Chapter 53: Community Ecology

1. Community Interactions Dominant/Keystone • Presentation includes: • Overview of Community Ecology • Vocabulary Disturbance Biogeographic factors Chapter 53: Community Ecology By: Becky Marder

2. Community • Community-assembly of populations of various species living close enough for interaction

3. Interactions • Interspecific reactions-key relationships in the life of an organism • +/+ (both benefit, mutualism) • +/- (one benefits at the expense of host, parasitism) • +/0 (one benefits, no expense of host, commencialism)

4. Interactions-Competition • 1. Competition-2+ species compete for a particular resource in short supply • Can lead to local elimination of one species=competitive exclusion principal • (survival of the fittest) • Niche-sum total of a species’ use of the biotic and abiotic resources • Resource partitioning-one species will change set of resources/niche it needs • Character displacement-characteristics to be more divergent in sympatric populations of two species than in allopatric populations

5. Predation • Predation (+/-)- if you don’t know what predation is, why are you even still in biology? • Cryptic coloration-camouflage, makes prey difficult to spot • Aposematic coloration-effective chemical defense often exhibiting bright warning coloration (ie yellow frog) • ***Batesian mimicry-harmless species mimicks harmful specie to appear dangerous • Mullerian mimicry-two dangerous species resemble each other. • Why? They increase their numbers and animals learn not to eat either one faster

6. Herbivory • 2. Herbivory(+/-) herbivore eats parts of a plant. Animal benefits because it gets energy. Plant suffers because IT DIES! • Plant defense-chemical toxins, spines, thorns

7. Parasitism and Disease • 3.Parasitism(+/-) • Parasite derives nutrients from another organism=host • Ectoparasites-parasites that feed on external surface of a host (ie lice) • Endoparasites-live within the body of their host (ie tapeworms) • 4. Disease(+/-) • Pathogens-disease-causing agents • Typically bacteria, viruses or protists. Sometimes fungi and prions

8. Trophic Structure • Trophic Structure-structure and dynamics of community depend to a large extent on the feeding relationships between organisms • Food Webs • Food Chains Food Chain Food Web

9. Dominant Species • Dominant species-species in a community that are the most abundant or that collectively have the highest biomass • Biomass-the total mass of all individuals in a population Invasive species-species generally introduced by humans, that take hold outside their native range (ie those fish…you know what I’m talking about…)

10. Keystone Species • Keystone species-not necessarily abundant in a community, HOWEVER they do exert strong control on community by their ecological roles/niches

11. Bottom Up and Top-Down Controls • Bottom-up Model-lower trophic levels influence higher trophic levels • A=plant, B=Herbivore C=carnivore • ABC, then presence or absence of A will impact B and C. • Top-down Model-predation controls trophic levels. (make sense? Top down…bottom up?) • CBA • Biomanipulation-technique for restoring eutrophic lakes that reduces populations of algae by manipulating the higher-level consumers in the community

12. Disturbiaaaaa bum bum bida • Disturbance-an event (storm, fire, flood, human activity) that changes a community • Ecological Succession-transition in species in a community, after an ecological disturbance • Primary Succession-process begins virtually lifeless, soil not intact (ie new volcanic island) • Secondary succession-existing community cleared by disturbance, soil intact. Often returns to normal state

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