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Biotic Factors

Biotic Factors. Competition Negative effect for both species. Interspecific : Competition between different species Intraspecific : Competition between the same species. Intraspecific competition Common in nature Outcome affected by Physical environment Other species

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Biotic Factors

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  1. Biotic Factors

  2. Competition • Negative effect for both species • Interspecific: Competition between different species • Intraspecific: Competition between the same species

  3. Intraspecific competition • Common in nature • Outcome affected by • Physical environment • Other species • Exists among 55-75% of the species • Mechanism: over use of the same resource

  4. Herbivory, Predation & Parasitism • Positive for one population • Negative for the other population

  5. Batesian mimicry • Mimicry of a non-palatable species by a palatable one • Positive for one population • Negative for the other population

  6. Neutralism • Coexistence of noninteracting species • Probably rare • Amensalism • One-sided competition • One species had a negative effect on another, but the reverse is not true.

  7. Mutualism and Commensalisms • Less common • Symbiotic relationships • Species are intimately associated with one another • Both species may NOT benefit from relationship • Not harmful, as is the case with parasitism

  8. Sea Anemone and Fish Fig. 46-4, p.823

  9. Niche • Grinnell (1918): a subdivision of a habitat that contains an organism's' dietary needs, its temperature, moisture, pH, and other requirements

  10. Gause's principle, known as competitive exclusion principle, where direct competitors cannot coexist

  11. Gause’s Experiment Paramecium caudatum Species grown together Paramecium aurelia Figure 47.6 Page 825

  12. Gause’s Experiment Competitive exclusion

  13. Resource Partitioning Resource partitioning

  14. A Variety of Mutualisms • Obligate mutualism • Ex. Many ruminants and symbiotic bacteria • Bacteria break down plant tissue to provide energy for their hosts • Ex. The roots of most plants and fungi • Mutualistic association between the fungus and root tissue - mycorrhizae

  15. Mutualisms and Community Process • Ex. Endophytes (fungi that live inside leaves) and vascular plant hosts - Defend host against herbivory

  16. Commensalism • Commensal relationship: one members benefits and the other is unaffected • Ex. An orchid and a tropical tree: orchids gain a place to live and the tree gains nothing • Ex. Cattle egrets and cattle: Cattle stir up insect prey for egrets

  17. Stop

  18. Predation • There are a variety of anti-predator adaptations, which suggests that predation is important in nature • Predator-prey models can explain many outcomes • Field data suggests that predators have a large impact on prey populations

  19. Predator-Prey Models Predator-prey interactions

  20. Predation • Experiments involving the removal or introduction of exotic predators provide good data on the effects of predators on their prey • Field experiments involving the manipulations of native populations show predation to be a strong force

  21. Antipredator Adaptations • Aposematic or warning coloration • Advertises an unpalatable taste • Ex. Blue jays and monarch butterflies • Caterpillar obtains poison from milkweed

  22. Antipredator Adaptations • Camouflage • Stick insects mimic twigs and branches • Zebra stripes: blend into grassy background • Mimicry

  23. Mimicry Wasp and mimics

  24. Antipredator Adaptations • Displays of intimidation • Ex. Toads swallow air to make themselves appear larger • Ex. Frilled lizards extend their collars to produce the same effect

  25. Herbivory • Plant chemical and mechanical defenses against herbivores • Mathematical models predict polyphagous herbivores have a greater effect on plants than monophagous herbivores

  26. Herbivory • Herbivores remove 15-18% of terrestrial plant biomass; over 50% in aquatic systems • Herbivores can change plant communities by preferentially eating dominant plant species

  27. Plant Defenses • Example of plant chemical defenses • Alkaloids • Mustard oils • Terpenoids

  28. Parasites • Parasites feed on a host, but generally do not kill it • Hosts have evolved many defenses (e.g., immune responses) against parasites

  29. Parasites • Parasites can substantially decrease host population size • Parasites can affect the structure of host communities

  30. Defining Parasites • Parasite: a predatory organism that feeds off another but generally does not kill it • Host: prey of a parasite • Parasitoid: Cases where the host does not survive but one host is insufficient for the development of the parasitoid

  31. Defining Parasites • Some parasites live with their host most of their lives (e.g., tapeworms) • Some parasites drop off after prolonged periods of feeding (e.g., ticks, leeches)

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