Community%20Ecology

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Community Ecology
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• Community group of populations of different
  species living close enough to interact

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Ecological niche the sum total of an organisms
use of abiotic/biotic resources in the environment
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• Interspecific competition resources are in short
  supply
• Competitive exclusion principle Two species
  cannot coexist in a community if their niches are
  identical.
• Resource partitioning differences in niches that
  enable similar species to coexist

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• Dominant species has the highest biomass or is
  the most abundant in the community
• Keystone species exert control on community
  structure by their important ecological niches
• Loss of sea otter ? increase sea urchins,
  destruction of kelp forests
• Grizzly bear (transfer nutrients from sea ? land
  by salmon diet)
• Prairie dogs (burrows, soil aeration, trim
  vegetation)

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Keystone species a species that plays a unique
and crucial role in the way an ecosystem functions
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Indicator Species any biological species that
defines a trait or characteristic of the
environment
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Invasive Species a plant or animal that is not
native to a specific location (an Introduced
species) and has a tendency to spread, which is
believed to cause damage to the environment,
human economy and/or human health.
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Invasive Species

• Organisms that become established outside native
  range
• Kudzu vine plant from Japan, noxious weed that
  kills trees shrubs

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Invasive Species

• Dutch elm disease fungus carried by beetles
• Arrived in U.S. on logs imported from Netherlands
• Death of many elm trees across U.S., Europe,
  Canada
• Try to cultivate resistant strains of elm trees

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Invasive Species

• Potato Blight fungus-like disease caused Irish
  Potato Famine in 1840s
• Arrived in Ireland from ships coming from U.S.
• Only 1 species of potato planted in Ireland ? all
  susceptible to disease
• 1 million people died
• Problem with monoculture lack of genetic
  diversity of crops

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Interspecific interactions

• Can be positive (), negative (-) or neutral (0)
• Includes
• Competition (-/-)
• Predation (/-)
• Symbiosis
• parasitism, mutualism, commensalism

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Predation (/-)

• Defensive adaptations include
• Cryptic coloration camouflaged by coloring
• Aposematic or warning coloration bright color
  of poisonous animals
• Batesian mimicry harmless species mimic color
  of harmful species
• Mullerian mimicry 2 bad-tasting species
  resemble each other both to be avoided
• Herbivory plants avoid this by chemical toxins,
  spines, thorns

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Symbiotic Relationships

• Symbiosis- two species living together

3 Types of symbiosis 1. Commensalism (/0) 2.
Parasitism (/-) 3. Mutualism (/)
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Symbiotic Relationships

• Commensalism-
• one species benefits and the other is neither
  harmed nor helped
• Ex. orchids on a tree

Epiphytes A plant, such as a tropical orchid or
a bromeliad, that grows on another plant upon
which it depends for mechanical support but not
for nutrients. Also called xerophyte, air plant.
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Symbiotic Relationships

• Commensalism-
• one species benefits and the other is neither
  harmed nor helped
• Ex. polar bears and cyanobacteria

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Symbiotic Relationships

• Parasitism- one species benefits (parasite) and
  the other is harmed (host)

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Symbiotic Relationships

• Mutualism- beneficial to both species
• Ex. cleaning birds and cleaner shrimp
• Ex. Lichen

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LICHEN This fungus and algae are likin one
another Algae gets ride with the fungus and can
expand into different environments Fungus gets
food the algae (autotroph) makes
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Type of relationship Species harmed Species benefits Species neutral
Commensalism
Parasitism
Mutualism
1 species
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Disturbances influences species diversity and
composition of ecosystems

• A disturbance changes a community by removing
  organisms or changing resource availability
  (fire, drought, flood, storm, human activity)
• Ecological succession transitions in species
  composition in a certain area over ecological
  time

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Primary Succession

• Plants animals invade where soil has not yet
  formed
• Ex. colonization of volcanic island or glacier

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Secondary Succession

• Occurs when existing community is cleared by a
  disturbance that leaves soil intact
• Ex. abandoned farm, forest fire