Chapter Summary
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53.1 Ecology Is the Study of the Interrelationships among Organisms and the Environment
Ecology differs from environmentalism, which involves the use of ecological knowledge to inform our stewardship of natural resources.
Ecologists have a use-
inspired focus to their research, motivated by a desire to improve Earth’s ecological problems. Ecology is studied at multiple levels of organization, ranging from individuals to the biosphere. Review Figure 53.1
53.2 Global Climate Is a Fundamental Component of the Physical Environment
Climate and weather both refer to atmospheric conditions, but climate represents conditions over years to millennia whereas weather represents conditions over days to weeks.
Solar radiation drives global climate. About 30 percent of the solar radiation that hits Earth is reflected back to space. The rest is absorbed either by the atmosphere (20%) or by Earth’s surface (50%). Greenhouse gases in the atmosphere allow sunlight into Earth’s atmosphere but trap heat radiating back out toward space. Review Figure 53.2, Animation 53.1
Latitudinal differences in solar energy input drive patterns of atmospheric circulation. Review Figures 53.3, 53.5
The interaction of Earth’s rotation and north–
south air mass movements generate prevailing winds, which in turn drive ocean currents. Review Figures 53.6, 53.7 The seasons are a consequence of Earth’s tilt and orbit around the sun. Review Figure 53.8
53.3 Topography, Vegetation, and Humans Modify the Physical Environment
On land, Earth’s topography creates rain shadows and temperature inversions, producing variation in temperature and precipitation Review Figure 53.9A and B, Animation 53.2
The topography of the ocean floor produces variation in water depth, which affects light penetration and water temperature, pressure, and movement, creating aquatic zones and ocean upwelling. Review Figure 53.9C and D
Vegetation, especially forests, affects climate through the process of evapotranspiration. Review Figure 53.10
53.4 Biogeography Is the Study of How Organisms Are Distributed on Earth
Patterns of biogeography are interconnected across a hierarchy of scales, ranging from global to regional to landscape to local. Review Focus: Key Figure 53.12
Biomes are groups of ecologically similar dominant plants that are shaped by patterns of temperature and precipitation. Review Figure 53.13, Activities 53.1, 53.2
Earth’s diversity varies from continent to continent, forming biogeographic regions and reflecting evolutionary isolation as a consequence of Earth’s geological history. Review Figure 53.14, Activity 53.3
Earth’s diversity varies with latitude. Hypotheses explaining this variation rely on multiple factors, including geographic area, time, climate, and productivity. Review Figure 53.15
53.5 Geographic Area and Humans Affect Regional Species Diversity
Species–
area relationships, in which species diversity increases with area and distance, have been shown for islands and area fragments. Review Figure 53.16 The theory of island biogeography states that the number of species on an island is a balance between immigration and extinction rates. Smaller islands have lower species diversity because they have higher extinction rates and lower immigration rates compared with larger islands. Review Figure 53.17, Animations 53.3, 53.4, Activity 53.4
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