Chapter 3
Ecosystems: What Are
They and How Do They
Work?
Core Case Study:
Have You Thanked the Insects Today?
• Many plant species depend on insects for pollination and plant
reproduction.
• Insects can control other pest insects by eating them.
• They also mix up the soil
Figure 3-1
Core Case Study:
Have You Thanked the Insects
Today?
• …if all insects disappeared, humanity
probably could not last more than a few
months [E.O. Wilson, Biodiversity expert].
– Insect’s role in nature is part of the larger
biological community in which they live.
why are honeybees dis.flv
honeybees part 2.flv
THE NATURE OF ECOLOGY
• Ecology is
– How organisms
interact with one
another and with
their nonliving
environment.
Figure 3-2
So, really intricate and amazing
interrelationships occur between
plants and animals.
Well, as mentioned earlier,
plants rely on insects, birds, and
rodents for pollination
Fynbos
biome
And, of course birds and
animals need plants……what what
Biosphere!!!!!!!
Re-wind: from this diagram I would like you
to remember the differences between good
and bad ozone, and the greenhouse vs. the
ozone layer
What Happens to Solar Energy
Reaching the Earth?
Solar energy
• Warms and lights up
the troposphere
• Drives the cycling of
matter
• Evaporates water and
drives weather and
climate
• 1% generates winds
• Green plants/algae use
less than .1% in
photosynthesis
Figure 3-8
What are the abiotic factors in this diagram?
Oxygen
(O2)
Sun
Producer
Carbon dioxide (CO2)
Secondary consumer
Primary
(fox)
consumer
(rabbit)
Precipitation
Falling leaves
and twigs
Producers
Soil decomposers
Water
Fig. 3-10, p. 57
Factors That Limit Population
Growth
• Availability of matter and energy resources can limit
the number of organisms in a population.
• Examples of limiting factors: (temperature,
sunlight, nutrients, dissolved oxygen,
salinity…etc)
Figure 3-11
Abundance of organisms
Upper limit of
tolerance
Few
No
organisms organisms
Population size
Lower limit of
tolerance
No
Few
organisms
organisms
Zone of
intolerance
Low
Zone of
physiological
stress
Optimum range
Temperature
Zone of
physiological
stress
Zone of
intolerance
High
Fig. 3-11, p. 58
Producers: Basic Source of All
Food
• Most producers
capture sunlight to
produce
carbohydrates by
photosynthesis:
• KNOW THE
FORMULA
Write the chemical equations for
photosynthesis and respiration. Explain how
these two processes are intertwined; include
the terms oxygen, carbon dioxide, light
reaction, dark reaction, chloroplasts,
mitochondria, photosynthesis, respiration,
glucose, water, sunlight, ATP, plants, animals.
Good luck!!
Energy Flow in an Ecosystem:
Losing Energy in Food Chains
and Webs
• In accordance with the 2nd law of
thermodynamics, there is a decrease in
the amount of energy available to each
succeeding organism in a food chain or
web.
Energy Flow in an Ecosystem: Losing
Energy in Food Chains and Webs
• Ecological
efficiency:
percentage of
useable energy
transferred as
biomass from
one trophic level
to the next.(240% range)
Figure 3-19
Productivity of Producers:
The Rate Is Crucial
• Gross primary
production
(GPP)
– Rate at which
an ecosystem’s
producers
convert solar
energy into
chemical
energy as
biomass. Figure 3-20
Gross primary productivity
(grams of carbon per square meter)
Fig. 3-20, p. 66
Net Primary Production (NPP)
• NPP = GPP – R
– Rate at which
producers use
photosynthesis to
store energy minus
the rate at which they
use some of this
energy through
respiration (R).
Figure 3-21
Sun
Respiration
Gross primary
production
Growth and reproduction
Energy lost
and unavailable
to consumers
Net primary
production
(energy
available to
consumers)
Fig. 3-21, p. 66
• What are nature’s three most productive and
three least productive systems?
Figure 3-22
• Chemosynthesis:
– Some organisms such as deep ocean bacteria draw
energy from hydrothermal vents and produce
carbohydrates from hydrogen sulfide (H2S) gas .
