Transcript Slide 1
COMMUNITIES Key Properties of Communities • Diversity – Species richness: total # of species – Species diversity: high if no one species predominates • Prevalent form of vegetation (terrestrial communities) • Stability-ability to resist change after disturbance • Trophic structure-feeding relationships Helpful? Harmful? Or no effect? COMMUNITY INTERACTIONS Interspecific Interactions in Communities Interspecific interaction #1 Competition Competitive exclusion • When cultured separately, both species go to carrying capacity • When cultured together, COMPETITION! • Slight reproductive advantage leads to elimination of inferior species Restating Competitive Exclusion in Nature • Niche: how a species fits into an ecosystem • Restate competitive exclusion principle: similar species CANNOT coexist if they have the exact same niche Competitive Exclusion Resource Partitioning • Competition between these lizards in Dominican Republic is minimized because lizards’ perches vary Resource Partitioning in Coastal Community Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Brown pelican dives for fish, which it locates from the air Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Herring gull is a tireless scarialavenger Ruddy turnstone searches under shells and pebbles for small invertebrates Knot (a sandpiper) picks up worms and small crustaceans left by receding tide Piping plover feeds on insects and tiny crustaceans on sandy beaches Resource partitioning with warbler species Three-way community interaction • 1) caterpillar injures plant • 2) caterpillar saliva stimulates plant to release a waspattracting vapor • 3) wasp stings caterpillar and then lays eggs in caterpillar Interspecific Interactions in Communities Interspecific interaction #2 Predation Predator-Prey Relations How do plants avoid being eaten by herbivores? Physical Defense: Thorns Chemical Defense: Poison Adaptations Related to Predation • Organisms have evolved certain adaptations – Predator adaptations (claws, poison, jaws…) – Plant defenses (thorns, spines, chemicals…) – Prey defenses (peppered moth) Cryptic Coloration= Camouflage Evolution of camouflage- example (video clip) Bright Coloration-warning symbol Mimicry is another form of coloration defense. Mimicry – a phenomenon in which one species benefits by a superficial resemblance to an unrelated species Deceptive Coloration Two forms of Mimicry: 1) Batesian mimicry – a palatable or harmless species mimics an unpalatable or harmful species. What would be the advantage of this? 2) Müllerian mimicry – two or more unpalatable or brightly colored species resemble each other What would be the advantage of this? Batesian Mimicry Can you tell the difference? Unpalatable Palatable Blue Jay eats Monarch Vomits Monarch Learns to avoid Monarchs! Cuckoo bee Yellow jacket Müllerian mimicry Both have stingers that release toxins What is a KEYSTONE? Keystone Species Keystone Predators Keystone Species http://www.grinningplanet.com/2004/06-22/keystone-speciesarticle.htm Keystone Predators • \ Watch video clips… • Camouflage, Combat, and Sharkboy (plus a good blood review!) • Trials of life Video Interspecific interaction #3: Symbiotic Relationships Symbiotic Relationships • An interspecific interaction in which one species, the symbiont, lives in or on another species, the host Parasitism = (+/-) interactions • A symbiotic relationship in which one organism benefits while the other is harmed • The parasite – Obtains its nutrients by living in or on its host organism Commensalism = (+/0) interactions Symbiotic relationship where one species benefits and the other is not affected positively or negatively Possible examples – 1. Clown fish and anemone 2. Remora (sucker fish) and sharks Mutualism = (+/+) interactions • Interactions where both species benefit Examples: • flowers and pollinators • Protozoa and termites • Nitrogen fixing bacteria in roots of plants Yucca and Yucca Moth Summary Find examples of these from the video Living Together, in the Trials of Life series. Species richness vs. diversity • Community 1 vs. Community 2: how do they compare in richness and how do they compare in diversity Prevalent Vegetation • Looks not only at type of vegetation, but also how arranged….this determines the type of animals that live in a community Community Stability • How does a community respond after a disturbance? • Ex: cedar and hemlock trees withstands lightning fires • Versus Grassland devastated by a fire Trophic Structure