Download Biological Communities CH 17-1

Species Interactions
Chapter 4 section 2
Interactions
• Interactions results from
two organisms that have
evolved in response to
each other.
Corpse Flower
Corpse Flower
• Smells like
rotting meat.
• Why?
• The
pollinators
for this plant are
carrion and dung
beetles.
Coevolution
• Back and forth
evolutionary adjustments
between two organisms in
an ecosystem
Predation: Predator &
Prey
•When one organisms feeds on
another
Parasitism
• One organism
that
feeds/lives off
a second
organism.
How does prey protect
itself?
• They develop adaptations to
protect themselves
• Create a secondary compound, a
chemical, that is used for self
defense
• Example: Poison Oak/Ivy –
Creates a sticky irritating oil to
protect itself from predators
How do predators adapt?
• Woodrat:
–Eats Poison
Oak
–Builds it
burrow
under
Poison Oak
nd
2
Example: Predator
Prey Adaptation
• Mustard plants secrete a chemical
that is toxic to insects
• Larvae from cabbage butterflies can
eat mustard plants with no toxic
Symbiosis
• A form of coevolution in which
two or more species living
together in a close long term
association
• Examples:
• Mutualism
• Commensalism
Mutualism
• A symbiotic relationship that is
beneficial to both species
Lumps are nodules of
nitrogen fixing
bacteria.
The bacteria make
nitrogen for the plant
in exchange for food
Commensalism
The sea anemone is an organism whose
defensive structure are stinging cells
located on its tentacles. A clown fish can
hide within the
tentacles and
benefit from being
protected. The
sea anemone is
neither harmed or
helped.
17-2: Competition shaping
communities
• The competition for
common resources, very
little resources, in one
community determine the
nature of that community
Niche
• The functional role of a species,
its activities and relationships,
within its ecosystem.
• Each organism has its own
niche, its own unique way that it
interacts with its environment,
biotic and abiotic factors
Fundamental niche
• The total range of
environmental conditions in
which a species can survive
and make use of
Example: Fundamental
niche
Example: Realized Niche
Character displacement
• When competing species
become physically different
due to its realized niche
• Believed to be caused by
evolution and the species
adaptation
nd
2
Example of Character
displacement
Why are the
beaks
different?
Competition results
• Where two species exist, a
species that is a better
competitor will drive out the
second species
• Competitive Exclusion:
Elimination of one species in
an area
Example: Competitive
exclusion
• Chthamalus stelatus
lives in shallow
water and is
exposed to air
during low tide
• Its Fundamental
Niche is shallow and
deep Ocean water
Example: Competitive
exclusion
• Balanus.
Normally
occupies lower
Ocean depths.
• Its Fundamental
niche is the
lower Ocean
depths
Example: Competitive
exclusion
• Balarus can out
• Chthamalus
stelatus can live in
both shallow and
deeper depths, but
cannot out compete
Balarus for space.
This makes its
realized niche in the
shallow portion of
the ocean
compete Chthamalus
stelatus for space, but
cannot survive when
exposed to air during
low tide. This makes
its fundamental and
realized niche the
deeper Ocean levels
Principle of competitive
exclusion
• The species that uses the
resources more effectively
will eventually exclude the
other
• If both species niches do not
overlap too much they can
both survive
A change of number of
Organisms in an ecosystem
• Predation lessons the effects of
competition.
• Predators keep the prey numbers in
check.
• This is important because some prey
can out compete other organisms for
available resources.
• This would result in less species
diversity for an ecosystem
Example: Aleutian Isles
• The disappearance of the otter, due to
being eaten by orcas, allowed sea
urchins to thrive.
• Sea urchins ate all the kelp which left
no food for many fish in this ecosystem
• With no food for the fish they left and
the number of organisms in the
Aleutian Isles shrunk