Transcript Primary Succession

Community Interactions
and
Ecosystem Changes
Modeling Energy Flow In
Ecosystems Revisited…
Ultimate source
of energy  Sun
Energy Flow in Ecosystems can be
modeled in Food Chains & Food Webs
Food Chains
Show 1 feeding
relationship from
producer
consumers
Food Webs
Interconnected food
chains
They show all of the
feeding relationships
in an ecosystem
Energy Pyramids and the
10% Rule
•Amount of available energy
decreases for higher consumers
•Amount of available energy
decreases down the food chain
•It takes a large number of
producers to support a small
number of primary consumers
•It takes a large number of primary
consumers to support a small
number of secondary consumers
5
Trophic Levels
indicate feeding
position in
ecosystems
TL 4
0.1%
TL 3
1%
TL 2
10%
TL 1
100%
Community Interactions in
Ecosystems
Predator Prey Interactions
• Predators help control the prey population size
– No natural predators = overpopulation of prey.
– Deer in NJ
• Prey can control the size of predators
– Few prey = few predators
– Many prey = many predators
– What would happen to a population of mountain lions if
they were reintroduced to NJ?
• Predators and prey might have no relationship
– If the predators rely on many sources of food, one
disappearing may have little effect
– Can you think of any examples of this?
Predator Prey Interactions Between Wolves &
Moose on Isle Royal
Competition
• Interaction between two or more organisms, or
groups of organisms, that use a common limited
resource
• May occur within or between populations
The Competitive Exclusion Principle
• No two species can occupy the same exact niche
• The species with the more rapid growth rate will out
compete the other
The Competitive Exclusion Principle
Number of Paramecium (cells/mL)
Population growth of two species of Paramecia alone or in mixed culture
over time
P. aurelia grown
alone, cells/mL
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
P. caudatum grown
alone, cells/mL
P. aurelia grown in
,mixed culture
cells/mL
P. caudatum grown
,in mixed culture
cells/mL
0
2
4
6
8
Time (days)
10
12
14
16
Symbiotic Relationships
Close long-term relationships between two or
more organisms
Parasitism +/One organism
benefits, the other
is harmed (but not
killed… usually)
• Mosquitoes
• Ticks/Fleas
Mutualism +/+
Commensalism +/0
Both organisms
benefit
• Lichen: Fungi
& Algae
• Insects &
flowers
One organism
benefits, the other is
unaffected
• Birds & Hooved
animals
• Fish & Anemone
• A dog becomes infested with fleas. The fleas
are thriving by feeding on the dog’s blood. The
dog is very uncomfortable but able to survive.
• Is this competition, predation, or symbiosis?
• An insect drinks nectar from a flower. The
insect gets a meal, and the flower gets
pollinated. The flower can now reproduce.
• What type of symbiosis is this?
• You eat some sushi that contains a tapeworm
larvae. It grows and feeds off the nutrients in
your intestines, robbing them from you. No
matter how much you eat, you become more
and more emaciated.
• What type of symbiosis is this?
• Barnacles attach
themselves to a
whale and feed on
particles in the water
as the whale moves.
The whale is
unharmed.
• What type of
symbiosis is this?
• A lion hides in the grass waiting for its next
meal
• Is this competition, predation, or symbiosis?
• Two grizzly bears are fighting over salmon
• Is this competition, predation, or symbiosis?
Changes in Terrestrial Ecosystems
Ecological Succession
Succession
• Natural, gradual
changes in the
types of species
that live in an area;
can be primary or
secondary
• Gradual changes in
community
structure over time
in response to
environmental
conditions
Primary Succession
• Begins in a place without
any soil
– Sides of volcanoes
– Landslides
– Flooding
• Starts with the arrival of
living things such as lichens
that do not need soil to
survive
• Called PIONEER SPECIES
Primary Succession
• Soil starts to form as lichens and the forces of
weather and erosion help break down rocks
into smaller pieces
• When lichens die, they decompose, adding
small amounts of organic matter to the rock to
make soil
Primary Succession
• Simple plants like ferns & mosses can grow in the
new soil
http://www.uncw.edu
http://uisstc.georgetown.edu
Primary Succession
• The simple plants die, adding
more organic material.
• The soil layer thickens, and
grasses, wildflowers, and other
plants begin to take over.
http://www.cwrl.utexas.edu
• These plants die, and they add
more nutrients to the soil.
• Shrubs and tress can survive now
http://www.rowan.edu
Primary Succession
• Insects, small birds, and mammals have begun to
move in
• What was once bare rock now supports a variety of
life
http://p2-raw.greenpeace.org
Secondary Succession
Occurs in areas that have been disturbed but have not lost their
soil; faster and different pioneer species than primary succession
End result of Succession:
• A stable group of plants and animals that is
the end result of the succession process
• Does not always mean big trees
– Grasses in prairies
– Cacti in deserts
Past and Current Beliefs
Up to ~1960’s
• If undisturbed, ecosystems achieve permanent structure; a
habitat/niche for each organism
• If disturbed, returns to the same permanent state 
“Climax community” over time
Now
•
•
•
•
All ecosystems are in continuing state of disturbance/change
Not all species at peak
Called a “mature community”
Moderate, frequent disturbances create communities with
high biodiversity
• Each disturbance goes through succession
Not every disturbance is a disaster...
The Intermediate
Disturbance
Hypothesis
Ecosystems that
experience
intermediate levels of
disturbance are more
diverse than those
with high or low
disturbance levels.
Not every disturbance is a disaster...
• Disturbances may kill some species, but allow others to benefit and
thrive. Therefore, the NPP of the ecosystem may remain unchanged- we
can say it is resistant.
• When a disturbance influences populations or communities, but not the
overall flow of energy and cycling of matter, we say the ecosystem has
high resistance.
• When an ecosystem’s flow of energy and matter are affected by a
disturbance, the rate at which recovers to original condition occurs can
be measured.
• That rate is called resilience.
• A highly resilient ecosystem would recovery quickly after a disturbance.
Values of Ecosystems
• Provision Services- Goods that
humans can use directly.
• Regulating services- The service
provided by natural systems that
helps regulate environmental
conditions.
• Support systems- The support
services that natural ecosystems
provide such as pollination,
natural filters and pest control.
• Cultural services- Ecosystems
provide cultural or aesthetic
benefits to many people.