CH19:populations and ecosystems

• ecology


  study of living organisms in their natural environment, includes both biotic and abiotic factors
• community 


  all the populations of the different species living and interacting in the same ecosystem
• population 


  a group of organisms of the same species which live in the same habitat at the same time where they freely interbreed
• ecosystem 


  living and non living factors
• biodiversity 


  the number of different species in an ecosystem and their relative abundance
• environment 


  includes both biotic and non biotic surroundings of organisms
• biotic 


  living factors in an organisms environment
• abiotic


  non living factors in an organisms environment
• habitat


  characteristics of the type of environment where an organisms normally lives
• autotrophs


  organisms which synthesise their own complex molecules from simple inorganic molecules eg. green plants and algae
• heterotrophs 


  organisms who obtain complex, energy rush, organic compounds from the bodies of other organisms eg. animals
• detrivores


  heterotrophic organisms who inject dead organic matter
• saprobionts


  heterotrophic organisms who secrete digestive enzymes onto dead organism matter and absorb digestive materials
• niche


  an organisms habitat + role + tolerance

  limits to all limiting factors consist of:

  -its role in the ecosystem

  -its tolerance to limits

  -its requirements for shelter or nesting sites
• intraspecific competition 


  individuals from the same species compete with one another for resources
• interspecific competition 


  different species compete for the same resources
• competitive exclusion principle


  occurs during inter specific competition since two species want to occupy the same niche, which forces one out
• co evolution

  process of reciprocal evolutionary change that occurs between pairs of species or along groups of species as they interact with one another
• frequency 


  likelihood of a species occurring in a quadrat

  • useful tor hard to count species eg grass
  • no detail of density
• % cover 


  an eaten ate if the area within a quadrat that a plant species covers

  • useful for hard to count species
  • rapid data collection
  • less useful if plants are overlapping
• succession 


  changes in a population over a period of time
• primary succession 


  successions that begins in lifeless areas, such as regions with no soil
• pioneer species 


  species which colonises an inhospitable environment and starts succession

  eg: moss

  • asexual reproduction
  • photosynthetic
  • extremophiles
  • wind dispersed spores/seeds
  • survived long dormancy periods
• climax community 


  the final stage of succession, in which populations of plants or animals remain stable and exist in balance with each other and their environment
• secondary succession 


  occurs when land has already sustained life is suddenly altered. plants and animals then recolonise the area

  examples:

  • volcanic eruption
  • fires
  • disease
  • floods
  • introduction of competitive species
  • land clearance
• conservation


  the management of the Earth’s natural resources by humans in a way that maximum use can be made of them in the future

  • personal
  • ethical
  • economic
  • cultural and aesthetic
  • medical