Transcript Community Ecology - Fulton County Schools

Community Ecology
AP Environmental Science
Milton High School
Species diversity
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Species richness
– number of
different species
Species evenness
– abundance of
individuals within
each of those
species
Habitat fragmentation causes
significant decline in species diversity
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Reduce species richness
Reduce amount of functional habitat
Cause isolation of a species
Possibility of genetic drift or inbreeding
Edge Effects Associated with
Habitat Fragmentation Can
Reduce Biodiversity
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Makes many species vulnerable to
stresses such as predators and fires
Creates barriers that can prevent some
species from colonizing new areas and
finding food and mates
Edge effect
Conservation Biologists
Protect Biodiversity
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Preserving large areas of habitat
Using migration corridors to link
smaller habitat patches
Bridges over roads
Tunnels under roads
Who benefits from wildlife corridors?
The Most Species-rich
Environments
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Tropical forests
Coral reefs
Deep sea
Large tropical lakes
Three Major Factors
Affect Species Diversity
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Latitude (distance from equator)
Depth (aquatic systems)
Pollution (aquatic systems)
Number of Species Found on an
Island Determined by a Balance
Between:
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Rate at which new
species immigrate
to the island
The rate at which
species become
extinct on the
island
Two features of an island which
affects its immigration and
extinction rate
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Island’s size
Island’s
distance from
the mainland
Canary Archipelago
What can you predict about
how each island was colonized
by wild species?
General principles of
island colonization
1) The closer the island is to another land mass, the higher the
probability of colonization.
2) The older the island, the more likely it will be colonized.
3) The larger the island, the more species are likely to be
established.
4) The geographic isolation reduces gene flow between
populations.
5) Over time, colonial populations become genetically divergent
from their parent population due to natural selection, mutation,
and/or genetic drift
Critical Roles of Keystone
Species
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Pollination of flowering plant species
Dispersion of seeds by fruit-eating animals
Habitat modification (Gopher tortoise)
Predation by top carnivores to control
populations of various species
Improving the ability of plant species to
obtain soil minerals and water
Efficient recycling of animal wastes
Sea Otter:
A keystone species
Sea otters feed on the sea urchin which eats the
base of the kelp plants (killing the kelp plants)
The Dodo bird inhabited the island
of Mauritius in the Indian Ocean
In 1505, the Portuguese became the
1st humans to set foot on Mauritius
 Dodo bird
source of food for
the sailors
 Dutch used
the island as a
penal colony and
brought pigs and
monkeys which
ate the eggs of
the dodo bird
A combination of human exploitation and
introduced species significantly reduced
the dodo population
The last dodo
bird was
killed in 1681
Scientists discovered a certain species of tree was
becoming quite rare on Mauritius. All of the remaining
trees of their species were about 300 years old and no
new trees had germinated since the late 1600’s.
Was it coincidence that the tree had stopped
reproducing 300 years ago and that the dodo
bird had become extinct 300 years ago?
The dodo ate the fruit of the tree and the seed
only became active and could grow after passing
through the digestive tract of the dodo bird.
Scientists
discovered the
turkey’s digestive
tract
accomplishes the
same task and
they are now
using turkeys to
begin a new
generation of the
tree Tambalacoque
Biological indicator species are unique
environmental indicators as they offer a
signal of the biological condition of a
particular habitat
Using bioindicators as
an early warning of
pollution or
degradation in an
ecosystem can help
sustain critical
resources
Fish are an excellent indicator
of watershed health because:
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Live in water all of their life
Differ in their tolerance
levels to amount and types
of pollution
Are easy to collect
Live for several years
Are easy to identify
Benthic macroinvertebrates are
good indicators because:
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Live in water for all or most of their life
Stay in areas suitable for their survival
Are easy to collect
Differ in their tolerance to amount and
types of pollution
Are easy to identify
Often live for more than one year
Have limited mobility
Are integrators of environmental
condition
Possible Causes of
Amphibian Declines
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Loss of habitat
Prolonged drought
Pollution (pesticides, nitrates, pH)
Increases in ultraviolet radiation
Increase parasitism
Overhunting
Epidemic diseases
Immigration or introduction of alien
predators and competitors
What is the
disadvantage?
