EVPP 110 Lecture
Instructor: Dr. Largen Fall 2002

• Ecosystem
• a concept in which the physical and biological components of the environment are considered as a single, interactive system
• two main categories
• terrestrial
• aquatic

• 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 ecosystem

• Biomes
• major communities of organisms that
• have a characteristic appearance
• are distributed over a wide land area
• defined largely by regional variations in climate

• 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 organisms

• distribution of biomes results from interaction of
• physical features of the earth
• two key physical factors
• amount of solar heat
• global atmospheric circulation
• together these factors dictate local climate
• two most important climatic factors are
• precipitation
• temperature

• 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 biomes

• why the tropics are warmer?
• since the earth is a sphere, some parts receive more energy from the sun than others on a 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 area

• 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 precipitation

• key natural and physical elements
• precipitation
• 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 ultimate source of most moisture

• 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 as temperature decreases

• 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 from which the wind is blowing)

• 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 different

• 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 temperature

• 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 ecosystems

• 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 seasons

• 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/ latitude

• 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 an 800 km increase in latitude
• this is reason "timberline" (the elevation above which trees do not grow) occurs at progressively lower elevations as one moves farther from the equator

• Biomes
• are terrestrial climax communities with wide geographic distribution
• concept is useful for describing in broad terms
• the general structure of the ecosystem
• the types of niches present
• of the same type from different areas will exhibit variations in the exact species present
• affected by two nonbiological factors
• temperature
• precipitation

• Biomes
• major biomes of the world
• desert
• grassland
• savanna
• tropical rainforest
• temperate deciduous forest
• taiga or boreal forest
• tundra

• deserts
• dry places where rainfall is <25 cm/yr
• so little that vegetation is sparse and survival depends on water conservation
• world’s great deserts are located in the interiors of continents
• Sahara in Africa
• Gobi in Asia
• Great Sandy Desert in Australia

• deserts
• organisms have evolved adaptations to help them survive
• restricting activity to times of the year when water is present
• avoiding high temperatures by living in deep, cool, & moist (sometimes) burrows
• emerging only at night when temperatures are lower, especially if active year round
• drinking large quantities of water when it is available (camels) &then survive long, dry periods

• Grasslands
• also known as temperate grasslands, prairies, steppes
• widely distributed throughout temperate regions
• ~ halfway between equator & poles
• rainfall is ~ 25cm -75cm per year
• tend to be windy with hot summers, cold to mild winters
• grasses make up 60%-90% of the vegetation

• Grasslands
• once covered much of interior North America, were widespread in Eurasia & South America
• often highly productive when converted to agricultural use
• many of the agricultural lands of the US & Canada were originally occupied by grasslands (prairies)
• roots of perennial grasses characteristically penetrate far into soil
• grassland soils, therefore, tend to be deep and fertile

• Grasslands
• temperate grasslands are often populated by herds of grazing mammals
• in North America, huge herds of bison and pronghorns once inhabited the prairies
• herds are almost all gone now
• most of the prairies have been converted into the richest agricultural region on earth

• Savanna
• great grasslands located in dry climates that border the tropics
• transitional between tropical rainforest and desert (on global scale)
• rainfall is 50cm-150cm /yr & occurs seasonally
• period of heavy rainfall followed by prolonged drought
• predominant plants are grasses
• with widely spaced, drought resistant trees
• landscape is open

• Savanna
• many of its animals and plants are active only during the rainy season
• fire is common and trees tend to be fire-resistant
• savannas are increasingly being converted to agricultural use
• causing the inhabitants of savannas to struggle to survive

• Tropical rainforest
• rainfall is >200cm/yr
• temperatures are warm and relatively constant, no frost
• richest ecosystems on earth
• contain ~ half of all species of terrestrial plants and animals
• in 1sq mi of tropical forest in Rondonia, Brazil there are 1200 species of butterflies
• which is twice the number found in the U.S. and Canada combined

• Tropical rainforest
• communities are diverse
• each kind of organism is often represented in a given area by only a few individuals
• located near the equator
• South America, Africa, southeast Asia
• are being destroyed
• many of the species in rainforests have never been seen by humans
• during our lifetime, a quarter of the world’s species will disappear with the rainforests

• temperate deciduous forests
• rainfall is 75cm-100cm per year
• in areas with warm climates (warm summers and cool winters)
• plants grow actively for ~1/2 year
• found in northeastern US, eastern Canada, Eurasia
• often populated by deer, beaver, bear, raccoon
• generally have a lower number of species but a higher number of individuals per species
• trees are the major producers

• Taiga
• rainfall is 25cm-100cm per year
• climate is humid due to low evaporation resulting from generally low temperatures
• winters are long and cold
• soil freezes in winter
• northern forests of coniferous trees such as hemlock, spruce, fir
• needle-shaped leaves limit moisture loss
• pyramid shapes accommodate snow
• is one of the largest ecosystems on earth

• Taiga
• has very short growing season for farming so few people live there
• populated by many types of large mammals and carnivores such as moose, elf, deer, wolves, bear, lynx
• has been used for fur trapping and lumber production
• located in a ring that extends across vast areas of Asia and North America
• also known as boreal forest, northern coniferous forest

• tundra
• located in the far north of the taiga and south of the polar ice
• rainfall is <25cm/yr
• soil layer is known as permafrost
• it is permanently frozen
• extremely cold and windy
• open, grassland that is often boggy
• enormous ecosystem that covers 1/5^th of the earth’s land area

• tundra
• no trees grow in the area
• herbs are perennials that grow rapidly during the brief summer
• populated by large grazing mammals such as musk-oxen, caribou, reindeer and carnivores such as wolves, foxes, lynx