Download Chapter 22

Chapter 22
Ecosystems and the Biosphere
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)
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
Chemosynthesis
 Some species of bacteria can produce
carbohydrates from inorganic molecules
 Example: bacteria found along
hydrothermal vents in the ocean
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
Net Primary Productivity
 The rate at which biomass accumulates
in an ecosystem
Can vary greatly in different ecosystems
Influenced by light,
temperature, and
precipitation
Consumers
 Organisms that get their energy by eating
other organisms
 Also called heterotrophs (“other feeders”)
 Examples: animals
Herbivores
 Consumers that eat only producers (plant
eaters)
 Examples: rabbits, deer, cows, sheep,
grasshoppers
Carnivores
 Consumers that eat only other
consumers (meat eaters)
 Examples: coyote, bobcat, shark,
alligator, hawk, owl, snakes
Omnivores
 Consumers that eat both plants and
animals
 Examples: humans, bears, pigs, gorillas,
rats, raccoons, some insects
Detritivores
 Consumers that feed on dead organisms,
animal waste, or fallen leaves and
branches
 Examples: vultures, maggots, carrion
beetles, earthworms
Decomposers
 Consumers that break down dead
organisms in an ecosystem (returns
nutrients to soil, water, and air)
 Examples: fungi and bacteria
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
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
Food Web
 Shows many feeding relationships that
are possible in an ecosystem
DDT
 Dichloro-Diphenyl-Trichloroethane
 Pesticide once used to prevent
mosquitoes from transmitting malaria to
humans
 Contaminated zooplankton small fish
large fish  eagles and ospreys
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
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
Energy Pyramid
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
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
22-2
Ecosystem Recycling
 Biogeochemical cycles: The movement
of water, minerals, and elements through
the environment
 Examples: the water, carbon, nitrogen,
and phosphorus cycles
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
Global Water Distribution
 97% of Earth’s water is
saltwater
 3% is freshwater, but
most of it is frozen as
icecaps or glaciers
 Less than 1% is
available as liquid
freshwater
Watershed
 An area of land
drained by a river
 Pollution anywhere in
a watershed can
pollute a river
The Carbon Cycle
 A process by which carbon is cycled
between the atmosphere, land, water,
and organisms
 Carbon is present in all living things
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
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
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
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
The Carbon Cycle
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”
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
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
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
The Nitrogen Cycle
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
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
The Phosphorus Cycle
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
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
22.3
Terrestrial Ecosystems
 Biomes: very large terrestrial ecosystems
that contain specific kinds of plants and
animals
 Biomes are influenced by climate and
altitude
Climate & Altitude
 Climate: the temperature and
precipitation of an area over a long
period of time
 Altitude: refers to the elevation above sea
level
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
Biomes of the World
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)
Common Plants & Animals
of the Tundra
 Plants: grasses,
sedges, mosses, and
lichens
 Animals: caribou,
musk ox, lemmings,
snowshoe hares,
snowy owls, arctic
fox
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
Common Plants & Animals
of the Tiaga
 Plants: evergreen
trees
 Animals: lynx,
moose, bears,
wolves, great gray
owls
Temperate Deciduous Forest
 Characterized by trees that lose their
leaves in the Fall
 Variable temperatures and moderate
precipitation
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
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
Common Plants & Animals of
the Temperate Grassland
 Plants: various
grasses (a lot has
been turned into
farmland!)
 Animals: pronghorn,
prairie dogs,
meadowlark, bison
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
Rain Shadow Effect
Common Plants & Animals of
the Desert
 Plants: cacti and
succulents
 Animals: lizards,
scorpions, jack
rabbits, roadrunners,
kit fox, snakes,
burrowing owls
Savannas
 Tropical or Subtropical grasslands with
scattered trees and shrubs
 Has alternating wet and dry seasons
Common Plants & Animals of
the Savanna
 Plants: various
grasses, few trees,
shrubs
 Animals: wildebeest,
zebras, gazelles,
giraffe, lions,
cheetahs, elephants
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
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)
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!)
Ocean Zones
 Photic Zone: the part
of the ocean that
receives light
 Aphotic Zone: the
cold, dark depths
where sunlight
doesn’t reach
The Intertidal Zone
 The area that includes the beaches, tidal
pools, and waves
 Organisms are adapted to the rise and
fall of the tides
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
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
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.
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.
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
Coral Reefs
 Limestone ridges built by
coral polyps
 Very diverse ecosystem
 Corals are invertebrates
that only live in shallow
tropical seas
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
The Oceanic Zone
 Nutrient levels are lower in this zone
 Deep sea organisms have reduced
skeletons and slower metabolism
Threats to the Oceans
 OVERFISHING!
 Trawl nets entangle and
kill many animals
 Industrial waste,
sewage, solid waste, oil
spills, toxic chemicals
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
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
Freshwater Zones
 Freshwater contains less than .005 %
salt (NaCl)
 Examples: lakes, ponds, streams, &
rivers
Lakes and Ponds
 Eutrophic: rich in
organic matter and
vegetation
 Oligotrophic:
contains little organic
matter
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
Streams
 Tributaries that flow
into larger bodies of
water
 Faster flowing
streams are highly
oxygenated and
contain more benthic
macroinvertebrates