What Shapes an Ecosystem?
Review of Biotic and Abiotic
Factors
• Ecosystems are influenced by a
combination of biological and physical
factors.
• Biotic factors
– include all the living things with which an
organism might interact.
• Abiotic Factors
– Physical, or nonliving, factors that shape
ecosystems.
Habitat and Niche
• Habitat
– all aspects of the area in which an
organism lives (includes both biotic and
abiotic).
– Habitats may change or disappear due
to natural causes or interference by
man.
Habitat and Niche
• Niche
– the role or place and position a species has in
its environment.
• An ecological niche includes all of the
factors that a species needs to survive,
stay healthy, and reproduce.
– food
– abiotic conditions
– behavior
Habitat and Niche
• Why do you think no two species can
share the same niche.
• One species is better suited to the niche
and the other will either be pushed out
or become extinct.
Community Interactions
• When organisms live together in
ecological communities, they interact
constantly.
• Community interactions include:
– Competition
– Predation
– Symbiosis
Community Interactions
• Competition:
– occurs when two organisms fight for the
same limited resource.
– Direct competition in nature often results
in a winner and a loser—with the losing
organism failing to survive.
How species avoid Competition
• The distribution of these warblers
avoids direct competition, because
each species feeds in a different part
of the tree.
Community Interactions
Predator
• Predation:
– occurs when one organism captures
and eats another.
Prey
Community Interactions
• Symbiosis:
– Any relationship in which two species
live closely together
– Includes:
– mutualism
– commensalism
– parasitism
Community Interactions
• Mutualism:
– both species benefit from the relationship.
Community Interactions
• Commensalism
– one member of the association benefits and the other is
neither helped nor harmed.
Ø
Human Our eyelashes
are home to tiny mites
that feast on oil
secretions and dead
skin. Without harming
us, up to 20 mites may
be living in one eyelash
follicle.
Commensalism
Ø Organism is not affected
+
+
Organism benefits
Demodicids Eyelash
mites find all they need to
survive in the tiny follicles
of eyelashes. Magnified
here 225 times, these
creatures measure 0.4
mm in length and can be
seen only with a
microscope.
Community Interactions
• Parasitism
– one organism lives on or inside another organism and
harms it.
0
Parasitism
+
_
Hornworm
caterpillar
The host hornworm
will eventually die as
its organs are
consumed
by wasp larvae.
_
Organism is not affected
0
Braconid
wasp
Braconid larvae
feed on their
host and
release
themselves
shortly before
reaching
the pupae
stage of
development.
Organism benefits
Ecological Succession
• Succession occurs following a disturbance
in an ecosystem and regenerates or
creates a community after a disturbance.
– a sequence of biotic changes
– damaged communities are regenerated
– new communities arise in previously
uninhabited areas
Ecological Succession
• There are two types of succession.
• primary succession — started by pioneer
species
Ecological Succession
• There are two types of succession.
– secondary succession — started by
remaining species