enviro exam 3

interactions affect the

structure and size of the community

density and dispersion of the population

realm of social behavior

the full range of actions, interactions and communication among individuals and groups

types of biotic interactions

mutualism (cooperation)

predation (parasitism)

competition

commensalism

amensalism

mutualism (cooperation)

both species benefit

predation (parasitism)

one species benefits at the cost of the other

competition

neither species benefit

commensalism

one species benefits, the other doesn’t change

ammensalism

one species is damaged the other one doesn’t change

examples of mutualism (cooperation)

stomach bacteria

pollinators

examples of predation (parasitism)

hawk/mouse

competition can be

interspecific or intraspecific

competition only happens when

it has to because neither one is benefiting from the relationship

liebig’s law of the minimum

growth or success is limited by the resource that is in shortest supply

intraspecific competition

individuals of the same species compete with each other for limited resources

interspecific resources

individuals of different species compete for the same limited resources

patterns of competition

scramble

contest

scramble competition

all individuals share a limited resource, no one gets enough

everyone is negatively affected

contest competition

individuals directly compete for a resource and the winners get access while the losers get nothing

mechanisms of competition

exploitative

interference

exploitative competition

organisms indirectly compete by using up the same limited resource, without directly interacting with each other

interference competition

organisms directly interact to block, exclude or prevent others from accessing resources

examples of exploitative competition

consumption

preemptive

consumption competition

organisms compete by using up the same limited resource, reducing how much is available for others

preemptive competition

an organism occupies a space or resource first and prevents others from accessing it

often without direct conflict

examples of interference competition

chemical

territorial

encounter

overgrowth

chemical competition

an organism releases chemicals that inhibit, harm or kill competitors, reducing their ability to survive or access resources

territorial competition

organisms compete by claiming and defending a specific area (territory), excluding others from its resources

encounter competition

individuals come across each other (encounter one another) and directly compete for a resource at that moment, with one gaining access and the other losing

overgrowth competition

an organisms physically grows over another organism, covering it and blocking its access to essential resources like light, oxygen or nutrients

possible outcomes of competition

species 1 wins

species 2 wins

a draw (stable equilibrium = coexistence)

unstable equilibrium

lotka-voltera model of competition

dN/dt = rN (K-N)/K

only looks at 1 species

population growth equilibrium for one species including competition with species 2

Dn/dt= r1N1 {(K1-[N1+alpha1,2N2]) / K1}

k1 is always on x-axis and k2 is always on y-axis

this generates graphs with what

4 possible arrangements of isoclines

isoclines

lines where there is no increase or decrease in population size

competitive exclusion principle (gauss-paramecia)

2 species that compete for the exact same limiting resource can’t stably coexist

one will outcompete the other → local extinction

resource partitioning allows for

coexistence of similar species

resource partitioning

similar species use the same limited resource is different ways so they don’t directly compete

competition restricts

niches

niche

organisms’ job description

fundamental niches

full range of environmental conditions and resources an organism could use to survive, grow and reproduce if there were no competition or predators

realized niches

the actual conditions and space where a species lives in nature

niche overlap

occurs when 2 species use the same resources or share similar environmental conditions

likely to compete here

niche compression

when a species is forced to use a smaller range of resources (a narrower niche) than it normally would, usually because of competition

competitive release

when a competing species is removed, a species is able to expand its niche and use more resources than it could before

specialists

narrow niche, use a specific range of resources

generalists

wide niche, use many resources

why do predators often focus on the prey that is the better competitor

because there are more of the better competitiors

lotka-volterra predator-prey model

dNh/dt = rNh - eNh - cNhNp

rNh=prey population

eNh=prey dying from natural death

cNhNp=predators eating prey

Nh=prey

Np=predators

big idea of lotka-volterra predatory-prey model

prey increases when reproduction is high

prey decreases when predators are abundant

predator equation

dNp/dt = fcNhNp - dpNp

fcNhNp = predator growth

dpNp = predators death

big idea of predator equation

predators increase when prey are abundant

predators decrease when prey are scarce

key thresholds for prey

prey grows when: Np < r/c

prey decreases when: Np > r/c

key thresholds for predators

predators grow when: Nh > d / (fc)

