ecology unit 6

competition

occurs when individuals experience limited resources

can occur through exploitation or direct interference, or may be apparent competition

intraspecific competition

competition among individuals of the same species

interspecific competition

competition among individuals of different species

resource

anything an organism consumes or uses that causes an increase in the growth rate of a population when it beecomes more available

renewable resources

resources that are constantly regenerated (food, sunlight, etc)

nonrenewable resources

not regenerated (space)

ecological factors

cannot be used or consumed are not considered resources

ex: temperature

liebig’s law of the minimum

states a population increases until the supply of the most limiting resource prevents it from increasing further

looks at each limiting source independently and it does not assume interactions between the resources

competitive exclusion principle

two species cannot coexist indefinitely when they are both limited by the same resource

tansley’s bedstraw experiment

example of 2 closely related species avoiding competition by diverging in resource use

competition coefficients alpha and beta

variables that convert between the number of individuals of one species and the number of individuals of the other species

alpha

converts individuals of species 2 into the equivalent number of individuals of species 1

beta

converts individuals of species 1 into the equivalent number of individuals of species 2

zero population growth isocline

population sies at which a population experience zero growth

outcome

the outcome of competition can be altered by abiotic conditions, disturbances and interactions with other species

exploitative competition

competition in which individuals consume and drive down the abundance of a resource to the point that other individuals cannot persist

interference competition

when competitors do not immediately consume resources but defend them

allelopathy

a type of interference that occurs when organisms use chemicals to harm their competitors

apparent competition

when two species have a negative effect on each other through an enemy including a predator, parasite, or herbivore

introduced species

species that is introduced to a region of the world where it has not historically existed

exotic species or non native species

invasive species

an introduced species that spreads rapidly and has negative affects on other species, human recreation, or human economies

mesopredators

relatively small carnivores that consume herbivores

top predators

predators that typically consume both herbivores and mesopredators

parasitoid

insect larva that lives on and obtains nutrition from its host

host does not die until parasitoid reaches maturity

huffaker predator prey lab experiment

used mites and oranges to study predator-prey population dynamics

proved spatial heterogeneity and differential dispersal rates are required to sustain long term population oscillation and prevent mutual extinction

lotka volterra model

mode of predatory prey interactions that incorporates oscillations in the abundances of predator and prey populations and shows predator numbers lagging behind those of their prey

equilibrium isocline

the population size of one species that causes the population of another species to be stable

aka zero growth isocline

P = r/c

prey population is stable

r is for predator population

N = m/ac

predator population is stable when

joint population trajectory

the stimulataneou trajectory of predator and prey populations

joint equilibrium point

the point at which the equilibrium isoclines for predator and prey populations cross

type 1 functional response

a functional response in which a predator’s rate of prey consumption increases in a linear fashion with an increase in prey density until satiation occurs

type 2 functional response

a functional response in which a predator’s rate of prey consumption begins to slow down as prey density increases and then plateaus when satiation occurs

type 3 functional response

a functional response in which a predator exhibits low prey consumption under low prey densities, rapid consumption under low prey densities, rapid consumption under moderate prey densities, and slow prey consumption under high prey densities

-pray switching

numerical response

a change in then umber of predators through population growth or population movement due to immigration or emigration

crypsis

camouflage that either allows an individual to match its enviornement or breaks up the outline of an individual to blend in better with the background enviornment

Cryptic prey

animals that avoid being seen, recognized, or detected by predators through crypsis

chemical defenses

allomone = signal from one organism to another of a different species

communicate to “go away and leave me alone”

warning coloration

a strategy in which distastefulness evolves in association with very conspicuous colors and patterns

aka aposematism

mimicry

species imitate other species in look and/or behavior

batesian mimicry

when palatable species evolve warning coloration that resembles unpalatable species

tricks predators

palatable species

species that is agreeable/easy/desirable to eat by predator

mullerian mimicry

several unpalatable species evolve a similar pattern of warning coloration

actually is dangerous and toxic

coevolution

when two or more species affect each other’s evolution

counter adaptations of predators to chemical defenses

dissecting prey

taste/smell and risk perception

foraging and learning

infection resitance

ability of a host to prevent an infection from occurring

infection tolerance

ability of a host to minimize the har once an infection has occured

parasite load

the number of parasites of a given species that an indvidual host can harbor

ectoparasite

a parasite that lives on the outside of an organism

harder to feed on host, less exposure to host immune system

endoparasite

a parasite that lives inside an organism

easier to feed on host and higher exposure to host immune system

emerging infectious disease

disease that is newly discovered or has been rare and then suddenly increases in occurrence

ex: deadly chytrid fungus in central america

white nose fungus in bats

parasite and host dynamics

are determine by the parasites ability to infect the host

horizontal transmission

when a parasite moves between individuals other than parents and their offpsring

vector

an organism that a parasite uses to disperse form one host to another

vertical transmission

when a parasite is transmitted from a parent to its offpsring

reservoir species

species that can carry a parasite but do not succumb to the disease that the parasite causes in other species

parasite and host populations

commonly flunctuate in regular cycles

ex: cyclic population fluctuation of caterpillars

cyclic population fluctuation of measles in human pop.

susceptible infected resistant (SIR) model

simplest model of infectious disease transmission that incorporates immunity

mutualism

fitness of both species is increased when 2 species are in mutualisitc relationship

ex: tree shrew and pitcher plant

generalist

species that interacts that many other species

specialist

species that ineract with one or a few other species

obligate mutualists

two species that provide fitness to each other and require each other to persist

facultative mutualists

two species that provide fitness benefits to each other, but whose interactions are not critical to the persistence of either species

mutualism with fungi

mycorrhizal fungi surround plant roots and help plants obtain water and minerals

bacteria

legumes such as this bean plant can form a mutualistic relationship with rhizobium bacteria

plant provides the bacteria with sugars from photosynthesis and a root nodule in which the bacteria can grow

the bacteria convert atmospheric nitrogen to ammonia, a form of nitrogen that the plant can use

substitute mutualist

aldabra tortoises were introduced onto a small island in the republic of Mauritius to act as a seed disperser for a population of crtiically endangered ebony trees