Lecture 21: What is a ecological community Flashcards
How can you distill the complex patterns of nature into one number?
Through the Shannon-Wiener diversity index (H’)
What is Pi within the Shannon-Wiener index?
The proportion of the i^th species
What is S within the Shannon-Wiener index?
The number of Species in a community.
How do you calculate (pi)?
you divide the species number by the total number of species within the population.
How do you calculate the H’ value?
You take the sum of pi In pi and multiply it by negative 1
What should the value be when you sum up pi?
1
This takes into account the who community (thus equaling 1)
How do you calculate species evenness?
Though the use of Pielou’s J
Within Pielou’s J, what is In(s)
The total number of species
When J = 1
What level of evenness is in the community?
Perfectly even
When j = 0
What level of evenness is in the community?
Very uneven
What is a Rank Abundance Curve?
Plot of relative abundance of species against their rank in abundance
(another tool to assess weather a species is dominant and to measure diversity)
What is rank abundance?
How abundant a species is compared to other species
What is Relative Abundance?
% or proportion of community individuals
What will a Abundance rating of 1 mean?
Means that they are the most abundant species within the community
How of you calculate richness on a Rank Abundance curve?
Where the X-axis value ends determines the amount of species in the community (the richness)
What will the slope of a Rank Abundance curve represent?
It represents the evenness of the community.
The steeper the slope the less even you are
True or false:
The shallower the slope the greater the evenness
True
What is the relationship between environmental complexity and species diversity?
In general, the more complex or heterogeneous
the environment, the greater species diversity.
What is included within environmental complexity?
– Vertical structure (trees? no trees?)
– Water movement (current? no current?)
– Nutrient availability
– Light availability…
What are the factors included within
(Simple
Homogeneous)?
Few factors that
influence
organisms
• Few niches
What are the factors included within (Complex
Heterogeneous)?
-Many factors that influence organisms
• Many niches
What is Species Composition?
The species that occur in a given community at a given time.
What is the Paradox of the Plankton.
How can there be so many species of plankton living in such a simple environment?
How are lakes Heretogenous with life?
They have seasonal cycles of temperature, oxygen, and nutrients that make complex environments for plankton and other microorganisms
Changes in and differences between
communities are not only indicated by the
number of species and the evenness of those
species, but the ______________
Species themselves
