Mutualism is ________.
positive species interaction
Competition
-/-
Neutral
0
Commensalism
+/0
Amensalism
-/0
Predation
+/-
Parasitism
+/-
Parasatoidism
+/-
Coevolution
the process in which two species undergo reciprocal evolutionary change through natural selection
Qualitative natures of species interactions can...
Be altered if the background environment changes
Niche
range of physical and chemical conditions under which that species can survive and produce (ex: hydra living is a specific temperature, salinity, and pH)
N-dimentional hypervolume
species that coexist differ in some aspect of their niche
Fundamental role
The environmental conditions under which a species can survive and reproduce; sometimes called a physiological niche; the set of environmental conditions under which a species can persist
Realized niche
Portion of the fundamental niche that a species actually uses as a result of interactions with other species
Competition can restrict the...
Fundamental niche
What can restrict the realized niche?
-Presence of predators or pathogens -mutualism/commensalism
Alpha = 1
Intraspecific and interspecific are equal to each other
Alpha is
Competition coefficient
Lotka-Voltera competition model: interspecific competition
simplest and best known two species model of competition
provides foundation for many other ecological models
predicts a full range of outcomes, depending on the values of K's and alpha's
Competition exclusion
One species eliminates the other
Stable coexistence
Persist together forever
Unstable coexistence
Persist together until perturbed
Interspecific competition affects...
The populations of 2 or more species adversely (-/-)
Intraspecific and Interspecific competition are likely occurring
Simultaneously
2 forms of Interspecific competition
Exploitation and interference
Most types of Interspecific interactions can be classified as 1/6 types
consumption competition -preemption competition -overgrowth competition -chemical interaction competition -territorial competition -encounter competition
consumption competition
Individuals of one species inhibit individuals of another by consuming a shared resource (squirrels, birds, etc eating acorns)
Preemption competition
Individuals of one species prevent occupation of an area by individuals of another species (sessile organism such as barnacles and clams)
character displacement
increased ecological differences between species in regions where they occur together
ecological release
the expansion of a species niche under conditions where their competitor species is absent; niche of the competitively-inferior species expands in the absence of the competitively-superior species
observational competition studies
negative correlations between species
attributed to present or past competition ("ghost of competition past")
cant determine cause and effect
other factors may be involved
experimental competition studies
addition/removal studies
manipulate presence and/or density of would-be competitors
must account for density effects
provides strong interference (strong evidence for or against)
difficult to do for many species
Connell, 1961
determined factors regulating distribution of Cthamalus stellatus and Semibalanus balanoides
one of the first studies to show interspecific competition through manipulative experiments
fundamental niche depends on...
physical (abiotic) conditions
realized niche depends on...
biotic and abiotic conditions
competitive exclusion principle
states that complete competitors cannot coexist
complete competitors
two distinct species that live in the same place and have exactly the same ecological requirements
competitive exclusion requires that...
competitors require exactly the same resources
environmental conditions remain constant
competition is influenced by
non-resource factors
environmental features that are not resources can...
influence the outcome of competition between species (ex: trout species)
temporal variation in the environment...
influences competitive interactions
why are there so many species?
non-resource variability
resources varying in time
resources can be a variety of things, water, light, food, microhabitats
disturbance
predation
consumption of one living organisms by another
predators are
heterotrophs
carnivores
consume animal tissue
herbivores
consume plant or algal tissue
omnivores
consume plant and animal tissue
true predator
kills its prey immediately upon capture, more of less
predators consume multiple prey organisms and function as ____________ throughout their lifetimes
agents of mortality
lethal effects
predators directly affect mortality rates through total combustion
prey directly affect predator birth/death rates
form modeled by L-V predator/prey model
predators may_______ affect prey birth/mortality rates through partial consumption (herbivory or parasitism)
directly
predators may __________ affect pre birth/ mortality rates through effects on prey behavior
indirectly
Lotka and Volterra on predation
developed 2 linked equations, one for prey and one for predator
plot results on a phase plane
Lotka-Volterra Predator- Prey Model
predicts population cycles
high latitude animals often have
population cycles
Optimal foraging: Type 1
number of prey consumed is linearly related to prey population size
more prey available, more are eaten
prey switching
predator doest eat the prey at low densities, relying on a different food source instead
apparent competition
a shared predator can make it appear that two species compete when they dont; two species that do not compete directly for resources affect each other indirectly because they share the same predator
competitive release
a predator can reverse competitive exclusion
trophic cascade
a predator of an herbivore can help a plant (the enemy of my enemy is my friend)
chemical defenses
Compounds released by prey to defend themselves from predators.
