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

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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

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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.

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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

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