36.2 Energy flows through ecosystems

There is a limited amount of energy in an
ecosystem.

It is divided among the different trophic levels.

This energy budget influences the types and
numbers of organisms in an ecosystem.

The producers store chemical energy (sugars) in
organic material, or biomass.
 biomass
-the mass of organisms
(living or dead).
Primary Productivity

The rate at which producers build biomass
is called primary productivity.

Primary productivity determines the maximum amount of
energy available to the higher trophic levels in an
ecosystem.

90% of Energy is “spent” at each step in
the food web. (metabolism, heat…)
Why a Pyramid?

Producers must comprise most of the mass of
the biotic part of an ecosystem


This is the ONLY place where energy (solar)
enters the ecosystem
Energy is always lost in the form of heat, so
energy transfers are no more than 10%
efficient (90% energy lost as heat)
3 Types of Ecological Pyramids
3 Types of Pyramids
1.) Energy Pyramid- depicts energy loss
from one trophic level to the next.
 Only
10% of available energy at a trophic
level is converted to biomass at the next
higher trophic level.
Figure 36-7
This generalized energy pyramid indicates that only 10
percent of the energy available at a trophic level is typically
converted to new biomass in the next trophic level.
The 10% Rule
2.) Biomass pyramid- depicts the actual biomass
(dry mass of all organisms) in each trophic level.
Pyramid of Numbers

36.3
Cycles
Water, Carbon, Nitrogen
Oxygen and Phosphorus
36.3 Chemicals Cycle in the Ecosystem
3 basic steps of Chemical cycling:
1.) Producers use chemicals from the
environment to make sugar. (photosynthesis)
2.) Consumers feed on producers, take in
nutrients, release wastes into the
environment.
3.) Decomposers break down dead organisms,
returning inorganic chemicals to the soil,
water, air producers.
The Nitrogen Cycle






Bacteria fix nitrogen from the air (N usable forms)
Producers get nitrates from the soil
Consumers get N by eating plants
Decomposition returns N to the air
N from fertilizers may contaminate water sources
Nitrogen can be fixed industrially from the air
 Production of ammonia
Nitrogen Cycle
Nitrogen Fixation: process by which some
bacteria convert (N) ammonia NH4+
These bacteria live in the soil or on the roots of
certain plants (beans or legumes).
Nitrification:
Converting
ammonium (NH4+)  nitrates (NO3-).

Bacteria that contribute to the Nitrogen Cycle
Nitrifying bacteriaconvert (ammonia) NH4+  NO3- (nitrates)
Denitrifying bacteriaConvert (nitrates) NO3-  N2 (nitrogen gas)
Nitrogen Fixing bacteriaConvert N2  NH3  NH4+ (ammonia) in the soil

Ammonium and nitrates move through the
food webs, and nitrogen gas is eventually
released back to the air.
C:\BIOLOGY Exp Life Pres Pro\Content\Transparency
36D.ppt
Figure 36-11From the atmosphere, nitrogen is
converted by bacteria to forms that plants and
animals can use to build amino acids, proteins, and
nucleic acids.
Aquarium Nitrogen Cycle
Water Cycle
3 major processes move water between land,
bodies of water, and the atmosphere:
1.) evaporation: liquid  gas
 transpiration: evaporation from a plant’s
leaves.
2.) condensation: gas liquid
3.) precipitation: rain, snow, hail and sleet
Water (hydrologic) Cycle
Plants absorb water from the soil
 Transpiration and cellular respiration return
water to the atmosphere
 Sun causes water to evaporate clouds form
 Precipitation returns water to the soil

Figure 36-12The three major processes of evaporation (including transpiration),
condensation, and precipitation continuously move water between the land,
bodies of water, and the atmosphere.
The Carbon Cycle

Plants remove CO2 from the air



6 CO2 + 6 H2O  C6H12O6 + 6 O2
Consumers give of CO2

(photosynthesis)
during cellular respiration
C6H12O6 + 6 O2  6 CO2 + 6 H2O
Burning fossil fuels releases carbon CO2
The Oxygen Cycle

