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Ecosystems
Chapter 48
All most all regions on the earth function as systems
running on energy from the sun processed through
photosynthesizers.
The Nature of Ecosystems
An ecosystem is an array of
organisms interacting with one
another and with the physical
environment, connect by a oneway flow of energy and a cycling
of materials.
• Ecosystems are open systems
through which energy flows and
material are cycled.
• Ecosystems require energy and
nutrient input and generate energy
(usually as heat) and nutrient output.
Energy cannot be recycled.
Availability of nutrients as well as
ENERGY profoundly influences the
structure of the ecosystem
The Nature of Ecosystems
Primary producers are autotrophs (self-feeders) that can
capture sunlight energy and incorporate it into organic
compounds
Consumers are heterotrophs (not self-feeders) that feed
on tissues of other organisms
Herbivores eat plants
Carnivores eat animals
Omnivores eat a variety of organisms
Parasites reside in or on living host & extract energy from
them
The Nature of Ecosystems
Primary producers are autotrophs (self-feeders) that can
capture sunlight energy and incorporate it into organic
compounds
Consumers are heterotrophs (not self-feeders) that feed on
tissues of other organisms
Decomposers are also heterotrophs and include fungi and
bacteria that extract energy from the remains or waste products
of organisms;-these
organisms
engage in extracellular
Detritivores
include
small invertebrates
that ingest digestion
decomposing particles of organic matter (detritus)
Structure of Ecosystems
Trophic (“feeding”) Levels are a hierarchy of energy transfers
(Who Eats Whom?)
1st level (closest to the energy source) - Primary producers (Autotrophs)
2nd level - Primary consumers (Herbivores)
3rd level - Secondary consumers (primary carnivores)
4th level - Tertiary consumers (secondary carnivores & parasites)
- decomposers feed on organisms from all levels
Energy Flow through the Ecosystem
21
top carnivores
decomposers/detritivores
carnivores
herbivores
5,060
383
3,368
producers
20,810
Kcal/ sq. m / yr
Ecological Pyramids (two types) -
(1) Biomass pyramid - makes provision for differences in
size of organisms by using the weight of the members in
each trophic level
(2) Energy pyramid - reflects trophic structure most
accurately b/c it is based on energy losses at each level
Food Chain
A simple sequence of who eats whom
is called a food chain.
Interconnected food chains comprise
food webs in which the same food
resource is often part of more than
one food chain….
Plants
Energy flows into ecosystems from the sun and due to heat losses
at each energy transfer step, you see a one-way flow of energy.
MARSH HAWK
HIGH ER
TROPHIC
LEVELS Complex
array of carnivores,
omnivores and
other consumers.
Many feed at more
than one trophic
level continually,
seasonally, or when
an opportunity
presents itself
CROW
UPLAND
SANDPIPER
GARTER SNAKE
FROG
WEASEL
SPIDER
SECOND
TROPHIC LEVEL
Primary consumers
(e.g., herbivores)
FIRST TROPHIC
LEVEL
Primary producers
The loss of energy at each
transfer in a food chain
limits the number of
trophic levels in each
ecosystem to 4 or 5.
EARTHWORMS, INSECTS
(E.G., GRASSHOPPPERS)
CLAYCOLORED
SPARROW
PRAIRIE VOLE
BADGER
POCKET
GOPHER
COYOTE
GROUND SQUIRREL
Biological Magnification in Food Webs
DDT is a synthetic organic pesticide.
DDT is water insoluble but winds can carry DDT in vapor form. DDT is
fat soluble, so it can accumulate in the tissues of organisms.
DDT can show biological magnification - it becomes more and more
concentrated in tissues of organisms at higher trophic levels of a food web
DDT and modified
forms, disrupt
metabolic
activities and are
often toxic to
many aquatic and
terrestrial animals.
DDT Residues
Ring-billed gull fledgling
Herring gull
Osprey
Green heron
Summer flounder
Sheepshead minnow
Hard clam
Flying insects
Mud snail
Shrimps
Green alga
Plankton
Water
75.5
18.5
13.8
3.57
1.28
0.94
0.42
0.30
0.26
0.16
0.083
0.040
0.00005
Biogeochemical Cycle
Overall movement of nutrients (ions & molecules) from the
physical environment, through organisms, & then back to the
environmental reservoir constitutes a biogeochemical cycle.
