Ecosystems and the Biosphere

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Chapter 22

• Ecosystems and the Biosphere

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22-1 Energy Transfer

• In an ecosystem, energy flows from the sun to
  autotrophs and then to other organisms
• Autotrophs make their
• own food (plants and
• some bacteria and
• protists)

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Producers

• Most producers are plants
• Photosynthesis plants use carbon dioxide, water,
  and solar energy to make glucose. (Oxygen is a
  byproduct)
• 6 CO2 6 H2O solar energy ? C6H12O6 6 O2

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Chemosynthesis

• Some species of bacteria can produce
  carbohydrates from inorganic molecules
• Example bacteria found along hydrothermal vents
  in the ocean

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Measuring Productivity

• Gross primary productivity the rate that
  producers in an ecosystem capture energy
• Biomass organic material
• Only energy stored as biomass
• is available to other organisms

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Net Primary Productivity

• The rate at which biomass accumulates in an
  ecosystem
• Can vary greatly in different ecosystems
• Influenced by light,
• temperature, and
• precipitation

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Consumers

• Organisms that get their energy by eating other
  organisms
• Also called heterotrophs (other feeders)
• Examples animals

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Herbivores

• Consumers that eat only producers (plant eaters)
• Examples rabbits, deer, cows, sheep,
  grasshoppers

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Carnivores

• Consumers that eat only other consumers (meat
  eaters)
• Examples coyote, bobcat, shark, alligator, hawk,
  owl, snakes

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Omnivores

• Consumers that eat both plants and animals
• Examples humans, bears, pigs, gorillas, rats,
  raccoons, some insects

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Detritivores

• Consumers that feed on dead organisms, animal
  waste, or fallen leaves and branches
• Examples vultures, maggots, carrion beetles,
  earthworms

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Decomposers

• Consumers that break down dead organisms in an
  ecosystem (returns nutrients to soil, water, and
  air)
• Examples fungi and bacteria

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Energy Flow

• Cellular respiration breaking down food to yield
  energy
• C6H12O6 6 O2 ? 6 CO2 6 H2O energy
• Cells use glucose and oxygen to produce carbon
  dioxide, water, and energy

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Food Chain

• A sequence in which energy is transferred from
  one organism to the next as each organism eats
  another organism
• Represents one strand of a food web

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Food Web

• Shows many feeding relationships that are
  possible in an ecosystem

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DDT

• Dichloro-Diphenyl-Trichloroethane
• Pesticide once used to prevent mosquitoes from
  transmitting malaria to humans
• Contaminated zooplankton? small fish? large fish
  ? eagles and ospreys

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Biomagnification

• DDT became more concentrated as it moved up the
  food chain
• Caused eggshell thinning in eagles and ospreys
• Banned in 1972, but is still present in some
  ecosystems
• Migratory birds are exposed to DDT in other
  countries that still use it

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Trophic Levels

• Refers to each step in the transfer of energy
  through a food chain or a food web
• Each time energy is transferred,
• some energy is lost and less
• energy is available to the next
• trophic level

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Energy Pyramid
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Energy Loss

• Since so much energy is lost at each level, there
  are fewer organisms at the higher trophic levels
• Ecosystems rarely have more than 4-5 trophic
  levels

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Quantity of Energy Transfers

• 10 of the total available energy at one trophic
  level is transferred to the next level
• Higher trophic levels contain less energy and can
  support fewer organisms

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22-2 Ecosystem Recycling

• Biogeochemical cycles The movement of water,
  minerals, and elements through the environment
• Examples the water, carbon, nitrogen, and
  phosphorus cycles

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The Water Cycle

• Water is a renewable resource because it is
  circulated through the water cycle
• The water cycle is the continuous movement of
  water between Earth and the atmosphere

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Global Water Distribution

• 97 of Earths water is saltwater
• 3 is freshwater, but most of it is frozen as
  icecaps or glaciers
• Less than 1 is available as liquid freshwater

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Watershed

• An area of land drained by a river
• Pollution anywhere in a watershed can pollute a
  river

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The Carbon Cycle

• A process by which carbon is cycled between the
  atmosphere, land, water, and organisms
• Carbon is present in all living things

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Short-term cycle

• Consumers eat producers and obtain carbon from
  the carbohydrates
• Some of the carbon is released back into the
  atmosphere as a byproduct of cellular respiration

