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1.4 Species and Interspecific Interactions

interspecific interactions

  • predation: a member of one species kills and feeds on a member of another species

    • eg. wolf (predator) / caribou (prey)

  • herbivory: the consumption of plant material by animals

    • eg. caribou (herbivore) / moss (plant)

  • symbiosis: a relationship between two species that live in intimate contact — types are parasitism, commensalism, and mutualism.

  • parasitism: a close relation between two species in which one benefits at the expense of the other but doesn’t necessarily kill it

    • eg. tapeworms (parasite) / wolf

  • commensalism: a close relation between two species in which one benefits, and the other is neither helped nor harmed

    • eg. arctic fox eats polar bear’s leftovers

  • mutualism: a close relation between two species in which they both benefit

    • eg. lichen — fungus (provides habitat) / algae (provides food)

  • competition: a relationship between two organisms that struggle for the same resource

  • resource: anything that an organism needs in order to survive or reproduce

    • eg. space, food, water, oxygen

  • when a resource is used by one organism, it becomes unavailable to others → limited

    • interspecific competition: competition between individuals of different species

    • intraspecific competition: competition between individuals of the same species

interaction type

effect of interaction

effect of interaction

species one

species two

competition

predation

+

herbivory

+

parasitism

+

commensalism

+

/

mutualism

+

+

*in this chart, “+” indicates a positive effect, “/” indicates a neutral effect, and “—” indicates a negative effect

competition

biological niches

  • niche: a species’ functional role in an ecosystem, all the physical, chemical, and biological conditions in which it lives and reproduces

    • what it eats, where it nests, when it reproduces

    • not a habitat (where a population typically lives)

  • principle of competitive exclusion: two species will not occupy the same niche, live in the same habitat, and compete for the same resources for very long

    • either one becomes extinct, or the species adapt/evolve to exploit different resources

  • resource partitioning: the idea that over evolutionary time, species divide up scarce resources and reduce competition

  • fitness: the ability of an individual to survive and produce offspring

    • a measure of reproductive success

types of species

tolerance limits

there are limits to the environmental conditions a living organism can endure

  • tolerance limits: the minimums and maximums beyond which a species cannot survive for each environmental factor

  • critical limiting factor: a single limiting factor which outweighs the rest in determining whether a species is present in an environment

types of species

  • specialist: a species with a narrow niche

    • eg. koalas only eat eucalyptus

    • more susceptible to extinction

  • generalist: a species with a broad niche

    • eg. raccoons are omnivores and eat nearly everything

    • less susceptible to extinction

  • indicator species: a species whose presence, absence, or abundance in a certain location indicates something about the environmental conditions present there

    • eg. lichens are sensitive to air pollution; thus, their presence indicates the amount of nitrogen in the air

  • native species: a species that naturally lives in a particular ecosystem

  • immigrant species/alien species: a species that has migrated or has been introduced by humans to a certain area

    • sometimes become invasive species, which damage the ecosystem

  • dominant species: the most abundant species in an ecosystem, or the one which has the greatest biomass in an ecosystem

    • are likely but not always important to the functions of an ecosystem due to their numbers

  • keystone species: a species that plays a role in an ecosystem that affects many other organisms

    • effects far exceed the species’ abundance in an ecosystem

    • removal of a keystone species changes an ecosystem’s composition

    • term comes from architecture, the keystone which keeps pieces of an arch from falling apart

1.4 Species and Interspecific Interactions

interspecific interactions

  • predation: a member of one species kills and feeds on a member of another species

    • eg. wolf (predator) / caribou (prey)

  • herbivory: the consumption of plant material by animals

    • eg. caribou (herbivore) / moss (plant)

  • symbiosis: a relationship between two species that live in intimate contact — types are parasitism, commensalism, and mutualism.

  • parasitism: a close relation between two species in which one benefits at the expense of the other but doesn’t necessarily kill it

    • eg. tapeworms (parasite) / wolf

  • commensalism: a close relation between two species in which one benefits, and the other is neither helped nor harmed

    • eg. arctic fox eats polar bear’s leftovers

  • mutualism: a close relation between two species in which they both benefit

    • eg. lichen — fungus (provides habitat) / algae (provides food)

  • competition: a relationship between two organisms that struggle for the same resource

  • resource: anything that an organism needs in order to survive or reproduce

    • eg. space, food, water, oxygen

  • when a resource is used by one organism, it becomes unavailable to others → limited

    • interspecific competition: competition between individuals of different species

    • intraspecific competition: competition between individuals of the same species

interaction type

effect of interaction

effect of interaction

species one

species two

competition

predation

+

herbivory

+

parasitism

+

commensalism

+

/

mutualism

+

+

*in this chart, “+” indicates a positive effect, “/” indicates a neutral effect, and “—” indicates a negative effect

competition

biological niches

  • niche: a species’ functional role in an ecosystem, all the physical, chemical, and biological conditions in which it lives and reproduces

    • what it eats, where it nests, when it reproduces

    • not a habitat (where a population typically lives)

  • principle of competitive exclusion: two species will not occupy the same niche, live in the same habitat, and compete for the same resources for very long

    • either one becomes extinct, or the species adapt/evolve to exploit different resources

  • resource partitioning: the idea that over evolutionary time, species divide up scarce resources and reduce competition

  • fitness: the ability of an individual to survive and produce offspring

    • a measure of reproductive success

types of species

tolerance limits

there are limits to the environmental conditions a living organism can endure

  • tolerance limits: the minimums and maximums beyond which a species cannot survive for each environmental factor

  • critical limiting factor: a single limiting factor which outweighs the rest in determining whether a species is present in an environment

types of species

  • specialist: a species with a narrow niche

    • eg. koalas only eat eucalyptus

    • more susceptible to extinction

  • generalist: a species with a broad niche

    • eg. raccoons are omnivores and eat nearly everything

    • less susceptible to extinction

  • indicator species: a species whose presence, absence, or abundance in a certain location indicates something about the environmental conditions present there

    • eg. lichens are sensitive to air pollution; thus, their presence indicates the amount of nitrogen in the air

  • native species: a species that naturally lives in a particular ecosystem

  • immigrant species/alien species: a species that has migrated or has been introduced by humans to a certain area

    • sometimes become invasive species, which damage the ecosystem

  • dominant species: the most abundant species in an ecosystem, or the one which has the greatest biomass in an ecosystem

    • are likely but not always important to the functions of an ecosystem due to their numbers

  • keystone species: a species that plays a role in an ecosystem that affects many other organisms

    • effects far exceed the species’ abundance in an ecosystem

    • removal of a keystone species changes an ecosystem’s composition

    • term comes from architecture, the keystone which keeps pieces of an arch from falling apart

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