Behavior between species:
COMMUNITIES & SPECIES INTERACTIONS
Remember what a COMMUNITY is?
How about an ECOSYSTEM?
Some common types of species interactions
Predation
Competition
Herbivory
Symbiosis
Three types of SYMBIOSIS
barnacles on whale
tapeworm
Parasitism
cleaner wrasse
Mutualism
Commensalism
Plants, herbivores & predators form
food chains and "food webs"
PRODUCERS
are eaten
by
PRIMARY
CONSUMERS
are eaten
by
SECONDARY
CONSUMERS
(often there are more
consumers
above secondary)
Example of an even longer food chain:
PRODUCERS
PRIMARY
CONSUMER
SECONDARY
CONSUMER
TERTIARY
CONSUMERS
Takes a lot of producers to
feed 1 consumer... why?
The 10% rule of BIOMASS
Food webs can be complex
concept of "ecological niche"
Because of COMPETITION
each species has its own NICHE
ECOLOGICAL NICHE = the way a species
"makes its living"; the "job" it has
What exactly does it eat? What eats it?
What habitat does it need? (etc.)
No two species that live in the
same area can have exactly the same ecological niche
DOMINANT species
The most abundant species
On land: usually is whichever tree/grass can out-compete the others
In marine ecosystems: sometimes is a filter-feeder (not a plant)
KEYSTONE species
Some examples:
Low abundance but has unusually big impact on the ecosystem
Without it the whole ecosystem will often "collapse"
Example: marine tidepools
MUSSELS
SEA STARS
"Keystone Predators" module
Three seaweeds (algae)
that photosynthesize:
Nori seaweed
Three SESSILE
consumers:
Mussel
Acorn Barnacle
Black pine
Coral weed
Gooseneck Barnacle
Three MOTILE
consumers:
Whelk (kind of snail)
Chitons
Starfish (Pisaster)
Info from first experiment (optional)
MUSSELS can out-compete
the 2 barnacles
Mussel
Acorn Barnacle
Gooseneck Barnacle
Info from second experiment (optional)
Mussel
Starfish (Pisaster)
Chitons
Seaweeds
Whelk (kind of snail)
Barnacles
Starfish are the only predator
that’s keeping the dominant mussels in check
MUSSELS
STARFISH
are eaten
by
Mussels can out-compete all other sessile creatures
But starfish eat mussels
STARFISH ARE KEYSTONE SPECIES
KEYSTONE species
Some examples:
Low abundance but has unusually big impact on the ecosystem
Without it the whole ecosystem will often "collapse"
Gray wolf: another “top predator”
ELK
GRAY WOLF
Example: Yellowstone
After eradication of wolf,
aspen and cottonwood trees started declining
why?
Elk eat aspen & cottonwood saplings in winter
(often GIRDLE them)
1995 - Wolves reintroduced to Yellowstone
Animals were wild Canada wolves (not zoo wolves)
captured 1995-96
Started hunting elk again...
...and moose
...and bison
Ecological effects
•Expected:
•Elk down
•Cottonwood & aspen up
•Riparian areas up
•Unexpected:
• Elk behavior also changes
• COYOTE DOWN
• RED FOX up
• BEAVER up, PONDS up
• PRONGHORN way up
The ecosystem was more complicated than we thought...
... and wolves have huge effects
Wolf actually
doesn’t eat
coyote - just
kills them because of
COMPETITION