11Unit 2:Terrestrial EcosystemsEVSC 1112Four Units of Course4Global Environments4Terrestrial Ecosystems4Aquatic Ecosystems4Environmental management3Ecosystems4Ecosystem– a concept in which the physical and biological components of the environment areconsidered as a single, interactive system– two main categories• terrestrial (unit 2)• aquatic (unit 3)4Ecosystems & Biomes4 Ecosystem– similar physical environments lead to• the evolution of organisms similar in form and function• similar ecosystems– this is known as the rule of climatic similarity• leads to the concept of the biome– which is a kind of ecosystem5Ecosystems & Biomes4Biomes– major communities of organisms that• have a characteristic appearance• are distributed over a wide land area– defined largely by regional variations in climate6Ecosystems & Biomes4 Biomes– the strong relationship between climate and life suggests that• if we know the climate of an area– we can predict what biome will be found there» approximate biomass» approximate productivity» dominant types of organisms27Ecosystems and biomes4 distribution of biomes results from interaction of– physical features of the earth– two key physical factors• amount of solar heat• global atmospheric circulation4 together these factors dictate local climate– two most important climatic factors are• precipitation• temperature8Climate shapes the character of ecosystems4 why are there variations in the earth’s climate?– different parts of the earth receive different amounts of energy from the sun• variations in the amount of energy received from the sun– responsible for» many of the major climatic differences on the earth» and, indirectly, for much of the diversity in the earth’s biomes9Climate shapes the character of ecosystems4 why the tropics are warmer?– since the earth is a sphere, some parts receive more energy from the sun than others ona per unit area basis• tropics are warmer than temperate regions– because they receive more sun energy per unit area• poles are colder than other areas– because they receive less sun energy per unit area10Climate shapes the character of ecosystems4 key natural and physical elements– precipitation• all organisms require water• on land, water is often scarce• important aspects– total amount per year– form in which it arrives– seasonal distribution• ecosystem productivity increase with increased precipitation1112Climate shapes the character of ecosystems4 key natural and physical elements– precipitation3• generally low near 30° N & S latitude– where air is descending & warming• partly as a result of this, all the great deserts of world lie near 30° N or S latitude• other major deserts are formed in the interiors of large continents– where precipitation is limited because of the great distance from the sea, the ultimatesource of most moisture13Climate shapes the character of ecosystems4 key natural and physical elements– precipitation• precipitation is generally higher near equator and 60° north and south latitude– where air is rising & cooling» releasing moisture it contains as its ability to hold the moisture decreases astemperature decreases1415Climate shapes the character of ecosystems4 key natural and physical elements– precipitation• rain shadow effect can produce deserts– some mountains intercept moist winds from the sea» air encounters mountains & then rises» as air rises, its ability to hold moisture decreases– results in increased precipitation on the windward side of mountains (the side fromwhich the wind is blowing)16Climate shapes the character of ecosystems4 key natural and physical elements– precipitation• rain shadow effect can produce deserts– air descends the other side of the mountains (the leeward side)» is warmed & moisture-holding capacity increases» which tends to inhibit precipitation– example, Sierra Nevada Mountains of CA» eastern sides much drier than western sides & vegetation often very different171819Climate shapes the character of ecosystems4 key natural and physical elements– temperature• most organisms are adapted to live within a relatively narrow range of temperatures– won’t survive if temperatures are significantly warmer or colder» ex., growing season of plants is influenced by temperature• ecosystem productivity increases with increased temperature42021Climate shapes the character of ecosystems4 key natural and physical elements– temperature is affected by latitude• tropical latitudes– temperatures higher in tropics» more sunlight falls per unit area– highest mean global temperatures occur near equator– there are no seasons in the tropics» there is little variation in mean monthly temperature in tropical ecosystems22Climate shapes the character of ecosystems4 key natural and physical elements– temperature is affected by latitude• temperate latitudes– temperatures decrease as you move from the equator toward temperate latitudes» less sunlight strikes earth per unit area– temperature variations increase because of increasingly marked seasons2324Climate shapes the character of ecosystems4 key natural and physical elements– temperature is affected by elevation• higher altitudes become progressively colder– at a given latitude, air temperature falls about 6°C/1000m increase in elevation– ecological consequences of temp varying w/elevation = temp varying w/ latitude25Climate shapes the character of ecosystems4 key natural and physical elements– temperature is affected by elevation• higher altitudes become progressively colder– in North America, a 1000m increase in elevation results in a temp drop ~ to that of an800 km increase in latitude– this is reason “timberline” (the elevation above which trees do not grow) occurs atprogressively lower elevations as one moves farther from the equator2627Figure: Vegetation, Latitude, Altitude28Figure: Temperature and latitude29Succession4 Succession– concept that communities proceed through a series of regular, predictable changes in structureover time• results in a climax community– a stable, long lasting community5– type that results depends largely on climate– occurs because activities of organisms cause changes in their surroundings• that make local environment suitable for other kinds of organisms30Succession4 Succession– pace and direction affected by several