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Ch 26 Community Ecology (Metapopulations in Patchy Environments…
Ch 26 Community Ecology
Diversity
Diversity and Scale
larger communities more diverse than small
species-area relationship
relationship between area and species richness
S=cA^z
Level of Scale
Local
Region
Biome
Biogeographical region
measuring diversity
alpha
number of species or growth forms that occur at local site
beta
compares differences between smaller sites in large region
gamma
number of species within a region
species abundance distribution
plot of the number of species in a region into abundant classes
Diversity and Latitude
different plants depending on environment on earth
far north
lower diversity than closer to the equator
equator
benign environment
higher latitude has more severe conditions
could change in temperatures were the same long enough
Predator-Prey Interactions
One Predator, One Prey
functional response
predator's feeding rate and handling time
prey-dependent
predator's functional response depends on prey density
Lotka-Volterra model
dN/dt=rN-aNP
rate of change with time of prey population
dP/dt=faNP-qP
rate of change of predator number
criticized for being to simplistic
zero growth isocline
line indicating population stability
paradox of enrichment
loss of a population from a habitat as a result of that habitat being altered to benefit the population
maximum sustained yield
amount of organisms population that can be harvested without population decreasing
fixed effort harvesting
technique that limits damage to a species by automatically decreasing harvests
fixed quota harvesting
limits damage to a species by setting limits on amount that can be harvested
Predator Selection Among Multiple Prey
optimal foraging theory
examine the interactions between these factors in an attempt to understand why herbivores eat the plants they do while ignoring the others
optimal diet model
makes four predictions
Competition Between Species
exploitation competition
occurs when organism actually consume a shared resource making it less available for organism
interference competition
one organism restricts another organism's access to resources even though the first might not using it.
resource
any substance or factor that can lead to increased growth rate as its availability is increased and that is consumed by an organism
Apparent Competition
predator may prey on several species
Beneficial Interactions Between Species
mutualism
two organisms interact with that both organisms benefit
facilitation
one organism helps another without receiving any benefit
first organism facilitates
nurse plants
presence of some plants creates conditions that allow other plants to become established
spiny desert shrubs
primary succession
organism becomes established on newly created substrates
Metapopulations in Patchy Environments
metapopulation
population that consists of several local populations interconnected by migration and gene flow between patches
makes four assumptions
a region of the environment is composed of many discrete patches in which the species can live
some patches are occupied by the species whereas other suitable patches are not
empty patches will become colonized by migration from occupied patches
populations within individuals patches have a probability of going extinct within that patch
source habitat
high quality patch
sink habitat
low quality
fugitive species
species that survives by colonizing new patches, flourishing temporarily, then colonizing more patches and dies out in old one
assisted dispersal
animals are capture in one area and released into another
Interconnectedness of Species: Food Chains and Food Webs
food chain
direct line of consumption
food web
various organisms eat or decompose others, and these in turn are consumed
keystone species
species that dramatically effects the structure of its community
portion size
number of individuals
energy flow web
difficult to make for real communities
