Species Interactions

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Species Interactions
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Habitat vs. Niche

• Habitat the place or set of environmental
  conditions in which a particular organism lives.
• Ecological niche the role played by a species
  in a biological community or the total set of
  environmental factors that determine species
  distribution

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Charles Elton, 1927

• Niches as community roles
• Describes how a species obtains food
• What relationships it has with other species
• Services it provides its community

http//www.dmclf.net/pics/predators-seal-crested.j
pg
4
G.E. Hutchinson

• Biophysical definition
• Range of physical and chemical conditions
  (temperature, light levels, acidity, humidity,
  salinity, etc.)
• Biological interactions (predators and prey
  present, defenses, nutritional resources
  available, etc.)

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Generalists vs. Specialists

• Raccoons or coyotes eat a wide variety of food
  and live in a broad range of habitats.
  (Generalists)
• Panda occupy a very narrow niche. (Specialist)

http//www.uszanders.com/Photo20Collection/slides
/15PH20Raccoons.jpg
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Law of Competitive Exclusion

• No two species will occupy the same niche and
  compete or exactly the same resources in the same
  habitat for very long.
• Niche specialization can create behavioral
  separation that allows subpopulations of a single
  species to diverge into separate species.

http//www.aidsmemorial.org/competition/images/pic
_home.jpg
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Predators and parasites prey on other organisms

• Predator an organism that feeds directly upon
  another living organism, whether or not it kills
  the prey to do so.
• Herbivores, carnivores, and omnivores are
  predators
• Scavengers, detritivores, and decomposers that
  feed on dead things are not.
• Predators prey most successfully on the slowest,
  weakest, least fit members of their target
  population.

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Predators and parasites prey on other organisms

• Coevolution process in which species exert
  selective pressure on each other.
• Parasites are organisms that feed on a host, or
  take resources from it, without killing the host.
  
• Pathogens disease-causing organisms (immune
  system is an evolved defense against pathogens in
  our environment)

http//elementy.ru/images/eltbook/coevolution.jpg
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Keystone Species

• A species or group of species whose impacts on a
  community are much larger than would be expected
  from more abundance.
• Wolves, certain tropical figs, mycorrhizae (fungi
  associated with tree roots)
• Keystone set otters/kelp/sea urchins

http//www.bullfrogfilms.com/photos/nat3image.jpg
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Competition

• Intraspecific competition competition among
  members of the same species (Limited by life
  cycles, shading, etc.)
• Interspecific competition competition between
  members of different species (weeds)
• Territoriality intense form of intraspecific
  competition in which organisms define an area
  surrounding their home site or nesting site and
  defend it primarily against other members of
  their own species

http//elementy.ru/images/eltbook/animal_territori
ality720.jpg
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Symbiosis

• Intimate living together of members of two or
  more species
• Commensalism one member benefits and the other
  is not substantially benefited or harmed.
• Mutualism both members of the partnership
  benefit

http//en.wikipedia.org/wiki/Goby