Ecology

• Species


  A group of organisms that can potentially interbreed to produce fertile, viable offspring
• Members of a species may be reproductively isolated in separate populations
• Community


  A group of populations of different species living together and interacting with each other
• Ecosystem


  A community and its abiotic factors
• Modes of nutrition


  • Autotrophs
  • Consumers
  • Detritivores
  • Saprotrophs
• Autotrophs


  Synthesize their own organic compounds from simple inorganic substances
• Heterotrophs


  Get organic molecules from consuming other organisms
• Mixotrophs


  Can do both autotrophy and heterotrophy
• Types of heterotrophs


  • Consumers
  • Detritivores
  • Saprotrophs
• Consumers


  Eat other organisms
• Detritivores


  Eat non-living remnants of living organisms
• Saprotrophs


  Release digestive enzymes and then absorb the products of digestion
• Autotrophs


  Make their own organic molecules from simple inorganic substances
• Heterotrophs


  Make their organic molecules from consuming autotrophs
• Types of consumers


  • Herbivores
  • Carnivores
  • Omnivores
  • Scavengers
• Detritus


  Particulate organic matter (decaying matter, fecal matter)
• Humus


  Decaying leaf litter mixed in the topsoil
• Nutrient cycling


  The supply of inorganic nutrients on Earth is finite, so they are constantly recycled after use
• Autotrophs obtain inorganic nutrients


  From the air, water and soil and convert them into organic compounds
• Heterotrophs ingest organic compounds


  And use them for growth and respiration, releasing inorganic byproducts
• When organisms die


  Saprotrophs decompose the remains and free inorganic materials into the soil
• The return of inorganic nutrients to the soil


  Ensures the continual supply of raw materials for the autotrophs
• Positive association


  Two species interact directly within a joint environment and co-exist
• Negative association


  Interactions are mutually detrimental (they do not coexist)
• Types of species interactions


  • Predator/Prey
  • Mutualism
  • Commensalism
  • Parasitism
  • Competition
• Predator/Prey


  One organism eats, the other is eaten
• Mutualism


  Both species benefit
• Commensalism


  One species benefits, the other is neither benefited nor harmed
• Parasitism


  One species benefits, the other is harmed
• Competition


  Species go after the same resources
• Competitive exclusion


  One species outcompetes and may cause the extinction of the other species in that particular area
• Resource partitioning


  The two competing species use the resources differently so that there is less competition
• Niche


  An organism's ecological role, including its habitat, activity patterns, resources obtained, and interactions with other species
• Fundamental niche


  The set of conditions under which an organism can live and reproduce
• Realized niche


  The set of conditions actually used by the organism after interactions with other species are taken into account
• Ecological Interactions


  Interactions between organisms in an ecosystem
• Chi Squared

  A statistical test used to determine if there is an association between two species
• Testing for association between two species using the chi-squared test

  1. Obtain data by quadrat sampling

  2. Recognize and interpret statistical significance
• Quadrat sampling


  • Can be used to estimate population density/size
  • Measure the distribution of species

  
• Quadrats


  • Placed repeatedly in a sample area to provide a reliable estimate
  • Can be placed systematically (e.g. in a belt transect) or randomly