Community Interactions

Community: Many different species interacting in the same environment. Three types of interactions: – Competition – Predation – Symbiosis

Competition Defined: Competing for resources – Water, nutrients, light, food, space – Occurs due to a limited number of resources Intraspecific competition: When organisms of the same species compete for resources. Interspecific competition: When organisms of differing species compete for resources. Competitive exclusion principle: No two species can occupy the same niche in the same habitat at the same time. –E–Example: What happens to the neighborhood coffee shop when a Starbucks is built next to it?

Predation Defined: when an organism captures and feeds on another organism. Predator = hunter Prey = hunted

Symbiosis Defined: a relationship between two or more species that live in direct contact with one another. Three types – Mutualism – Commensalism – Parasitism

Mutualism Defined: both species benefit from a relationship. Ex: Lichens (fungus and Algae) Ex: Clown fish and anemones Ex: Cleaner birds and crocodiles Fungus obtains nutrients from the algae Algae lives amongst the fungal cells Fish receives protection and a home Anemone feeds on undigested food from the fish Bird receives food Crocodile has parasites removed

Commensalism Defined: One member of a symbiotic relationship benefits and the other is neither helped nor harmed Ex: Cattle and Birds – Birds eat insects stirred up by the cattle Ex: Barnacles and whales – Barnacles grow on whale

Human Our eyelashes are home to tiny mites that feast on oil secretions and dead skin. Without harming us, up to 20 mites may be living in one eyelash follicle. Demodicids Eyelash mites find all they need to survive in the tiny follicles of eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope. + Organism benefits + Ø Ø Organism is not affected Commensalism

Parasitism Defined: One creature benefits and one creature (the host) is harmed Endoparasitism: A parasite that inhabits the inside of an organism. – Ex: Tapeworm feeds within a human’s intestines absorbing his/her nutrients Ectoparasitism: A parasite that inhabits the outside of an organism. – Ex: A leech feeds on the blood of an organism from a host’s skin.

Identify these relationships

Review 1)What is a community? 2)Name the 3 types if community interactions. 3)When do organisms usually compete? 4)How do predators and prey interact? 5)Name the 3 types of symbiosis. 6)What is the competitive exclusion principle? 7)How does mutualism, commensalism, and parasitism differ? 8)How is predation and parasitism differ?