Transcript Community Ecology

CHAPTER 53
COMMUNITY ECOLOGY
Introduction

What is a Community?
Different species living together in an area

Individualistic hypothesis - chance
assemblage due to similar abiotic requirements
Fig. 53.1a

An interactive hypothesis - closely linked
species locked in by mandatory biotic
interactions.
Fig. 53.1b
•The ecological niche = organism’s use of
abiotic/biotic resources in the environment.
Habitat = "address"
Sir Deciduous Oak Tree,
The Oak Forest,
England,
U.K.
•The ecological niche = organism’s use of
abiotic/biotic resources in the environment.
Habitat = "address"
Niche = how organism fits into
environment
What is the niche of a
lizard?
Temperature range
Where it perches
When it is active
No two organisms can have
the same ecological niche
Principle of Competitive Exclusion
And Resource Partitioning
No two organisms can have the same
ecological niche - Competitive Exclusion
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Character Displacement - species living
close together differ more in traits than
those living far away
Interspecific Interactions
Realized - max. range that a species has occupied in
reality due to competition/other factors
Interspecific Interactions
Potential/Fundamental Niche - max. range that a
I)species
Competition
(-/-)
can occupy
Realized and
Potential Niche
Interspecific Interactions
II) Predation

Herbivory
(+/-)

Parasitism
Interspecific Interactions

Predation -ways to
avoid it
1)Cryptic
Coloration =
camouflage
Interspecific Interactions

Avoiding Predation
2)Aposematic
Coloration=
warning
coloration
Interspecific Interactions

Avoiding Predation
3)Batesian Mimicry –
harmless species
mimics harmful
Interspecific Interactions

Avoiding Predation
4)Mullerian Mimicry – 2
unpalatable species resemble
each other. Why?
Interspecific Interactions

Predation (+/-)

Parasitism is a
type of predation
“Scientists have discovered a way to
kill the malaria parasite - by targeting
its sweet tooth.” –BBC News
Interspecific Interactions

Predation (+/-)

Parasitism
Interspecific Interactions

Predation (+/-)
a) Ectoparasite
c) ParasitoidismNasonia

Parasitism - types:
b) Endoparasite
Interspecific Interactions
III) Mutualism
(+/+)
Coevolution- change
in one species affects
evolution of another species
Ex. Nitrogen fixing bacteria in the root of legumes, bees and flowers,
cellulose digesting bacteria in gut of cows
Interspecific Interactions

Commensalism (+/0)
One benefits, one neithergains/loses: dung beetle, birds on cattle, Nemo
and anemone!
Symbiosis - term describes
‘living together’

Commensalism (+/0)
Predation (+/-)

Mutualism (+/+)
Trophic Structure  Food chain
•(V – vegetation;
Feeding
relationships (trophic levels)
herbivores - H; Predators - P)
•How change in biomass of one
level affects another
•N  V  H P : Bottom-up
•N V  H P : Top-down
How long can a food chain be?
•V  H: Intermediate
-1) Energetic hypothesis 100kg plant = 10kg cow=1kg lion
-2) Dynamic stability
Long chains less stable
Unpredictable envt. = short chain
Energetic hypothesis wins!!! - more
producers = longer food chains
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Leaf litter amount
Biomanipulation-change the ecology through
the use of living organisms; Lake Vesivarji –
Finland-Top down or bottom up?
Pike
Roach
Increase pike fish, which eventually = decrease
in algal blooms; decrease in Eutrophication
Trophic Structure

Food web interconnected food
chains
Dominant species - highest
biomass (sum of weight of all
individuals in a population)

Sugar maple - shade
out other plants and
take in most water
What happens if dominant species
is removed?
 Something else takes over usually

Can a species be non-dominant
and still control the community?



Sea star preys on
mussels
Mussels eat
algae/small
invertebrates
Sea star’s absence
results in decrease of
algae/invertebrates in
the community
Keystone species – strongest
control over community due to its
niche
 Sea Star -few
but ‘powerful’
Keystone species –

Sea Otter
Disturbances – environmental changes
(volcanoes, fires…..!)

Density Independent Factor - keeps population size
in check; dominant species growth is curbed

Non-equilibrium
Fig. 53.16
Succession –
Transition in Species Composition Over Ecological
Time; Predictable order of species (first - easily dispersed
species; later - superior competitors)
1980
1981
After
Before
Primary Succession -soil ‘gonner’

Soil has been removed
by volcano
1) Short lived weed
growing through the
ash
Early successional
Community
Primary Succession

2) Herbaceous plants
and grasses
Primary Succession

3) Shrubs (willow)
and short lived trees
(alder)
Mid successional
Community
Primary Succession
Climax Community
??????
4) Long-lived trees
(fir, hemlock, pine)
Primary Succession
A) Glaciation
Soil has been
removed
B) Volcanic Lava Flows
C) Volcanic Explosions
D) Faulting raising sea floor
Secondary Succession- soil ‘Okey
dokey’
A) Forest Fires
Soil is intact
B) Disease
C) Climatic Conditions - Hurricane, tornado,
drought, windstorms, etc........
D) Human Disturbance – urban development,
clearing woods, grazing etc..........

Soil concentrations of
nutrients show changes
over time.
Fig. 53.20
Compare the Kentucky old growth
forest and Crater lake National
park.
What happened in Crater lake
national forest?
Biodiversity
•Species richness, the
total number of species
in the community.
•Relative abundance of
the different species.
 Species richness
may be equal,
but relative
abundance
may
Fig. 53.21
be different.
Species
richness
generally
declines
along an
equatorialpolar
gradient
WHY???
Tropical areas
-show more speciatio
in evolutionary time
-no glaciation
- are older because th
growing season is
longer
-show more
evapotranspiration
Evapotranspiration (Climate)
Fig. 53.24
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Biodiversity
Species
richness is
more in
larger
islands
Biodiversity
Species
richness is
more in
larger
islands,
closer to
the
mainland