1 Communities, Biomes, and Ecosystems Section 1: Community Ecology Section 2: Terrestrial Biomes Section 3: Aquatic Ecosystems Living organisms can be studied at different levels of complexity. From least to most complex, these levels are (in an ecological context): Individual Population Community Ecosystem Biome Biosphere Biological Complexity Biosphere Biome Ecosystem Community Population Individual 3.1 Community Ecology Communities A biological community is a group of interacting populations that occupy the same area at the same time. Oasis 3.1 Community Ecology Limiting Factors Any abiotic factor or biotic factor that restricts the numbers, reproduction, or distribution of organisms is called a limiting factor. Includes sunlight, climate, temperature, water, nutrients, fire, soil chemistry, and space, and other living things 3.1 Community Ecology Range of Tolerance An upper limit and lower limit that define the conditions in which an organism can survive The ability of any organism to survive when subjected to abiotic factors or biotic factors is called tolerance. Law of Tolerance The law of tolerance states that For each abiotic factor, an organism has a range of tolerances within which it can survive. Number of organisms Tolerance range Optimum range Unavailable niche Marginal niche Preferred niche Marginal niche Unavailable niche Examples of abiotic factors that influence size of the realized niche:
2 3.1 Community Ecology Ecological Succession The change in an ecosystem that happens when one community replaces another as a result of changing abiotic and biotic factors is ecological succession. There are two types of ecological succession primary succession and secondary succession. Ecological Succession Ecological succession is the process by which communities in a particular area change over time. Succession takes place as a result of complex interactions of biotic and abiotic factors. Past community Some species in the past community were out-competed or did not tolerate altered abiotic conditions. Community composition changes with time Present community The present community modifies such abiotic factors as: Light intensity and quality Wind speed and direction Air temperature and humidity Soil composition and water content Future community Changing conditions in the present community will allow new species to become established. These will make up the future community. 3.1 Community Ecology The establishment of a community in an area of exposed rock that does not have any topsoil is primary succession. Primary Succession Primary succession refers to colonization of a region where there is no pre-existing community. Examples include: newly emerged coral atolls, volcanic islands newly formed glacial moraines islands where the previous community has been extinguished by a volcanic eruption A classical sequence of colonization begins with lichens, mosses, and liverworts, progresses to ferns, grasses, shrubs, and culminates in a climax community of mature forest. In reality, this scenario is rare. Hawaii: Local plants are able to rapidly recolonize barren areas Mount St Helens Revegetation: Mt St Helens Primary succession more typically follows a sequence similar to the revegetation of Mt St Helens, USA, following its eruption on May 18, The vegetation in some of the blast areas began recovering quickly, with fireweed growing through the ash within weeks of the eruption. Animals such as pocket gophers, mice, frogs, and insects were hibernating below ground and survived the blast. Their activities played an important role in spreading seed and mixing soil and ash.
