COMMUNITY ECOLOGY

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COMMUNITY ECOLOGY
MILLER CHAPTER 8
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I. Community Structure

• A. FOUR CHARACTERISTICS
• 1. Physical Appearance
• Size, Stratification, Distribution of
  populations/ species
• 2. Species Diversity or Richness
• Number of different species
• 3. Species Abundance
• Number of individuals of each species
• 4. Niche Structure
• Number of ecological niches

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Rainforest

• Distribution of populations and species can be
  vertical

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Community Structure Appearance and Species
Diversity
Fig. 8.2, p. 174
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Edge Effects

• Differences in physical properties at boundaries
  and in ecotones
• Ex Sunlight, temperature, wind, humidity
• Pheasants and white tailed deer are more
  plentiful in these areas.
• Wildlife managers create patches and edges to
  increase these populations

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EDGE EFFECTS ON FORESTS
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BIODIVERSITY

• What is it and why should we care about it?

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II. The Extent Of BIODIVERSITY

• BIODIVERSITY-
• the number and types of organisms on the earth.
• The most species rich environments are
• -Tropical rain forests
• -Coral reefs
• -Deep sea
• -Large tropical lake
• Those communities with the largest number of
  different species generally have only a few of
  each species or low species abundance

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Coral Reefs
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A. 3 Factors that affect Species Diversity

• 1) Latitude-
• Diversity increases as you move closer to the
  equator
• Latitudinal Species Diversity Gradient
• REASONS
• -resource availability
• -higher evolution rate
• -parasites keep down domination
• -speciation greater than extinction

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Latitudinal Species Diversity Gradient
ANTS
BIRDS
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• Local variations within terrestrial ecosystems
• Diversity tends to increase with
• - increased solar radiation

- increased precipitation
- decreased elevation
- strong seasonal variations
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• 2) Depth-
• Aquatic diversity increases as you get deeper up
  to 6,000 ft. Its high at the bottom as well
• Depth-species diversity gradient
• REASONS
• -Increased stability
• -Lack of nutrients in the mid-depths
• -Increased nutrients at bottom
• 3) Pollution-
• -kills or impairs species

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B. HUMAN EFFECT ON BIODIVERSITY

• Habitat destruction due to increased human
  population
• Illegal-hunting/poaching
• Introduction of exotic species

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III. General Types of Species

• 1. Native
• - Normally live and thrive in an ecosystem
• 2. Non-native
• - Often called exotic, alien or invasive
• Introduced species tend to crowd out native
  species
• May not have any natural population controls

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Lamprey
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ASIAN CARP
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Snakehead Fish
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Lionfish
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FEARSOME FROGS
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• 3. Indicator
• - Serve as an early warning that an ecosystem is
  being damaged
• Ex Birds, Trout, Frogs
• 4. Keystone
• - Species that have a greater importance in the
  structure of the community
• Controversial among scientists

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Species Interactions

• 1.) COMPETITION
• 2.) PREDATOR/PREY
• 3.) SYMBIOSIS

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A) COMPETITION

• 1. Intraspecific
• -Competition between members of the same species
  
• -Territoriality Patrol their area

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2. Interspecific -Competition between 2 or more
different species -Most common -Two types
include Interference Exploitation
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• Interference Competition
• One species limits another's access to a resource

• Exploitation Competition
• Competing species have equal access to the
  resources but differ in how fast they use it

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COMPETITIVE EXCLUSION PRINCIPLE
The niches of 2 species cannot overlap completely
or for an extended period of time
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3. Reducing Competition
Resource Partitioning Divide scarce resources so
species use them at different times and/or
places Ex Lions/ Leopards, Owl/Hawk
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2. PREDATION (predator/prey)

• Predator

• Prey

• Prey acquisition

• Predator Avoidance

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How do Prey Defend Themselves?

1. Quick escape
2. Keen sense of smell and sight
3. Protective shells
4. Spines or thorns
5. Camouflage
6. Chemical warefare

1. Warning coloration
2. Mimicry
3. Imitate a dangerous species
4. Behavior

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http//rainforests.mongabay.com/0306.htm
MIMICRY
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3. Symbiotic Species Interactions

• Symbiosis
• Long lasting relationship where species live
  together
• 3 types of symbiotic relationships
• A. Parasitism
• B. Mutualism
• C. Commensalism

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PREDATION
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A. Parasitism

• Species feeds on part of another organism
• Host is usually harmed
• Parasite is usually smaller than the host
• Rarely kills the host quickly
• Endo/Ecto parasites

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Endo- and Ecto- Parasites

• Endo-parasite
• A parasite that lives inside the body
• Ecto-parasite
• A parasite that lives outside the body

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Schistosomiasis
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Tapeworm bladders inside the brain of a women
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Ascaris worms that migrated to a persons liver
and blocked its major vessels.
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• Elephantiasis

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Wuchereria bancrofti
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SHOW CLIP NEVER UNDERESTIMATE THE BODY
SNATCHERS
UNITED STREAMING TAPEWORMS BODY
SNATCHERS
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B. Mutualism

