Lec 22 (Ecological communities) Flashcards
What is a community?
“an association of potentially interaction species inhabiting some defines area, at some particular scale, over some particular span of time.”
Biosphere? Ecosystem? Community? Population? Individual?
Biosphere: All space occupied by living
things on Earth
Ecosystem: A region containing interacting
abiotic and biotic factors
Community: Population of species that occur
together in the same space and
time
Population: Individuals of the same species
that co-occur in space and time
Individual: Living entities that are genetically
and physically discrete
Community structure?
attributes of a community, such as
the number of species or the distribution of individuals among species within the
community
Species are described by their diversity, richness, and evenness… what are these?
Species Diversity: a measure of diversity that
increases with species evenness and species
richness
Species Richness (s): the number of species in a community
Species Evenness: the relative abundance of
species in a community
What are the three types of species diversity?
Gamma: diversity within a region or
landscape
Alpha: diversity within a locality within a
region or landscape
Beta: the difference between the diversity of
a region or landscape, and a locality within
the region or landscape
An entire forest would be?
What about just a snapshot of a forest?
- Gamma
- Alpha (a subset of gamma)
-What is Beta Diversity?
A measure of the diversity
among locations within a
region.
Example: Compare β
between the forest and
field
So, there’s a lot of species out there. Almost too
many to count or investigate individually. Because of this, ecologists often study _______ or groups of __________organisms.
- guilds
- similarly functioning
Talk about Species Dominance
More often than not, communities include a
“dominant” species, one that is more common
than all others.
Most species in the community will occur in
moderate abundances.
Few species will dominant or be rare.
Species Richness vs. Species Evenness
Richness is a measure of the number of different kinds of organisms present in a particular area.
Evenness compares the similarity of the population size of each of the species present.
-Why does species evenness matter?
-Leads us to ask why one species is lower than another one
Rank Abundance Curve?
-plot of relative abundance of species against their rank in abundance.
assess dominance and diversity in community.
What is the Relationship Between Environmental
Complexity and Species Diversity?
In general, the more complex the environment, the greater species diversity.
heterogeneous vs homogenous
heterogeneous= complex
Homogenous= simple
Few factors that influence
organism, Few niches=?
Many factors that influence organisms and Many niches=?
Homogenous/simple (Alberta plains)
Heterogenous/complex (rainsforest)
Paradox of the Plankton… Lakes are?
- Complex
- As you go deeper in water there is less oxygen and temperatures drop (get colder)
- Different seasons cause changes to the water (temp, O2 content) making lakes heterogenous/complex
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… this is known as
Species composition. What is species composition?
Species composition: the species that occur in a
given community at a given time
Why is species composition important?
Shifts in species composition to
non-native species often leads to
changes (usually decreases) in
species richness and evenness
What are Biotic Invaders (Non-native species, Invasive Species)
Species that establish a new range in which
they proliferate, spread, and persist to the detriment of the environment.
