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2/2/2015 AFTER THIS LECTURE, YOU WILL BE ABLE TO: Compare and contrast the major types of species interactions Characterize feeding relationships and energy flow, using them to construct trophic levels and food webs Distinguish characteristics of a keystone species Characterize succession and notions of community change Perceive and predict the potential impacts of invasive species in communities Explain the goals and methods of restoration ecology Describe the terrestrial biomes of the world Species Interactions and Biomes Chapter 4 CENTRAL CASE STUDY: BLACK AND WHITE AND SPREAD ALL OVER TYPES OF SPECIES INTERACTIONS In 1988, ballast water discharged from a ship accidentally released zebra mussels into Lake St. Clair By 2010, they had spread to 30 states They cause millions of dollars of property damage each year COMPETITION OCCURS WITH LIMITED RESOURCES Competition: multiple organisms seek the same limited resource Food, water, space, shelter, mates, sunlight, etc. Intraspecific competition: between members of the same species High population density: increased competition Interspecific competition: between members of different species Strongly affects community composition Leads to competitive exclusion or species coexistence RESULTS OF INTERSPECIFIC COMPETITION Competition is usually subtle and indirect One species may exclude another from using the resource Zebra mussels displaced native mussels in the Great Lakes Quagga mussels are now displacing zebra mussels Or, competing species may be able to coexist Natural selection favors individuals that use different resources or shared resources in different ways 1 2/2/2015 RESOURCE PARTITIONING Resource partitioning: competing species coexist by specializing By using different resources (small vs. large seeds) Or using shared resources differently (active during day vs. night) AN EXPLOITATIVE INTERACTION: PREDATION • Exploitation: one member benefits while the other is harmed (+/interactions) – Predation, parasitism, herbivory Predation: process by which individuals of one species (predators) capture, kill, and consume individuals of another species (prey) PREDATION CAN DRIVE POPULATION DYNAMICS Interactions between predators and prey structure food webs The number of predators and prey influences community composition Predators can, themselves, become prey PREDATION AFFECTS THE COMMUNITY PREDATION HAS EVOLUTIONARY RAMIFICATIONS Increased prey populations increase food for predators Predators survive and reproduce Increased predator populations decrease prey Predators starve and their populations decrease Decreased predator populations increase prey populations PREY DEVELOP DEFENSES AGAINST BEING EATEN Natural selection leads to evolution of adaptations that make predators better hunters Individuals who are better at catching prey: Live longer, healthier lives Take better care of offspring Prey face strong selection pressures—they are at risk of immediate death Prey develop elaborate defenses against being eaten 2 2/2/2015 AN EXPLOITATIVE INTERACTION: PARASITISM PARASITE – HOST RELATIONSHIPS Parasitoids: insects that parasitize other insects Kill the host Parasitism: a relationship in which one organism (parasite) depends on another (host) For nourishment or some other benefit Coevolution: hosts and parasites become locked in a duel of escalating adaptations Has been called an evolutionary arms race Each evolves new responses to the other It may not be beneficial to the parasite to kill its host The parasite harms, but doesn’t kill, the host AN EXPLOITATIVE INTERACTION: HERBIVORY Herbivory: animals feed on the tissues of plants Widely seen in insects May not kill the plant But affects its growth and reproduction Defenses against herbivory include: Chemicals: toxic or distasteful Thorns, spines, or irritating hairs Herbivores may overcome these defenses Two or more species benefit from their interactions Each partner provides a service the other needs (food, protection, housing, etc.) Symbiosis: a relationship in which the organisms live in close physical contact (mutualism and parasitism) Microbes within digestive tracts Mycorrhizae: plant roots and fungi Coral and algae (zooxanthellae) MUTUALISTS HELP ONE ANOTHER Pollination: bees, bats, birds, and others transfer pollen from one flower to another, fertilizing its eggs POLLINATION 3 2/2/2015 ECOLOGICAL COMMUNITIES Community: an assemblage of populations of organisms living in the same area at the same time Members interact with each other Interactions determine the structure, function, and species composition of the community Community ecologists are interested in how: MYCORRHIZAE Species coexist and interact with one another Communities change, and why these patterns exist ENERGY PASSES AMONG TROPHIC LEVELS One of the most important species interactions Who eats whom? Matter and energy move through the community Trophic levels: rank in the feeding hierarchy