Transcript Principles of Ecology

Principles of Ecology
Dr. James Looney
AP Biology
West Windsor-Plainsboro HS North
Abiotic factors determine the make-up
and characteristics of ecosystems
• What are abiotic factors?
• What are the most important abiotic factors
that determine whether a region is a desert, a
grassland, or other type of biome?
Abiotic factors
• Abiotic factors are physical, non-living factors.
• Abiotic factors include
– Temperature (both average and seasonal patterns
are important)
– Precipitation (average, seasonal patterns, and
forms of precipitation)
– Amount of Sunlight
– Wind
– Soil conditions (nutrients, pH)
Identify some abiotic factors in this Delaware Shore ecosystem
Abiotic factors
• What are the most important physical
parameters in an environment that effect
abiotic factors?
Abiotic factors
• What are the most important physical
parameters in an environment that effect
abiotic factors?
• Location! Location! Location!
– In particular, latitude and altitude are the two
most important physical parameters.
• Explain WHY.
How does latitude effect the amount of sunlight that strikes a
given location each year? How does latitude effect seasonal
weather patterns?
2. Nutrients cycle in ecosystems
• One example of nutrient cycling is seen in the
nitrogen cycle.
• What types of organisms play important roles
in the nitrogen cycle?
• What roles do bacteria play?
• Why do organisms need nitrogen?
All organisms require
nitrogen for the synthesis of
amino acids (and proteins)
and nucleic acids.
Figure 2.31 The Nitrogen Cycle
Courtesy EPA
Source:
http://www.epa.gov/maia/html/nitrogen.html
Animals excrete nitrogen in
nitrogenous wastes: mammals
excrete urea in urine, fish
excrete ammonia, and birds
and insects excrete uric acid.
See Fig. 44.8 in Campbell
Biology.
Disturbances
• Disturbances in the nitrogen and phosphorous
cycle may lead to
– Depletion of nutrients in an ecosystem
Disturbances
• Disturbances may also lead to cultural
eutrophication where an excess of nutrients
accumulate in an ecosystem.
• Of particular importance are ocean, stream,
and lake dead zones.
• Where are these dead zones located, and
what causes dead zones?
Cultural eutrophication
• A single nutrient may be a limiting factor. If
that nutrient is added, for example, to a lake,
stream, or other body of water, algae and
plant blooms may occur.
• While this may happen with any nutrient,
Phosphorous is often limiting in many aquatic
systems.
Carbon also cycles,
typically on a broader
scale.
Identify where and
how carbon fixation
occurs.
The Carbon Cycle
How much carbon is
being added to the
atmosphere on a
yearly basis?
Where are the
major sinks or
reservoirs of carbon
in the world?
The Carbon Cycle: An increase in
carbon dioxide in the atmosphere has
been measured over the last 50 years.
Levels of carbon dioxide in the
atmosphere have increased since
measurements began in 1958.
This graph is known as the
Keeling Curve in honor of Charles
Keeling (1928-2005) who
measured carbon dioxide levels at
the Mauna Loa Observatory in
Hawaii beginning in 1958.
3. Energy, unlike nutrients, does not
cycle but is lost to the environment as
you travel up the food chain.
• How is energy lost to the environment?
For example, what activities
does a mouse do where
energy will be lost to the
environment?
4. All communities of organisms in an
ecosystem are dependent on the
producers
• The producers (the autotrophs) capture
energy from a physical source and convert it
to chemical energy.
• What are the producers in
– Aquatic systems like the open ocean?
– Grasslands?
– The tundra?
– Deep Sea thermal vents?
Producers: Photosynthetic
• Most producers are photosynthetic and
capture the energy from sunlight.
A marsh near Cape Elizabeth, Maine where grasses are abundant.
Producers: Chemosynthetic
In some ecosystems,
like the deep sea
thermal vent shown to
the left, producers
(chemosynthetic
bacteria) capture
energy from inorganic
compounds like
hydrogen sulfide and
convert that energy into
chemical energy.
5. Productivity measures the energy
captured by autotrophs
• Gross primary productivity measures the energy transformed
by autotrophs into chemical energy(Joules)/unit area/year.
Since some of this energy is used by producers for their own
energy requirements for metabolism, growth, etc. and is not
available to the next highest trophic level . . .
• Net primary productivity is also measured and more
accurately reflects the contribution producers make to the
food chain.
• Productivity can also be measured in dry biomass produced
(g/unit area/year)
6. All organisms interact with the
environment and require specific
adaptations for their survival.
• Can you give specific examples of organisms
and their adaptations from each type of
ecosystem found in the world?
Adaptations: antifreeze proteins
Many fish in the Antarctic,
like the one to the right
(Macropteris maculatus),
produce antifreeze proteins.
These antifreeze proteins
inhibit ice crystal growth in
their bodies and allow the
fish to live in subzero
waters.
7. All organisms interact with other
organisms.
• Competition may occur between organisms of
two different species (interspecific
competition) or between organisms of the
same species (intraspecific competition)
The Competitive Exclusion Principle
Conducting laboratory experiments with two
species of Paramecium, the Russian ecologist
G. F. Gause concluded that two species of
organisms competing for the same limiting
resources can not coexist together. When
grown separately, each species thrives. When
grown together, only one species
(Paramecium aurelia) survives and the other
dies. See Campbell Biology page 1160
Competition
• Competition (a -/- interaction) may also occur
between organisms of the same species.
In the WW-P HS North
ecology study site,
succession is occurring.
In the foreground,
several small oak trees
are growing close
together, competing for
space and limited
resources.
Come back in 10 or 20
years and see which oak
tree(s) wins the race to
the top!
Types of interactions: Predation
• +/- interaction where the predator kills and
eats the prey.
Types of Interactions: Herbivory
• +/- interaction where the herbivore eats part
of a plant or alga but doesn’t kill it.
Plant defenses against predation
Tear a portion of a leaf from
a milkweed plant(shown in
the middle of the photo) and
a milky substance will flow
out. Most herbivores find the
substance noxious and avoid
eating the plant.
An exception to the above
is the monarch butterfly
which lays its eggs on
milkweed The caterpillar of
the monarch is able to eat
the milkweed and in fact will
incorporate the noxious
substance from the milkweed
in its tissue as an adult.
A variety of other plants produce substances
which act as a deterrent to herbivores.
Types of interactions: Mutualism
• +/+ interaction where both organisms benefit
• Mutualism is a type of symbiosis, a close
interaction between two organisms.
Mutualism: Nitrogen-fixing bacteria in
the root nodules of legumes
A soybean plant (above; a
type of legume) with root
nodules. The root nodules
are visible above and to
the right of the pencil tip.
Root nodules contain nitrogen-fixing bacteria. How are the bacteria beneficial to the plant?
How is the plant beneficial to the bacteria?
Mutualism
• How many other forms of mutualism can you
identify?
Mutualism
• Did you think of . . .
– Pollinators and flowering plants?
– Bacteria in the digestive tracts of humans?
– Bacteria in the digestive tracts of termites, cows,
and other types of animals?
– “Fungus roots” (mycorrhizae), mutualistic fungusplant root associations
– Alga and coral?