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Population Growth Curves. Exponential vs. Logistic Growth Predator-Prey Population Cycles. Fig. 38.4. Figures 38.3 and 38.5. What do Ecologists Study?. Ecosystem : all interactions between living things ( community ) and physical factors in a given area

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population growth curves

Population Growth Curves

Exponential vs. Logistic Growth

Predator-Prey Population Cycles

what do ecologists study
What do Ecologists Study?
  • Ecosystem: all interactions between living things (community) and physical factors in a given area
    • Biotic (living) vs. abiotic (non-living) factors (ex., floods, droughts)
  • Habitat: place where organism lives; can be general or specific (biomes are major climatic zones)
  • Niche: organism’s way of life; multi-dimensional; in theory, only one species can occupy a niche (ecological speciesconcept)
  • Energy Flow: producers, autotrophs, phytoplankton; consumers, heterotrophs, zooplankton, herbivores, carnivores, omnivores, detritivores, decomposers
    • Food Chains: ~90% energy loss each trophic step
    • Food Webs: more realistic; note importance of krill in Southern Ocean food web (shared resource, not necessarily limited)
    • Food Pyramids: less biomass (and abundance) at higher levels; decomposers act on all trophic levels
  • Biogeochemical Cycles: hydrologic, carbon, nitrogen cycles
    • Carbon cycle: related to global warming theory
what relationships exist between organisms in ecosystems
What Relationships Exist Between Organisms in Ecosystems?
  • Predation and Anti-predation
    • Diet Specialists/Generalists: specialists can have morphological, behavioral, and physiological adaptations for capturing/assimilating prey; scarcity of prey can lead to extinction of diet specialists
    • Anti-predation: cryptic and warning colorations, mobbing, displays
  • Competition: assumes a limited (not just shared) resource; removal experiments used to test for effects on fitness
    • Intraspecific: between members of same species; most intense is between males for access to females
    • Interspecific: between separate species; can lead to competitive exclusion
    • Scramble: rare in nature; all may get less than needed
    • Contest: mechanisms; ex. harems vs. sneakers (ex., wrasse, marine iguana)
  • Symbiosis: evolved life-relationship between two or more species
    • Mutualism: both species benefit (ex. anemone and clownfish)
    • Parasitism: one benefits, other is harmed; endo- and ectoparasites
    • Commensalism: one benefits, other with no effect; least common, examples often debated (exs. whale shark with pilotfish; reef shark with remora? – debatable, since remora may cause hydrodynamic drag)
  • Facilitation: organism indirectly benefits others (ex., earthworms aerate soil, nightly excretion of ammonium by blacksmith benefits algae)
why is biodiversity important
Why is Biodiversity Important?
  • Biodiversity: variation among living organisms
    • Species diversity: number of species in an ecosystem; increases with stability/uninterrupted evolution (ex., deep sea, tropical rain forests), and available niches; decreases with isolation
    • Genetic diversity: variation within a species
      • If low, more vulnerable to catastrophic changes/extinction
  • Importance of Biodiversity
    • Ecosystem stability: keystone species are those with influence disproportionate to their abundance (ex. sea otter in Alaska)
    • Genetic reserves; esp. regarding agriculture; endemic species are unique to particular habitat (ex. marine iguana in Galapagos Is.)
    • Practical uses (ex. medicine, future foods)
    • Aesthetic and ethical value: biophilia, Gaia Hypothesis
  • Largest Threats to Biodiversity

1. Habitat loss and fragmentation: conservation incl. wildlife corridors

2. Introduced species (especially on islands)

3. Hunting/poaching; illegal trade  international treaty (CITES)

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