3 3.1 Community Ecology The orderly and predictable change that takes place after a community of organisms has been removed but the soil has remained intact is secondary succession. Secondary succession occurs where an existing community has been cleared by a disturbance that does not involve complete soil loss. Such disturbance events include hurricane damage, forest fires and hillside slips. Secondary Succession Because there is still soil present, the ecosystem recovery tends to be more rapid than primary succession, although the time scale depends on the species involved and on climatic and edaphic (soil) factors. Hurricane Forest fire Effects of Latitude and Climate Weather is the condition of the atmosphere at a specific place and time. One of the keys to understanding these communities is to be aware of latitude and climatic conditions. The distance of any point on the surface of Earth north or south from the equator is latitude. Biomes The biosphere encompasses all living things on Earth. It comprises a number of aquatic and terrestrial biomes. Biomes are the largest geographically based biotic communities that can be conveniently recognized. Biomes within the same category have specific, characteristic features. Ocean biome Terrestrial Biomes Terrestrial biomes are recognized for all the major climatic regions of the world and are classified on the basis of their predominant vegetation type. The same biome may occur in widely separated regions. Desert biome
4 The average weather conditions in an area, including temperature and precipitation, describe the area s climate. Biomes are classified by their plants, temperature, and precipitation. The graph shows how temperature and precipitation influence the communities. Predicting Biome Distribution Temperature and precipitation are excellent predictors of biome distribution. Temperature decreases from the equator to the poles. Predicting Biome Distribution Temperature and precipitation act together as limiting factors to determine the type of desert, grassland, or forest biome in a region. Polar Arctic region Latitudinal regions Subarctic region Temperate region Equatorial Tropical region Annual precipitation (mm) Tundra cm per year -34 C 12 C Geographic location: South of the polar ice caps in the Northern Hemisphere Abiotic factors: soggy summers; permafrost; cold and dark much of the year
5 Tundra Tundra Communities The tundra biome is found in the Arctic and high in the mountains at all latitudes. It is dominated by lowgrowing perennial plants. The Arctic tundra is very wet even though rainfall is low and this is because the water cannot drain down through the permafrost (permanently frozen ground). Tundra: northern Canada Dominant plants Perennial herbs and small shrubs. Floral richness Generally low; higher in tropical alpine regions. Faunal richness Low: many birds migrate in for summer, a few species of insects are abundant in summer. Soil biota Few species Arctic tundra, summer Migrating caribou, the Arctic Arctic tundra Physical Factors in Tundra Example: Greenland 73 N Temperature range: 28 C Total annual rainfall: 23 cm Boreal Forest cm per year -54 C 21 C Geographic location: northern part of North America, Europe, and Asia Abiotic factors: summers are short and moist; winters are long, cold, and dry The boreal forest biome extends in a broad band across both North America and Eurasia. It is the world s largest biome. It is found at high latitudes, south of the tundra and is dominated by coniferous trees. The winters are long and severe, while the summers are short, and mild and humid. Boreal Forest (Taiga) Taiga Communities Dominant plants Trees (evergreens), shrubs, and perennial herbs. Floral richness Low in the tree tops, higher in the understorey. Faunal richness Low, but with summer peaks in migratory birds. Soil biota Very rich in the deep litter layer.
