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Visualizing Environmental Science Ecosystems and Evolution Chapter 6 Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. Earth’s Major Biomes • Biome—a large, relatively distinct terrestrial region with similar climate (longterm weather pattern), soil, plants, and animals, regardless of where it occurs in the world – Encompasses many interacting ecosystems © 2014 John Wiley & Sons, Inc. All rights reserved. Factors That Affect Biomes • Temperature and precipitation have a predominant effect on biome distribution – Latitude • Temperature most important factor near poles • Precipitation more important in tropical and temperate regions • Elevation also affects biomes – Going from warmer to colder climates © 2014 John Wiley & Sons, Inc. All rights reserved. Arctic Tundra • Treeless biome in the far north that consists of boggy plains covered by lichens and mosses • Permafrost—layer of permanently frozen ground – Climate change causing permafrost to thaw • Harsh, cold winters and extremely short summers and seasonal snow melting • Alpine tundra occurs at higher elevations of mountains, above tree line • Low primary productivity and low resilience © 2014 John Wiley & Sons, Inc. All rights reserved. Boreal Forest/Taiga • Coniferous forests of pine, spruce, and fir, in the Northern Hemisphere, just south of tundra • Winters extremely cold and severe • Little precipitation, 20 in/year • Soil is acidic and mineral poor • Caribou, wolves, bear, moose, rodents, rabbits, lynx, birds in summer, lots of insects • Top source of industrial wood and fiber, leading to loss of forest © 2014 John Wiley & Sons, Inc. All rights reserved. Temperate Rain Forest • Coniferous forest with high precipitation, dense fog and cool weather • Northwest coast of NA, SE Australia, SA • Mild winters, cool summers • Slow decay, poor soil • Hemlock, fir, cedar, spruce, epiphytes, mosses, lichens and ferns • Squirrels, wood rats, elk, mule deer, birds, amphibians and reptiles • High producer of lumber and pulpwood • Overharvesting old-growth forest is an issue; see chapter 13 for debate over clearcutting © 2014 John Wiley & Sons, Inc. All rights reserved. Temperate Deciduous Forest • Forest biome that occurs in temperate areas where precipitation ranges from 30–50 in/year • Hot summers, cold winters • Topsoil rich in organic matter • Broad-leaf hardwood trees, lose leaves seasonally • Originally puma, wolves, and bison, now absent • Deer, bears, small mammals, birds • Original forests in Europe and NA mostly destroyed by logging and urbanization © 2014 John Wiley & Sons, Inc. All rights reserved. Temperate Grassland • Tallgrass prairies and shortgrass prairies • Hot summers, cold winters, and less rainfall (10 – 30 in/year) than in temperate deciduous forest biome • Soil rich in organic matter • More than 90% of tallgrass prairies were plowed for agriculture, NA’s rarest biome • Bison graze on mixed-grass prairie in Custer State Park, South Dakota © 2014 John Wiley & Sons, Inc. All rights reserved. Chaparral • Mild, moist winters; hot, dry summers • Referred to as having a “Mediterranean climate” • Small-leaved evergreen shrubs and small trees dominate • Lush vegetation during rainy winter season • Wildfires common in late summer and autumn – Many fire adapted plants that grow after a fire • Thin, unfertile soil © 2014 John Wiley & Sons, Inc. All rights reserved. EnviroDiscovery Using Goats to Fight Fire • California has 6000 wildfires each year with many people living in fire-prone chaparral • Goats are being used to clear hills of vegetation during the 6month fire season – 350 goats can clear an acre of heavy brush per day • Rare/endangered plant species are fenced off © 2014 John Wiley & Sons, Inc. All rights reserved. Desert • • • • • • • Plant growth limited by lack of precipitation Found in both temperate and tropical regions Daily temperature extremes Less than 10 inches of rain/year Sparse vegetation that includes cacti, yucca, and sagebrush Soil is low in organic matter but high in mineral content Animals – Typically small, mostly nocturnal – Insects, arachnids, desert-adapted amphibians, many reptiles • Threatened by human encroachment and environmental damage from off-road vehicles – Soil easily eroded and less vegetation grows to support native animals © 2014 John Wiley & Sons, Inc. All rights reserved. Savanna • Tropical grassland • Large herds of herbivores such as wildebeest, antelope, giraffe, zebra, elephant • Large carnivores such as lions and hyenas • Low or intense seasonal rainfall, 34–60 in/year, but with prolonged dry periods • Widely scattered or clumped trees such as the acacia • Low mineral-content soil • Savanna lost as land is converted into rangeland for cattle • Africa, N Australia, South America, W India © 2014 John Wiley & Sons, Inc. All rights reserved. Tropical Rain Forest • Lush, species rich forest that occurs where the climate is warm and moist year-round • Rains almost daily, 80–180 in/year • Weathered, mineral-poor soil • High species richness and diversity • Three layers of vegetation • In tropical dry forests precipitation seasonal • Industrial expansion and human population growth threaten the rain forests © 2014 John Wiley & Sons, Inc. All rights reserved. Florida’s Terrestrial Habitats • Imperceptible elevation changes • Pine Flatwoods – Acidic soil – Clay hardpan • Stores water • Lessens root penetration – Fire dependent – Species • Saw palmetto • Slash pine • Deer, fox, raccoon, possum, panther, snakes, burrowing owl Image and Habitat information from the South Florida Water Management District