Consumers: Eating and Recycling
to Survive
• Consumers (heterotrophs) get their food by
eating or breaking down all or parts of other
organisms or their remains.
– Herbivores
• Primary consumers that eat producers
– Carnivores
• Secondary consumers eat primary consumers
• Third and higher level consumers: carnivores that eat
carnivores.
– Omnivores
• Feed on both plant and animals.
Decomposers and Detrivores
Burying Beetles Video -- National Geographic
– Decomposers: Recycle nutrients in ecosystems.
– Detrivores: Insects or other scavengers that feed on
wastes or dead bodies. Generally scavengers are
considered to be larger animals and detrivores are Figure
insects.
3-13
Detrivores
Longhorned
beetle
holes
Decomposers
Termite
and
Bark beetle Carpenter
carpenter
ant
engraving
galleries ant work Dry rot
fungus
Time
progression
Wood
reduced
to
Mushroom
powder
Powder broken down by decomposers
into plant nutrients in soil
Fig. 3-13, p. 61
Aerobic and Anaerobic
Respiration: Getting Energy for
Survival
• Organisms break down carbohydrates and
other organic compounds in their cells to
obtain the energy they need.
• This is usually done through aerobic
respiration.
– The opposite of photosynthesis
Aerobic and Anaerobic
Respiration: Getting Energy for
Survival
• Anaerobic respiration or fermentation:
– Some decomposers get energy by breaking
down glucose (or other organic compounds)
in the absence of oxygen.
– The end products vary based on the chemical
reaction:
•
•
•
•
Methane gas
Ethyl alcohol
Acetic acid
Hydrogen sulfide
Two Secrets of Survival: Energy
Flow and Matter Recycle
• An ecosystem
survives by a
combination of
energy flow and
matter recycling.
Figure 3-14
Biodiversity Loss and Species
Extinction: Remember HIPPO
• H for habitat destruction and
degradation
• I for invasive species
• P for pollution
• P for human population growth
• O for overexploitation
Why???????
But what’s wrong with corn?” you might ask.
In a sense, nothing. In its whole form, corn is a cheap,
filling source of starch and vitamins, and its obvious
versatility makes it an important culinary staple. As it
has been, for thousands of years. But only the tiniest
fraction of our corn supply ends up boiled and buttered,
or even converted to cornmeal. Given current farm bills
and modern commodity agriculture, large-scale corn
producers receive government subsidies—to the tune of
4 billion dollars a year—making the crop ludicrously
(and, in a sense, artificially) cheap.
That creates the incentive to sell, sell, sell, in every
possible form. And since we can only eat so much corn on
the cob, that means conjuring all sorts of corn-based
derivatives. So we end up with corn processed beyond
recognition, into forms that eliminate virtually all of its
nutritional content.
Of course then we also have
URBAN DEVELOPMENT
Why Should We Care About
Biodiversity?
The health of a species reflects the health of an ecosystem
which reflects of the health of the biosphere which is
where humans live. “We are all connected”
Some species are so critical to the functioning of an
Ecosystem that they are called
KEYSTONE SPECIES
1800’s sea otters hunted for fur
Sea otters eat sea urchins, so with no
predators, they began to multiply
Sea urchins eat kelp, which then
began to disappear
Fish begin to decline
because Kelp are the
breeding grounds for
fish, this affected
fishermen's catches.
California Sea Otter Tax Check-Off - Defenders of Wildlife
Flower power. Rosy periwinkle has given rise to
drugs used to treat childhood leukemia and Hodgkin's
disease.
Spider find. A compound in the venom of black
widow spiders found in the Negev Desert in
Israel may hold promise for treating strokes
It had to be yew. The drug Taxol,
made from the bark of the Pacific yew,
helps fight breast and ovarian
cancers.
Food
Webs
• Trophic levels are
interconnected
within a more
complicated food
web.
Figure 3-18
Animation: Prairie Food Web
PLAY
ANIMATION
Which of the following ecosystems has the highest
average net primary productivity?
a.
agricultural land
b.
open ocean
c.
temperate forest
d.
swamps and marshes
e.
lakes and streams
Which of the following ecosystems has the lowest
level of kilocalories per square meter per year?
a.
open ocean
b.
tropical rain forest
c.
agricultural land
d.
lakes and streams
e.
temperate forest
Ecosystem egg
• 1. What does the light reaction in
photosynthesis produce?
