Community Ecology
interconnectedness of species: food chains and food webs #
metapopulations in patchy environments
preditor-prey interactions
Diversity
beneficial interactions between species
diversity and scale
diversity and latitude #
one preditor, one prey
competition between species #
predator selection among multiple prey
apparent competition
scale: size of physical geographical amount of land
larger areas are more diverse than smaller ones
species-area relationship
relationship between area and species richness
expressed by: S=cA^z
levels of scale: local,region, biome, biogeographical region
temperatures as well as other factors affect diversity over latitude
helps us understand how we human predators should harvest our various prey
Lotka-Volterra model
net rate of change
dN/dt=rN-aNP
equation for the net rate of change of predator numbers is dP/dt=faNP-qP
the line indicating population stability is called zero growth isocline
three factors are initially important in a predators choice of prey
probability that a particular prey individual will be encountered
the decision by the predator to attack an individual once it has been encountered
the probability that an attacked prey will be successfully eaten
optimal diet model
several species often compete for the same resources
exploitation competition
resource competition occurs when the organisms actually consume a shared resource, thus making it less available to other organisms
interference competition
one organism restricts another organisms access to resources even though the first might not be using it
an increase in one species that is associated to the decrease in another, they appear to be in competition
mutualistic relationship
when two organisms interact in a way that both benefit
facilitation
mutualism
if one organism helps out another without receiving any benefit
building dams and creating ponds
nurse plants
plants that alter a small area of habitat immediately below themselves such that is more favorable to the survival of seedlings of other plants as compared to nearby areas not below the nurse plant
spiny desert shrubs
metapopulation
if several local populations are interconnected by migration and gene flow between the patches
a common model of metapopulations make four assumptions:
source habitat
sink habitat
can migrate between patches through:
a region of the environment is composed of many discrete patches in which these species can live
empty patches will become colonized by migration from occupied patches #
some patches are occupied by the species whereas other suitable patches are not
populations within individual patches have a probability of going extinct within that patch
high-quality patch
lowquality patch
flying
walking
swimming
etc.
food chain
direct line of consumption
choose one predator identify their main prey and plant species that supports them
food web
network of numerous interrelationships
trace all the prey of the top carnivores and then trace the food source of those prey species and so on
energy flow web
trace how energy flows through the community
extremely difficult to construct for real communities
keystone species
the presence or absence of a certain species that dramatically affects the structure of their community
has an impact out of proportion to its size or the number of individuals present