Oxygen is produced by photosynthesis



6 CO2 + 6 H2O  C6H12O6 + 6 O2
The largest chemical process on earth!
Oxygen is required by cellular respiration

C6H12O6 + 6 O2  6 CO2 + 6 H2O
Figure 36-10
Many life processes and human activities contribute
to the cycling of carbon in the biosphere.
36.4 Human Activities






Burning Fossil fuels adds CO2 to the atmosphere.
Carbon cycle is also affected by by deforestation.
Deforestation: the clearing of forests for
agriculture, lumber, and other uses.
It clears plants that absorbs CO2, burning the trees
releases CO2 into the atmosphere.
CO2 traps the sun’s heat, producing the green
house effect.
As CO2 levels in the atmosphere rise, more heat is
trapped, and the average temperature rises Global
warming.
Causes of Deforestation
Green House Effect

Figure 36-14
The greenhouse effect is a natural process that stops
all of the sun's heat from escaping rapidly back to
space. This process can be altered by human
activities that affect the levels of greenhouse gases
in the atmosphere.
Ozone
 Pollutants
can affect ozone (O3)
molecules.
 Ozone
(O3) absorbs ultraviolet light.
 Ozone
layer: region high above the
Earth’s surface that shields organisms
from the sun’s damaging rays.
 Pollution
damages our ozone layer.
Figure 36-18
Free chlorine atoms in the atmosphere react with
and destroy ozone molecules. Over time, the loss of
ozone has resulted in an ozone "hole"—an area of
very low ozone concentrations located over
Antarctica.
The following pictures are provided courtesy
of NASA. They show the extent of ozone
thinning. Dark blue colors correspond to the
thinnest ozone, while light blue, green, and
yellow pixels indicate progressively thicker
ozone.
October 1999 (average)
Historically, the Antarctic ozone hole is
largest during October. This image shows
the data from the Total Ozone Mapping
Spectrometer (TOMS) Earth Probe, for
the month of October 1999
September 3rd 2000
The ozone hole grew quicker than usual
and exceptionally large. By the first week
in September the hole was the largest
ever at that time 11.4 million square miles.
For the first time it reached towards South
America and to regions of high population.
September 17th 2001
Satellite data show the area of the 2001
Antarctic ozone hole peaked at a size
roughly equal to that of recent years about
the same area as North America.
Researchers have observed a leveling-off
of the hole size and predict a slow
recovery.
Definitions


Bioaccumulation: is the process by which
substances not readily broken down or
excreted can build up and be stored in living
tissue (usually in fatty tissue.)
Biomagnification: is the process by which
substances become more concentrated in the
bodies of consumers as one moves up the food
chain (trophic levels).
Figure 36-17
In this Great
Lakes food
chain, the
concentration
of PCBs
measured in
herring gull
eggs was
almost 5000
times higher
than that
measured in
phytoplankton.
The
concentration
increased at
each
successive
trophic level.
Case Study:
PCBs




PCBs, or polychlorinated
biphenyls, are a group of
man-made chemicals.
Introduced in 1929 and widely used in
electrical transformers, cosmetics,
varnishes, inks, carbonless copy paper,
pesticides and for general
weatherproofing and fire-resistant
coatings to wood and plastic.
The federal government
banned the production of
PCBs in 1976
PCBs can effect the
immune system, fertility,
child development and
possibly increase the risk
of certain cancers



DDT is a pesticide that was
widely used until being
banned in the U.S. in 1972
DDT accumulates in living
tissue, particularly in fat
tissue
High concentrations in some
bird species caused failure
of eggs by thinning the shells
Case Study:
DDT
Case Study:
Methyl Mercury
What makes methylmercury so
dangerous?
Methylmercury is rapidly taken up but
only slowly eliminated from the body by
fish and other aquatic organisms, so each
step up in the food chain (bio)magnifies
the concentration from the step below.
Bioaccumulation factors (BAF's) of up
to 10 million in largemouth bass have
been reported for the Everglades.
Fish-eating birds, otters, alligators, raccoons and
panthers can have even higher bioaccumulation factors.
U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology
This page is: http://sofia.usgs.gov/sfrsf/rooms/mercury/achilles_heel/cause.html
Mercury Health Effects
Miscellaneous terms

Biodiversity – a measurement of the
amount of different kinds of organisms
(species) in a location.

Climatograph – displays the seasonal
variations in temperature and precipitation
for a location
Climatograph