8.3 - interactions between living things

succession

the process of gradual change in species compositon in a community over time

→ often occurs due to the natural impacts of species on their environment

primary succession

happens in areas w/o soil or previous life (bare rock, volcanic lava, parking lots)

starts with pioneer species - like mosses and lichens

ex. mount st helens over time

process of succession

lichens/moss break down rock → form soil → plants grown →insects, birds, shrubs, trees arrive → complex forest ecosystem

secondary succession

occurs in areas where a disturbance has removed life, but soil remains (floods, fires, abandoned farmland)

recovery is faster in primary

veg returns → animals return → re establishment of community

climax communities

stable, self-sustaining ecosystem formed at the end succession (Sonoran desert, oak-hickory forests) cha

characteristics of climax communities

high biodiversity, complex food webs, species are replaced by the same kind, maintaining stability

invasive species

non-native species introduced to an ecosystem

spread rapidly - lack natural predators

can disrupt food webs and harm native species

responsible for 40% of endangered species

often introduced by humans

kudzu vine (invasive)

introduced from Asia - 1876

grows up to a ft per day in summer

planted to prevent erosion - now overgrows forest

difficult to remove - drought/frost tolerance

zebra mussels (invasive)

arrived in great lakes from Europe - 1980s

reproduce rapidly

filter plankton → food shortages for fish

algae blooms and damage infrastructure

found in 29+ states

symbiosis

long-term interaction between 2 different organisms

each organism is a symbiont

obligatory (symbiosis)

organisms depend on each other to survive

facultative (symbiosis)

organisms can live independently, but benefit from the relationship

mutualism

both organisms benefit from the relationship

ex. lichen: fungus + algae (obligatory mutualism)

commensalism

one organism benefits, the other is unaffected

ex. barnacles on turtle shells - barnacles transported, turtle unaffected

parasitism

one organism benefits, the other is harmed

ectoparasites (parasitism)

live on surface

ex. mosquitoes and ticks - feed on host’s blood, cause itching or disease

endoparasites (parasitism)

live inside host

ex. plasmodium falciparum - causes malaria, tapeworms and flukes - absorb nutrients