6 Physical Factors in Boreal Forests Example: Fort Vermillion, Alberta 58 N Temperature range: 41 C Total annual rainfall: 31 cm Temperate Forest cm per year -30 C 30 C Geographic location: south of the boreal forests in eastern North America, eastern Asia, Australia, and Europe Abiotic factors: well-defined seasons; summers are hot, winters are cold Temperate Woodland and Shrubland cm per year 10 C 40 C Geographic location: surrounds the Mediterranean Sea, western coast of North and South America, South Africa, and Australia Abiotic factors: summers are very hot and dry; winters are cool and wet Temperate forests occur throughout mid latitudes where there is a high annual rainfall. Temperate forests are usually deciduous, but where seasonal fluctuations are moderated by proximity to the coast, the forests are evergreen and are termed temperate rainforests. Temperate rainforests occur in south-eastern Australia, New Zealand, along the Pacific North-West coast of the United States. Temperate Forests Temperate deciduous forest Temperate rainforest Temperate Deciduous Forests Temperate deciduous forests occur throughout mid latitudes where there is sufficient moisture to support large trees. They occur in eastern North America, eastern Asia, and in parts of western Europe. Rainfall is evenly distributed throughout the year, with cold, snowy winters and warm, moist summers. Temperate Forest Communities Dominant plants Trees and shrubs Floral richness Rich shrub layer. many tree species in southeast USA and East Asia. Faunal richness Rich: many migrant birds. The richest biome in amphibians. Rich in summer in insects. Soil biota Rich
7 Physical Factors in Temperate Forests Example: Madison, Wisconsin 43 N Temperature range: 31 C The temperature fluctuates dramatically between summer and winter. Total annual rainfall: 81 cm Ample falls throughout the year. Temperate Grassland cm per year -40 C 38 C Geographic location: North America, South America, Asia, Africa, and Australia Abiotic factors: summers are hot; winters are cold; moderate rainfall; fires possible Temperate grasslands or prairies occur in mid latitudes, in regions that are relatively dry for much of the year. They occur in many parts of the world, and include: The Pampas of Argentina Temperate Grasslands The South African veldt The Great Plains of the USA Grasslands are highly productive and large regions have been converted to agriculture. Grassland Communities Dominant plants Perennial grasses and other herbaceous pasture plants Floral richness Relatively rich. Faunal richness Relatively rich in mammal fauna. relatively few birds because of the simple structure. Soil biota Rich North American bison Pronghorn antelope Physical Factors in Temperate Grasslands Example: Pueblo, Colorado 38 N Temperature range of 24 C The temperature fluctuates widely, with hot summers, cold winters. In some grasslands, most precipitation occurs in the winter. In others, the majority falls in summer. Total annual rainfall: 31 cm Desert 2 26 cm per year high: 20 C 49 C; low: -18 C 10 C Geographic location: every continent except Europe Abiotic factors: varying temperatures; low rainfall
8 Desert Environments Desert environments experience extremes in temperature and humidity, but they are not uniform with respect to these factors. Physical conditions vary widely within the one general environment. Crevices, burrows, and the presence of rock overhangs and vegetation create microclimates where extremes in physical conditions are reduced compared to the desert surface. Hot Deserts Deserts are arid regions (annual rainfall generally less than 25 cm). The hot desert biome is found in two belts, centered at 30 latitude north and south of the Equator. Hot deserts receive most of their rainfall in summer. The driest regions are in central Australia and the middle of the Sahara Desert. The temperature range is approximately 30 C, and the winter and summer are both very warm. Rainbow Valley, central Australia Sahara Desert Hot Desert Communities Dominant plants Succulent plants such as cacti; many different growth forms. Floral richness Relatively high; many annuals. Faunal richness Very rich in rodents, reptiles, and butterflies; the richest bee communities on Earth. Physical Factors in Hot Deserts Example: Khartoum, Sudan 15.5 N Temperature range: 9 C The winter and summer are both very warm. Annual total rainfall: 15 cm Soil biota Poor in species Cold Deserts The cold desert biome is found in dry regions in the mid to high latitudes, especially in the interiors of large continents. Cold deserts also occur at high altitudes in the rain shadows of mountain ranges. Cold deserts receive most of their small amount of rainfall in winter. Cold Desert Communities Dominant plants Low stature shrubs and herbaceous plants. Floral richness Low, with few species. Faunal richness Rich in seed-eating birds, ants, and rodents but low in most other taxonomic groups. Sagebrush steppe, California, USA Los Glaciares National Park, Argentina Soil biota Poor in species Sagebrush steppe, California, USA
