Precipitation Patterns 60ºN 30ºN Descending dry air absorbs moisture Descending dry air absorbs moisture 0º (equator) Ascending moist air releases moisture 30ºS 0º 60ºS 23.5º 23.5º 30º 30º Arid zone Arid zone Tropics Global Wind Patterns 66.5ºN (Arctic Circle) 60ºN Westerlies 30ºN Northeast trades Doldrums 0º (equator) Southeast trades 30ºS Westerlies 60ºS 66.5ºS (Antarctic Circle)

  18. Air flowing close to Earth’s surface creates predictable global wind patterns. • Cooling trade winds blow from east to west in the tropics; prevailing westerlies blow from west to east in the temperate zones. • Proximity to bodies of water and topographic features contribute to local variations in climate. • Seasonal variation also influences climate.

  19. Bodies of Water • The Gulf Stream carries warm water from the equator to the North Atlantic. • Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments. • During the day, air rises over warm land and draws a cool breeze from the water across the land. • As the land cools at night, air rises over the warmer water and draws cooler air from land back over the water, which is replaced by warm air from offshore.

  20. The great ocean conveyor belt:Cold Current = Labrador / Warm = Gulf Stream Labrador current Gulf stream Equator water Warm Cold water

  21. 2 Air cools at high elevation. Cooler air sinks over water. 3 Warm air over land rises. 1 Cool air over water moves inland, replacing rising warm air over land. 4 Moderating effects of a large body of water on climate

  22. Mountains • Mountains have a significant effect on: • The amount of sunlight reaching an area • Local temperature • Rainfall • Rising air releases moisture on the windward side of a peak and creates a “rain shadow” as it absorbs moisture on the leeward side.

  23. How mountains affect rainfall Leeward side of mountain Wind direction Mountain range Ocean

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