• 2. Which law of thermodynamics accounts
for the 10% rule?
• 3. Which terrestrial ecosystem has the
highest GPP?
• 4. which aquatic ecosystem has the
highest GPP?
Ecosystem egg continued
• 5. which aquatic ecosystem has the lowest
GPP?
• 6. which terrestrial ecosystem has the
lowest GPP?
• 7. Primary productivity would be greatest
at which line of latitude?
• 8. Primary productivity would be greatest
in which ocean realm of the Arctic ocean
Eco egg continued
• 9. What % of sunlight reaching the earth is
actually used by plants for the process of
photosynthesis?
• 10. What is likely the biggest threat to
biodiversity on this planet?
• 11. Good ozone can be found where?
• 12. Bad ozone is caused by what?
• 13. Good ozone does what for the planet?
Eco egg continued
• 14. Which greenhouse gas is a product of
anaerobic respiration?
• 15. Aside from habitat destruction, what is
the other main cause of loss of biodiversity
on the planet?
• 16. The phenomenon causing global
warming occurs in which layer of the
atmosphere?
• 17. What do humans do that is messing up
or breaking down the ozone layer?
Eco egg cont
• 18. Give one example of an abiotic factor
and one example of a biotic factor in an
ecosystem.
• 19. What is the Edge effect and how does
is influence biodiversity?
• 20. What is the formula for NPP?
• 21. What is an example of a keystone
species
• 22. give the formula for cellular respiration
Eco egg continued
• 23. Please give an example of an aquatic
tertiary consumer? (2 pts)
• 24. What’s the difference between a
detrivore and a scavenger and a
decomposer (3pts)
• 25. what is the MOST limiting factor in the
Arctic Ocean? (1pt)
• 26. what is the ultimate source of energy
for life on earth? (1 pt)
• 27. Name a primary consumer (1 pt)
Eco egg cont
• 28 What is a likely result of lack of genetic
diversity in a food crop like corn? (2pts)
• 29. What is the process called in which
organisms make food from hydrogen
sulfide gas coming from hydrothermal
vents? (2 pts)
• 30. What is the approximate efficiency of
energy transfer going from one trophic
level to the next? (2pts)
Last question…..not on the test
but worth a buncha points
• Describe in detail the “corn controversy”
relate it to the concepts covered in this
class. (5 pts)
SOIL: A RENEWABLE
RESOURCE
• Soil is a slowly renewed resource that
provides most of the nutrients needed for
plant growth and also helps purify water.
– Soil formation begins when bedrock is broken
down by physical, chemical and biological
processes called weathering.
• Mature soils, or soils that have developed
over a long time are arranged in a series of
horizontal layers called soil horizons.
SOIL: A RENEWABLE RESOURCE
Figure 3-23
Oak tree
Wood
sorrel
Lords and
ladies
Fern
O horizon
Leaf litter
Dog violet
Grasses and
small shrubs
Earthworm
Millipede
Honey
fungus
Mole
Organic debris
builds up
Rock
fragments
Moss and
lichen
A horizon
Topsoil
B horizon
Subsoil
Bedrock
Immature soil
Regolith
Young soil
Pseudoscorpion
C horizon
Mite
Parent
material
Nematode
Root system
Mature soil
Red Earth
Mite
Springtail
Actinomycetes
Fungus
Bacteria
Fig. 3-23, p. 68
Animation: Soil Profile
PLAY
ANIMATION
Layers in Mature Soils
• Infiltration: the downward movement of
water through soil.
• Leaching: dissolving of minerals and
organic matter in upper layers carrying
them to lower layers.
• The soil type determines the degree of
infiltration and leaching.
