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Community Ecology IB: 2.1.6, 2.1.7 Ch. 8 Videos – extinction clip on exotics, clip on coral reefs Syllabus Statements • 2.1.6: Define the terms species, population, community, niche and habitat with reference to local examples • 2.1.7: Describe and explain population interactions using examples of named species Vocabulary • • • • • Community Competition Mutualism Niche Parasitism Definitions 1. 2. 3. 4. 5. Population a group of individuals of a certain species in a given area at a given time: blue crabs in the Halifax river Community interacting groups of populations in an area: the scrub community on campus Species a group of individuals who can interbreed to produce fertile, viable offspring: FL panthers Niche The role of an organism in its environment (multidimensional): nocturnal predator of small mammals in the forest Habitat Where an organism typically lives: mangrove swamps Community Structure • Consider the spatial distribution of organisms • Physical appearance: Size, stratification, distribution of populations and species • Species diversity and richness: number of different species • Species abundance: number of individuals of each species • Niche structure: number, uniqueness and interaction of niches available 100 30 20 50 10 ft m Tropical rain forest Coniferous forest Deciduous forest Thorn forest Thorn scrub Tall-grass prairie Short-grass prairie Comparison of types, sizes and stratification of species in different terrestrial communities (complexity) Desert scrub Community Differences • Aquatic systems deep ocean, sandy beach, lakes, rivers, wetlands • Physical structure varies – Most habitats are mosaics, vegetation patches – Sharp edges or broad ecotones (transition zones) – Physical properties differ at edges = edge effect – Forest edge may be sunnier, drier, warmer • different species at the edge • Many wild game species found here • Edges can fragment habitat vulnerability & barriers What is a niche • The organisms role in its environment • How it responds to the distribution of resources • Many dimensions to it – therefore an ndimensional hypervolume • No two species can occupy the same niche for any period of time • If a niche is vacant organisms will quickly adapt to fill it • Fundamental Niche Everything that the organism could possibly do given a competitor free environment • Realized Niche Everything the organism does after competition limits them Biodiverse Communities • • • Top species rich environments are tropical rainforests, coral reefs, deep sea, large tropical lakes Usually high diversity but low abundance Factors for increased diversity 1. Latitude: most diverse near equator 2. Depth: marine communities peak about 2000m 3. Pollution: more pollution less species On land increases in solar radiation, precipitation, seasonal variation, decreased elevation 1,000 Species Diversity Species Diversity 200 100 0 90ºN 100 10 60 30 0 Latitude 30ºS 60 80ºN 60 40 Latitude Effects of Latitude 20 0 © 2004 Brooks/Cole – Thomson Learning 25 25 Species diversity Snails Tube worms 20 20 15 15 10 10 5 5 Coast Deep Sea 0 Coast Deep Sea 0 0 2,000 4,000 6,000 0 2,000 Depth (meters) Effects of Depth 4,000 Depth (meters) 6,000 Number of diatom species Unpolluted stream Polluted stream Number of individuals per diatom species The Island Effect • Isolated ecosystems studied by MacArthur and Wilson in 1960’s • Diversity effected by island size & degree of isolation • Island Biogeography theory: diversity effected by – Rate of species immigration to island – Rate of extinction on island – Equilibrium point = species diversity © 2004 Brooks/Cole – Thomson Learning Rate of immigration or extinction High Low Equilibrium number Number of species on island (a) Immigration and extinction rates Island Biogeography • Immigration and Extinction Effected by 1. Size: – small island has less immigration (small target), – Small island has fewer resources, more extinction 2. Distance from mainland: – Closer to mainland more chance of immigration • Applied in conservation for “habitat islands” like national parks surrounded by development © 2004 Brooks/Cole – Thomson Learning Rate of immigration or extinction High Low Small island Large island Number of species on island (b) Effect of island size Number of species (percentage of sample studied) Island Biogeography Data • South Pacific Islands study looked at bird diversity as distance from New Guinea increased NEW GUINEA 50 25 12.5 Number of amphibian and reptile species 6.25 0 2,000 4,000 6,000 8,000 10,000 Distance from New Guinea (kilometers) SABAMONTSERRAT CUBA Hispaniola Cuba Puerto Rico Jamaica 100 10 Saba Redonda 1 10 Montserrat © 2004 Brooks/Cole – Thomson Learning • Caribbean Island study found bigger islands had more species diversity than smaller islands which were otherwise similar 100 100 1,000 10,000 100,000 Area (square miles) Communities have different “Types” of Species • Native species = species that normally live and thrive in a particular community • Nonnative species = species that are accidentally introduced into an area • Keystone species = species that are more important than their abundance or biomass suggest • Indicator species = species that serve as early warnings of damage in a community Nonnative Species • Also called exotics, aliens, or introduced sp. • FL examples include fire ants, hydrilla, potato vine, peacock bass, … – Occupy niches excluding native organisms – Reproduce rapidly in absence of natural predators – Usually are very adaptable to human disturbed environments Common Florida Exotics Indicator Species • Mostly species that respond quickly to changes in the environment • Birds indicate tropical forest destruction • Trout indicate pollutant presence in water • Amphibians are a classic indicator – Frogs case study p 170 – Frog decline and deformities Keystone Species • Strong interactions with other species affect the health and survival of those species • They process material out of proportion to their numbers • Roles include: pollination, seed dispersion, habitat modification, predation by top carnivores, efficient recycling of animal waste Sea Otters Keystone