www.sfwmd.gov Florida’s Terrestrial Habitats • Scrub – Highest elevation – Sandy, well drained soil – Species • Sand Pine • Scrub oak • Deer, fox, raccoon, possum, panther, snakes, gopher tortoise, bobcat Image and Habitat information from the South Florida Water Management District www.sfwmd.gov Florida’s Terrestrial Habitats • Hardwood Hammock – Lowest elevation – Cooler – Species • • • • Gumbo Limbo Oaks Cabbage Palm (state tree) Deer, fox, raccoon, possum, panther, snakes, Image and Habitat information from the South Florida Water Management District www.sfwmd.gov Aquatic Ecosystems • Aquatic ecology – Freshwater ecosystems include • Standing-water (lakes and ponds) • Flowing-water (rivers and streams) • Wetlands (marshes and swamps) – Categories of organisms • Plankton—phytoplankton and zooplankton • Nekton—fish and turtles • Benthos—bottom-dwellers © 2014 John Wiley & Sons, Inc. All rights reserved. Freshwater Ecosystems • Occupy 2% of earth’s surface, yet play important role in hydrologic cycle • Standing-water, lakes and ponds have three zones – Littoral, limnetic, profundal • Zonation accentuates thermal stratification, temperature changes with depth • Human effects include eutrophication, unnatural nutrient enrichment © 2014 John Wiley & Sons, Inc. All rights reserved. Freshwater Wetlands • Marshes, dominated by grass-like plants, and swamps, dominated by woody shrubs • Shallow fresh water cover for at least part of the year • Water-tolerant vegetation • Waterlogged soils – Anaerobic, low rate of decomposition – Rich in organic material • Ecosystem services include wildlife habitat, flood mitigation and filtration of ground water • Wetlands threatened by pollution, development and agriculture © 2014 John Wiley & Sons, Inc. All rights reserved. Brackish Ecosystems: Estuaries • Estuary—coastal body of water, partly surrounded by land, with access to the ocean and fresh water from a river • Water levels rise and fall with tides • Salinity fluctuates from fresh water to brackish • Highly productive ecosystems with rapid nutrient circulation • Salt marshes—shallow wetlands with salt-tolerant grasses • Mangrove forests—tropical equivalent of salt marshes © 2014 John Wiley & Sons, Inc. All rights reserved. Three Species of Florida Mangroves •Red Mangroves usually grow near the shore of the water. It has red roots and is often referred to as the “walking mangrove” because its roots raise over the water. •Black Mangroves grow in higher areas Their roots spread near the trunk in shapes of fingers or pencils pointing up, exposing the roots to needed oxygen. •White Mangroves grow even higher than the black mangrove, and its roots aren’t visible. These trees tend to get rid of salt on the backs of the leaves. •Significant losses due to coastal development and aquaculture Community Responses to Changing Conditions Over Time: Succession • Ecological succession—the process of community development over time, through a sequence of species • Resident species modify the environment, making it more suitable for later species • Former concept of a stable ‘climax community’ has been replaced with reality that communities continue to change • Primary and secondary succession have specific species compositions © 2014 John Wiley & Sons, Inc. All rights reserved. Primary Succession • Change of species over time in a previously uninhabited environment • No soil, bare rock surfaces • Begins with pioneer community composed of acidic lichens that break up rock and form soil • Lichensmossesshrubseventually specific trees • Note the stages of primary succession on glacial moraine © 2014 John Wiley & Sons, Inc. All rights reserved. Primary Succession • Sandbars • Lava flows that have cooled © 2014 John Wiley & Sons, Inc. All rights reserved. Secondary Succession • Change in species composition after a disturbance in an area previously inhabited • Abandoned farmland, forest fire, clear-cut forest • Soil already present • Can take more than 100 years for secondary succession to occur • Typically crabgrasshorseweedpine treeshardwood trees © 2014 John Wiley & Sons, Inc. All rights reserved. Developing and Understanding of Evolution © 2014 John Wiley & Sons, Inc. All rights reserved. Galápagos Islands • Evolution—the cumulative genetic changes in populations that occur during successive generations • Charles Darwin (1809–1882) proposed the mechanism of evolution (i.e., not idea of evolution) in “The Origin of Species by Means of Natural Selection” (1859) – Environment plays crucial role in which traits are inherited – Accumulation of favorable traits leads to increased survival (fitness) Evolution Through Natural Selection • Four observations guide natural selection (NS) – – – – High reproductive capacity Limits on population growth Heritable variation Differential reproductive success © 2014 John Wiley & Sons, Inc. All rights reserved. Darwin’s Finches • While on the Galapagos Islands off the coast of Ecuador, Darwin studied plants and animals on each island, including 14 species of finches • He concluded that the finches had a common mainland ancestor, but had become geographically isolated and adapted to different diets © 2014 John Wiley & Sons, Inc. All rights reserved. Environmental InSight Evidence for Evolution • Fossil record – Fossils show how organisms evolved over time • Comparative anatomy – Similarities among organisms demonstrate how they are related • Biogeography – The study of geographic locations of organisms • Molecular biology – Showing relationships on a molecular level such as sharing an enzyme or nucleotide base © 2014 John Wiley & Sons, Inc. All rights reserved.