Soil Profiles of the
Principal
Terrestrial Soil
Types
Figure 3-24
Mosaic of
closely
packed
pebbles,
boulders
Weak humusmineral mixture
Desert Soil
(hot, dry climate)
Dry, brown to
reddish-brown
with variable
accumulations
of clay, calcium
and carbonate,
and soluble
salts
Alkaline,
dark,
and rich
in humus
Clay,
calcium
compounds
Grassland Soil
(semiarid climate)
Fig. 3-24a, p. 69
Acidic
light-colored
humus
Iron and
aluminum
compounds
mixed with
clay
Tropical Rain Forest Soil
(humid, tropical climate)
Fig. 3-24b, p. 69
Forest litter leaf
mold
Humus-mineral
mixture
Light, grayishbrown, silt loam
Dark brown
firm clay
Deciduous Forest Soil
(humid, mild climate)
Fig. 3-24b, p. 69
Acid litter
and humus
Light-colored
and acidic
Humus and
iron and
aluminum
compounds
Coniferous Forest Soil
(humid, cold climate)
Fig. 3-24b, p. 69
Leaf mold, a humus-mineral mixture, and silty loam
are indicative of
a.
coniferous forest soil.
b.
deciduous forest soil.
c.
tropical forest soil.
d.
grassland soil.
e.
desert soil.
Soil comprised of litter and humus, and is acidic
due to the accumulation of needles
a. desert soil
b. grassland soil
c. tropical rainforest soil
d. coniferous forest soil
e. deciduous forest soil
Soils found in mid-latitude grasslands would be most
accurately described as having
a. a high acid content with little organic matter
b. a deep layer of humus and decayed plant material
c. a layer of permafrost right below the O-horizon
d. a high content of iron oxides and very little
moisture
e. a small amount of nutrients but an abundant
decomposer food web
Some Soil Properties
• Soils vary in the
size of the particles
they contain, the
amount of space
between these
particles, and how
rapidly water flows
through them.
http://techalive.mtu.edu/meec/module06/Porosity.htm
Figure 3-25
Sand
0.05–2 mm
diameter
Silt
0.002–0.05 mm
diameter
Water
High permeability
Clay
less than 0.002 mm
Diameter
Water
Low permeability
Fig. 3-25, p. 70
The porosity of a soil is defined to
be the volume of the pores as a
percentage of the total volume of
soil. Sandy soils have porosities
ranging from 30 to 40 percent,
compared with 40 to 60 percent for
clays. Porosity provides a measure
of the amount of water that each soil
can retain. Clay soils have a higher
porosity and can hold more water.
(smaller pores, but more of them)
More on soils
• If a soil is acidic, that can be a problem,
because when the pH is low, this causes
the release or “freeing up” of aluminum
ions.
• Then the soil tends to want to uptake
aluminum rather than the nutrients needed
• So to recap, acidic soil releases aluminum
and this can burn the plants leaves and kill
the plant
Give a brief description of what
pH is…………show chart from
booklet here.
How can this problem be solved?????????????
Eutrophication!!!!!!
• Happens when excess nitrogen or
phosphorus from fertilizers or animal
manure runs off into water ways
• Causes the excess growth of algae
• The algae eventually dies and
decomposes
• The decomposing bacteria take dissolved
oxygen out of the water
• Aquatic life (like fishies) dies off (a perfect
example of this is the Salton Sea or the
Gulf of Mexico)
Legumes as nitrogen fixers
• Legumes (soybeans, alfalfa, clover) have
specialized bacteria on their root nodules
that “fix” nitrogen from the air and put it
into the soil
• So, they work perfectly as “cover crops” to
renew soil nitrogen on plots of land that
are “resting” in between plantings
MATTER CYCLING IN
ECOSYSTEMS
• Nutrient Cycles: Global Recycling
– Global Cycles recycle nutrients through the
earth’s air, land, water, and living organisms.
– Nutrients are the elements and compounds
that organisms need to live, grow, and
reproduce.
– Biogeochemical cycles move these
substances through air, water, soil, rock and
living organisms.
The Water Cycle
Figure 3-26
Animation: Hydrologic Cycle
PLAY
ANIMATION
Water’ Unique Properties
• There are strong forces of attraction between
molecules of water.
• Water exists as a liquid over a wide
temperature range.
• Liquid water changes temperature slowly.
• It takes a large amount of energy for water to
evaporate.
