Transcript File

Community Interactions
Organisms not only live together in ecological
communities, but they also constantly interact with one
another. These interactions, which include predation and
competition, help shape the ecosystem in which they
live.
1. Based on your own experiences, define predation.
Give one example of predation.
2. Based on your own experiences, define competition.
Give one example of competition.
Living and Non-living Factors
Living things
ECOSYSTEM
Non-living things
Biotic and Abiotic Factors
Living things =
BIOTIC FACTORS
ECOSYSTEM
Non-living things =
ABIOTIC FACTORS
Biotic and Abiotic Factors

The living (biotic) and nonliving (abiotic) parts
of an ecosystem are always interacting.

The biotic and abiotic factors of an ecosystem
shape that ecosystem.
http://www2.for.nau.edu/courses/hart/for479/images/alpine01.jpg
Community Interactions

Not only do the biotic and
abiotic parts of an ecosystem
always interact, the living
things are always interacting
with each other.

When organisms live together
in an ecological community,
they constantly interact.

A community is a collection of
different populations that live
together in a certain area.
Community interactions can powerfully
affect an ecosystem.

Three main types of interactions between the
living (biotic) things in an ecosystem:


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Competition
Predation
Symbiosis
Competition

Competition occurs when organisms try to
use the same resources in the same place at
the same time.

A resource is any necessity of life, such as water,
nutrients, light, food, or space.
Competition
In a forest, for example, trees with large
leaves may compete for sunlight by growing
tall, spreading out their leaves, and blocking
the sunlight from shorter trees.

Direct competition in nature often results in a
winner and a loser. The loser then fails to
survive and dies.
www.rr.ualberta.ca/ Index.asp?page=News&news=633
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Competitive Exclusion Principle

Two species cannot occupy the same niche in
the same habitat at the same time.


Habitat – the place where an organism lives that
provides all of its needs
Niche – the job of a living thing in its community
Figure 4-5 Three Species of
Warblers and Their Niches
Competitive Exclusion Principle
Section 4-2
Cape May Warbler
Feeds at the tips of branches
near the top of the tree
Bay-Breasted Warbler
Feeds in the middle
part of the tree
Spruce tree
Yellow-Rumped Warbler
Feeds in the lower part of the tree and
at the bases of the middle branches
Each of these warblers has a different niche in its spruce tree habitat. By feeding
in different areas of the tree, the birds avoid competing with one another for food.
Go to
Section:
Predation
Predation is a community interaction in which
one organism captures and feeds on another
organism.


The predator is the organism that does the killing
and eating
The prey is the food
necsi.org/.../ co-evolution_predator.html
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Symbiosis


Symbiosis is a relationship between two
species that live close together.
Three classes of symbiosis in nature
1. Mutualism
2. Commensalism
3. Parasitism
www.unibas.ch
Mutualism

In mutualism, the relationship benefits both
species.
http://wc.pima.edu/~bfiero/tucsonecol109/animals/Images/inter01.jpg
Commensalism
In commensalism, one organism benefits from the
relationship and the other is neither helped nor harmed.
http://www.cbu.edu/~seisen/ExamplesOfCommensalism_files/image002.jpg

Parasitism
In parasitism, one organism lives on or inside
another organism and harms it.
http://userwww.sfsu.edu/~biol240/labs/lab_03symbiosis/media/viscumalbum.jpg
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