Measuring Species
Diversity
Starter exercise
Think about what’s ahead . . .
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Discuss in pairs the title of this section.
What do you think it is about?
Do you know anything about it already?
What might we be discussing during this
section?
What is species diversity?
• Species diversity comprises the number of
different species in an ecosystem (the
species richness) and the proportion of
each species in the ecosystem (the
relative abundance).
How do you measure it?
• You can measure species diversity by
measuring species richness or species
evenness.
Species richness
• The number of different species in an
ecosystem.
Species evenness
• Relative abundance – the proportion of
each species in the ecosystem.
So what does that tell us?
• A community where a dominant species is
abundant has less species diversity than
one with the same species richness but
where the abundance of species is more
evenly distributed.
Measuring species diversity
• When carrying out a practical investigation
into the species diversity of a local area,
you can use a species diversity index.
Species diversity index (1)
• Scientists have developed a variety of
mathematical equations (or indices) that
incorporate both species richness and
evenness into a single measure of species
diversity (eg the Shannon–Wiener index
and Simpson’s index).
Species diversity index (2)
• Different diversity indices assign different
weightings to species richness and
evenness, so the most useful index to
choose depends on the circumstances.
Habitat fragmentation
• Habitat fragmentation is the fragmentation
in an organism’s habitat.
• Work in pairs to discuss this concept –
what is it? How does it happen? Could we
reduce it?
Task
Using your new knowledge create a diagram
showing two communities.
Highlight the one with the higher species
diversity.
(You don’t need to draw organisms, colour
or shape can be used to distinguish between
species.)