CAMPBELL BIOLOGY IN FOCUS URRY • CAIN • WASSERMAN • MINORSKY • REECE 40 Population Ecology and the Distribution of Organisms Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge, Simon Fraser University © 2016 Pearson Education, Inc. SECOND EDITION Discovering Ecology . Ecology is the scientific study of the interactions between organisms and the environment . These interactions determine the distribution of organisms and their abundance . Modern ecology includes observation and experimentation © 2016 Pearson Education, Inc. Research questions an ecologist might ask following the discovery of a new species of frog include . What environmental factors limit the geographic distribution of this species? . How do interactions with other species affect population size? © 2016 Pearson Education, Inc. Figure 40.1-1 © 2016 Pearson Education, Inc. Figure 40.1-2 © 2016 Pearson Education, Inc. Ecologists study interactions from the scale of individual organisms to the entire globe © 2016 Pearson Education, Inc. Figure 40.2 Global ecology Landscape ecology Ecosystem ecology Community ecology Population ecology Organismal ecology © 2016 Pearson Education, Inc. Organismal ecology considers how an organism’s structure, physiology, and behavior meet environmental challenges . Organismal ecology includes physiological, evolutionary, and behavioral ecology © 2016 Pearson Education, Inc. Figure 40.2-1 Organismal ecology © 2016 Pearson Education, Inc. Population ecology considers factors affecting population size over time . A population is a group of individuals of the same species living in an area © 2016 Pearson Education, Inc. Figure 40.2-2 Population ecology © 2016 Pearson Education, Inc. Community ecology considers the whole array of interacting species in a community . A community is a group of populations of different species in an area © 2016 Pearson Education, Inc. Figure 40.2-3 Community ecology © 2016 Pearson Education, Inc. Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components of the environment . An ecosystem is the community of organisms in an area and the physical factors with which they interact © 2016 Pearson Education, Inc. Figure 40.2-4 Ecosystem ecology © 2016 Pearson Education, Inc. Landscape ecology focuses on the exchanges of energy, materials, and organisms across multiple ecosystems . A landscape (or seascape) is a mosaic of connected ecosystems © 2016 Pearson Education, Inc. Figure 40.2-5 Landscape ecology © 2016 Pearson Education, Inc. Global ecology is concerned with the biosphere, or global ecosystem, which is the sum of all the planet’s ecosystems . Global ecology examines the influence of energy and materials on organisms across the biosphere © 2016 Pearson Education, Inc. Figure 40.2-6 Global ecology © 2016 Pearson Education, Inc. Concept 40.1: Earth’s climate influences the distribution of terrestrial biomes . The long-term prevailing weather conditions in an area constitute its climate . Four major physical components of climate are temperature, precipitation, sunlight, and wind © 2016 Pearson Education, Inc. Abiotic factors are the nonliving chemical and physical attributes of the environment . Biotic factors are the other organisms that make up the living component of the environment © 2016 Pearson Education, Inc. Global Climate Patterns . Global climate patterns are determined largely by solar energy and the planet’s movement in space . The warming effect of the sun causes temperature variations, which drive evaporation and the circulation of air and water . This causes latitudinal variations in climate © 2016 Pearson Education, Inc. Latitudinal variation in sunlight intensity is caused by the curved shape of Earth . Sunlight strikes the tropics, regions between 23.5 north and 23.5 south latitude, most directly . At higher latitudes, where sunlight strikes Earth at an oblique angle, light is more diffuse © 2016 Pearson Education, Inc. Figure 40.3-1 Atmosphere 90N (North Pole) Low angle of incoming sunlight 23.5N (Tropic of Cancer) Sun overhead at equinoxes 0 (Equator) 23.5S (Tropic of Capricorn) Low angle of incoming sunlight 90S (South Pole) © 2016 Pearson Education, Inc. Global air circulation and precipitation patterns are initiated by intense solar radiation near the equator . Warm, wet air rising near the equator creates precipitation in the tropics . Dry air descending at 30 north and south latitudes causes desert conditions . This pattern of precipitation and drying is repeated at the 60 north and south latitudes and the poles © 2016 Pearson Education, Inc. Figure 40.3-2 66.5N (Arctic Circle) Descending 60N dry air 30N absorbs Westerlies moisture. 