Assessment 2.3.5: Apply Simpson’s diversity index and outline its significance

Topic 2.2 : Measuring abiotic components of the system
Topic 2.3: Measuring biotic components of the system



Content

Assessment 2.2.1: List the significant abiotic (physical) factors of an ecosystem.

The three main type of ecosystem are terrestrial; freshwater and marine.

Terrestrial: Land-based
Freshwater: Rivers, lakes and wetlands
Marine: The sea, estuaries, salt marshes and mangroves

The significance of abiotic factors varies for one ecosystem to another. Here are some:
  • Light (T F M)
  • Temperature (T F M)
  • Soil (T)
  • Turbidity (F M)
  • Wind Speed (T)
  • Dissolved Oxygen (F M)
  • Aspect/Slope (T)
  • Flow Rate (F)
  • Salinity (M)
  • Elevation (T)
  • pH (F)
  • Wave action (M)

T= Terrestrial
F=Freshwater
M=Marine


Assessment 2.2.2: Describe and evaluate methods for measuring at least three abiotic (physical) factors within an ecosystem.

Terrestrial
  • Light: can be measured using a light-meter. Care must be taken to test the light intensity in the same time of day and with same atmospheric conditions
  • Temperature: can be measured using a electronic thermometer. The temperature must be taken at a standard depth
  • Wind: can be measured using a digital anemometer. Gusty conditions may lead to large variations in data
Freshwater
  • Light: can be measured using a light-meter. Care must be taken to test the light intensity in the same time of day and with same atmospheric conditions
  • Temperature: can be measured using a electronic thermometer. The temperature must be taken at a standard depth
  • pH: can be measured using a pH meter. The meter must be cleaned between each reading and the reading must be taken from the same depth
Marine

  • Light: can be measured using a light-meter. Care must be taken to test the light intensity in the same time of day and with same atmospheric conditions
  • Temperature: can be measured using a electronic thermometer. The temperature must be taken at a standard depth
  • Salinity: can be measured using a electrical conductivity (with a data-logger). There could be measuring error with the equipment

http://en.wikipedia.org/wiki/Abiotic_component

http://yesitsyomoma.wordpress.com/2011/04/13/revision-topic-2-2-measuring-abiotic-components-of-the-system/ (further reading)


Assessment 2.3.1: Construct simple keys and use published keys for the identification of organisms

Sample

external image IDkey3.gif

http://en.wikipedia.org/wiki/Identification_key


Assessment 2.3.2: Describe and evaluate methods for estimating abundance of organisms

There are two ways of estimating abundance of organisms: the Lincoln index or Quadrat

The Lincoln Index:

N= (n1 * n2) / M

N= total population size of aniamls in the study site
n1= number of animals captured on first day
n2= number of animals recaptured
M= number of marked animals recaptured on the second day

  • Also known as the "capture–mark–release–recapture:
  • Allow the estimation of the total population size of an animal

It should be considered that
  • Animals mix freely back into the population after marking
  • Second sample has at least 10% recapture
  • Animals are as likely to be trapped in both sample periods

Quadrat*

  • Suitable for animals that don't move quickly e.g. snails
  • Quadrat size depends on the size of the organisms in the habitat

File:Quadrat sample.JPG
File:Quadrat sample.JPG


Percentage cover: two dimensional estimate of the spread of the organism within a simple frame quadrat as a percentage

Percentage frequency: No. of occurrences in the quadrats/ No. of quadrats taken * 100 = Percentage Frequency

Population Density: number of individuals of each species per unit area.

*More information needed

Assessment 2.3.3: Describe and evaluate methods for estimating the biomass of trophic levels in a community

Extrapolation method: the mass of one organism or the average mass of a few organisms, is multipled by the total number of organisms present to estimate total biomass*

*Biomass is taken as the mass of an organisms minus water content. Water is not included in biomass measurements because the amount varies from organism to organism, it contains no energy and is not organic.


Assessment 2.3.4: Define the term diversity

Diversity: as a function of two components: the number of different species and the relative numbers of individuals of each species.

external image biodiversity-300x257.jpg


Assessment 2.3.5: Apply Simpson’s diversity index and outline its significance

Simpson's diversity

D= N(N-1) / sum of n(n-1)

D = diversity index

N = total number of organisms of all species found

n = number of individuals of a particular species

A high value of D suggests a stable and ancient site, and a low value of D could suggest pollution, recent colonization or agricultural management

wpeB4.jpg (18408 bytes)
wpeB4.jpg (18408 bytes)


http://sciencebitz.com/?page_id=282 (More info)