Types of Species Interactions

Species interactions In every ecosystem species interact in a variety of ways. –They can be positive (+), negative (-), or have no effect (0). Each species develops adaptations to deal with these interactions. If a species cannot adjust to it’s community members (two species in the same niche) then it will go locally extinct.

Symbiosis Close interaction between species.Close interaction between species. 5 types of symbiosis5 types of symbiosis –Predation –Parasitism –Competition –Mutualism –Commensalism Think: Which community is most diverse and why.

Predation Predators capture, kill, and consume prey.Predators capture, kill, and consume prey. –Predators are adapted to role. –Prey are adapted to survive predator (+,-)(+,-) Think: Which species determines the number of the other. (or is that a trick question??) What adaptations do each of these organisms have in their role as predator or prey?

Parasitism Parasite is helped.Parasite is helped. Host is harmed.Host is harmed. –Ectoparsites (outside of body, e.g. Tick) –Endoparasites (inside body, e.g. Tape worm) (+,-)(+,-) think: Why does a parasite usually not kill its host? Some caterpillars like this one have growths that look like parasite eggs to discourage a parasitic wasp from laying eggs on them. (I’ve seen them in tropical forests)

Mutualism Both species benefit.Both species benefit. LichensLichens –2 layers of fungi –Algae cells inside. –Algae is kept moist –Fungi get food. (+,+)(+,+) Do you think that mutualism relationships species specific? Why?

Commensalism One species benefits.One species benefits. One species is not effected.One species is not effected. –Lichens growing on a tree limb. –Cattle egrets and live stock. (+,0)(+,0) The whale is not harmed by the barnacles, but the barnacles benefit by getting food & a place to live.

Competition Results from niche overlap.Results from niche overlap. –Competitive exclusion. –When two species directly compete, one will go extinct. Think: What, most likely, is being competed for in this study?

Strategies to avoid Competition –Character displacement –Competitors evolve to different niches. –Resource partitioning. –Each competing species uses a portion of the resource. –Results in less competition between species. Think: How do the Barn Owl and Red Tail Hawk demonstrate character displacement.

Communication: Signals in color MimicryMimicry –Prey evolve defenses through natural selection. –Coloration mimics poisonous organism. –Warning coloration

Plant defenses Plants are defending against herbivory.Plants are defending against herbivory. –Thorns, spines, sticky hairs. –Secondary chemicals NicotineNicotine StrychnineStrychnine DigitalisDigitalis Poison oakPoison oak

Summary Review (paragraph form) 1. Explain symbiosis and give an example of each kind. 2.What is the difference between Ectoparsites and Endoparasites? 3.Name two ways plants defend against herbivory. 4.In what ways to similar species avoid competition?