Communities
• A community is a group of populations in the
same location that interact with each other
and the nonliving environment
• A population is group of members of the
same species living in the same location
• Species are found in either random, uniform
or clumped dispersion patterns
A savanna community in Chobe
National Park, Botswana
Types of Species
• Native
• Non-native
• Indicator (serve as early warnings of
environmental problems, amphibians)
• Keystone (determine types and numbers of
other species, sea stars)
• Foundation (create and enhance habitat that
benefits other species, elephants)
• Invasive (non-native, cause ecological harm,
economical harm, or both, English ivy)
Types of Species Interactions
• Predation-one organism feeds on another
• Competition-organisms attempt to use the same
resource
• Symbiosis-two organisms live closely together
Predation
• Examples:
– Red Tail Hawk
feeding on a small
mammal
– Blue Whale feeding
on krill, (a small
shrimp-like animal)
– 1st order consumers
eating plants
Predator – Prey Interactions
• Predation is a key regulator of animal populations
Factors Affecting Predation
• Prey size
– Usually take animals
that are smaller than
themselves (provides
most energy gain for the
least energy cost)
– Large prey is harder
to chase and subdue
– Higher risk of being
injured when taking
large prey
Animal Defenses
– Camouflage
• Cryptic coloration (makes prey difficult to see)
• Defensive markings (confuses and discourages
predators)
Camouflage
(coloration, body type, or behavior that
disguises the animal)
• Defensive markings (used to confuse or
discourage predators)
• Fake eye spots
– Predators can’t locate the head
– Prey may appear much larger
• Mechanical defenses
• Sharp quills or spines
Chemical defenses
Production of distasteful and
toxic compounds
The bright colours of this Yellow-
winged Darter dragonfly serve
as a warning to predators of
its noxious taste
Usually associated with warning
colors - bright and
conspicuous color patterns
Chemical defenses are often indicated by
Aposematic Coloration
Monarch Butterfly: Retains
cardiac poisons from when it
was a larvae Cobalt Blue Poison Dart Frogs
• Golden dart frog
– Most poisonous animal known to • Rough skinned newt
man
– Also produces TTX
– Tetradotoxin (TTX)
• Potent neurotoxin
– Enough poison to kill 7
• 10,000 times more lethal than
people
cyanide
• Enough poison in one frog to kill
up to 200 people
• Causes convulsions and
paralysis
Coevolution: Mutual influence on the evolution of
two species due to their interactions with each other
()
• Rough skinned newt • Common garter snake
- Becoming more – Becoming more tolerant
poisonous of TTX poison
•Mimicry - One species closely resembles another
-Batesian Mimicry - harmless species resembles dangerous
species
-Mullerian Mimicry - dangerous species resembling each other
Example: bees and wasps
(a) Cuckoo bee
(b) Yellow jacket
Batesian Mimicry and Warning
Coloration
• Arizona Coral Snake (poisonous) • Arizona Mountain King
Snake (not poisonous)
“Red next to yellow kill a fellow” “Red next to black venom lack”
Mullerian Mimicry
• The viceroy butterfly (top)
appears very similar to the
noxious tasting monarch
butterfly (bottom).
• Originally thought to be an
example of Batesian
mimicry
• Found that the viceroy is
actually more unpalatable
than the monarch
Symbiosis-two species living closely together
• 3 types:
– Mutualism = both species benefit from the
relationship
– Commensalism = one member benefits and the other
is neither helped nor harmed
– Parasitism = one organism lives in or on the other
and harms it
Mutualism
Mycorrhizae and White Oak Tree
Mutualism
Great White Shark and Remora
Mutualism
Lichen
Commensalism
Bromeliad and Tamarind Tree
Commensalism
White Egret and Buffalo
Parasitism
Liver Fluke and Elk
Parasitism
Mistletoe and White Oak Tree
Succession
• The gradual change in species composition in an
area over time
• Primary succession is the establishment of life on
lifeless ground, no soil present
– Bare rock exposed by a glacier or severe erosion, newly
cooled lava, an abandoned parking lot, a newly created
shallow pond
• Secondary succession results from some
disturbance in an ecosystem that already existed,
soil is present
– Abandoned farms, burned or cut forests, heavily polluted
streams, other damaged or flooded lands
Secondary Succession
(a) Soon after fire. As this photo taken soon ( b) One year after fire. This photo of the same
after the fire shows, the burn left a patchy general area taken the following year indicates
landscape. Note the unburned trees in the how rapidly the community began to recover. A
distance. variety of herbaceous plants, different from
those in the former forest, cover the ground.
Long-term effects of fire on a tall
grass prairie community in Kansas
(a) Before a controlled burn. (b) During the burn. The detritus (c) After the burn. Approximately one
A prairie that has not burned for serves as fuel for fires. month after the controlled burn,
several years has a high proportion virtually all of the biomass in this
of detritus (dead grass). prairie is living.