1. dN1/dt=rmax1N1((K1-N112N2)/K1)
    • dN/dt: change in population size over time
    • N: population size
    • K: carrying capacity
    • α12: effect of an individual from sp 2 on an individual from sp 1
    • α21: effect of an individual from sp 1 on an individual from sp 2
  2. Types of mutualism
    • Facultative: can live without eachother
    • Obligate: require eachother for survival
  3. Plants and Mycorrhizae
    • Higher leaf water potentials
    • Greater access to P
    • More efficient at H2O conduction
    • Increased surface area gave more contact with moisture and greater surface are for absorption
  4. Ants and Acacia trees
    • Ant benefited from thorns (habitat), nectaries (sugar), and beltian bodies (fat)
    • Acacias inhabited by ants grew much faster than those without
    • Protection from herbivorous insects,
  5. Ants and Aspen Sunflower
    • Aspen sunflowers have extrafloral nectaries that provide the ants with sugar and fat
    • Ants were content to use this source and did not collect blossom nectaries
    • Gave protection from seed predators
    • Facultative relationship (frost can still kill sunflowers)
  6. Coral mutualisms
    • Zoozanthellae provides organic compounds (photosynthesis) receives nutrients (N and P)
    • Corals control rate of Zoozanthellae population growth and density through secretions
    • Crustacean mutualists acted as protectors from sea stars, received large quantities of lipids in exchange
  7. Evolution of mutualism models
    • Successful: Give and receive benefits
    • Unsuccessful: Give, but do not receive benefits
    • Non-mutualists: Neither give nor receive benefits
    • If fitness of successful mutualists does not exceed fitness of unsuccessful or non-mutualists natural selection will eliminate the interaction
  8. Define community, guild, life form
    • Community: Interacting species inhabiting a defined area (includes # species, relative abundance, species diversity)
    • Guild: organisms with the same way of making a living
    • Life form: structure AND growth dynamics
  9. Preston's relative abundance patterns
    • Concept of distribution of commonness/rarity
    • This resulted in lognormal distributions (bell shaped curves)
    • Very few species are extremely common or extremely rare
    • Most species are moderately frequent
  10. Image Upload 1
    • Shannon-Weiner index/species diversity
    • Two factors for species diversity: species richness & species evenness
    • pi=proportion of the ith species
  11. Environmental complexity and diversity
    • Coexisting species must have lack of niche overlap
    • Heterogeneity (being different) is key for species coexistance
    • With increased environmental complexity there is increased specialization (heterogeneity), and thus increased diversity
  12. Algal niches
    • Phytoplankton paradox: simple environments with similar species competing for same nutrients, but no competitive exclusion
    • Algal niches are defined by nutrient requirements (P:S)
    • When P was high sp 1 dominated, when S was high sp 2 dominated, when the two were relatively equal coexistence occurred.
  13. Heterogeneity and diversity in tropical forests
    • Organization 1: large # species in most communities
    • Organization 2: large # plant communities in any area
    • Abiotic factors and microvariations allow for heterogeneity
  14. Disturbance and diversity
    • Departure from average conditions (difficult to determine "average")
    • alt: Discrete, punctuated killing, displacement, or damaging of 1+ individuals that directly or indirectly creates opportunity for new individuals to establish.
    • alt 2: Any event (discrete in time) thatdisrupts ecosystem, community, or population structure and changes resources, substrateavailability, or physical environment
    • 2 characteristics: frequency and intensity
  15. Intermediate disturbance hypothesis
    • Disturbance is important to diversity
    • Both HIGH and LOW levels reduce diversity (intermediate is key)
    • Time between intermediate events is enough for establishing species, but not enough for competitive exclusion
    • somewhat bell-shaped curve
    • Different sized intertidal rocks AND prairie dogs
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