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Community Interactions
Objective: A3 - Interpret relationships,
including predation, parasitism, commensalism,
mutualism, & competition among organisms.
- such as, competition, predation, and
symbiosis can powerfully affect an ecosystem
Every morning in
Africa
A gazelle wakes up &
“knows”
It must run faster that
the fastest lion
Or it will be killed.
Every morning, a lion
wakes up & “knows”
It must outrun the
slowest gazelle
Or it will starve to death
It doesn’t matter
whether you are a
lion or a gazelle
When the sun comes up,
You better be
running …
Competition:
• Occurs when organisms of the same or
different species attempt to use an
ecological resource in the same place at
the same time
• Things that reduce competition
- being active at different times of
the day
- establishing territories
- establishing hierarchies
- requiring different resources at
different times of the life cycle
Predation:
Hunter & hunted
Predator - prey
Predator and Prey
Adaptations
- Camouflage
(cryptic coloration)
- Warning
coloration
• Marked with bright or contrasting colors as
a warning that the animal is venomous or
noxious.
- Distasteful
- Horns for
protection
- Hooves
for running
fast
- Deceptive markings
(eyespots)
- Sharp Hearing
- Mimicry
Example:
Monarch & Viceroy
- Sting
- Poisonous
- Offensive Odors /
Repellant Chemicals
- Ability to run fast
- Sharp horns
- Sharp tearing teeth
- Claws for piercing
Lynx & hare
Predator – prey
graph
Symbiosis:
• Mutualism  
– both species benefit
from the relationship
Rhino & Oxpecker
Lichen = alga & fungus
Rhizobium
(nitrogen fixing bacteria)
& legume nodules
E. coli & human gut
• Commensalism 
– one organism benefits
and the other is neither
helped nor harmed
(a one-way relationship)
Clownfish & Sea Anemones
Shark & Remora
Spanish
moss
growing
on trees
• Parasitism  
– one organism
benefits and the other
is harmed
Endoparasites
Tapeworms
Ectoparasites
Caterpillar & wasp larvae
Mosquito
Leeches
Ticks & mammals