Download COMMUNITY

Community Ecology
Chapter 19
Part B
Community

An association of all the populations of
species that occupy the same habitat


Habitat: Physical and chemical features of an
area where a species normally lives.
Niche: The specific resources a species needs
for survival and reproduction
Community


Directly or indirectly species in a habitat
affect each other as part of the community
structure.
Five factors shape community structure
Community Structure

Climate and Topography


Temperature, rainfall, soil types, etc
Kinds and amounts of food and other
resources

Nutrient poor or extreme habitats don’t
support very many species
Community Structure

Adaptive traits



Allow them to survive and exploit specific
resources
Population sizes and history
Interactions between species
Questions

Match the following to Habitat or Niche



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
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Many organisms share
“Profession” of organism
Area where the organism lives
Only one species
Overlap results in competition for resources
All the biotic (living) and abiotic (non-living)
factors
Questions



How does climate influence community
structure?
How would poor soil affect community
structure?
How would population size influence
community structure?
Species Interactions

Interactions among species can be grouped
by their effects on both participants


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Indirect
Commensalism
Mutualism
Competition
Exploitation
Species 1
None
Helpful
Helpful
Harmful
Helpful
Species 2
None
None
Helpful
Harmful
Harmful
Indirect Interactions

No direct effect on each other

Songbird and tree


Bird eats caterpillar, indirectly benefitting the tree
Grass and Canadian lynx

Rabbits eat grass, which are in turn eaten by lynx

Good grass  plenty of rabbits  food for the lynx
Commensalism

Helps one species, but does not affect the
other

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Birds build a nest in a tree
Commensal ferns attach to the trunk of a tree

More access to sunlight
Mutualism

Both species benefit

Insects and plants
Insect transfer pollen between plants
 Plant provides nectar


Birds and plants
Bird disperses seeds
 Plant provides fruit

•Sea anemone
provides
shelter
•Pink anemone
fish chases off
butterfly fishes
(bite off anemone’s
tentacles)
p.704b
Mutualism

Faculative Mutualism


Either species can survive without the other
Obligate Mutualism


Both species cannot survive without the other
Yucca plant and the yucca moth
Fig. 40-3a, p.707
Competitive Interactions


Disadvantage to both organisms
Occurs when niches are similar and overlap
between two species

Limits the resources available to either
species
Competitive Interactions

Competition takes two forms

Interference competition


one species actively prevents another from
accessing some resource
Exploitative competition

Each species reduces the amount of resources
available to the other by using that resource
Competitive Interactions

Effects of competition

Competitive exclusion

One species will outcompete the other when they
require identical or very similar resources
Paramecium caudatum
Paramecium aurelia
Competitive Interactions

Effects of competition

Resource partitioning
Species become adapted in different ways to
subdivide similar resources
 Allows competing species to co-exist
 Essentially reduces each species’ niche

Alpine chipmunk
Alpine zone
Lodge pole pine
chipmunk
lodge pole zone
Least chipmunk
Forest zone
Merriam’s chipmunk
Base of mountain
Sierra Nevada: competition keeps nine
species of chipmunks in different habitats
Exploitation


One species benefits at the cost of the other
Predation

One organism feeds on another, but does not
live in or on them

Interaction between predator and prey
influences both species’ population size
PREY
POPULATION
PREDATOR
POPULATION
Fig. 42.7, p. 724
Lynx - - - Hare
Exploitation

Predation

Interactions between predators and prey have
led to co-evolution

Each population exerts selective pressure on the
other
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Prey needs to escape
Predator needs dinner
Traits that confer an advantage for survival will be
selected
Exploitation

Predation

Prey adaptations
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Difficult to eat
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Hard, sharp parts
Chemicals that taste bad
Warning colorations

Conspicuous color pattern
 Poison dart frogs
 Skunk
 Wasp’s black and yellow stripes
Exploitation

Predation

Prey adaptations

Mimicry

Wasp stings (warning
coloration)
Close resemblance in form or behavior to a dangerous
organism
Non-stinging insects which mimic the wasp’s
coloration: non-stinging wasp, beetle, and a fly
Exploitation

