Ecology

• what is succession

  change in an ecological community over time due to abiotic factors
• process of succession

  Pioneer species colonise e.g lichen

  They die and decompose which changes abiotic conditions making the environment less hostile

  This means another species can colonise which outcompetes the lichen

  Over time process repeats and biodiversity increases

  Climax community formed
• difference between primary and secondary succession

  primary starts with bare rock as environment hasn't been colonised. secondary is where climax community has been disrupted by event but you start with soil
• why should sampling be random

  to eliminate bias
• why should we use a large number of samples

  to ensure population is accurately represented
• when should we do quadrat and transect sampling

  quadrat - uniform distribution

  transect - uneven distribution
• quadrat sampling method

  Lie two tape measures at right angle to create gridded area

  Use random number generator to generate two coordinates

  Place quadrat and count number of organisms in quadrat

  repeat at least 30 times and calculate mean

  population = (area of quadrat / area of field) x mean
• transect sampling method

  Place transect at right angle to shore line

  Place quadrats at regular intervals along transect line

  Collect data

  Repeat by placing another 30 transects at right angle to shore line

  Work out percentage cover different distances from shore line
• When would you use mark-release-recapture

  when estimating total population of moving organisms
• mark-release-recapture process

  initial sample of population captured

  mark individuals and release back into environment, recording number marked

  Allow time for individuals to redistribute in their environment

  Collect second sample

  Count number of captured that are marked

  Estimate size of population = (number of organisms initially caught x number of organisms caught in second sample) /number of organisms marked

  Repeat to get more accurate results
• ethics of mark-release-recapture

  mark must not be toxic

  mark must not increase chance of predation

  mark must not reduce chance of reproduction
• assumptions made in mark-release-recapture

  no births or deaths

  no immigration or emigration

  animals redistribute evenly
• type of competition between members of different species

  interspecific
• type of competition between members of same species

  intraspecific
• what is an ecosystem

  interaction between all abiotic and biotic factors of an environment
• what is carrying capacity

  maximum size of population in an area
• define population

  total number of organisms of a species in an area that can breed together to produce fertile offspring
• define community

  all organisms in an area
• define species

  organisms which can breed together to produce fertile offspring
• define niche

  organisms role in a community
• advantage of measuring dry mass

  true indicator of growth as water has a mass
• define climax community

  stable community
• features of a climax community

  same species present over a long period of time

  constant abiotic factors

  population stable
• what limits size of populations in a climax community

  nutrient availability

  number of producers providing energy

  diseases/predators

  competition

  space for niche's
• how to prevent succession

  grazing of land

  setting managed fires
• what is conservation

  protection and management of ecosystems
• reasons for conserving an ecosystem

  protecting habitats

  protecting endangered species

  reducing global warming

  reduce erosion

  tourism