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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

Figures 38 3 and 38 5
Figures 38.3 and 38.5

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)