Population Growth Curves Exponential vs. Logistic Growth

1
Population Growth Curves

• Exponential vs. Logistic Growth
• Predator-Prey Population Cycles

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Figure 53.12
3
Figure 53.22
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Figure 53.25
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Figure 53.20
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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 organisms way of life multi-dimensional
  in theory, only one species can occupy a niche
  (ecological species concept)
• 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

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Figure 52.19
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Figure 54.11
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Figure 55.10
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Figure 55.9
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Figure 55.14a
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Figure 55.14b
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Figure 55.14c
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Figure 55.14d
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What Relationships Exist Between Organisms in
Ecosystems?

• Predation and Anti-predation
• Diet Specialists/Generalists specialists can
  have morphological, behavioral, and
  physiological adaptations for capturing/assimilati
  ng 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)

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Figures 54.2and 54.3
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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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Figure 54.15
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Figure 56.17