Exam 3 by Branna Campbell

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150 Terms
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Mutualism is ________.
positive species interaction
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
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
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
consumption of one living organisms by another
predators are
consume animal tissue
consume plant or algal tissue
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)
predators may __________ affect pre birth/ mortality rates through effects on prey behavior
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
knowt flashcard image
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
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
- 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
- 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
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
r =
growth rate
N1 =
population size
proportion of carrying capacity
interspecific competition: logistic growth rate equation
(dN1/dt) = rN1 (1 - (N1/K1) - (alpha21*N2/K1)
temporal change in community structure at a given location; seen in both terrestrial and aquatic environments
2 different types of succession
primary and secondary
primary succession
occurs at a location that was not previously occupied by a community; a newly exposed surface
secondly succession
occurs at a location that was previously occupied by a community and then underwent a disturbance that removed all or part of the existing community
the changes in environmental conditions that lead to changes in the physical and biological structures of communities are varied but fall into two major classes;
autogenic and allogenic environmental change
autogenic environmental change
the result of the presence and activities of organisms within the community
allogenic environmental change
result of a feature of the physical environment, so is governed by physical rather than biological processes
early succession
high availability of light at the ground level; seedlings are successful
later succession
taller plants reduce availability of light at ground level; decrease rate of photosynthesis and slows growth of shaded plants
resource ratio hypothesis
succession is based on a trade-off in characteristics that enable plants to complete for light and nitrogen (essential resources)
high frequency of disturbance
later succession species will never colonize; diversity stays low
intermediate disturbance
colonization occurs, but competitive displacement is lower; species coexist, resulting in maximum diversity
no disturbance
later successional species displace earlier species; diversity declines
intermediate disturbance hypothesis
the highest species diversity is seen at intermediate frequencies of disturbance
ecological succession
understanding how communities change over time after disturbance
How do communities assemble over time?
regional species pool -> dispersal filter -> colonization -> environmental filter -> trait distribution -> community interaction -> local community (species abundance/ composition)
coexistence of species often involves...
partitioning available resources
observations of similar species living in the same habitat suggest that they are able to...
coexist because they partition the available resources; each species uses a portion of the resource not used by the other it lives with
Optimal foraging: Type 2
- linear until an asymptote is reached - at large pre population sizes, predators are encountering more prey than they have time/appetite to eat = incorporates handling time
Optimal foraging: Type 3
- sigmoidal curve (S-curve) - prey can be hard to find at low densities - predator might not have the reach image for the prey- predator doesn't recognize the prey as prey
indirect effects of predators
- "the enemy of my enemy is my friend" - a shared predator can make it appear that two species compete when they dont ("apparent competition") - a predator can reserve competitive exclusion - a predator of an herbivore can help a plant ("trophic cascade")
group of species inhabiting a given area and interacting directly and indirectly
the role of a keystone species may be to
- create or modify habitats - influence interactions among other species
the removal of a keystone species can lead to
- changes in community structure - loss of biodiversity
a keystone species has a
disproportionate impact on the community relative to its abundance
food chain
- representation of feeding relationships within a community - diagram representing the flow of energy from the prey (consumed) to the predator (consumer)
food web
diagram representing the complex interactions of predators and prey
food web links
the arrows from costumed to consumer
basal species
usually autotrophs (A) that do not feed other species but are fed on by other species
intermediate species
herbivores (H) or carnivores (C) that feed on other species and are the prey of other species (may also be omnivores)
top predators
(P) feed on intermediate and sometimes basal species (if omnivores) but are not preyed upon themselves
the number of possible species interactions (links) in a community...
increases with species richness (S)
niche dimension
a measurable extent of some kind, such as lunch, breadth, depth, or height (ex: nutrient availability, temperature, light availability, food availability, etc)
community structure is an expression of
species ecological niche
null model
assumes that the presence and abundance of the individual species in a community are only based on independent responses of each species to the current abiotic environment
competition and predation can...
reduce abundance or exclude species
mutualism can...
increase abundance or extend the distribution of a species
spatial changes in community structure; result of differences in species tolerance and interactions along environmental gradients
frequently superior competitive ability for resources is associated with a
higher metabolic or growth rate, which often restricts the ability to tolerate environmental stress
plant adaptations to variations in light, water and nutrient availability show trade-offs between
characteristics that allow for growth under low resource availability versus those that allow for high rates of photosynthesis and growth under high resource availability