Revision:Ecological Techniques

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Ecological Techniques

Describe one method used to measure each of three abiotic characteristics of a habitat

• Light
  • Intensity
  • Duration
    • Determined astronomically, and predictable for any location.
  • Quality
    • All Light sensor
• Temperature
  • Thermometer
• PH
  • Universal Indicator
• Humidity
  • Expressed in relative humidity, i.e. the water content of a given volume of air relative to the same volume of saturated air. Measured using a whirling hygrometer.

Define random sample

A method to ensure that every individual in a population has an equal chance of being observed.

Describe one technique used to estimate the population size of one animal species based on capture-mark-release-recapture method

Use capture-mark-release-recapture method.

Then use Lincoln Index: Population size = (n₁ x n₂)/n₃

Where:

• n₁ = number initially caught
• n₂ = total number individuals caught in second sample
• n₃Number of marked individuals caught in second sample

Describe one method of random sampling used to compare the population numbers of two plant species based on quadrat methods

 Using random number tables, choose a large number of quadrats at random to measure.  You can measure data in three ways - the number of organisms present, a simple yes or no for the presence of a species, or the percentage cover.  For the number of organisms/percentage cover of a species, calculate a mean for each species to compare.

Evaluate graphical representations of ecological data

Define mean

The average value obtained by dividing the total of a set of values by the number of values.

Define mode

The most frequent value in a set of observations.

Define median

The central value in a set of observations arranged in order.

State what we mean by Standard Deviation

The term standard deviation is used to summarise the spread of variables around the mean and that 68% of the values fall within one standard deviation of the mean.

Calculate the means and standard deviation of two different frequency distributions

S.D ₁

Describe how standard deviation is useful in comparing the means and the spread of ecological data between two or more sites

• Small standard deviation indicates that the data is clustered around a small mean value.
• Large standard deviation indicates that the data is spread around a large mean value.
• When comparing two means and two standard deviations the closer the two the more likely that they are drawn from the same population.
• Dependent on sample size.
• Larger samples make more reliable sample results.

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