ecosystems and evolution - palm beach state …...earth’s major biomes •biome—a large,...
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Visualizing Environmental Science
Ecosystems and EvolutionChapter 6
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Earth’s Major Biomes
• Biome—a large, relatively distinct terrestrial region with similar climate (long-term weather pattern), soil, plants, and animals, regardless of where it occurs in the world
– Encompasses many interacting ecosystems
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• 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
Factors That Affect Biomes
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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
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• 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
Boreal Forest/Taiga
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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 clear-cutting
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• 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
Temperate Deciduous Forest
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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
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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
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EnviroDiscoveryUsing 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 6-month fire season– 350 goats can clear an acre of heavy
brush per day
• Rare/endangered plant species are fenced off
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• 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
Desert
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• 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
Savanna
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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
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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
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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
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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
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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
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Primary Succession• Sandbars
• Lava flows that have cooled
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Secondary Succession
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• 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
Developing and Understanding of Evolution
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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
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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
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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.