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