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 BiologyPopulation Biology

Competition Resource Partitioning - species with niche overlap, share/partition resources (see balanus)

Realized vs Fundamental Niche What happened When Balanus was removed? Figure 41.3 Ocean Chthamalus Low tide Experiment Low tide High tide Ocean Balanus realized niche Chthamalus realized niche Chthamalus fundamental niche Results

Competition can lead to character displacement Figure 41.4 Beak depth (mm) Beak depth G. fuliginosa G. fuliginosa, allopatric G. fortis, allopatric G. fortis Los Hermanos Daphne Santa María, San Cristóbal Sympatric populations Percentages of individuals in each size class

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

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 (c) Batesian mimicry: A harmless species mimics a harmful one. (d) Müllerian mimicry: Two unpalatable species mimic each other. Poison dart frog Nonvenomous hawkmoth larva 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

Pack Behavior Herding Behavior (zebra) Schooling fish Swarming insects Can your friends help?

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 themShow 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

Community Biodiversity Keystone Species - needed to maintain biodiversity (often top predators) Figure Experiment Results Year Number of species present ’64 Without Pisaster (experimental) With Pisaster (control) 5 ’66’65’67’69’68’70’72’71’73 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.

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 Sea Urchin Population = _____________ Sea Weed Population = ______________ Fish Population = _________________ Seal Population = _________________ Orca Population = _________________ Increases Decreases

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) Lichen Ants & Acacia tree Figure 41.7 (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

Worksheet: SuccessionSuccession Why are moderate disturbances in an ecosystem necessary to maintain biodiversity? Ex. Forest fires