9 Physical Factors in Cold Deserts Example: Cheyenne, Wyoming 41 N Temperature range: 23 C The winters are cold; summers are much warmer. Annual total rainfall: 38 cm Tropical Savanna cm per year 20 C 30 C Geographic location: Africa, South America, and Australia Abiotic factors: summers are hot and rainy; winters are cool and dry Savanna & Thorn Forests Tropical savannas are found in central and eastern Africa, and in tropical and subtropical regions of South America and Australia. Thorn forests are found on the equatorial sides of hot deserts. Both have mild, dry winters and mild, wet summers. Unlike savanna, thorn forests generally lack grasses. This reflects the increased aridity of the climate. Savanna Communities Dominant plants Shrubs and small trees; grasses. Floral richness Moderate in thorn forest. Low in savanna. Faunal richness Rich mammal fauna, moderately rich in birds, reptiles, and insects. Soil biota Rich Physical Factors in Savannas Example: Kayes, Mali 14 N Temperature range: 10.7 C Annual total rainfall: 74 cm Tropical Seasonal Forest >200 cm per year 20 C 25 C Geographic location: Africa, Asia, Australia, and South and Central America Abiotic factors: rainfall is seasonal
10 A Tropical Rainforest Tropical Rain Forest cm per year 24 C 27 C Geographic location: Central and South America, southern Asia, western Africa, and northeastern Australia Abiotic factors: humid all year; hot and wet The high species diversity of tropical rainforests can be supported because of the wide variety of microhabitats provided by the layered structure of the forest. The physical conditions at the uppermost level are quite different to those at the forest floor with respect to light intensity (and quality), wind speed, and humidity. Canopy Subcanopy Understorey Ground layer Light: light intensity Wind: wind speed Hum: humidity Rainforest Factors Light: 70% Wind: 15 kmh -1 Hum: 67% Light: 50% Wind: 12 kmh -1 Hum: 75% Light: 12% Wind: 9 kmh -1 Hum: 80% Light: 6% Wind: 5 kmh -1 Hum: 85% Light: 1% Wind: 3 kmh -1 Hum: 90% Light: 0% Wind: 0 kmh -1 Hum: 98% Tropical evergreen forests are found in equatorial regions where total annual rainfall exceeds 250 cm and the dry season lasts for no more than 2-3 months. These forests are species-rich. The climate is warm and rainy all year round. Tropical Rainforests Rainforest Communities Physical Factors in Tropical Rainforests Dominant plants Trees and vines Example: Iquitos, Peru 3 S Floral richness Extremely high; the richest of all biomes. Temperature range: 2.2 C Annual total rainfall: 262 cm Faunal richness Extremely rich in mammals, birds, amphibians, and arthropods. Soil biota Very rich, but not well known.
11 Mountains If you go up a mountain, you might notice that abiotic conditions, such as temperature and precipitation, change with increasing elevation. Polar Regions Border the tundra at high latitudes Polar regions are cold all year. Penguins in Antarctica Freshwater Ecosystems Only about 2.5 percent of the water on Earth is freshwater. Rivers and Streams The characteristics of rivers and streams change during the journey from the source to the mouth. Fast-moving rivers and streams prevent much accumulation of organic materials and sediment. Usually, there are fewer species living in the rapid waters. In slow-moving water, insect larvae are the primary food source for many fish, including American eel, brown bullhead catfish, and trout. Lakes and Ponds The temperature of lakes and ponds varies depending on the season.
12 Lakes and ponds are divided into three zones based on the amount of sunlight that penetrates the water. The area closest to the shore is the littoral zone. The limnetic zone is the open water area that is well lit and is dominated by plankton. The profundal zone is the deepest areas of a large lake. It is much colder and lower in oxygen than the other two zones. Transitional Aquatic Ecosystems Areas of land such as marshes, swamps, and bogs that are saturated with water and that support aquatic plants are called wetlands. Bog Marine Ecosystems The intertidal zone is a narrow band where the ocean meets land. Communities are constantly changing in this environment as a result of disturbance. Rocky Shore Environments Rocky shore environments typically exhibit marked physical gradients as a result of tidal movements. Horizontal and vertical gradients in salinity, temperature, dissolved oxygen, and exposure time are reflected in the communities found at different positions on the shore. Horizontal: from the low tide to the high tide marks Vertical: from the bottom to top surfaces of rocks and boulders.