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Long-term cycle

• Carbonates (found in bones, shells, coral) do
  not break down easily
• Calcium carbonate deposits form limestone
• Limestone is one of the largest carbon sinks on
  Earth

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Fossil Fuel

• When living organisms die, their remains still
  contain carbon
• Over time, the remains of ancient organisms
  changed into coal, oil, and natural gas

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Humans and the Carbon Cycle

• When we burn fossil fuels, we release carbon
  dioxide into the atmosphere
• Increased levels of carbon dioxide contributes to
  global warming

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The Carbon Cycle
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The Nitrogen Cycle

• The process by which nitrogen is cycled between
  the atmosphere, bacteria, and other organisms
• The atmosphere is 78 nitrogen, yet most
  organisms (including humans) cannot use it until
  it has been fixed

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Nitrogen-Fixing Bacteria

• Legume plants, such as soybeans and clover, have
  root nodules that contain nitrogen-fixing
  bacteria
• The bacteria fixes the nitrogen into a usable
  form

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All Life is Interconnected

• All organisms need nitrogen to build proteins
• The bacteria alter the atmospheric nitrogen for
  plants to use
• Animals obtain the nitrogen they need when they
  eat plants

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Decomposers

• Bacteria break down wastes and dead organisms to
  return nitrogen to the soil
• Some of the nitrogen is transformed into a gas
  and is returned to the atmosphere

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The Nitrogen Cycle
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The Phosphorus Cycle

• The movement of phosphorus from the environment
  to organisms and then back to the environment
• This cycle is very slow
• Phosphorus moves from phosphates in rock to
  living organisms and eventually to the ocean

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Phosphates

• When rocks erode, they release phosphates into
  the soil and water
• Plants absorb phosphates through their roots
• Phosphates are also added to the soil when
  organisms die and decompose

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The Phosphorus Cycle
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Fertilizers

• Fertilizers contain both nitrogen and phosphorus
• Fertilizers can enter an aquatic ecosystem
  through runoff
• Excess nitrogen and phosphorus in an aquatic
  ecosystem can result in an algal bloom

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Artificial Eutrophication

• Sewage and fertilizer runoff enter lakes and
  ponds and causes an algal bloom
• When the algae dies, the decomposition from
  bacteria uses most of the oxygen and the fish
  suffocate and die

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22.3 Terrestrial Ecosystems

• Biomes very large terrestrial ecosystems that
  contain specific kinds of plants and animals
• Biomes are influenced by climate and altitude

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Climate Altitude

• Climate the temperature and precipitation of an
  area over a long period of time
• Altitude refers to the elevation above sea level

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Biomes

• Each biome is made up of many different types of
  ecosystems.
• There are seven major biomes tundra, taiga,
  temperate deciduous forest, temperate grassland,
  desert, savanna, and tropical rainforest

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Biomes of the World
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Tundra

• A cold biome located across northern North
  America, Europe and Asia
• The ground is permanently frozen at a depth of
  10-36 inches (trees can't grow)
• Receives little precipitation and a very short
  growing season (2 months)

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Common Plants Animals of the Tundra

• Plants grasses, sedges, mosses, and lichens
• Animals caribou, musk ox, lemmings, snowshoe
  hares, snowy owls, arctic fox

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Taiga

• A forested biome dominated by conifers (pine,
  fir, hemlock, and spruce)
• Needles are specialized leaves that help the
  trees survive the long, cold winters

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Common Plants Animals of the Tiaga

• Plants evergreen trees
• Animals lynx, moose, bears, wolves, great gray
  owls

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Temperate Deciduous Forest

• Characterized by trees that lose their leaves in
  the Fall
• Variable temperatures and moderate precipitation

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Common Plants Animals of the Temperate
Deciduous Forest

• Plants beech, maple, oak, hickory, sycamore,
  elm, birch
• Animals white-tailed deer, raccoons, foxes,
  squirrels, great-horned owls

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Temperate Grasslands

• Regions that are dominated by grasses and have
  variable temperatures
• Found in the interior of continents
• Also called prairies, steppes,
• pampas, and veldt

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Common Plants Animals of the Temperate Grassland

• Plants various grasses (a lot has been turned
  into farmland!)
• Animals pronghorn, prairie dogs, meadowlark,
  bison

