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

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