Exam 3 by Branna Campbell

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

r =

growth rate

N1 =

population size

-N1/K1

proportion of carrying capacity

interspecific competition: logistic growth rate equation

(dN1/dt) = rN1 (1 - (N1/K1) - (alpha21*N2/K1)

Succession

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")

community

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

zonation

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