Lecture 20 CH 27 - Species Interactions

Species interactions

The various ways in which a species can interact with other species, such as predation, competition, parasitism, mutualism ,and commensalism

Competition

An interaction that affects two or more species negatively as they compete over food or other resources

Amensalism

One-sided competition between species, in which the interaction is detrimental to one but not the other

Predation

An interaction in which the action of a predator results in the death of its prey

Herbivory

A form of species interaction in which herbivores feed on plants

Parasitism

A symbiotic association in which one organism feeds off another but does not normally kill it

Pathogen

An agent, such as a virus, bacterium, or parasite which causes disease symptoms in humans or other species

Mutualism

An interaction where both species benefit

Commensalism

Benefits one species and leaves the other unaffected

Summary of types of species interactions

Intraspecific

Between individual of the same species

Interspecific

Between individual of different species

Exploitation competition

Organisms compete indirectly through consumption of a limited resource

Interferenece competition

Individuals interact directly with one another by physical force or intimidation

Allelopathy

The suppression of growth of one species due to the release of toxic chemicals by another species

Niche

The unique set of habitat resources a species requires as well as its effect on the ecosystem

Species with the same requirements cannot live together in the same place with the same resources - They ____ occupy the same niche

Cannot (Gause study on paramecium species

Competitive exclusion principle

The idea that two species with the same resource requirement cannot occupy the same niche

Resource partitioning

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

Morphological difference may allow

Co existence

Sympathetic

Same geographic area

Allopathic

Different geographic area

Size differences did not occur in ___ species

Allopatric

Character displacement

Tendency for two species to diverge in morphology and resources use due to competition

-example: Galapagos finches

Comparison of feeding characters of sympathetic and allopatric species

Fundamental niche

Most species perform best over a physiologically optimal range of conditions

Realized niche

The actual range of an organism in nature

Predation, Herbivory and parasitism

Are interactions that have a positive effect for one species and a negative effect for the other.

-categories of predation can be classified by

-how lethal they are

-length of association between consumer and prey

Antipredator strategies

Chemical defense, aposematic coloration and camouflage

Chemical defense

-example bombardier beetle ejects hot spray

Aposematic coloration

Warning coloration which advertises an organisms unplatatable taste

Example - many lethal tropical fogs have bring coloration

Camouflage

Cryptic coloration

Catalepsis - maintenance of a fixed body position

-example- stick insects, sea horses

Mimicry

Resemblance of mimic to another organism

Mullerian mimicry

Noxious species converge to reinforce warning

-black and yellow stripes on bees and wasps

Batesian mimicry

Palatable mimic resembles unpalatable model

Example - scarlet king snake and coral snake

Herbivory

-involves the consumption of plant material or the material of similar life-forms such as algae

-can be lethal to plants

-often nonlethal because many plant species, particularly larger ones can regrow

Mechanical defense - plant defenses

-thorns and spines

-tough fibers

-silica in grasses and palms

Secondary metabolites

Molecules that are produced by secondary metabolism

Host plant resistance

The ability of plants to prevent Herbivory via either chemical or mechanical defenses

Herbivores can overcome plant resistance by

Detoxify - two pathways, oxidation and conjugation

Oxidation

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

Conjugation

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

Invertebrates herbivores like insects have a ____ effect on plants populations than vertebrate herbivores such as mammals, at least in terrestrial systems

Stronger

Parasite

An organism that feeds on another organism, called the host, for a relatively long time, but does not normally kill it outright

Host

Prey

Predatory organism

is termed a parasite