populations and ecosystems

• Ecosystem: A ‘functional’ ‘self-sustaining unit’. A definable area (can be very large, for example the whole planet, to very small, for example a few grams of soil) with its own community of organisms and physical factors all interacting together.
• • Species: A group of individuals with similar characteristics, behaviour and/or biochemistry that are able to interbreed and produce fertile offspring.
• • Habitat: The part of the ecosystem in which particular organisms live.
• Population: ALL the interbreeding organisms of one species living in a particular habitat at the same time. 
• • Community: ALL the populations of ALL the species that live together in a particular ecosystem. This is the living part of the ecosystem – how that interact together.

   
• • Niche: The role an organism has in its community. What it eats/when it eats/how it eats/where it lives/basically its way of life. 
  • 2 types: Fundamental vs Realised niche
• • carrying capacity of the population - max population size that can be supported by available resources over periods of time (ecosystems) - dynamic process
• Interspecific competition = between members of different species for resources that are limited
• Intraspecific competition = between members of the same species (more intense level of competition as their resources they need are the same) for resources that are limited
• • Competitive advantage - utilisation of the resources better e.g- foraging on the floor and in trees to get better food availability results in one species outcompeting the other when they're occupying the same ecological niche
• Mark, release, recapture:

  1.) capture a sample of the population (N1)

  2.) mark the captured organisms

  3.) release and redistribute them back into the population

  4.) capture a 2nd sample (N2)

  5.) estimate population size = N1 X N2/N3. N3= number of marked individuals in the second sample
• mark release recapture limitation- Time between N1 and N2 - organisms must have enough time to equally redistribute back into the population  - however if the time between N1 and N2 is too long organisms may potentially die , effecting/changing pop size
• ecological succession- The natural changes that take place to a community over long periods of time- emphasis on changes in species present
• Pioneer species- First colonisers on a new, bare piece of ground - in primary succession
• Pioneer Species (and secondary colonisers etc) change the environmental conditions - making it less hostile/more nutrient, more favourable for other species, so there is more competition for resources
• In ecological succession Each arriving species outcompete the previous as they utilize resources better - increasing biodiversity
• Describe the pattern of a typical predator-prey relationship in terms of population change.

  • Prey is eaten by predator, resulting in predator population increasing and prey population decreasing.
  • Fewer prey means increased competition for food, so predator population decreases.
  • Fewer predators means more prey survives, and the cycle begins again.
• Why are ecosystems described as being dynamic?

  • Populations constantly rise and fall.
  • Any small change can have a large effect.
  • Biotic and abiotic factors may alter the conditions of the ecosystem.
• What is the climax community and how is it reached?

  The final stage of succession, where the ecosystem is balanced and stable. It is reached when the soil is rich enough to support large trees or shrubs, and the environment is no longer changing.
• Conservation involves: protection and management of natural resources involving human intervention to maintain ecosystems and biodiversity
• succession;

  the gradual change in a community over time due to changes in environmental factors
• Species richness is a measure of the number of different species in a community.