Main nutrient reservoirs
in the environment
fraction of
nutrient
available to
ecosystem
geochemical cycle
primary
producers
herbivores,
carnivores,
parasites
detritivores,
decomposers
Environment serves as a reservoir for the nutrients
3 Categories of Biogeochemical Cycles
1. In the hydrologic cycle, oxygen and hydrogen move
as water molecules.
2. In the atmospheric cycles, elements can move in the
gaseous phase; examples include carbon (mainly CO2) and
nitrogen.
3. In sedimentary cycles, the element does not have a
gaseous phase; an example is phosphorus.
Hydrologic Cycle
water slowly moves on a global scale from the oceans, through the
atmosphere, onto land, then back to the ocean
ATMOSPERE
wind driven water vapor
40,000
evaporation
from ocean
425,000
precipitation
into ocean
385,000
precipitation
onto land
111,000
evaporation from land
plants 71,000
surface and
groundwater
flow 40,000
OCEAN
LAND
Carbon Cycle
diffusion between
atmosphere and ocean
ATMOSPHERE
(mainly carbon dioxide)
volcanic action
BICARBONATE &
CABONATE
DISSOLVED IN
OCEAN WATER
photosynthesis
combustion of fossil fuels
TERRESTRIAL
ROCKS
photosynthesis
aerobic
respiration
aerobic
respiration
deforestation
LAND FOOD
WEBS
MARINE FOOD WEBS
incorporation into
death,
sediments
sedimentation
combustion of
wood
SOIL
WATER
uplifting over
geologic time
MARINE SEDIMENTS, INCLUDING
FORMATIONS WITH FOSSIL FUELS
sedimentation
leaching
runoff
death, burial, compaction over geologic time
PEAT,
FOSSIL
FUELS
Carbon Cycle is the global movement of carbon through ecosystems.
Carbon in the atmosphere is in the form of carbon dioxide and carbon
in water is in the form of bicarbonate and carbonate.
Greenhouse Gases and a Warmer Planet
(pg 888-889)-READ!
Greenhouse effect
CO2, Ozone, Methane, Nitrous oxide, CFC’s
Rays of sunlight
penetrate the lower
atm & warm the
Earth’s surface
The surface radiates heat to the lower
atm. Some heat escapes into space. But
greenhouse gases & water vapor absorb
some infrared energy and radiate a
portion of it back towards Earth.
Increased concentrations of
greenhouse gases trap more
heat near Earth’s surface
resulting in the Earth’s
surface temp. to rise.
Greenhouse Gases and a Warmer Planet
(pg 888-889)-READ!
Global warming - long-term higher temperatures at
the Earth's surface
If the temperature of the lower atmosphere were to
rise by 4˚C (7˚F) then the sea levels may rise by as
much as 2 feet.
Greenhouse Gases
CO2
Fossil Fuel burning
Deforestation
GASEOUS
N ITROGEN (N2) IN
ATMOSPHERE
NITROGEN
FIXATION
by industry for
agriculture
FOOD WEBS
ON LAND
FERTILIZERS
NITROGEN FIXATION
bacteria convert to ammonia
(NH3+) ; this dissolves to
form ammonium (NH4+)
uptake by
autotrophs
excretion, death,
decomposition
uptake by
autotrophs
NITRO GENOUS WASTES,
REMAINS IN SOIL
NO3IN SOIL
AMMONIFICATION
NH3-, NH4+
IN SOIL
bacteria, fungi convert the
residues to NH3 ; this
DENTRIFICATION
by bacteria
NITRIFICATION
bacteria convert NO2- to
nitrate (NO3-)
dissolves to form NH4+
NITRIFICATION
loss by
leaching
bacteria convert NH4+
to nitrate (NO2-)
NO2IN SOIL
loss by
leaching
Sedimentary Cycle
Most phosphate moves in the
form of (PO4-3) phosphate ion
mining
excretion
FERTILIZER
GUANO
agriculture
uptake by
autotrophs
MARINE
FOOD
WEBS
weathering
DISSOLVED IN
OCEAN WATER
uptake by
autotrophs
weathering
death,
decomposition
sedimentation
DISSOLVED IN
SOILWATER,
LAKES, RIVERS
death,
decomposition
leaching, runoff
setting out
MARINE SEDIMENTS
uplifting over
geolgic time
ROCKS
LAND
FOOD
WEBS
Eutrophication
- any activity that adds dissolved nutrients to an ecosystem
Runoff from agricultural applications of fertilizers adds large
amounts of phosphorous to aquatic ecosystems.
Human activities are accelerating the process of eutrophication. We
are adding nutrients to aquatic ecosystems that are naturally low
in those nutrients & so promote destructive algal blooms.