13 Rocky Shore Factors Hypothetical values for physical factors in rock pools at different places on a rocky shore. Salin: salinity Temp: temperature DO: dissolved oxygen Exp: exposure time (per 12 hour tidal cycle) Open Ocean Ecosystems The photic zone is shallow enough that sunlight is able to penetrate. Salin: 42 gl Salin: 39 gl -1 Temp: 28 C Temp: 28 C DO:20% Exp: 12 h DO:30% Exp: 10 h Salin: 38.5 gl -1 Temp: 26 C DO:42% Exp: 8 h Salin: 37 gl -1 Salin: 36 gl -1 Salin: 35 gl- -1 Temp: 22 C Temp: 19 C Temp: 17 C DO:57% Exp: 6 h DO:74% Exp: 4 h DO:100% Exp: 0 h Open Ocean Ecosystems Below the photic zone lies the aphotic zone an area where sunlight is unable to penetrate. Open Ocean Ecosystems The benthic zone is an area along the ocean floor that consists of sand, silt, and dead organisms. Open Ocean Ecosystems The deepest region of the ocean is called the abyssal zone. Communities and Biomes Chapter Diagnostic Mosses and lichens are the first organisms to appear during which ecological stage of an ecosystem? A. primary succession B. secondary succession C. climax community D. end succession
14 Chapter Diagnostic Chapter Diagnostic Which biome is the most diverse? A. tundra B. tropical savanna C. tropical seasonal forest D. tropical rainforest Where is most of Earth s freshwater supply contained? A. in groundwater B. in streams C. in glaciers D. in wetlands 3.1 Formative What is a group of interacting populations that occupy the same area at the same time? A. a biome B. a community C. an ecosystem D. an environment 3.1 Formative Which is true of the zone of physiological stress? A. It is outside the range of tolerance. B. It is the optimum zone for survival. C. Organisms are unable to survive in this zone. D. There are fewer organisms in this zone. 3.1 Formative What occurs in the process of ecological succession? A. Environmental factors affect the survival of organisms. B. One biological community replaces another in the ecosystem. C. Organisms adapt to new biotic and abiotic factors. D. Pioneer species move in and replace existing species. 3.2 Formative By what characteristics are biomes primarily classified? A. by their average weather conditions B. by their latitudes and climates C. by the type of animal communities within them D. by the type of plant communities within them
15 3.2 Formative Which biome contains short grasses, caribou, polar bears, and has a layer of permafrost below the surface of the soil? A. taiga B. tundra C. arctic grassland D. polar regions 3.2 Formative Which biome is called a steppe in Asia, a prairie in North America, and a rangeland in Australia? A. boreal shrubland B. moderate meadowland C. temperate grassland D. tropical savanna 3.2 Formative Which is the most diverse of all biomes? A. desert B. tundra C. woodland D. tropical rainforest 3.3 Formative Why do oligotrophic lakes contain fewer plant and animal species than eutrophic lakes? A. They have swifter currents. B. They exist near urban areas. C. They exist at higher latitudes. D. They contain less organic matter. 3.3 Formative Which region of the lake has the highest biodiversity? A. littoral zone B. limnetic zone C. profundal zone D. benthic zone 3.3 Formative Which is the most diverse ecosystem? A. estuary B. salt marsh C. swamp D. wetland
16 3.3 Formative What makes an estuary such a unique ecosystem? A. the accumulation of nutrient-rich sediments and detritus B. the mixture of waters with different salt concentrations C. the variety of species adapted to live in slow currents D. the wide variety of waterfowl that nest and feed Chapter Assessment Look at the figure. Which is not true of the profundal zone? A. dominated by plankton B. deepest area of the lake C. very little light penetrates D. lower in oxygen Chapter Assessment Based on the information in the graph, what can be inferred about carbon dioxide in the atmosphere? Chapter Assessment Answer: The measured increase of carbon dioxide (CO 2 ) in the atmosphere is mainly due to the burning of fossil fuels. As carbon dioxide levels have increased, the average global temperature has increased. Chapter Assessment Use the figure below to infer which abiotic factor might limit the survival of steelhead trout. Answer: Temperature Standardized Test Practice What is the most critical limiting factor for a polar bear? A. precipitation B. soil type C. sunlight D. temperature
17 Standardized Test Practice The mature community in this diagram is a true climax community. A. true B. false Standardized Test Practice For which biome was this data collected? Average precipitation: cm per year Temperature range: 10 C 40 C Abiotic factors: summers are very hot and dry; winters are cool and wet A. desert B. boreal forest C. temperate woodland D. tropical seasonal forest Standardized Test Practice Standardized Test Practice What type of community is likely to exist near the top of a mountain? What type of organisms enables fish to live in the limnetic zone? A. tundra B. arctic desert C. coniferous forest D. temperate grassland A. bottom dwellers B. crustaceans C. insects D. plankton Standardized Test Practice What is the approximate average temperature and annual precipitation in the boreal forest biome? Average temperature ( C) Average precipitation (cm) A B C D