Download Interrelationships Between Organisms

2/1/2014
What is it
Interrelationships Between
Organisms
Date: ______________
Ecosystems
• Ecosystem: community (all organisms in
a given area) and the abiotic factors
(non-living) that affect them
– Abiotic factors:
water, soil, climate
– What would be
some biotic
factors?
Interactions
• Organisms in an ecosystem CONSTANTLY
interact.
• These interactions create stability in
ecosystems.
• What are the types of
interactions?
– Predation
– Competition
– Symbiosis
• What is an ecosystem?
• How do organisms rely on each
other, even if they are members of
different species?
• What are predators? Prey?
• What is a niche?
• What is competition?
What makes an ecosystem stable
• Stable ecosystems have…
–Population numbers of each organism
fluctuate at a predictable rate
–Supply of resources in the physical
environment fluctuates at a
predictable rate
–Energy flows through the ecosystem at
a fairly constant rate over time
Predation
• Predation: interaction between
species in which one species
(PREDATOR) eats the other (PREY)
–Regulates population and causes it to
become stable
–Fluctuations are
predictable
• At some point, the prey
population grows so
numerous, they are easy to find
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A typical predator-prey relationship…
• As the prey population increases,
predator population increases.
• As the predator population increases,
the prey population decreases.
Competition
• Competition: relationship that occurs when 2+
organisms need the same resource at the same time
– It can be between members of the SAME or
DIFFERENT species
– Usually occurs with organisms that share the same
niche
• Niche: role of an organism in its environment, including the food it
eats, how it obtains that food, and how it interacts with other
organisms
• 2 species with identical ecological niches cannot exist in the same
habitat
• Competition usually results in a decrease in the
population of a species less adapted to compete for a
particular resource
Symbiotic Relationships
Parasitism
• Symbiotic relationship: two different species live
together in direct contact
– Balance of the ecosystem is adapted to this
relationship
– If the population of either species becomes
unbalanced, populations of both will fluctuate in an
uncharacteristic manner
• Types
– Parasitism
– Mutualism
– Commensalism
• What is it?  One organism (parasite) benefits
while the other (host) is harmed.
• Parasite generally does not kill the host – a
good parasite only uses the host for its needs.
Parasitism Examples
Mutualism
•
•
•
•
•
Mistletoe
Lice
Bacteria
Tapeworms
Heartworms
– If a parasite does kill the host, it can have a
negative affect on the parasite. The parasite
needs to have a living host long enough for the
parasite to reproduce and
spread.
• Parasite can live ON or IN the
host.
• What is it?  Both organisms benefit.
• Both organisms work closely together
and help each other survive
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Mutualism Examples
• Bacteria that live in
the digestive tracts of
termites – help the
termites digest wood
• Plant roots that
provide food for
fungi that break
down nutrients the
plant needs
Commensalism
• What is it?  One organism BENEFITS
while the other is NOT AFFECTED.
• Difficult to determine – how do we
know whether the other organism is
harmed or helped?
Commensalism Examples
• Barnacles that attach to
whales are dispersed to
different environments
where they can obtain
food and reproduce.
• Burdock seeds that
attach to organisms and
are carried to locations
where they can
germinate.
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