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Deserts

• Areas that receive less than 25 cm of rainfall
  per year
• Most deserts are hot, but there are also cold
  deserts
• Desert vegetation is sparse and has a waxy
  coating that prevents water loss

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Rain Shadow Effect
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Common Plants Animals of the Desert

• Plants cacti and succulents
• Animals lizards, scorpions, jack rabbits,
  roadrunners, kit fox, snakes, burrowing owls

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Savannas

• Tropical or Subtropical grasslands with scattered
  trees and shrubs
• Has alternating wet and dry seasons

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Common Plants Animals of the Savanna

• Plants various grasses, few trees, shrubs
• Animals wildebeest, zebras, gazelles, giraffe,
  lions, cheetahs, elephants

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Tropical Rain Forests

• Areas near the equator that have a warm, wet
  climate and a year-round growing season
• Most biodiversity is found in tropical rainforests

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Common Plants Animals of the Tropical Rain
Forest

• Plants trees, epiphytes, understory plants
• Animals parrots, jaguar, monkeys, insects,
  sloth, snakes, lizards (contains 1/5 of all known
  species)

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22-4 Aquatic Ecosystems

• Water covers ¾ of Earth
• 97 of all water on our planet is saltwater
• 3 is freshwater (less than 1 is liquid
  freshwater!)

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Ocean Zones

• Photic Zone the part of the ocean that receives
  light

• Aphotic Zone the cold, dark depths where
  sunlight doesnt reach

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The Intertidal Zone

• The area that includes the beaches, tidal pools,
  and waves
• Organisms are adapted to the rise and fall of the
  tides

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Tides

• Tides are the cyclic rising and falling of
  Earth's ocean surface caused by the tidal forces
  of the moon and the sun acting on the oceans

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High and Low Tides

• During the day, the Earth rotates 180 degrees
  in 12 hours. The moon, meanwhile, rotates 6
  degrees around the earth in 12 hours. The moon's
  rotation and its gravitational pull mean that any
  given coastal city experiences a high tide
  approximately every 12 hours

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Spring Tide

• When the sun and moon are aligned, there are
  exceptionally strong gravitational forces,
  causing very high and very low tides which are
  called spring tides, though they have nothing to
  do with the season.

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Neap Tides

• During the moon's quarter phases the sun and moon
  work at right angles, causing the bulges to
  cancel each other. The result is a smaller
  difference between high and low tides.

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The Neritic Zone

• The most productive zone in the ocean
• Upwelling refers to currents that carry nutrients
  up from the bottom
• Coral reefs, plankton, sea turtles, fish, squid,
  etc. are found in this zone

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Coral Reefs

• Limestone ridges built by coral polyps
• Very diverse ecosystem
• Corals are invertebrates that only live in
  shallow tropical seas

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Threats to Coral Reefs

• Coral reefs are fragile
• Divers cut pieces of coral to sell
• Also threatened by oil spills, pollution, sewage,
  pesticides, and silt runoff

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The Oceanic Zone

• Nutrient levels are lower in this zone
• Deep sea organisms have reduced skeletons and
  slower metabolism

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Threats to the Oceans

• OVERFISHING!
• Trawl nets entangle and kill many animals
• Industrial waste, sewage, solid waste, oil
  spills, toxic chemicals

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Hydrothermal Vents

• Areas that release water that is rich in minerals
  and can exceed 750 C
• Chemosynthetic bacteria uses hydrogen sulfide
  (H2S) to make their own food
• Many organisms along a vent get their food
  directly from the bacteria

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Estuaries

• Areas where freshwater rivers and streams flow
  into the sea
• Examples bays, salt marshes, mud flats
• Receive a lot of light and nutrients
• Important breeding grounds for many species

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Freshwater Zones

• Freshwater contains less than .005 salt (NaCl)
• Examples lakes, ponds, streams, rivers

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Lakes and Ponds

• Eutrophic rich in organic matter and vegetation

• Oligotrophic contains little organic matter

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Rivers

• Bodies of water that flow down a gradient

Headwaters where a river begins (usually as a
mountain stream) As a river flows down a
mountain, it becomes wider, warmer, slower, and
has less oxygen
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Streams

• Tributaries that flow into larger bodies of water
• Faster flowing streams are highly oxygenated and
  contain more benthic macroinvertebrates