predators decrease when: Nh < d / (fc)

break down predator prey cycle in 4 parts

prey increasing, predators increasing

prey decreasing, predators increasing

prey decreasing, predators decreasing

prey increasing, predators decreasing

what population lags in predator prey interactions

predator populations

predator responses to prey

reproductive response

aggregative response

developmental response

functional response

developmental response

if you have lots of food as a predatory, you will develop better and faster than if you have limited food

functional response

when there are lots of a certain kind of food, you may become better at handling it

ways to catch food as a predator

chase it down

sit and wait: ambush

use tools

cooperate with others

pros and cons of cooperating with others

pros: more efficient, protection (vigilance), ore time to eat, can’t handle prey along

cons: have to share, increased conspicuousness, have to obtain more food

how do prey species fight back

compensatory response

defensive responses

compensatory response

when a population increases its growth, survival or reproduction after being reduced, helping it bounce back

types of defensive responses

constitutive vs inducible

constitutive defenses

defenses that are constantly present, regardless of whether a predatory is around

inducible defenses

defenses that are activated only when a trait is detected

prey defenses

mechanical

chemical

social

behavioral: alarm calling

camouflage: crypsis

defenses that advertise danger

aposematic coloration

mimicry: batesian vs mullerian

aposematic coloration

bright, noticeable colors that signal the prey is toxic or harmful

batesian mimicry

model: dangerous

mimic: harmless

mullerian mimicry

both species are harmful

special forms of predation

parasitism

cannibalism

true predators

grazers

parasites

cannibalism

eating members of own species to reduce population density and competition/stress

true predators

kill prey quickly and eat a lot of prey over their lifetime

grazers

eat only part of the organism, usually don’t kill it, feed on many individuals

parasites

take small amounts from host, don’t kill host outright, interact with few hosts in lifetime

parasites usually need host for more than just food, they need

a place to live and transportation to the next host

transmission from one host to another of the same species may require a

vector (carrier)

micro parasites

very small parasites that reproduce inside the host and cause disease

bacteria, viruses, protozoans

macro parasites

larger parasites that live in or on a host and do not multiply inside the host

fleas, ticks, worms, plants

holo parasite

completely dependent on their host for nutrients

hemi parasites

can photosynthesize but steal water and nutrients from a host

ecto parasite

parasites that live on the outside of their host’s body

endo parasite

parasites that live inside the body of their host

parasites will

“partition the resource”

definitive host

the host when a parasite reaches sexual maturity and reproduces sexually

intermediate host

the host when a parasite lives and develops but does not reproduce sexually

parasites can be spread by

direct contact (transmission): spend basically whole life cycle with one host

indirect transmission: parasite passed between hosts through an intermediate step, different parts of life cycle are spent with different hosts

facultative parasite

can live with or without a host

parasitism is optional

obligate parasite

must have a host to survive

can’t live independently

temporary parasite

only visits the host briefly (usually to feed)

permanent parasite

lives on/in the host for most or all of its life

kleptoparasitism

stealing food/resources from another organism instead of hunting or gathering for itself

temporary facultative intrapsecific

can lay more eggs

“spreading around” your kids, safer

temporary obligate interspecific

specialized behaviors of young

central place foraging

animal collects food and returns to a home base

costs: search time, travel tome

handling time

time to catch, eat and process food

risk-sensitive foraging

animals consider risk vs reward

risk of predators, risk of not getting enough food

optimal foraging

animals try to maximize energy gained and minimize time, effort and risk

optimal foraging theory

animals behave in ways that max energy gained and minimize costs

marginal value theorem

how long an animal should stay in one food patch before leaving

food in a patch gets used up over time to the rate of energy gain decreases the longer you stay