Five Basic Types of Interactions
Between Species
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Interspecific competition
Predation
Parasitism
Mutualism
commensalism
“sucking” disc does not harm shark
Remora
Commensalism
Bacteria in your intestines
Significant Niche Overlap – one
of the competing species must
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Migrate to another area
Shift its feeding habits or behavior
through natural selection or evolution
Suffer a sharp population decline
Become extinct in that area
How Species Avoid
Predators
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Run, swim, fly fast
Highly developed sense
of smell or sight
Protective shells
Thick bark
Spines
camouflage
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Parts that break off
Chemical warfare
Warning coloration
Behavioral strategies
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Puffing up
Mimicry
Schooling
Living in large groups
Spreading their wings
Avoiding predators
Examples of Primary
Succession
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Bare rock exposed by glacial retreat or
severe soil erosion
Newly cooled lava
An abandoned highway or parking lot
Newly created shallow pond or
reservoir
Pioneer species start soil
formation process by:
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Trapping wind-blown soil particles and tiny pieces
of detritus
Producing tiny bits of organic matter
Secreting mild acids that slowly fragment and break
down the rock
Lichen
Examples of Secondary
Succession
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Abandoned farmlands
Burned or cut forests
Heavily polluted streams
Land that has been dammed or
flooded
Three Aspects of Stability
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Persistence – resist disturbance
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Constancy – keep within limits
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Resilience – bounce back
Role of positive and negative feedback
loops in the stability of an ecosystem
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Negative feedback loops promote stability in
a dynamic system
Positive feedback loops usually leads to one
or more populations being wiped out (local
extinction)
Positive feedback loop = causes a system to change further in
the same direction (positive refers to the direction of change,
rather than desirability of the outcome)
Negative feedback loop = causes a system to change in the
opposite direction
Positive feedback loop
A warmer atmosphere
will melt ice and this
changes the Earth’s
albedo which further
warms the atmosphere
An increase in temperature will melt the
permafrost in the tundra causing a release
of trapped carbon dioxide and methane
(both are greenhouse gases)
Negative feedback loop
Predator-prey relationship
The moose population will
rise and fall in response to
the wolf population
Positive and negative feedback loops coupled together
1.
2.
3.
4.
5.
6.
The settlers of Easter Island found plenty of natural resources
The Islanders had many children and the population went up
The island’s tree and soil resources were used faster than they could be renewed
Without trees Islanders could not build traditional seagoing canoes
All of the island’s natural resources were used up
Both the population and the civilization collapsed
Example of negative
feedback loop
An example of negative feedback is body temperature regulation. If
blood temperature rises too high, this is sensed by specialized
neurons in the hypothalamus of the brain. They signal other nerve
centers, which in turn send signals to the blood vessels of the skin.
As these blood vessels dilate, more blood flows close to the body
surface and excess heat radiates from the body. If this is not
enough to cool the body back to its set point, the brain activates
sweating. Evaporation of sweat from the skin has a strong cooling
effect, as we feel when we are sweaty and stand in front of a fan.
Read more: Homeostasis - Biology Encyclopedia - cells, body, examples,
function, human, process, system, organisms, blood
http://www.biologyreference.com/Ho-La/Homeostasis.html#ixzz11mSI4EzD
Example of positive
feedback loop
An example of its beneficial effect is seen in blood clotting. Part of the
complex biochemical pathway of clotting is the production of an
enzyme that forms the matrix of the blood clot, but also speeds up
the production of still more thrombin. That is, it has a self- catalytic ,
self-accelerating effect, so that once the clotting process begins, it runs
faster and faster until, ideally, bleeding stops. Thus, this positive
feedback loop is part of a larger negative feedback loop, one that is
activated by bleeding and ultimately works to stop the bleeding.
Read more: Homeostasis - Biology Encyclopedia - cells, body, examples,
function, human, process, system, organisms, blood
http://www.biologyreference.com/Ho-La/Homeostasis.html#ixzz11mSpKQyy
The End