Species II • Habitat modification – Elephants – knock over trees in savannah to promote grass growth & recycle nutrients – Bats & birds – regenerate deforested areas by depositing plant seeds in their droppings – Beavers – create ponds forming habitats for many pond dwelling species like fish, ducks, & muskrats Keystone Species III • Top predators exert stabilizing effect by feeding on and regulating certain species – Wolves, leopards, lions, gators, sharks, otters • Over 300+ species are found on the wolf kills made in Yellowstone Wolves • http://www.wolfquest.org/index.php Waste removal •Dung beetles – remove bury and recycle animal waste •Establish new plants •Aerate soil •Reduce disease causing microorganis ms Species Interactions • Interactions may be harmful, beneficial, or have no effect at all • Competition: Intraspecific or Interspecific • Predation, Mutualism (Symbiosis), Commensalism, Parasitism Intraspecific Competition • Competition between members of the same species for a common resource • Resource: food, space, mates, etc. • Territoriality – Organisms patrol or mark an area – Defend it against others – Good territories have • Abundant food, good nesting sites, low predator pop. – Disadvantage = Energy, Reduce gene pool Territoriality Examples Interspecific Competition • • • • • 2 or more different species involved Competing for food, space, sunlight, water, space, nesting sites or other limited resource If resources abundant, they can be shared but in nature they are always limited If fundamental niches overlap competition One of the species must… 1. 2. 3. 4. Migrate if possible Shift feeding habits or behavior = Evolve Suffer a sharp population decline Become extinct Connell’s Barnacles Methods of competition 1. Interference • • One species limits access of others to a resource, regardless of its abundance Hummingbird territoriality, Desert plant allelopathy 2. Exploitation • • Species have equal resource access, differ in speed of use Quicker species = more of it & hampers growth, reproduction and survival of other species Allelopathy Competitive Exclusion Principle • One species eliminates another in an area through competition for limited resources – Two Paramecium species – Identical conditions grown apart both do well – Grown together one eliminates the other • The niches of two species cannot overlap significantly for a long period of time High Relative population density Paramecium aurelia Paramecium caudatum Low 0 2 4 6 8 10 12 Days Each species grown alone 14 16 18 High Relative population density Paramecium aurelia Paramecium caudatum Low 0 2 4 6 8 10 12 Days Both species grown together 14 16 18 Avoiding Competition • Resource partitioning = dividing of scarce resources to species at different – Times – Methods of use – Different locations • Species occupy realized niche, a small fraction of their fundamental niches – Lions vs leopards, hawks vs. owls Number of individuals © 2004 Brooks/Cole – Thomson Learning Species 1 Species 2 Region of niche overlap Number of individuals Resource use Species 1 Species 2 Resource use Predation • Members of one species feed directly on all or part of a living organism of a different species • Individuals predator benefits, prey harmed • Population prey benefits: take out the weak, greater resource access, improved gene pool • Predator plays important ecological role Predation Predation strategies 1. Herbivores – sessile prey, no need to hurry 2. Pursuit – speed (cheetah), eyesight (eagles), cooperation (wolves) 3. Ambush – camouflage for hiding (praying mantis), lures (anglerfish) Ambush Predators Prey defenses • Camouflage – change color, blend with environment, • Chemical warfare – produce chemicals which are poisonous, irritating, bad smelling or tasting • Warning coloration – bright colors advertise inedibility (mimics take advantage of this) • Behavioral strategies – Puffing up, mimicking predators, playing dead, schooling Warning coloration Batesian mimicry Mullerian mimicry Span worm Wandering leaf insect Poison dart frog Viceroy butterfly mimics monarch butterfly Bombardier beetle Hind wings of io moth resemble eyes of a much larger animal Foul-tasting monarch butterfly When touched, the snake caterpillar changes shape to look like the head of a snake Parasitism • • • One species feeds on part of another organism (the host) without killing it Specialized form of predation Parasite Characteristics 1. 2. 3. 4. • Usually smaller than the host Closely associated with host Draws nourishment from & slowly weakens host Rarely kills the host Examples = Tapeworms, ticks, fleas, fungi Parasites Malaria According to the World Health Organization there are 300 to 500 million clinical cases of malaria each year resulting in 1.5 to 2.7 million deaths The disease kills more than one million children - 2,800 per day each year in Africa alone. In regions of intense transmission, 40% of toddlers may die of acute malaria. In the early 1960s, only 10% the world's population was at risk of contracting malaria. This rose to 40% as mosquitoes developed resistance to pesticides and malaria parasites developed resistance to treatment drugs. Malaria is now spreading to areas previously free of the disease. Mutualism • Symbiotic relationship where both species benefit • Pollination, Nutrition, Protection are main benefits • Not really cooperation, both benefit by exploiting the other Mutualism II Examples 1. Lichens – fungi & algae living together food for one, structure for the other 2. Plants and Rhizobium bacteria one gets sugars the other gets nitrogen 3. Oxpeckers and Rhinos food for one, less parasites for the other 4. Protists and termites break down wood for one, nutrients for the other Oxpeckers and black rhinoceros Clown fish and sea anemone Human Intestinal Symbionts • One species benefits the other is neither harmed nor helped – Examples 1. Herbs growing in the shade of trees 2. Birds building nests in trees 3. Epiphytes = “Air plants” which attach themselves to the trunk or branches of trees -they have a solid base to grow on and better access to sunlight & rain Commensalism What interaction is this? What interaction is this? What interaction is this?