Unit 8: Topic 5, 6, and 7 - Community Ecology, Biodiversity, and Disruptions

community

community

• a group of populations of different species living closely and capable of interacting

habitat

• a place or part of an ecosystem occupied by an organism

ecological niche

• the role and position a species has in its environment

  • fundamental niche: the niche potentially occupied by the species if there were no limiting factors (predators, competitors, etc)

  • realized niched: the portion of the fundamental niche the species actually occupies

interspecific interactions

• interactions of individuals from one species with individuals of another species

  • competition

  • predation

  • herbivory

  • symbiosis (parasitism, mutualism, commensalism)

  • facilitation

competition

• • • / - relationship where individuals of different species compete for limited resources

  • competitive exclusion principle

competitive exclusion principle

• two species competing for the same resource cannot coexist permanently

  • the competitor with even a slightly better advantage will eliminate the inferior competitor

niche partitioning

• natural selection drives competing species into different patterns of resource use, or different niches

predation

• • / - relationship where one species (predator) kills and eats the other species (prey)

  • adaptations of both predators and prey have been refined by natural selection

    • cryptic coloration: camouflage

    • Batesian mimicry: harmless species mimics a harmful one

    • mullein mimicry: two or more bad-tasting species resemble each other

herbivory

• • / - relationship where one organism eats part of a plant or alga

symbiosis

• when 2 or more species live in direct contact with one another

  • parasitism

  • mutualism

  • commensalism

parasitism

• • / -

• when one organism (parasite) derives nourishment from another (host)

mutualism

• • / +

• when both organisms benefit from the relationship

commensalism

• • / 0

• when one organism benefits and the other is neither harmed nor benefitted

facilitation

• • / + OR 0 / +

• when one species has a positive effect on the survival and reproduction of another without intimate association of symbiosis

  • common in plant species (i.e. some plants make soil more hospitable for other plant species)

species diversity

• aka biodiversity

• the variety of different organisms within a community

  • species richness: the number of different species

  • relative abundance: the proportion each species represents of all individuals in the community

NOTE: biodiversity boosts ecosystem productivity; the greater the biodiversity in an ecosystem, the more resilient it is

Simpson’s diversity index

• calculate diversity based on species richness and relative abundance

• high diversity index means high biodiversity

• low diversity index means low biodiversity

invasive species

• organisms that become established outside of their native range/ecosystem, usually by human activity

  • ex: a ship brining produce from another country may have insects in the crates holding the produce

• causes harm to the environment

• grow and reproduce quickly

• the intentional or unintentional introduction of an ________________ can allow the species to exploit a new niche that is free of predators and competitors

keystone species

• not usually abundant, but other species in an ecosystem rely on them because of their important ecological niches

  • ex: coral

    • Coral reefs serve as a _______________ because many other organisms rely upon it as a source of food and protection

  • ex: honey bees

    • bees are a ______________ because they serve as pollinators

• contribute to maintaining the diversity of the ecosystem

  • if ______________ were to be removed from an ecosystem it would have a rippling effect

    • often ecosystems collapse

disturbance

• an event that changes a community by removing organisms from it or altering resource availability

  • fires, droughts, human activities, etc.

ecological succession

• the gradual process by which the species composition of a community changes and develops over time after a disturbance

• primary succession

• secondary succession

primary succession

• a series of changes on an entirely new (previously lifeless) habitat that has not been colonized

  • ex: gradual growth of plants

secondary succession

• a series of changes that clears an existing community, but leaves the soil intact

  • ex: wild fire

human disturbances

• human activity is the strongest disturbance to an ecosystem

  • the main threats to biodiversity are:

    • habitat loss

    • invasive species

    • overharvesting

    • global change

• have lead to a significant increase in the number of endangered species

habitat loss

• single greatest threat to biodiversity

  • agricultural development and urbanization

    • clear cutting, cattle grazing, farmland

overharvesting

• organisms are harvested faster than their population can rebound

  • harvesting of ivory in elephants (now banned)

  • overfishing

global change

• alteration to climate, atmospheric chemistry, and ecological systems that reduce the capacity of Earth to sustain life

  • air/water pollution

    • acid rain

  • CO2 emissions

  • ocean acidification

biogeographical factors

• large scale factors that contribute to a range of diversity observed

  • latitude: species are more diverse in tropics than at the poles due to climate

  • area: larger areas are more diverse because they offer greater diversity of habitats

pathogens

• disease causing organisms and viruses

  • have the most effect on new habitats or ecosystems with less biodiversity