30N Ascending Northeast trades moist air releases 0° moisture. Southeast trades 30S 0° Westerlies 60S 66.5S (Antarctic Circle) © 2016 Pearson Education, Inc. Figure 40.3-2a 66.5N (Arctic Circle) 60N Westerlies 30N Northeast trades 0 Southeast trades 30S Westerlies 60°S 66.5S (Antarctic Circle) © 2016 Pearson Education, Inc. Variation in the speed of Earth’s rotation at different latitudes results in the major wind patterns . Trade winds blow east to west in the tropics . Westerlies blow west to east in temperate zones © 2016 Pearson Education, Inc. Figure 40.3-2b Descending dry air 30N absorbs moisture. Ascending moist air releases moisture. 0 © 2016 Pearson Education, Inc. Regional Effects on Climate . Climate is affected by seasonality, large bodies of water, and mountains © 2016 Pearson Education, Inc. Seasonality . Seasonal variations of light and temperature increase steadily toward the poles . Seasonality at high latitudes is caused by the tilt of Earth’s axis of rotation and its annual passage around the sun . Belts of wet and dry air straddling the equator shift throughout the year with the changing angle of the sun . Changing wind patterns affect ocean currents © 2016 Pearson Education, Inc. Figure 40.4 March equinox December solstice 60N Constant tilt of 23.5 30N June solstice 0 (Equator) 30S September equinox © 2016 Pearson Education, Inc. Bodies of Water . Oceans, their currents, and large lakes moderate the climate of nearby terrestrial environments . The California Current carries cold water southward along western North America . The Gulf Stream carries warm water from the equator to the North Atlantic © 2016 Pearson Education, Inc. Figure 40.5 Labrador Current California Gulf Stream Current PACIFIC ATLANTIC OCEAN OCEAN © 2016 Pearson Education, Inc. 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 warmer air from offshore © 2016 Pearson Education, Inc. Mountains . Rising air releases moisture on the windward side of a peak and creates a “rain shadow” as it absorbs moisture on the leeward side . Many deserts are found in the “rain shadow” of mountains © 2016 Pearson Education, Inc. Figure 40.6 Air flow Windward side Leeward side of mountains of mountains Mountain range Ocean © 2016 Pearson Education, Inc. Mountains affect the amount of sunlight reaching an area . In the Northern Hemisphere, south-facing slopes receive more sunlight than north-facing slopes . Every 1,000-m increase in elevation produces a temperature drop of approximately 6C © 2016 Pearson Education, Inc. Climate and Terrestrial Biomes . Biomes are major life zones characterized by vegetation type (terrestrial biomes) or physical environment (aquatic biomes) . Climate determines vegetation type and limits the distribution of terrestrial biomes . Latitudinal patterns in terrestrial biomes reflect the latitudinal patterns of climate © 2016 Pearson Education, Inc. Figure 40.7 30N Tropic of Cancer Equator Tropic of Capricorn 30S Tropical forest Temperate broadleaf forest Savanna Northern coniferous forest Desert Tundra Chaparral High mountains Temperate grassland Polar ice © 2016 Pearson Education, Inc. A climograph plots the annual mean temperature and precipitation in a region . Biomes are affected not just by average temperature and precipitation, but also by the pattern of temperature and precipitation through the year © 2016 Pearson Education, Inc. Figure 40.8 Desert Temperate broadleaf Temperate forest Tropical forest grassland ) C 30 15 Northern coniferous forest 0 Arctic and alpine tundra Annual mean temperature ( temperature mean Annual -15 0 100 200 300 400 Annual mean precipitation (cm) © 2016 Pearson Education, Inc. Natural and human-caused disturbances alter the distribution of biomes . A disturbance is an event that changes a community by removing organisms and altering resource availability . For example, frequent fires kill woody plants and can prevent savanna from transitioning into woodland © 2016 Pearson Education, Inc. General Features of Terrestrial Biomes . Terrestrial biomes are often named for major physical or climatic factors and for vegetation © 2016 Pearson Education, Inc. Vertical layering is an important feature of terrestrial biome . In a forest it might consist of an upper canopy, low- tree layer, shrub understory, ground layer of herbaceous plants, forest floor, and root layer . Layering of vegetation provides diverse habitats for animals © 2016 Pearson Education, Inc. Terrestrial biomes usually grade into each other, without sharp boundaries . The area of intergradation, called an ecotone, may be wide or narrow © 2016 Pearson Education, Inc. Major features of terrestrial biomes include their