D1.Community - Community Ecology THE REALM OF ECOLOGY...

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Unformatted text preview: Community Ecology THE REALM OF ECOLOGY Biosphere • Biosphere Ecosystems • Ecosystem • Community Ecology: Communities Interactions among members of all of the species in a given habitat. Community Ecology Community Ecology Community: All the populations of organisms living together in a given place Characteristics: • Biodiversity — Populations Organisms Habitats have organisms adapted to living there. – Species richness – Relative abundance • Dominant vegetation • Stability/disturbance Redwood forest community The Niche Concept • A population’s Habitat is the area in which it lives “address” • Niche is a population’s total use of biotic and abiotic resources - “profession” • Multiple species within a community share habitat, but have different niches – The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place Heyer Why do species Y & Z coexist? • Individualistic Hypothesis – Y & Z need similar physical environment • Interactive Hypothesis – Y needs Z 1 Community Ecology Community Ecology Interspecific Interactions Y Z – + + + o – – o + – competition trophic — parasites & predators commensalism mutualism amensalism Interactions among members of all of the species in a given habitat. A. B. C. D. A. Example of Competitive Exclusion Competition • Interspecific Competition = when two species compete for the same limited resource • Competitive Exclusion = the elimination of a population due to competition Species A Species B • Two barnacle populations require the same resource: space • When Balanus is removed Chthamalus spreads lower – Fundemental niche Species A & B Gause’s experiment w/ Paramecium Competition & Resource Partitioning Competition Resource • in Anolis lizards Competitive Interactions Trophic Interactions Symbiotic Interactions Amensal Interactions • When both species compete Balanus displaces Chthamalus Barnacle populations illustrating competitive exclusion – Realized niche Competition & Resource Partitioning Competition Resource A. insolitus usually perches on shady branches. A. ricordii A. ricordii A. insolitus A. alinigar A. distichus A. cybotes A. christophei A. cybotes A. etheridgei A. distichus perches on fence posts and other sunny surfaces. Heyer • in shorebirds A. etheridgei Figure 53.3 2 Community Ecology Competition & Character Displacement Trophic (Feeding) Interactions B. – allopatry – sympatry B. Percentages of individuals in each size class • Geospiza spp. on islands of the Galapagos 60 Los Hermanos 40 G. fuliginosa , allopatric 20 Quaternary consumers Tertiary consumers Secondary consumers Daphne Carnivore 40 G. fortis , allopatric 20 Santa Mar ía, San Crist óbal 40 Sympatric populations 8 10 12 Beak depth (mm) 14 Trophic (Feeding) Interactions (Feeding) Zooplankton Herbivore 20 0 Carnivore Primary consumers 0 60 Carnivore Carnivore 0 60 Carnivore Carnivore Primary producers 16 Plant Figure 54.11 A terrestrial food chain Phytoplankton A marine food chain Primary producers • Autotrophs (“self feeder”) – Photosynthetic plants, protists, bacteria – Chemoautotrophic bacteria • Obtain nutrients from nonliving materials – Inorganic compounds, minerals • A very localized food chain: Tomato plant Æ hornworm caterpillar Æ parasitoid wasp Tomato Consumers • Heterotrophs (“feed on others”) – Herbivores (“plant eater”) • Primary consumers: eat producers – Carnivores (“meat eater”) • Secondary consumers: eat other consumers Heyer – CO2 to make organic backbones –Carbon fixation Decomposition is an important part of an ecosystem • Detritivores (detritus = decaying matter) vAnother level of consumer vRecycle matter back into the abiotic world 3 Community Ecology Biomagnification A food web • Efficiency of transfer creates a food pyramid. • Pyramid effect may result in biomagnification of environmental contaminants. • Trophic patterns are rarely linear • Typically ~10% [5 –20%] efficiency of transfer between levels • I.e., to grow or reproduce, 10x the added energy & mass must be consumed. • Thus there must be a lot of primary production to support long food chains. – Esp ., compounds sequestered in fat or skeleton. + – Consumers: Herbivory, Predation & Partivory Predation Partivory Predation and Adaptations • Mechanisms of defense have evolved in every species (size, flee, hide, venom) • Coevolution = a series of reciprocal adaptations in two species (a type of “arms race”) Coevolution : caterpillar and passionflower vine • Herbivory Consumers – One species (herbivore) eats part of a producer (prey) + – Herbivory Coevolution 1. Plants develop physical and chemical feeding deterrents. 2. Specialized grazers develop mechanisms and strategies to get past the plant defenses. • Now they have that resource to themselves. 