Community Ecology Feral cat populations can be damaging to ecosystems. Why? Structure of the Community Habitat: particular place an organism lives Ecological Niche: the role it plays in the community (includes food sources, reproduction, placement) Interspecific Competition: competition between different species A. Competitive Exclusion Principle - no two species can occupy the same niche B. Resource Partitioning - species with niche overlap, share/partition resources 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. Saw-tooth pattern Prey Defenses Camouflage (cryptic coloration) - blending in Mimicry - one species resembles another as a defense (milk snake) Other Defenses Herding Behavior (zebra) Startle Behavior (blowfish) Anatomical defense (porcupine) Chemical defense (skunk) Symbiotic Relationships Symbiosis - intimate relationship between two or more species Parasitism - one individual is harmed, the other benefits (ticks & deer) Mutualism - both benefit (ants and aphids) Commensalism - one benefits, other is neither harmed or benefited (barnacles and whales) Community Development Ecological Succession - involves a series of species replacements Secondary Succession - occurs after an area is disturbed (prairie fire) Primary Succession - occurs where there is no life, not even soil formation (volcanic island) Pioneer Species - first species to inhabit an area Climax Community - when the species replacement slows and the ecosystem stabilizes; mature species are present (Goal of ecological succession) Community Biodiversity Intermediate Disturbance Hypothesis - moderate disturbances in an ecosystem are necessary to maintain biodiversity Keystone Species - needed to maintain biodiversity (often top predators) KEYSTONE SPECIES: SEA OTTER Sea otters eat sea urchins Sea urchins eat kelp What happens when you remove the otters? The Essential Otters Invasive and Parasitic Species The interesting cases of: 1. Cowbirds 2. Kudzu 3. Asian Carp 4. Lionfish 5. Zebra mussels *Each of these have a negative impact on the environment. Parasitic Bird? Cowbirds (and cuckoos) lay their eggs in other birds nests. Kudzu Invasive Species (exotics) Asian Carp in the Mississippi (Video) The problem being addressed is that the Asian Carp have started to take over the rivers and subsidiaries of our nations waterways. The Carp are voracious feeders that feed mostly on plankton. The problem with this is that the young offspring of the fish native to the rivers also feed on mostly plankton. If the carp are eating most of the plankton then it leaves very little for the offspring of native fish to feed on and they basically die of starvation. This means the carp are threatening the entire ecosystem of the riverways. Zebra Mussels in the Great Lakes Primary Production: synthesis of organic compounds from carbon dioxide (atmospheric or dissolved) Gross Primary Productivity (GPP): total amount of chemical energy created by producers, per unit of biomass, in a given length of time Net Primary Productivity: Chemical Energy Remaining GPP energy used for cellular respiration/maintenance The following is a food web for a meadow habitat that occupies 25.6 km 2. The primary producers biomass is uniformly distributed throughout the habitat and totals 1,500 kg/km 2. Developers have approved a project that will permanently reduce the primary producers biomass by 50 percent and remove all rabbits and deer. Which of the following is the most likely result at the completion of the project? (A) The biomass of coyotes will be 6 kg, and the biomass of hawks will be 0.5 kg. (B) The biomass of coyotes will be dramatically reduced. (C) The coyotes will switch prey preferences and outcompete the hawks. (D) There will be 50 percent fewer voles and 90 percent fewer hawks. Try these: 1. In a lakeside community, an introduced species hunts by diving for fish, the native duck populations decrease in number. This is due to: a. intraspecific competition b. competitive exclusion c. resource partitioning d. aggressive mimicry 2. Which of the following is not an example of symbiosis? A. ants harvest nectar from flowers b. ticks feed from deer c. clown fish live within sea anemones d. bear eating salmon 3. A squid releases ink to distract predators: a. herd defense b. mimicry c. startle defense d. camouflage 4. The first species to enter a new habitat are: a. pioneer species b. aberrant species c. parasitic species d. climax species 5. A niche is best described as: a. an organism's way of life b. the place an organism lives c. all the interacting parts of an ecosystem d. a biological balance 6. During resource partitioning, two different populations: a. compete until only one survives b. mimic each other c. share resources, but occupy different niches d. consume all the resources in a habitat