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Chapter 26, Species Abundance, Apparent Competition, Predator Prey Graph,…
Chapter 26
Concepts
communities
group of species in the same place at the same time
must have boundaries in time and space
population biology focuses on
members of a single species
species growth
species interbreeding
species survival
etc.
community ecology takes species interactions into account
succession is the predictable sequence of changes
a climax community is a stable, self-sustaining community
many community restoration projects have begun
human development has lead to habitat loss and habitat fragmentation
Diversity
diversity and scale
scale of studies matter
larger areas are more diverse than smaller ones
larger areas will have more variations in
types of soil
topography
geology
etc.
species-area relationship
relationship between area and species richness
expressed by the formula S=cA^z
species abundance distribution
a plot of the number of species in an area
does not describe most species accurately
diversity and latitude
diversity varies with latitude
geographical and geological components also contribute to diversity
examples of latitudinal diversity
equator hosts moderate temperatures with consistent rainfall
poles have extreme temperatures and little light
species richness is measured as a simple count of present species
studies of diversity may also focus on
presence
absence
or relative abundance of herbs, shrubs, trees, or of annuals, perennials, and ephemerals
Predator-Prey Interactions
one predator, one prey
fundamental aspects of predator-prey relationships
predator's feeding time (time to find prey)
predator's handling time (time to consume prey)
functional time
two aspects of the relationships constitute this time
prey dependent
lines indicating population stability are called zero growth isocline
paradox of enrichment
improving conditions for prey may create unstable relationship
important factor in loss of species diversity
maximum sustained yield
point where harvesting where species remains stable
this point is unknown
alternatives to maximum sustained yield
fixed effort harvesting
population health is determined by amount of species harvested with particular amount of effort
theoretically, harvest will not damage species severely
fixed quota harvesting
harvesters are allowed a certain amount no matter the effort or time taken
could be extremely detrimental
predator selection among multiple prey
three factors affect choice of prey
probability that prey will be encountered
decision by predator to attack (based on defenses)
probability that attacked prey will be eaten
optimal foraging theory
examines the interactions between these factors
produced the optimal diet model
optimal diet model makes four predictions
predators should evolve to prefer prey with maximum nutrient yield
if high-yield prey become scarce, predators then attack low-yield prey
some prey will always be eaten, and others will never be eaten
probability of plant being eaten depends on the abundance of surrounding prey
competition between species
resources
any substance or factor that can lead to increased growth rates
become scarce as species use them
types of competition
interspecies competition
exploitation competition
interference competition
interspecies competition is where several species compete for resources
exploitation competition is where resources are consumed and made less available
interference competition is where one organism restricts access to resources
invasive species can increase from a very low population density even with competitors
apparent competition
where species appear to be competing for resources, but are not
Metapopulations in Patchy Environments
metapopulations
interconnectedness o populations between suitable environments
crucial in conservation biology
four assumptions of metapopulations
a region of the environment is composed of many suitable patches
some patches are occupies while others are not
empty patches will become colonized by migration
populations within a patch can go extinct in that patch
qualities of patches
high-quality patch (source habitat)
low-quality patch (sink habitat)
fugitive species
species that colonize and reproduce new patches before dying
an example is weeds
lifespan is relatively short
assisted dispersal
also called assisted migration
for species with no (or a disrupted) migration corridor
species are captured and moved
Interconnectedness of Species
ways to study species interactions
food chain
food web
energy flow web
food chain
a direct line of consumption
only has one species per segment in the chain
food web
a network of numerous interrelationships in an environment
many relationships will occur between predator and prey
energy flow web
traces flow of energy through the environment
extremely complicated
keystone species dramatically affect the structure of the community
Beneficial Interactions Between Species
mutualism
interaction where both organisms benefit
also known as a mutualistic relationship
facilitation
interaction where one organism benefits and the other remains neutral
one organism facilitates the presence of the other
nurse plants
example of facilitation
plants that alter surrounding areas to be more favorable
primary succession
another example of facilitation
where plants begin to grow in previously inhabitable areas
community interactions
human development affects species
succession
predator-prey interactions can be measured
diversity can affect predator-prey interactions