3. Back to step 1. Heyer 4 Community Ecology Herbivory • Specialist herbivores acquire resistance to chemical defense of specific prey + • Predation Consumers – One species (predator) kills & consumes another species (prey) – Predation fi Coevolution • Speed fi in both species Speed + – Predation fi Coevolution • Stealth – Ambush instead of chase Cryptic Coloration (Camouflage) Chemical defenses • Chemical warfare – Predator learns to avoid species – Examples • Eucalyptus oil, oleander shrubs, stinkbugs, skunks, cane toads w Works for both predator and prey Heyer Stink beetle 5 Community Ecology + Sometimes defenses don’t work! – Avoiding Predation • Aposematic (Warning)Coloration Aposematic (Warning)Coloration • Grasshopper mouse sticks stinky end into ground to munch head Mimicry • Color and patterns of warning coloration are copied Mimicry • Color and patterns of warning coloration are copied Stingless Wasp Fly Yellow Jacket Beetle (a) Cuckoo bee (b) Yellow jacket Figure 53.8 • In Müllerian mimicry, multiple noxious or unpalatable species resemble each other. Mimicry • Color and patterns of warning coloration are copied • In Batesian mimicry, harmless species mimic dangerous or toxic species. Mimicry • Color and patterns of warning coloration are copied anterior end of a green parrot snake venomous coral snake posterior end of a hawkmoth caterpillar • In Batesian mimicry, harmless species mimic dangerous or toxic species. Heyer non-venomous king snake • In Batesian mimicry, harmless species mimic dangerous or toxic species. 6 Community Ecology Mimicry • In Batesian mimicry, harmless species mimic dangerous or toxic species. • Only works if predators learn to avoid real danger! + – Avoiding Predation • Startle Coloration Figs. 1.25 –1.27 Predation and Diversity • Keystone Predator = a species that reduces the population density of the strongest competitors • Predation can help maintain species diversity • Partivory Pisaster sea star eating a mussel Consumers – One species (partivore) consumes part of another species (host) without killing or consuming all of it Predation and Diversity • Keystone Predator = a species that reduces the population density of the strongest competitors • Predation can help maintain species diversity C. Pisaster sea star eating a mussel Symbiosis • Sym- : “together”; -bios: “living” • One species living in, or on, or in tight association with another species • Symbiont and Host • Three types of symbiosis –Parasitism –Commensalism –Mutualism Aedes aegypti feeding on human Heyer 7 Community Ecology Parasitism Parasitism • Symbiont benefits at the expense of the host • Trophic parasite feeds off tissues of host (partivore) – Ectoparasites & Endoparasites – Not all partivores are parasites (symbionts)! • Symbiont benefits at the expense of the host • Other kinds of parasite cost their host something else • E.g., “brood parasite”: Cuckoo “foster” their young in other species nests tick Parasitoid Commensalism • Parasite or slow predator? – A “good” parasite does not kill its host • Parasitoid wasp stings & paralyzes spider — but does not kill it • Lays eggs inside spider • Wasp larvae hatch & consume living spider • Spider killed when larva metamorphose & emerge Eagles nesting in conifers • Symbiont has no significant effect on host +o Commensalism Mutualism Both symbiont & host benefit from the relationship Acacias & ants • Manta & remoras S. Am. Acacias provide shelter, nectar & antfood to harbor Pseudomyrmex ants Ants defend the acacias from herbivores, pathogenic fungi, & competing vegetation Heyer 8 Community Ecology ++ Mutualism Anthozoans & Zooxanthellae Termites & Trichonympha Amensalism: A species is neither benefited nor harmed by another species, but the activity, metabolism or defenses of the first species inhibits or eliminates the second species Harmful algal blooms (HAB) • Overgrowth of photosynthetic cyanobacteria or protists • Consumption of dO 2, decreased light penetration, and/or production of toxic metabolites impacts other aquatic spp . Amensalism: A species is neither benefited nor harmed by another species, but the activity, metabolism or defenses of the first species inhibits or eliminates the second species Human amensalism • Agricultural & urban development, and waste production • Negatively impact many species Burrowing owls • Inhabit old tunnels of prairie dogs or ground squirrels in dry grasslands • Populations nation-wide threatened by habitat loss • Listed as endangered & CA Species of Special Interest Competition or Amensalism? • If Balanus distribution is the same whether or not Chthalamus is present, should it be called a competitive or amensal interaction? Barnacle populations illustrating competitive exclusion Pathogens • Microorganisms that cause disease • May be trophic or amensal – Sudden Oak Death (SOD) Heyer 9 ...
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This note was uploaded on 09/02/2011 for the course BIOL 6C taught by Professor Sundram during the Spring '09 term at DeAnza College.

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