prey weapons
prey having physical defense mechanisms like hard shells or thorns to protect or fight their predators
plant defenses: physical and chemical
plants evolved spines, thorns, and chemical toxins, such as morphine, strychnine, and nicotine, against herbivores.
feigning death
faking death
predator swamping
a prey strategy in which the per capita predation rate is reduced at high prey density
schooling, flocking, group living
prey that tend to group together in order to survive (ex: prairie dogs, birds)
escape tactics
being fast and/or maneuverable
camoflauge & startling displays
an adaptation that allows an organism to blend in with its envoronment
symbiosis
the intimate and protracted association between two or more individuals of different species; can be positive, negative, or neutral
all parasitic relationships are...
symbiotic relationships
larger species is typically considered the...
host species
parasitism
feed on the live host organism
an intimate relationship, with the parasite living on or in the host at least part of its life cycle
actively is harmful but generally not lethal, at least in the short term
parasitoids
attack the prey indirectly by laying eggs on the host's body
and intimate association with a single host
the eggs hatch and the larvae feed on the host, eventually killing it
parasites increase their fitness by using the host in a close, prolonged association for
food, habitat, & dispersal; usually dont kill the host
Host fitness is often decreased by the parasite through
stunted growth
emaciation
behavior modification
sterility
parasites generally
are much smaller than the host
are highly specialized
reproduce more quickly and in larger numbers than the host
parasites are found in many groups such as
viruses
bacteria
protists
fungi
plants
invertebrates
vertebrates
facultative symbiosis
species can survive individually when separated
obligate symbiosis
species can not survive without the relationship
generalist symbiosis
interaction can be among many different species
specialist symbiosis
interactions can only be among a small set of species
invasive species
a non-native species that can sores on its own and does harm to the environment
species interactions help determine invasion success through
lack of competition
release from predators
mutualism
species composition
Biological structure of a community
absolute abundance
number of individuals of each species in a community can be counted or estimated
relative abundance
the proportion of each species relative to the total number of individuals of all species living in the community
relative abundance equation
pi = ni/N
pi = proportion of individuals of species I
ni = number of individuals of species I
N = total number of individuals of all species
rank abundance diagram
plots rank abundance (x-axis) against corresponding relative abundance (y-axis)
species richness
the number of species in the community (long curve)
species evenness
how equally individuals are distributed among the species (flat curve)
species dominance
when a single or few species predominant within a community and therefore have a large impact on the functioning of the ecosystem
diversity
multiple indices that incorporate both evenness and richness into one number
Alpha > 1
interspecific competition > interspecific competition
Alpha < 1
interspecific < infraspecific competition
overgrowth competition
individuals of one species grow over individuals of other species, inhibiting access to a resource (taller plants shading shorter plants)
chemical interaction competition
individuals of one species release growth inhibitors or toxins that inhibits or kills other species (allelopathy in plants- secretion of chemicals that inhibit germination of other species)
territorial competition
behavior of one species that excludes another species from a specific location that is defended as a territory ( a bird keeping other birds from nesting in its territory)
encounter competition
non-territorial encounters of individuals of different species affect one or more of the species involved (scavengers fighting over a dead animal carcass)
intraspecific competition: logistic growth rate equation
(dN1/dt) = rN1 (1-N1/K1)
dN1/dt =
population growth over time