Download Community Interactions - LaPazColegio2014-2015

Interactions In Ecological Communities
 An ecological community consists of all the interacting
populations in an ecosystem.
 The populations in a community interact in the following
ways:




Competition
Predation
Parasitism
Mutualism
Type of
Interaction
Effect on
Species A
Effect on
Species B
Competition
between A and B
Harms
Harms
Predation
by A on B
Benefits
Harms
Parasitism
by A on B
Benefits
Harms
Mutualism
between A and B
Benefits
Benefits
Competition
 Intraspecific
 between 2 members of
the same species in a
population
 Interspecific
 between members of
different species within
a community
Competitive Exclusion
Competitive Exclusion
P. aurelia
P. caudatum
(a) Grown in separate flasks
(b) Grown in the same flask
Fig. 27-1
What is a NICHE?
 each species occupies a unique ecological niche that
encompasses all aspects of its way of life
 type of habitat in which it lives, the environmental
factors necessary for its survival, and the methods by
which it acquires its nutrients
 define how the species exists within its ecosystem
What Are Predator–Prey Interactions?
 Predators and prey co-evolve.
 When a predator consumes its prey, one species benefits at
the expense of another
 Parasites live on or inside their prey, or host, and feed on
its body without necessarily killing it
 Herbivores are also predators that do not necessarily kill
the prey on which they feed
Predator–Prey Interactions
 Camouflage (cryptic coloration) conceals both predators
and their prey
Predator–Prey Interactions
 MIMICRY: Harmless animals may evolve to resemble
poisonous ones
A Prey Mimics Its Predator
Fig. 27-11
Predator–Prey Interactions
Camouflage Assists Predators
Fig. 27-6
Chemical Warfare
Fig. 27-12a
What Is Symbiosis?
 an intimate, prolonged interaction between organisms
of different species
 one species always benefits, but the second species may be
unaffected, harmed, or helped
 commensalism:
 one species benefits and the other is unaffected
 parasitism:
 one species benefits and the other is harmed
 mutualism:
 both species benefit
What Is Symbiosis?
 lichen is a mutualistism between an algae and a
fungus, which appears to be a single organism.


fungal body provides support and protection
photosynthetic algae provides food
Succession
 During succession, most terrestrial communities go
through stages
 Succession begins with arrival of a few hardy plants,
called pioneers

The pioneers alter the ecosystem in ways that favor competing
plants, which eventually displace the pioneers
 Succession often progresses to a relatively stable and
diverse climax community
 Recurring disturbances can set back the progress of
succession

The continuous disturbances maintain communities in
earlier, or subclimax, stages of succession
How Does A Community Change Over Time?
 two types of succession
 Primary succession: begins on bare rock, on sand, in a
clear glacial pool, or at some other location where there is
no trace of a previous community

This process may take thousands or even tens of thousands of
years
 Secondary succession: begins only after an existing
ecosystem is disturbed; for example, by a forest fire or
abandonment of a farm field
Primary Succession
rock scraped
bare by a
glacier
0
lichens and
moss on
bare rock
bluebell,
yarrow
blueberry,
juniper
spruce-fir
climax forest:
jack pine,
black spruce, white spruce,
balsam fir,
aspen
paper birch
1,000
Fig. 27-16
Succession in Progress
Fig. 27-15a
Secondary Succession
plowed
field
ragweed,
crabgrass,
Johnson
grass
Virginia pine,
eastern red
blackberry,
smooth sumac cedar
aster,
goldenrod,
Queen Anne's lace,
broom sedge grass
oak-hickory
climax forest:
white and black oak,
bitternut and
shagbark hickory
100
0
Fig. 27-17
Succession in Progress
Fig. 27-15b
Succession in Progress
Fig. 27-15c
Succession in a Small
Freshwater Pond
Fig. 27-18