Predation

Prey adaptations

Last chance trick

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Look larger and more intimidating: hissing, puff up, eyeshaped spots
Play dead
Squirt irritating chemicals
Exploitation

Predation

Prey adaptations
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Camouflage

Form, patterning, color, or behavior blend with the
surroundings
Lithops
Exploitation

Predation

Predator adaptations
Stealth
 Camouflage
 Traps
 Avoid repellents

Grasshopper mice plunge the chemical-spraying tail end of
the beetle into the ground and feast on the head end
Exploitation

Herbivory

Animal eats a plant or plant parts

Plant adaptations


Recover quickly
 Prairie grasses
Deterrents: thorns, tough leaves, bad tastes
Exploitation

Parasitism

A parasite feeds on the host without
immediately killing it

Many live in or on the host


Endoparasite lives inside the host (tape worm)
Ectoparasite feeds while attached to external parts of the
host (tick)
Strangleweed
Fig. 40-14a, p.714
Roundworms in
pig intestines
Fig. 40-15, p.714
Exploitation

Types of parasitism

Brood parasites
Female lays eggs in a different species’ nest
 The foster parent then pays the cost of caring for
the young

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Parasitoid
Insects that lay their eggs in other insects
 The larvae hatch, develop, and eat the host’s body

Questions

For the following pictures indicate what
type(s) of species interaction is involved
Yucca
plant can
only be
pollinated
by a
yucca
moth
Yucca
moth
can
only lay
eggs in
yucca
plant
Whistling
Thorn Acacia
provides
protection for
ant larvae and
honey-like
secretions
used by the
ants as food.
Ants provide
protection
against
herbivores
by swarming
out as soon
as the tree is
touched.
Canadian
Lynx
Grass
Preying
mantis
Remains of
insect
Tree
Bird builds
nest in tree
Human feet
Fungus
Fig. 40-17a, p.715
Community “Stability”

Not always very stable

actually an uneasy balance
Community “Stability”

Climax community

Typical array of plants under prevailing
habitat conditions

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Forest: trees
Prairie: grasses
“Stable” community
Community “Stability”

Disturbance

Disrupts the climax community


Fire, volcano, empty farm field, tidal wave, etc
The type of disturbance influences species
richness (biodiversity)

Number of different species within a community
Community “Stability”

Community Succession

Disturbed area develops through a sequence
of predictable stages to a final “stable” array
of species
Community “Stability”

Community Succession

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As each stage grows they change the
environment
Changed environment is favorable for the
next stage
New stage then out-competes previous array
of species
Community “Stability”

Community Succession

Pioneer species

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Lichens, moss, fireweed
Stages of temporary species (seres)

Typically each stage increases in height

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Wild flowers, grass
Bushes/shrubs
Trees
Climax species
Barren land
Pioneer
Species
Climax
community
Temporary
Stage
May 1980
6-9 years later
Pioneer species
12 years later
Seedlings of the dominant climax
community species: Douglas firs
Community Stability

Keystone species

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Major effect on community stability
Removal of a keystone species can
dramatically change the diversity of species
in that habitat
Sea stars are the
keystone species
in this example.
Grazing periwinkles affect the number
of algal species in different ways in
tide pools and on rocks
Periwinkles graze on Enteromorpha
the dominant alga in tide pools,
promoting the survival of less
competitive algal species
Periwinkles find Chondrus, which is the
dominant alga on rocks, to be tough so
they eat other less competitive algal
species reducing diversity
Community Stability

Species introductions

Exotic invaders
Non-native species
 Invasive

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Out compete natives
Community Stability

Species introductions
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Kudzu in the South
Rabbits in Australia
Caulerpa taxifolia
Gypsy moth
Kudzu in the South
Caulerpa taxifolia
Rabbits in Australia
Questions

Describe the community succession of a
Missouri farm field if it was left alone.
Questions
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Missouri
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Bare soil
Annuals, legumes, grasses
Herbaceous perennials
Shrubs
Intolerant trees (shade)
Mid-tolerant trees
Tolerant trees (woodland climax)
Summary
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Community
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Habitat
Niche
Community structure
Species interactions
Community stability