Download sea urchin population down

CO 47
Communities
Concept of the Community
Community = assemblage of populations
interacting with one another
Example: squirrel, moose, bear, fox, wolf,
pine tree, termites, bacteria....etc
Cobra vs Mongoose
interspecific interactions
With a partner, think of an example of each and label +’s &
-’s
Examples:
• Competition
• Predation
• Herbivory
• Symbiosis:
• parasitism
• mutualism
• Commensalism
• effects can be summarized as positive (), negative
(−), or no effect (0)
Structure of the Community
Habitat = particular place an organism lives
Ecological Niche: the role it plays in the community or the specific set
of biotic and abiotic resources used by an organism
Fundamental Niche - niche potentially occupied by that species
Realized niche - niche actually occupied by that species due to
competition
Niche – each member of this community gathers food in a
unique way
Interspecific Competition: competition between
different species (-,-)
Competitive Exclusion
Principle - no two species
can occupy the same
niche
Graph illustrates what
happens when you grow
two different species of
protists separately and in
the same container
(where competition can
occur).
Summarize the results.
Virtual LabPopulation
Biology
Competition
Resource Partitioning
- species with niche overlap,
share/partition resources
(see balanus)
Realized vs Fundamental Niche
Figure 41.3
Experiment
Chthamalus
Balanus
What happened
When Balanus was
removed?
High tide
Chthamalus
realized niche
Balanus
realized niche
Ocean
Low tide
Results
High tide
Chthamalus
fundamental niche
Ocean
Low tide
Figure 41.4
G. fortis
Beak
depth
Percentages of individuals in each size class
Competition can
lead to character
displacement
G. fuliginosa
60 Los Hermanos
40
20
0
60 Daphne
40
20
0
G. fuliginosa,
allopatric
G. fortis,
allopatric
Sympatric
60 Santa María, San Cristóbal
populations
40
20
0
16
8
10
12
14
Beak depth (mm)
Predation (/− interaction)
one species, the predator, kills and eats the other, the prey
Predator Adaptations:
Teeth
Claws
Vision
Speed
Strength
Camouflage
Working together
(
Sea Lion vs Whale
Chimps
http://www.youtube.com/watch?v=A1WBs74W4ik
Prey Defenses
hiding, fleeing, forming herds or schools,
active self-defense, Camouflage (cryptic
coloration) - blending in
Figure 41.5
(a) Cryptic
coloration
Canyon
tree frog
(b) Aposematic
coloration
Poison
dart frog
(c) Batesian mimicry: A harmless species mimics
a harmful one.
Nonvenomous
(d) Müllerian mimicry: Two unpalatable
hawkmoth larva
species mimic each other.
Venomous green
parrot snake
Cuckoo bee
Yellow jacket
Individual
Defenses
Startle Behavior (blowfish)
Anatomical defense (porcupine)
Chemical defense (skunk)
Predator Prey Interactions communities follow this pattern. Prey
species increase in number, followed
by predator species. Then Prey
species decline, followed by predator
species decline. The cycle repeats.
a
the Lynx and the Hare
Can your friends help?
Pack Behavior
Herding Behavior (zebra)
Schooling fish
Swarming insects
Herbivory (/− interaction)
an herbivore eats parts
of a plant or alga
Herbivores have
specialized teeth or
digestive systems
Plant defenses include
chemical toxins and
protective structures
Symbiotic Relationships
Symbiosis - intimate relationship between two
or more species
Parasitism - one individual is harmed, the other
benefits (ticks & deer)
Mutualism - both benefit (flowers & honeybees)
Commensalism - one benefits, other is neither
harmed or benefited (clown fish & sea
anemone)
Parasitism
•
one individual is harmed,
the other benefits
•
Does the parasite kill the
host?
Ex:
Show them!
Ecto- versus endo-, what’s the
deal?
Parsitoidism!
Example: Whale and Barnacle
Barnacles attach themselves to whales and filter
feed as whales swim through the water.
This is an example of: commensalism.
Bison and …
As bison walk
through the
grass, insects
jump out of the
way. The cowbird
follows the bison
and eats the
insects.
This is an example
of:
commensalism.
Cowbird
Figure 41.15
if Pisaster was removed from
the community, the populations
of mussels grew unchecked.
Without a predator to control
their numbers, the mussels
soon took over the community
and crowded out other
species, greatly reduced the
community's diversity.
Number of species
present
Community
Biodiversity
Keystone Species needed to maintain
biodiversity (often Results
20
top predators)
15
Experiment
With Pisaster (control)
10
Without Pisaster (experimental)
5
0
1963’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73
Year
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
Over fishing and Over Hunting
Key Stone Species: An organism that
is necessary for keeping an
ecosystem in balance.
Example: Sea Otter
Sea Otter’s Niche:
Eats sea urchins.
Uses rocks and shells to break
opened sea urchins
Predators: Sharks and Humans
Uses seaweed to anchor themselves
while they eat and sleep.
How sea otters keep their ecosystem in
balance:
Otters keep the sea urchin population down.
Sea urchins eat away at the base of sea weed.
Fish and other sea life rely on the sea weed
forests for food and shelter.
Over Hunting Key Stone Species
How do you think the decreasing otter
population effects the kelp forest
ecosystem?
Otter Population is Down Increases
Sea Urchin Population = _____________
Decreases
Sea Weed Population
= ______________
Decreases
Fish Population = _________________
Decreases
Seal Population = _________________
Decreases
Orca Population = _________________
Over Hunting Key Stone Species
Result: Urchin Barrens
KEYSTONE SPECIES: SEA OTTER
Sea otters eat sea urchins
Sea urchins eat kelp
What happens when you remove the otters?
Case Studies in
Keystone Species
Mutualism
both benefit (flowers & honeybees)
Figure 41.7
Lichen
Ants & Acacia tree
(a) Ants (genus Pseudomyrmex) in
acacia tree
(b) Area cleared by ants around an
acacia tree
Community Disturbance…
Ecological Succession
Ecological Succession - involves a series of species
replacements
Primary Succession - occurs where there is no soil
formation (volcanic island)
Secondary Succession - occurs after an area is
disturbed (prairie fire)
Pioneer Species - first species to inhabit an area
Climax Community - when the species replacement
slows and the ecosystem stabilizes
Figure 47.18cde
Why are moderate disturbances in an ecosystem necessary to maintain biodiversity?
Ex. Forest fires
Worksheet: Succession