Community Interactions

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Community Interactions

• AP Biology - 2005

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Community

• A division of an ecosystem that describes all of
  the organisms that live in an area
• Focuses on interactions within the community
• Establishes a niche a set of conditions under
  which an organism exists

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Interactions

• Focus on resources available in the community
• Food
• Water
• Space
• Mates
• Nesting sites
• Hiding places
• Light
• Macro and micronutrients

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Limiting Resources

• There are only so many resources in a community
  for all of the organisms
• This limits the growth of populations of
  organisms within this community
• It leads to specialized interactions within the
  members of this community
• ( population dynamics)

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Interactions

• Interspecific Between different species
• Intraspecific Within the same species

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Interaction links and Examples

• http//eebweb.arizona.edu/Animal_Behavior/lycaenid
  s/lycaen2.htm

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Ecological relations( 1)

• One organism benefits in a relationship the other
  is harmed or is eaten
• Example predator prey and parasite host
• Rating /-
• Lynx and hare predator and prey
• Malaria, red blood cell, and human parasite and
  hosts

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Cyclic predator-prey relationships
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Experiment
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Experiment( con)
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Ecological relations( 2)

• Two organisms compete for the same resources.
  This is known as competition.
• Rating -/- or /-
• Examples
• Competition for mates intraspecific
• Competition for space plants allelopathy
• Competition for nutrients and space fungi and
  bacteria - antibiotics

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Mutualism

• Both organisms benefit
• Rating /
• Zooxanthellae and coral polyp
• Legumes and Rhizobium
• Leaf cutter ant and fungal garden
• Ant and acacia

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Leaf cutter ants and fungal gardenshttp//www.blu
eboard.com/leafcutters/what.htm
http//cas.bellarmine.edu/tietjen/Ecology/fungus.h
tm
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Ant and the Acacia
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Commensalism

• One organism benefits the other is neither
  harmed or benefits
• /0
• Examples Pinnepidia crab and tube worm

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Amensalism

• Animals can have a negative effect on the
  environment
• 0/-
• Animals trampling the grass on the way to the
  water hole

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Contradictions

• Not all organisms fit the description exactly
• The definition for symbiosis is changing to
  include only those interactions between organisms
  of two different species whose metabolism is
  altered by the interaction

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Competition- Interspecific

• Allelopathy How plants guard their space by
  releasing molecules into the environment that
  deters other plants from occupying their space
• http//www.units.muohio.edu/dragonfly/itc/index.ht
  mlx

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Intraspecific Competition
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Interspecific Competition

• Barnacle species on a rocky shore
• Establishes zonation of organisms
• Niche determined by ability to barnacles to
  tolerate dehydration

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• Competition may restrict species ranges.
• Two species of barnacles live on North Atlantic
  seashores, but as adults, one species lives
  higher in the intertidal zone than the other,
  with little overlap between the two (a phenomenon
  called intertidal zonation).
• If one of the species is removed experimentally,
  the vertical range of the other species becomes
  greater.
• The higher-zone barnacle outcompetes the other
  because it is more hardy when exposed to air in
  the lower zone, the other barnacle is able to
  smother or crush higher-zone intruders.

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Barnacle Competition
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Batesian Mimicry

• Two different species resemble each other. One
  is unpalatable. The palatable receives the
  benefit of birds not wishing to eat it because
  they have eaten the unpalatable one with bad
  results.

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It pays to advertise
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Keystone Species

• http//www.prairiedogs.org/keystone.html
• A keystone species is a species whose very
  presence contributes to a diversity of life and
  whose extinction would consequently lead to the
  extinction of other forms of life. Keystone
  species help to support the ecosystem (entire
  community of life) of which they are a part.

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Succession

• Succession begin when an area is made partially
  or completely devoid of vegetation because of a
  disturbance. Some common mechanisms of
  disturbance are fires, wind storms, volcanic
  eruptions, logging, climate change, severe
  flooding, disease, and pest infestation.

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Plant Succession
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Succession in a Glacial Moraine
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Degradative succession

• The dead body of an organism is reduced to basic
  molecules by decomposers
• Plants may produce litter
• Deciduous trees may produce layer of litter -
  compost

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Coevolution

• The changes in one species may affect the changes
  in another species over time
• Adaptations may occur
• The organisms can develop a close association
• Pollinators and flowers a key example of
  coevolution

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Yucca Moth
http//waynesword.palomar.edu/ww0902a.htm
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Yucca and moth

• Female yucca moths only lay their eggs in the
  ovules of yucca flowers. A female Tegeticula(
  Yucca moth) lays no more than 5 eggs in the
  ovules.
• After she has laid the eggs she scrapes the
  pollen from the flowers anthers and flies to
  another Yucca where she transfers the pollen and
  lays 5 more eggs

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Island Biogeography

• Immigration of mainland species to island birds
  flying other animals and plants and animals
  drifting on trees or floating on rafts of
  vegetation in the currents in the ocean
• ( new plants and animals) Seeds also carried by
  birds
• Isolation of species after immigration
• Novel adaptations
• New species develop allopatric speciation
• New genetic species

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Galapagos
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Darwins finches and the Galapagos Islands

• http//www.rit.edu/rhrsbi/GalapagosPages/DarwinFi
  nch.html