Chapter 21 — Community Ecology

Ecological community

is made up of interacting populations of different species

keystone species

a species that plays a fundamental role in supporting an entire community (ex: keystone in an arch → top middle part of an arch that holds/connects everything together; stabilizes the arch’s overall structure)

pollinator

an organism that transfers pollen between plants of the same species, allowing reproduction (bumble bees are the main; others are monarch butterflies, green-eyed hook-tailed dragonfly, hummingbird, long-nosed bat)

food web

the complex set of interconnected feeding relationships in the community

food chain

a linked series of feeding relationships within a food web

trophic level

an organisms position in a food chain/web based on how it obtains food

autotroph

an organism that produces its own food

Ex: plants (photosynthesis), algae, phytoplankton

Heterotrophs

an organism that obtains food by consuming other organisms

• primary consumer: consumer that eats producers

• Secondary consumer: a consumer that eats other consumers

• Top consumer: a consumer at the highest trophic level

Energy flow

Energy in one direction through a food chain from producers to consumers (10% passed to next organism)

energy loss

as energy moves up trophic levels, most of it is lost to the environment (90%)

symbiosis; sym- = together/with and bio- = life → sym + bio =living together

a close relationship between organisms of different species

mutualism

a form of symbiosis in which both species benefit; win-win

Ex: bees and flowers → bees get nectar and pollen or food, flowers benefit from successful reproduction

commensalism

a form of symbiosis in which one species benefits and the other in unaffected

Ex: bees living in hollowed out oak tree → natural bee swarms make safe hives on trees, the tree is not harmed

parasitism

Form of symbiosis in which a parasite benefits while the host is harmed

Ex: varroa mite feeds on bee’s blood, weakens bees’ immune system and spreads viruses

niche

the space, environmental conditions, and resources that a species needs in order to survive and reproduce

competition

occurs when species’ niches overlap and they compete for resources; limits size of competing populations and may even drive one population out

competitive exclusion principle

The concept that when two species compete for resources in an identical niche, one is inevitably eliminated from that niche

generalist niche

honey bees have a broad, ecological niche

invasive species

an introduced species that does harm in a new environment

western honey bee

native (from) to Europe, Middle East, and Africa; not native to the US → introduced species = result of human activity (European settlers); now compete with native bee species

African honey bee

an invasive species that can be aggressive (“killer-bees”), chase away other pollinators for food sources, and swarm/sting animals near its hives

how organisms compete for resources

food partitioning: speculating on a food another species can’t have

Generalist foraging patterns: traveling great distances for a wider variety of foods

Defensive behaviors: chase/harm other species away from available foods

neonicotinoids

causing colony collapse disorder (CCD); highly toxic chemicals that impair bees’ ability to find and return to the hive