• Liquid water can dissolve a variety of
compounds.
• Water expands when it freezes.
Effects of Human Activities
on Water Cycle
• We alter the water cycle by:
– Withdrawing large amounts of freshwater.
– Clearing vegetation and eroding soils.
– Polluting surface and underground water.
– Contributing to climate change.
The Carbon Cycle:
Part of Nature’s Thermostat
http://www.epa.gov/climatechange/kids/carbon_cycle_version2.html
Figure 3-27
Fig. 3-27, pp. 72-73
Animation: Carbon Cycle
PLAY
ANIMATION
Effects of Human Activities
on Carbon Cycle
• We alter the
carbon cycle by
adding excess CO2
to the atmosphere
through:
– Burning fossil fuels.
– Clearing vegetation
faster than it is
replaced.
Figure 3-28
CO2 emissions from fossil fuels
(billion metric tons of carbon equivalent)
High
projection
Low
projection
Year
Fig. 3-28, p. 74
The Nitrogen Cycle:
Bacteria in Action
Figure 3-29
Gaseous nitrogen (N2)
in atmosphere
Food webs on land
Nitrogen fixation
Fertilizers
Uptake by autotrophs Excretion, death,
decomposition
Ammonia, ammonium in soil
Nitrogen-rich wastes,
remains in soil
Ammonification
Loss by
leaching
Nitrification
Uptake by
Loss by
autotrophs denitrification
Nitrate in soil
Nitrification
Nitrite in soil
Loss by
leaching
Fig. 3-29, p. 75
Animation: Nitrogen Cycle
PLAY
ANIMATION
Effects of Human Activities
on the Nitrogen Cycle
• We alter the nitrogen cycle by:
– Adding gases that contribute to acid rain.
– Adding nitrous oxide to the atmosphere
through farming practices which can warm the
atmosphere and deplete ozone.
– Contaminating ground water from nitrate ions
in inorganic fertilizers.
– Releasing nitrogen into the troposphere
through deforestation.
Effects of Human Activities
on the Nitrogen Cycle
• Human
activities such
as production of
fertilizers now
fix more
nitrogen than all
natural sources
combined.
Figure 3-30
Global nitrogen (N) fixation
(trillion grams)
Nitrogen fixation by natural processes
Year
Fig. 3-30, p. 76
The Phosphorous Cycle
Figure 3-31
mining
excretion
Fertilizer
Guano
agriculture
uptake by
uptake by weathering
autotrophs
autotrophs
leaching, runoff
Dissolved
Land
Marine
Dissolved
in Soil Water,
Food
Food
in Ocean
Lakes, Rivers
Webs
Webs
Water
death,
death,
decomposition
decomposition
weathering
sedimentation
settling out
uplifting over
geologic time
Rocks
Marine Sediments
Fig. 3-31, p. 77
Animation: Phosphorous Cycle
PLAY
ANIMATION
Effects of Human Activities
on the Phosphorous Cycle
• We remove large amounts of phosphate
from the earth to make fertilizer.
• We reduce phosphorous in tropical soils
by clearing forests.
• We add excess phosphates to aquatic
systems from runoff of animal wastes and
fertilizers.
The Sulfur Cycle
Figure 3-32
Sulfur
trioxide
Water
Acidic fog and
precipitation
Sulfuric acid
Ammonia
Oxygen
Sulfur dioxide
Ammonium
sulfate
Hydrogen sulfide
Plants
Dimethyl
sulfide
Volcano
Industries
Animals
Ocean
Sulfate salts
Metallic
sulfide
deposits
Decaying matter
Sulfur
Hydrogen sulfide
Fig. 3-32, p. 78
Animation: Sulfur Cycle
PLAY
ANIMATION
Effects of Human Activities
on the Sulfur Cycle
• We add sulfur dioxide to the atmosphere
by:
– Burning coal and oil
– Refining sulfur containing petroleum.
– Convert sulfur-containing metallic ores into
free metals such as copper, lead, and zinc
releasing sulfur dioxide into the environment.
http://teachers.sduhsd.k12.ca.us/bbodas/biogeochemical cycleactivity 2007.pdf