Topic 5- Ecology Flashcards
Give the definition of the following terms:
a) Ecosystem
b) Community
c) Population
d) Habitat
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Give the definition of biotic and abiotic factors
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List the biotic factors that can affect the numbers and distribution of species in an ecosystem
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List the abiotic factors that can affect the numbers and distribution of species in an ecosystem
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Name the two sampling techniques that can be carried out in an ecological study
Random sampling
Systematic Sampling
State how to determine which method is appropriate based on the area of study (give examples)
Random sampling using quadrats: to find the total number of organisms appropriate when two areas are being compared
systematic sampling using transects: used to observe changes in distribution across areas of the habitat.
Appropriate when there is a environmental gradient (i.e. a change in abiotic factors over a distance), always used when investigating succession
Devise a valid and reliable method for carrying out systematic sampling
- Lay out a transect (tape measure) along the environmental gradient
(you may need to stipulate the length of transect) - Place a minimum of 10 quadrats down alongside the transect at regular intervals e.g. every 1 metre
- Collect both relevant and valid abiotic and biotic data at sampling sites (you will need to be specific to the context of the q here, i.e. are you asked about % cover or species richness, what abiotic factors are relevant? You might need to say HOW you estimate % cover)
- Place down another 2 parallel transects and repeat steps 1-3
- Record data in a table (IV is the abiotic data and DV is the biotic
data) - Analysis of data can be done using Spearman’s rank which analyses if there is a significant correlation between the abiotic and biotic data
Devise a valid and reliable method for carrying out random sampling
- In each sampling site, lay out a defined area for sampling using two tape measures (you may need to stipulate the size of area)
- Use random co-ordinate generator to select sampling sites
- Lay down a minimum of 10 quadrats in each area
- Collect both relevant and valid abiotic and biotic data at randomly chosen sites (you will need to be specific to the context of the q here, i.e. are you asked about % cover or species richness, what abiotic factors are relevant? You might need to say HOW you estimate % cover)
- Record the data in a table (IV is the abiotic data and DV is the biotic data)
- Analysis of data can be done using Student t-test which analyses if there is a significant difference in the mean % cover/% frequency/species richness (depending on what you have been asked to devise) between the two areas
Explain how a frame quadrat can be used to estimate percentage cover of a species
– % frequency (objective data) =
(number of quadrats in which specific species found
÷ total number of quadrats) × 100
– % cover (subjective data) = estimate the total area in a quadrat covered by one species
E.g. if the species appears in 12 squares, % cover = 12 × 4% or 48%
1) State when it would be appropriate to use a student t test stats analysis.
when comparing frequencies between two samples
State how you would select the correct critical value to compare to in an unpaired student t test
n-2
4) State how you would write a conclusion to a student t test if:
a)the result was significant
b)b) the result was insignificant
a) value of t is higher than the critical value
b) the value of t is lower than the critical value
State when it would be appropriate to use a Spearman’s rank correlation analysis.
Used to assess the strength of a correlation or relationship between two continuous variables that can be ranked
State how you would correctly write a hypothesis for the Spearman’s rank correlation
null hypothesis
State how you would select the correct critical value to compare to in Spearman’s rank correlation
value of n and at a 5% significant level
