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BIOLOGY 403: PRINCIPLES OF ECOLOGY (Niche and Species-Species Interactions)

BIOLOGY 403: PRINCIPLES OF ECOLOGY (Niche and Species-Species Interactions) . THE ECOLOGICAL NICHE I. We have all probably used the term ‘niche’ before. What does it mean? DEFINITION a species functional role (“place”) in a community in relation to other species.

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BIOLOGY 403: PRINCIPLES OF ECOLOGY (Niche and Species-Species Interactions)

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  1. BIOLOGY 403: PRINCIPLES OF ECOLOGY (Niche and Species-Species Interactions)

  2. THE ECOLOGICAL NICHE I • We have all probably used the term ‘niche’ before. • What does it mean? • DEFINITION • a species functional role (“place”) in a community in relation to other species

  3. THE ECOLOGICAL NICHE (II) • It is more than just the physical place (‘address’) where a species lives, it also includes its role in the system (its “occupation / lifestyle”). • The Ecological Niche is a multidimensional (‘hypervolume’) concept that includes where an organism lives AND also includes what it does, how it does it, when it does it, etc. It is its total role in the ecosystem.

  4. ‘TYPES’ OF NICHE • Fundamental or Hypothetical • the total range of physical, chemical and biological factors a species can utilize / survive if there are no other species affecting it • Realized or Actual • that portion of the fundamental niche that a species actually uses. • Species never live under ‘perfect’ conditions but where an ‘acceptable’ ECOLOGIC SUM of conditions exists.

  5. NICHE EXCLUSION PRINCIPLE(= Competitive Exclusion Principle)(= Gause’s Law) • DEFINITION • In a stable community no two species can occupy the same niche • That is to say, no two species can coexist if they need all the same things in the same place, at the same time, etc. • The greater the degree of niche overlap, the greater the competition for scarce resources AND the more likely one species will eliminate the other.

  6. GAUSE & PARAMECIUM(too much niche overlap)

  7. LIMITING NICHE OVERLAP (I)

  8. LIMITING NICHE OVERLAP (II)

  9. LIMITING NICHE OVERLAP (III)

  10. INTERSPECIFIC INTERACTIONS • Neutral Interactions • none of the interacting species is affected by the others • Is this really possible??????????? • Positive Interactions • at least one of the interacting species is benefited and the other(s) is (are) not harmed • Negative Interactions • at least one of the interacting species is harmed during the interaction

  11. Positive Interactions (I) • Commensalism • one species is benefited and the other(s) is (are) not affected • without continuous contact : Vulture / Predator • with continuous contact: Turtle / Alga • Protocooperation • both species are benefited BUT the relationship is NOT obligatory • without continuous contact: Squirrel / Oak Tree • with continuous contact: some Mycorrhizae (a fungus / plant root relationship)

  12. Positive Interactions (II) • Mutualism • both species are benefited AND the relationship IS obligatory • without continuous contact:many Pollinator / Plant relationships • with continuous contact: • Termites / ProtozoansHumans / E. coliLichen (alga / fungus)?most Mycorrhizae (fungus / plant root relationships)

  13. NEGATIVE INTERACTIONS (I) • Competition • both species are harmed during the interaction • Imperfect • neither species is eliminated but one or both are reduced in number (some niche overlap) • Pontin’s work with 2 species of ants of the genus Lasius • Perfect • one species is eliminated (too much niche overlap) • Gause’s work with 2 species of Paramecium

  14. NEGATIVE INTERACTIONS (II) • Predation • one is helped (fed) --- one is harmed (eaten); • a direct attack in which one species (the predator) benefits by killing and eating another (the prey) • Wolf / Deer • Are both helped?????? • Parasitism • one is helped (fed) --- one is harmed (weakened); • a direct attack in which the parasite benefits by taking small quantities of materials from its host over an extended period of time and generally does not kill the host. • Tape Worm / Human

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