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CO 47 Communities Concept of the Community Community = assemblage of populations interacting with one another Example: squirrel, moose, bear, fox, wolf, pine tree, termites, bacteria....etc Cobra vs Mongoose interspecific interactions With a partner, think of an example of each and label +’s & -’s Examples: • Competition • Predation • Herbivory • Symbiosis: • parasitism • mutualism • Commensalism • effects can be summarized as positive (), negative (−), or no effect (0) Structure of the Community Habitat = particular place an organism lives Ecological Niche: the role it plays in the community or the specific set of biotic and abiotic resources used by an organism Fundamental Niche - niche potentially occupied by that species Realized niche - niche actually occupied by that species due to competition Niche – each member of this community gathers food in a unique way Interspecific Competition: competition between different species (-,-) Competitive Exclusion Principle - no two species can occupy the same niche Graph illustrates what happens when you grow two different species of protists separately and in the same container (where competition can occur). Summarize the results. Virtual LabPopulation Biology Competition Resource Partitioning - species with niche overlap, share/partition resources (see balanus) Realized vs Fundamental Niche Figure 41.3 Experiment Chthamalus Balanus What happened When Balanus was removed? High tide Chthamalus realized niche Balanus realized niche Ocean Low tide Results High tide Chthamalus fundamental niche Ocean Low tide Figure 41.4 G. fortis Beak depth Percentages of individuals in each size class Competition can lead to character displacement G. fuliginosa 60 Los Hermanos 40 20 0 60 Daphne 40 20 0 G. fuliginosa, allopatric G. fortis, allopatric Sympatric 60 Santa María, San Cristóbal populations 40 20 0 16 8 10 12 14 Beak depth (mm) Predation (/− interaction) one species, the predator, kills and eats the other, the prey Predator Adaptations: Teeth Claws Vision Speed Strength Camouflage Working together ( Sea Lion vs Whale Chimps http://www.youtube.com/watch?v=A1WBs74W4ik Prey Defenses hiding, fleeing, forming herds or schools, active self-defense, Camouflage (cryptic coloration) - blending in Figure 41.5 (a) Cryptic coloration Canyon tree frog (b) Aposematic coloration Poison dart frog (c) Batesian mimicry: A harmless species mimics a harmful one. Nonvenomous (d) Müllerian mimicry: Two unpalatable hawkmoth larva species mimic each other. Venomous green parrot snake Cuckoo bee Yellow jacket Individual Defenses Startle Behavior (blowfish) Anatomical defense (porcupine) Chemical defense (skunk) Predator Prey Interactions communities follow this pattern. Prey species increase in number, followed by predator species. Then Prey species decline, followed by predator species decline. The cycle repeats. a the Lynx and the Hare Can your friends help? Pack Behavior Herding Behavior (zebra) Schooling fish Swarming insects Herbivory (/− interaction) an herbivore eats parts of a plant or alga Herbivores have specialized teeth or digestive systems Plant defenses include chemical toxins and protective structures Symbiotic Relationships Symbiosis - intimate relationship between two or more species Parasitism - one individual is harmed, the other benefits (ticks & deer) Mutualism - both benefit (flowers & honeybees) Commensalism - one benefits, other is neither harmed or benefited (clown fish & sea anemone) Parasitism • one individual is harmed, the other benefits • Does the parasite kill the host? Ex: Show them! Ecto- versus endo-, what’s the deal? Parsitoidism! Example: Whale and Barnacle Barnacles attach themselves to whales and filter feed as whales swim through the water. This is an example of: commensalism. Bison and … As bison walk through the grass, insects jump out of the way. The cowbird follows the bison and eats the insects. This is an example of: commensalism. Cowbird Figure 41.15 if Pisaster was removed from the community, the populations of mussels grew unchecked. Without a predator to control their numbers, the mussels soon took over the community and crowded out other species, greatly reduced the community's diversity. Number of species present Community Biodiversity Keystone Species needed to maintain biodiversity (often Results 20 top predators) 15 Experiment With Pisaster (control) 10 Without Pisaster (experimental) 5 0 1963’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73 Year http://www.nature.com/scitable/knowledge/library/keystone-species-15786127 Over fishing and Over Hunting Key Stone Species: An organism that is necessary for keeping an ecosystem in balance. Example: Sea Otter Sea Otter’s Niche: Eats sea urchins. Uses rocks and shells to break opened sea urchins Predators: Sharks and Humans Uses seaweed to anchor themselves while they eat and sleep. How sea otters keep their ecosystem in balance: Otters keep the sea urchin population down. Sea urchins eat away at the base of sea weed. Fish and other sea life rely on the sea weed forests for food and shelter. Over Hunting Key Stone Species How do you think the decreasing otter population effects the kelp forest ecosystem? Otter Population is Down Increases Sea Urchin Population = _____________ Decreases Sea Weed Population = ______________ Decreases Fish Population = _________________ Decreases Seal Population = _________________ Decreases Orca Population = _________________ Over Hunting Key Stone Species Result: Urchin Barrens KEYSTONE SPECIES: SEA OTTER Sea otters eat sea urchins Sea urchins eat kelp What happens when you remove the otters? Case Studies in Keystone Species Mutualism both benefit (flowers & honeybees) Figure 41.7 Lichen Ants & Acacia tree (a) Ants (genus Pseudomyrmex) in acacia tree (b) Area cleared by ants around an acacia tree Community Disturbance… Ecological Succession Ecological Succession - involves a series of species replacements Primary Succession - occurs where there is no soil formation (volcanic island) Secondary Succession - occurs after an area is disturbed (prairie fire) Pioneer Species - first species to inhabit an area Climax Community - when the species replacement slows and the ecosystem stabilizes Figure 47.18cde Why are moderate disturbances in an ecosystem necessary to maintain biodiversity? Ex. Forest fires Worksheet: Succession