• Abiotic Factors


  Rainfall

  pH

  Temperature

  Humidity/lack thereof

  Presence/level of pollution
• Areas with high biodiversity (7)

  - Large number of successful species

  
  

  - Relatively benign climate with more ecological niches

  
  

  - Presence of many species

  
  

  - Few specific adaptations to enviroment

  
  

  - Complex food web

  
  

  - Change in enviroment has a relatively small effect on the ecosystem as a whole

  
  

  -High biodiversity index (above 0.5)
• Areas with low biodiversity (7)

  - Few successful number of species

  
  

  - Stressful/extreme enviroment with few ecological niches

  
  

  - Relatively few species live in the habitat

  
  

  - Very specific adaptations to the enviroment

  
  

  - Simple food webs

  
  

  - Enviromental change has a major effect on the ecosystem as a whole

  
  

  - Low biodiversity index (below 0.5)
• Methods of sampling animals (6)

  - Pooter

  - Sweep net

  - Pitfall traps

  - Tree beating

  - Kick Sampling

  - Quadrats (for slow moving animals)
• Methods of sampling plants (2)

  - Frame quadrat

  - Point quadrat
• pooter (5)


  - Used to catch small insects

  - Insects drawn into the holding chamber via the inlet tube

  -Filter before the mouthpiece prevents them being sucked in by the mouth
• Sweep net


  Used to catch insects in areas with long grass.
• Pitfall traps


  - Used to catch small, crawling inverterbrates e.g. beetles, slugs, spiders etc

  - Hole dug into ground which insect falls into.

  - Must be deep enough so that the insects cant crawl out.

  - Trap must be covered so it doesnt fill up with rainwater
• Kick sampling


  - Used to study organisms living in a river

  - River bank and bed is 'kicked' for a period of time to disturb the substrate

  - A net is held downstream for a set period of time in order to catch any organisms released into the flowing water.
• Tree beating


  - Used to take samples of the inverterbrates living in a tree/bush

  - Large white cloth stretched out under the tree.

  - Tree is shaken/beaten to dislodge inverterbrates.

  - Animals will fall onto the sheet where they will be colected and studied.
• Point quadrat


  - Consists of a frame containing a horizontal bar

  - At set intervals long pins are pushed through the ground along the bar

  - Each species of plant the pin touches is recorded
• Frame quadrat


  - Square frame divided into equal grids

  - Type and number of species within each grid is recorded
• How do you collect the most valid and representative sample of ana area with a quadrat?

  - Quadrats should be used following arandom sampling technique

  - To study how the presence and distribution of organisms across some land varies, quadrats can be placed systematically along belt/ine transect
• Three main ways of using frame quadrats

  DENSITY - If individual large plants can be seen clearly, count the number of them in a 1m by 1m square quadrat. (density per metre). Gives ABSOLUTE measure.

  
  

  FREQUENCY - used to study biodiversity in grassland. If each gird represents 1% and there is 1 buttercup in 65/100 grids then the frequency of occurence of buttercups would be 65%.
• How to get an average vaue of a particular organism per metre squared.

  calculate mean of individual quadrat results.
• How to work out total population of an organism in an area that has been sampled.

  multiply mean value per petre squared by the total area.
• Sampling


  Can be used to estimate the number of organisms in an area without counting them all.

  
  

  Number of individuals of a species present in an area = ABUNDANCE

  
  

  Can be used to measure a characteristic of an organism
• Results of the sample can be used to make

  Generalisations/estimates about the ...number... of organisms

  
  

  Generalisations/estimates about the ...distribution... of organisms

  
  

  Measured ...characteristics... of an organism. E.g. Sample of 200 wheat plants found the average height to be 50cm.
• Sampling is necessary because we can't usually gather data from the entire population due to:

  Large/inaccessible population (it's impossible in most cases to study the actual entire population)

  
  

  Lack of resources

  
  

  Sampling is the only method available when data gathering process damage the item from which we require data.
• Random sampling


  Selects individuals by chance

  Each individual in the population has an equal likelihood of selection.

  Random number tables/computers used.

  You have no involvement in deciding which organisms to compare.
• Tyes of non random sampling

  - Opportunistic

  - stratified

  - Systematic
• Opportunistic


  Uses organisms that are conveniently available.

  
  

  Weakest form of sampling as it may not be representative of the whole population.
• Stratified


  Population divided into stratas (sub groups) based on a particular characteristic.

  Random sampling is taken from each strata proportional to its size.
• Advantages of stratified sampling


  Minimises sample selection bias.

  
  

  Ensures certain population segments are not over/under represented.
• Disadvantage of stratified sampling


  Unusable when you can't classify every member of the population into a sub group.
• Systematic sampling


  Different areas within an overall habitat are identified and sampled separately.

  
  

  E.g. May be used to study how plant species change as you move inland from the sea.

  
  

  Often carried out using line/belt transects.
• Line Transect


  Simply a straight line marked across a habitat.

  
  

  Species that touch the line at regular intervals are identified and recorded.

  
  

  Results are converted into a drawing that shows the distribution of organisms.

  
  

  Used to show how communities change along a gradient.

  
  

  Good way to show the changes qualitatively.
• Belt Transect


  Quantitative

  
  

  Similar to the line transect but gives information on abundance as well as presence/absence of species.

  
  

  Involves placing quadrats along a line taken through an ecosystem

  
  

  Short distance - quadrats placed continuously - continuous belt transect

  
  

  Long distance - quadrats placed at intervals - interrupted belt transect
• Advantages (systematic)


  More straightforward than random sampling as you don't have to measure the coordinates for each sample.
• Disadvantages (systematic)


  Method is biased as area you choose to put down in the transect may not be representative of the whole habitat.
• Sample selection bias


  May occur accidentally or deliberately.

  
  

  E.g. You may choose a particular area to sample because it has more flowers in it or it look interesting.

  
  

  Sampling bias can be reduced/eliminated by random sampling where there is no human involvement.
• Chance


  Organisms selected may not be representative of the whole population.

  
  

  E.g five worms picked at random in a sample may be the longest worms in the populations so the average height taken from this sample would be unreliable.

  
  

  Chance can never be completely removed from the sample but it can be minimised by using larger samples.

  
  

  Greater number of individuals studied=lower the probability that chance will affect the result. Bigger sample=more reliable sample.
• Factors that increase genetic biodiversity

  - Mutations in the DNA of the organism, creatign a new allele

  - Interbreeding between different populations .This causes alleles to be transferred between the two different populations - GENE FLOW.
• Factors that decrease genetic biodiversity

  Selective breeding (only a few members of a species are selectively bred for their desired characteristics)

  
  

  Captive breeding programmes

  
  

  Artificial cloning (e.g. cutting from plant)

  
  

  Natural selection - alelles coding for less advantageous characterstics decline drastically from a population or are lost altogether.

  
  

  Genetic bottlenecks

  
  

  Founder effect

  
  

  Genetic drift
• Genetic bottleneck


  Few individuals of a population survive disease/environmental change/habitat destruction. Only their allelles are passed on to the successive generation, reducing the gene pool.
• Founder effect


  Small number of individuals create a new colony, geographically isolated from the original. the gene pool for this new population is small.
• Genetic drift


  The process of change in the genetic composition of a population due to chance or random events rather than by natural selection, resulting in changes in allele frequencies over time.
• Polymorphic gene


  A gene with more than one allele
• monomorphic gene


  a gene with only one allele
• locus (plural loci)


  Position of a gene on a chromosome