biological diversity practice problems

7/30/2019 Biological Diversity Practice Problems

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Biological Diversity Practice Problems:http://www.countrysideinfo.co.uk/simpsons.htm

Biological diversity can be quantified in many different ways. The two main factors takeninto account when measuring diversity are richness and evenness.

1.Richness

The number of species per sample is a measure of richness. The more species presentin a sample, the 'richer' the sample.

Species richness as a measure on its own takes no account of the number ofindividuals of each species present. It gives as much weight to those species whichhave very few individuals as to those which have many individuals. Thus, one daisy has

as much influence on the richness of an area as 1000 buttercups.

2.Evenness

Evenness is a measure of the relative abundance of the different species making up therichness of an area.

For example, we might have sampled two different fields for wildflowers. The results arein the table below. Both samples have the same richness (3 species) and the same total

number of individuals (1000). However, the first sample has more evenness than thesecond. This is because the total number of individuals in the sample is quite evenlydistributed between the three species. In the second sample, most of the individuals arebuttercups, with only a few daisies and dandelions present. Sample 2 is thereforeconsidered to be less diverse than sample 1.

Numbers of IndividualsFlower Species Sample 1 Sample 2

Daisy 300 20Dandelion 335 49Buttercup 365 931

Total 1000 1000*A community dominated by one or two species is considered to be less diverse than one in which several differentspecies have a similar abundance.


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**As Species richness and evenness increase, so diversity increases. Simpson's Diversity Index is a measure ofdiversity which takes into account bothrichness and evenness.

3. Simpson's Reciprocal Index

The Simpson's Diversity Index is a measure of diversity which takes into account both

richness and evenness. The value of this index starts with 1 as the lowest possiblefigure. This figure would represent a community containing only one species. Thehigher the value, the greater the diversity. The maximum value is the number of species(or other category being used) in the sample. For example if there are five species inthe sample, then the maximum value is 5.

N = the total number of organisms of all speciesn = the total number of organisms of a particular species

Sample Problem 1: Calculate the Simpson's Index (using the Reciprocal Formulaabove) for the two Wildflower fields (Sample 1 and Sample 2)

For Sample 1 and Sample 2, N is the same (1000)

For Sample 1, what is n(n-1) foreach species? Sample 2?- Daisy = _______ = _______- Dandelion = _______ = _______- Buttercup = _______ = _______

n(n-1) = _____ n(n-1) = _____Now calculate a single value for Simpson's Diversity (D) for each sample.

Sample 1:

Sample 2:

D = N(N-1)n(n-1)


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Sample Problem 2: Siemann et al. (1997) collected the following data on oak savannaarthropod communities to investigate the effects of prescribed burning on arthropods. Theabundance data below represent the number of individuals per family (rather than perspecies) collected in sweep-net sampling during a two year period (1992-1993) (fromSiemann et al. 1997). This is a small subset of the actual data which was truncated tosimplify the activity for learning purposes only.

Order Family 1992 1993Coleoptera Chrysomelidae 128 58Helodidae 164 5Scarabaeidae 1 2Staphylinidae 5 2

Diptera Anthomyiidae 262 172Chamaemyidae 27 29Chloropidae 87 1Platystomatidae 345 137

Syrphidae 100 29Hemiptera Miridae 2177 55Homoptera Cicadellidae 1465 86

Delphacidae 272 21Membracidae 265 23

Lepidoptera Noctuidae 72 5Pyralidae 13 20

Odonata Coenagrionidae 0 202

1. What is the richness (in terms of numbers of unique families present instead ofspecies) of this oak savanna in 1992? ______ In 1993? ______

2. In which year was there more evenness? Explain.3. Calculate the Simpson's (Reciprocal) Index for the the oak savanna in 1992 using

the following:a) N = _________ N(N-1) = _________

b) What is the SUM of all the species counts n(n-1) for 1992 = _________

c) Simpson's Reciprocal Index = _______________________ (1992)

4. Do all the same calculations for 1993. Comment on the significance of anydifferences. (Use the back of this sheet).


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biological diversity practice problems

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