Ecology The study of how organisms interact with each other and their environment The primary goal of ecology is to understand the distribution and abundance of organisms Chapter 52 An Introduction to Ecology 52 1 Levels of Ecological Study There are five main levels of ecology cid 127 Organisms Populations Communities Ecosystems The Biosphere Organismal Ecology Population Ecology Community Ecology Ecosystem Ecology Global Ecology function Abiotic Factors Biotic Factors At the organism level researchers look at morphological physiological and behavioral adaptations that allow the organisms to live in a particular environment A population is a group of individuals of the same species who live in the same area at the same time cid 127 When researchers focus on populations they study how the number and distribution of individuals in a population changes over time A community consists of populations of different species that interact with each other within a particular area cid 127 When researchers study communities they look at the interactions between species and the consequences of those interactions An ecosystem consists of all the organisms in a particular region as well as the nonliving components The physical and chemical components air water and nonliving parts of soil are called abiotic Researchers study how the nutrients and energy move along organisms and through the surrounding atmosphere soil and water The Biosphere is a thin zone surrounding the Earth where all life can exist both land and water ecosystems The biosphere is 5 km below land and 10 km in the deepest trenches of the sea as well as 10 km up into the atmosphere Conservation Biology Applies All Levels of Ecological Study Conservation Biology is the effort to study preserve and restore threatened genetic diversity in populations species diversity in communities and ecosystem 52 2 What Determines the Distribution and Abundance of Organisms Biogeography is the study of how organisms are distributed geographically The geographic distribution of organisms is called the range No single species can survive in all environmental conditions present on earth No enzyme can function well in both extremely high and extremely low temperatures Because of fitness trade offs organisms tend to be adapted to a limited set of abiotic factors Biotic factors are the living aspects of an environment interactions with other organisms These limit the ability of a species to persist in a given area as well History Matters Past Abiotic and Biotic Factors Influence Present Patterns Dispersal is the movement of individuals from their place of origin to the location where they live and breed as adults The Wallace Line Barriers to Dispersal The Wallace Line separates species with Asian and Australian Affinities It formed because a deep trench in the ocean maintained a water barrier to dispersal even when ocean levels dropped during glaciations Landforms on either side of the line remained isolated at a time when most other islands became connected The Influence of Humans Humans have transported thousands of species across physical barriers to new locations both on purpose and on accident Exotic species are ones that are not native It is invasive if it spreads rapidly and competes successfully with native species The microorganisms that humans introduce to new areas can also dramatically affect species distributions by causing disease The range of every species on Earth is limited by a combination of abiotic and biotic factors that occured in the past and occur in the present Biotic and Abiotic Factors Interact 52 3 Climate Patterns Why Are the Tropics Wet Hadley cells Climate consists of the long term weather conditions found in a particular area cid 127 Weather consists of the short term atmospheric conditions of temperature precipitation sunlight and wind cid 127 When average annual rainfall is mapped for regions around the globe it is clear that areas along the equator receive the most moisture Locations 30 degrees latitude north and south of the equator are among the driest on the planet Air heated by the strong sunlight along the equator expands lowering its pressure and causing it to rise warm air holds a lot of moisture cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 As air rises above the equator it radiates heat into space and expands into the larger volume of the atmosphere thus lowering its density and temperature As rising air cools its ability to hold water declines thus creating high levels on precipitation along the equator As more air is heated along the equator the cooler older air above earths surface is pushed poleward cid 127 When the air mass has cooled enough its density increases and it begins to sink As it sinks it absorbs more and more solar radiation reflected from Earth s surface and begins to warm while being pushed to the surface by higher density As the air warms it also gains the ability to hold more water The air approaching the Earth holds on to its water and little rain occurs where it returns to air above it the surface Why Are the Tropics Warm and the Poles Cold regions closer to the poles arrives at a low angle much less energy is received per unit area What Causes Seasonality in Weather its axis there would be no seasons What Regional Effects Do Mountains and Oceans Have on Climate receive this dry air are said to be in rain shadow cid 127 Over the course of a year regions at or near the equator receive much more sunlight per unit area and therefore much more energy per unit area than At the equator the sun is often directly overhead At an angle of 90 degrees the Earth receives the maximum sunlight per unit area Because the Earth s surface slopes away from the equator the sun strikes the surface at lower and lower angles moving toward the poles When sunlight In March and September the equator faces the sun most directly During these months the tropics receive the most solar radiation If the Earth did not tilt on cid 127 Once cooled air has passed the crest of a mountain range the air is relatively dry because much of its moisture content has already been released Areas that cid 127 While the presence of mountain ranges tends to produce extremes in precipitation the
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