Chapter 57; Species Interactions

Brooker et al. Biology Textbook

ecosystem

all the organisms in a particular region and the environment in which they live

community

all the species that inhabit a common environment and interact with one another

understanding species interactions informs:

climate change modeling, biodiversity conservation, agriculture and food security

intraspecific competition

between individuals of the same species

interspecific competition

between individuals of different species

exploitation competition

organisms compete indirectly through the consumption of a limited resource

interference competition

individuals interact directly with one another by physical force or intimidation

competitive exclusion principle

complete competitors cannot coexist

species coexistence

similar species can coexist if they occupy different niches

resource partitioning

differentiation of niches, both in space and time, that enables similar species to coexist in a community

fundamental niche

all environmental conditions where a species is able to live (precompetitive)

realized niche

where the species actually lives (postcompetitive)

sympatric speciation

speciation despite same geographic area

allopatric speciation

different geographic areas cause species to split into two

character displacement

tendency for two species to diverge in morphology and resource use due to competition (ex. finches)

predation is classified by:

how lethal they are for prey, length of association between prey and consumer

types of antipredator strategies

chemical, aposematic coloration, camouflage, mimicry, displays of intimidation, armor and weaponry

example of chemical defense

bombardier beetle ejects hot spray

aposematic coloration

warning coloration which advertises an organism’s unpalatable taste

camouflage

cryptic coloration

catalepsis

maintenance of a fixed body position

mullerian mimcry

noxious species converge to reinforce warning (bees and wasps)

batesian mimicry

palatable mimic resembles unpalatable model

displays of intimidation

deceive predator about ease of eating prey (ex. porcupine fish)

armor and weaponry

shells, horns, antlers, claws, pincers, stingers

two hypothesis for why plants aren’t fully consumed

predators and parasites keep herbivore population low, plant defenses against herbivores

mechanical defenses of plants

thorns and spines, tough fibers, silica in grasses and palms

secondary metabolites

non-essential and with increasingly specialized functions. Their role is often well defined (antibiotics) but sometimes mysterious (alkaloids)

primary metabolites

essential for the maintenance of life, found in all organisms

Atropine

made by belladonna, poisonous

host plant resistance

ability of plants to prevent herbivory via chemical or mechanical defenses

commercial development of host plant resistance

reduces need for chemical insecticides

Bt corn

genetically modified to incorporate gene for Bt toxin from soil bacterium

herbivores can overcome plant resistance by detoxifying with these two paths

oxidation, conjugation

oxidation

catalysis of secondary metabolite to corresponding alcohol by mixed-fuction oxidases

conjugation

unites results of oxidation with another molecule to create inactive and readily excreted product

how much of all animals are parasites?

40-50%

parasitoids

kill host

holoparasites

lack chlorophyll and are totally dependent on the host plant for water and nutrients

hemiparasites

can photosynthesis, but depend on their host for water and mineral nutrients

monophagous

parasites who feed on 1 or a few closely related hosts

polyphagous

parasites who feed on many different host species

microparasites

multiply within hosts, sometimes within cells

macroparasites

live in host but release infective juvenile stages outside host’s body

ectoparasites

live on outside of the host body (fleas and ticks)

endoparasites

live inside the host body (tapeworm and bacteria)

mutualism

close associations between species in which both species benefit (pollination)

commensalism

one member derives a benefit while the other is unaffected (seed dispersal via hooks)

resource-based mutualism

both species receive a benefit in the form of resources

what does the fungus release as ant food

gongylidia

defensive mutualism

one species receives food or shelter in return for defense

dispersive mutualism

species receives food in return for transporting pollen or seeds

obligatory mutualism

neither species can live without the other

facultative mutualism

interaction is beneficial but not essential

ideal pollinator has _____ to one species

fidelity

phoresy

one organism uses another for transportation

example at cheating commensalism

orchid produces no nectar, but mimics nectar producers, so if visited by bees and gets its pollen dispersed

bottom-up factors

plant quality and abundance control herbivores and the predators that feed on them

top-down factors

predators and parasites control herbivore or plant prey, trophic cascade

trophic cascade

effects cascade down to all feeding levels of a system

thermodynamic properties of energy transfer

energy transfers are never 100% efficient

nitrogen-limitation hypothesis

organisms select food in terms of nitrogen content