Transcript Community Ecology

Community Ecology
No organism lives alone. Each organisms affects and
is affected by other species and its environment.
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Species Interactions
Just as populations contain interacting members
of a single species, communities contain
interacting populations of many species.
There are five major types of interactions, or
symbiotic relationships among species:
•Predation (+/-)
•Parasitism (+/-)
•Competition (-/-)
•Mutualism (+/+)
•Commensalism (+/o)
A symbiotic relationships is one in which different
species live in close association with one another.
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Predation
Organisms depend on each other
for survival. Many organisms
feed on other organisms. The
organism that is eaten is called
the prey.
The organism that kills and eats the prey is called
the predator.
Predators are an important part of an ecosystem.
Predators often kill the weak members of a
population. They keep the population size of prey
animals in balance.
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For Example:
The Mouse is
considered the
predator when it
preys on plants
The snake is the
predator when it
preys on the
mouse, which is
then the prey.
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Parasitism
Parasitism is one kind of symbiotic relationship.
A parasitic relationship is one in which one
organism is helped and the other is harmed. The
organism that a parasite lives on is called the
host.
FYI ~ Ticks, for example, can be
parasites of dogs. The dog is the
host. Ticks feed on the blood of
the dog and may pass diseases to
the dog. Although parasites harm
their host, they usually do not kill
them. This is because the
parasite depends on the host for
survival.
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FYI ~ Parasitism
In a bizarre parasitic death sentence, a fungus
turns carpenter ants into the walking dead and
gets them to die in a spot that's perfect for
the fungus to grow and reproduce.
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Competition
Competition results from niche overlap – two or
more species competing for the same resource(s).
One can be negatively impacted by the presence
of the other because they will have less food or
space.
Sea Anemones are constantly
engaged in competition for
territory.
Cheetahs and lions can also
be in competition, since both
species feed on the same
prey.
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Commensalism
Commensalism is a relationship in which one
organism benefits and the other organism is
not harmed but does not benefit either.
Example: cattle egrets eat lizards forced
out of hiding by buffalo’s movements.
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FYI ~ Commensalism
Spanish moss often
grows on the limbs
of trees. The moss
benefits from the
tree by having a
place to live. The
tree does not
benefit from the
moss, but it is not
harmed by the moss,
either.
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FYI ~ Commensalism
Barnacles adhering to the skin of a whale is an example
of commensalism. For a hungry barnacle, the rim of a
whale’s nostril isn’t a terrible place to be. When the
whale swims through a cloud of plankton for a meal,
the barnacle which also feeds on the tiny, floating
organisms, too, gets free table service.
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Mutualism
Mutualism is a relationship that helps both
organisms.
Example:
-Pollinators and plants have one of the
most important mutualistic relationships.
Pollinators-animals
that carry pollen.
Plants try to attract
pollinators by using
flowers.
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FYI ~ Mutualism
An acacia tree has thorns on its branches.
However, there are some animals, such as
giraffe, that can eat around the thorns.
When this happens, ants that live on the
acacia tree attack the animal.
The ants defend the tree
from being eaten. At the
same time, the ants feed
on milky sap produced by
the tree…
The tree gets protection,
the ant gets food !!
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FYI ~ Mutualism
The great barracuda spends much of its life just floating in the water,
but during this time it is taking part in a mutualistic relationship with
a little fish known as the cleaner wrasse. The barracuda sits in the
water with its mouth partly open and its gills flared to allow the
wrasse to eat off dead skin and parasites. This relationship could even
be considered obligate mutualism because without the wrasse, the
barracuda's gills would be clogged with dead skin and without the
barracuda, the wrasse would have no source of food.
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Check Your Understanding
Answer the questions in complete sentences:
1. What is an ecosystem?
2. What is a community?
3. What is a niche?
4. What does symbiosis mean?
5. CRITICAL THINKING:
A bumble bee helps pollinate flowering
plants while getting nectar from the
flower. What type of relationship does
this represent?
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Properties of Communities
 The ability of a community to bounce back after
major disturbances depends on several
properties of the community:
– the interactions of species within the
community (predator-prey relationships)
– the number of species (richness) the
community contains
– the kind of species the community contains
(diversity)
– The stability of the community (its resistance
to change)
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Succession
The populations of an ecosystem can change quite a
bit over a long period of time.
The gradual, sequential re-growth of species in an
area is called succession.
Normally in succession, the
plants are the populations that
re-grow first. Then, animal
populations will return to the
community.
This rotting log is an example of an
ecosystem undergoing succession.
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Two Types of Succession
Primary Succession: life begins to grow in an area
where there was previously no life and no soil.
Ex: bare rock, a sand dune, volcanic eruption, glacier
Secondary Succession: life repopulates an area that
has been destroyed, but the soil has remained.
Ex: forest fire, flood, devastating human activity
http://www.quia.com/jfc/2524430.html?AP_rand=5
02495504
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Succession
Any possible area that has the potential to be a new
habitat is an invitation to many species to set up
residence.
These hardy species that are the first begin a new
community are called pioneer species (i.e. crabgrass,
ragweed, algae, moss, lichen)
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Succession
It can take more than 100 years for an ecosystem to go
through all of the stages of succession.
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Succession
TAKE THIS QUIZ
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Succession
Succession continues until it has reached a stable
new community. This community is referred to
as a climax community.
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FYI ~Humans Can Change Ecosystems
Humans have an effect on the ecosystems they live
in. For example, for many years, people in the
western US feared wolves. Gray wolves were hunted
and killed until there were few left. People did not
realize that the wolves were an important part of
the ecosystem.
The wolves kept the
populations of other animals
in balance by feeding on
herbivores such as deer &
rabbits. By reducing the
number of wolves, humans
changed the balance in the
ecosystem.
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