• 2 species are in a relationship that is
  beneficial to both
• Providing Food
• Protection

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Examples of Mutualisms

• Roots and Rhizoids (Nitrogen Cycle)
• Bacteria in the digestive system
• Protozoans in termite guts
• Birds catching a ride
• Clownfish and sea anemones

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Mycorrhizae is the relationship between a fungus
and a higher plant's root system. In this
relationship, the plant feeds the fungus, while
the fungus supplies the plant with mineral
nutrients ( especially phosphorous) and according
to some sources additional moisture.
Ant-acacia mutualism "In this relationship found
most commonly in Central America savannas, the
ant hollows out the large thorns of the plant for
nests, feed on sweet secretions from the four
nectaries at the base of each petiole and on the
protein rich Beltian bodies found on the tips of
the leaves, which together provide an almost
complete diet for the ant. The ants in return
protect these trees from invertebrate as well as
vertebrate herbivores. With any movement of the
branch, the ants emerge releasing a nasty odor as
well as physically attacking the surprised
herbivore. They are quite effective.
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C. Commensalism

• Relationship that benefits one species but
  neither helps nor harms the other

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Examples of Commensalisms
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Orchids
In the ecology of orchids, commensalisms with 
different types of fungi is essential, because
their seeds have lost nutritive tissue so they
can sprout and develop only with the help of 
other organisms.

• One animal attaching to another animal for
  transportation only.
• More indirect dependency, in which the second
  organism uses something the first created,
  however after the death of the first. An example
  is the hermit crabs that use gastropod shells to
  protect their bodies.

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An epiphyte is a non-parasitic plant that grows
on another living plant, depending on it only for
support. Growing on another plant like a tall
tree allows a normally low-growing epiphyte to
access more sunlight and avoid browsing animals
on the forest floor.

• Using a second organism for housing. Examples are
  epiphytic plants (such as many orchids) which
  grow on trees, or birds that live in holes in
  trees.

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V. Ecological Succession Communities in
Transition

• Primary succession

-Pioneer species
-Successional species

• Secondary succession

• Climax Community

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V. Ecological Succession

• A. TYPES OF SUCCESSION
• 1. Primary Succession
• -Succession that occurs where no ecosystem
  existed before. (bare rock, lava, etc.
• -Initiated by PIONEER SPECIES (moss and lichens)
  and progresses to SUCCESSIONAL SPECIES (early,
  mid, and late)

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Examples of Pioneer Species

• Pioneer species initiate recovery following
  disturbance in both primary AND secondary
  successions
• Pioneers "pave the way" for later colonists by
  altering the biotic and abiotic environment
• soil stabilization
• soil nutrient enrichment (organic matter and
  biological nitrogen fixation)
• increased moisture holding capacity
• light availability
• temperature
• exposure to wind

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1. Primary Succession- Succession that occurs
where no ecosystem existed before.
Exposed Rock
Fig. 8.15, p. 188
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PRIMARY SUCCESSION ALASKA, HAWAII
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2. Secondary Succession

• -Succession that occurs where an ecosystem
  previously existed
• EX Abandoned fields, polluted streams, strip
  mines

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Clearcutting and Succession
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The Stages of Succession
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2.Secondary Succession Succession that occurs
where an ecosystem previously existed
Fig. 8.16, p. 189
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SUCCESSION
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Succession and Wildlife
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B. 3 Factors that affect HOW and the RATE of
succession
One set of species makes an area suitable for
species with different niche requirements

• Facilitation

Early species hinder the establishment and growth
of other species

• Inhibition

Species are unaffected by members of another
species from earlier stages of succession

• Tolerance

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C. Disturbances in Succession

• -Disturbance a change in environmental
  conditions that disrupts an ecosystem or
  community.
• -Categorized as CATASTROPHIC
• (natural or human-caused.)
• Categorized as GRADUAL, (natural or
  human-caused.)

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Catastrophic
NATURAL HUMAN CAUSED
Fire Deforestation
Flood Overgrazing
Earthquake Pesticide application
Volcanic Eruption Urbanization
Hurricane/ Tornado Water Pollution
Disease Loss of Habitat
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Gradual
NATURAL HUMAN-CAUSED
Climate Change Groundwater depletion
Ecological Succession Exotic Species Introduction
Immigration Toxic Contamination
Disease Excessive Tourism
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VI. Ecological Stability

• Constant dynamic change in response to changing
  conditions
• 1. Inertia or Persistence
• Ability to resist being disturbed or altered
• 2. Constancy
• Ability to keep its s within the limits imposed
  by limited resources
• 3. Resilience
• Ability to bounce back after a disturbance

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Precautionary Principle

• When there is evidence that an activity harms the
  environment we should take precautionary measures
• Better Safe than Sorry

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• The types, relative sizes and stratification of
• plants and animals vary in different biomes.
• Distribution of populations and species
• can be vertical or horizontal in a terrestrial or
  aquatic ecosystem
• Physical structure
• is usually a mosaic of VEGETATION PATCHES with
  sharper edges and wider ecotones
• EDGE EFFECTS
• differences in the physical structure and
  properties at boundaries and ecotones.