PRODUCERS: THE FIRST TROPHIC LEVEL Producers, or autotrophs (“self-feeders”): organisms capture solar energy for photosynthesis to produce sugars Green plants Cyanobacteria Algae They capture solar energy and use photosynthesis to produce sugars Producers (autotrophs) Consumers Detritivores and decomposers CONSUMERS: CONSUME PRODUCERS •Primary consumers: second trophic level Organisms that consume producers Herbivorous grazing animals Deer, grasshoppers Secondary consumers: third trophic level Organisms that prey on primary consumers Wolves, rodents, birds Tertiary consumers: fourth trophic level Predators Hawks, owls DETRITIVORES AND DECOMPOSERS Organisms that consume nonliving organic matter Detritivores: scavenge waste products or dead bodies Millipedes, soil insects Decomposers: break down leaf litter and other nonliving material Fungi, bacteria Enhance topsoil and recycle nutrients 4 2/2/2015 ENERGY, BIOMASS, AND NUMBERS PYRAMIDS OF ENERGY, BIOMASS, AND NUMBERS Most energy that organisms use in cellular respiration is lost as waste heat Less and less energy is available in each successive trophic level Each trophic level contains only 10% of the energy of the trophic level below it There are also far fewer organisms and less biomass (mass of living matter) at the higher trophic levels FOOD WEBS SHOW RELATIONSHIPS & ENERGY FLOW SOME ORGANISMS PLAY BIG ROLES Food chain: a series of feeding relationships Food web: a visual map of feeding relationships and energy flow among organisms Keystone species: has a strong or wide-reaching impact Far out of proportion to its abundance Removing a keystone species has substantial ripple effects Alters the food web Large-bodied secondary or tertiary consumers SPECIES CAN CHANGE COMMUNITIES TROPHIC CASCADE Trophic cascade: predators at high trophic levels indirectly promote populations at low trophic levels By keeping species at intermediate trophic levels in check Extermination of wolves led to increased deer populations … Which overgrazed vegetation … Which changed forest structure Ecosystem engineers: physically modify the environment Beaver dams, prairie dogs, ants 5 2/2/2015 PRIMARY SUCCESSION Communities experience many types of disturbance Removal of keystone species, natural disturbances (fires, floods, etc.) Human impacts cause major community changes Resistance: a community resists change and remains stable despite the disturbance Resilience: a community changes in response to a disturbance, but later returns to its original state Or, a disturbed community may never return to its original state COMMUNITIES RESPOND TO DISTURBANCES Succession: the predictable series of changes in a community After a severe disturbance Primary succession: disturbance removes all vegetation and/or soil life Glaciers, drying lakes, volcanic lava covering the land Pioneer species: the first species to arrive in a primary succession area Lichens: fungi + algae SECONDARY SUCCESSION Secondary succession: a disturbance has removed much, but not all, of the biotic community Fires, hurricanes, logging, farming Aquatic systems can also undergo succession Ponds eventually fill in to become terrestrial systems Climax community: remains in place with few changes Until another disturbance restarts succession COMMUNITIES MAY UNDERGO SHIFTS Community changes are more variable and less predictable than early models of succession suggested Conditions at one stage may promote another stage Competition may inhibit progression to another stage Chance factors also affect changes Phase (regime) shift: the overall character of the community fundamentally changes Some crucial threshold is passed, a keystone species is lost, or an exotic species invades Example: overfishing and depletion of fish and turtles has allowed algae to dominate coral reef communities INVASIVE SPECIES THREATEN STABILITY Alien (exotic) species: non-native species from somewhere else enters a new community Invasive species: non-native species that spreads widely and become dominant in a community Introduced deliberately or accidentally Growth-limiting factors (predators, disease, competitors, etc.) are absent Major ecological effects Pigs, goats, and rats have destroyed island species But some invasive species (e.g., honeybees) help people 6 2/2/2015 INVASIVE MUSSELS MODIFY COMMUNITIES CONTROLLING INVASIVE SPECIES Techniques to control invasive species include: Removing them manually Applying toxic chemicals Drying them out, depriving them of oxygen Introducing predators or diseases Stressing them with heat, sound, electricity, carbon dioxide, or ultraviolet light Control and eradication are hard and expensive Prevention, rather than control, is the best policy ALTERED COMMUNITIES CAN BE RESTORED Humans have dramatically changed ecological systems Severely degraded systems cease to function Restoration ecology: the science of restoring an area to an earlier (pre-settlement) condition Tries to restore the system’s functionality (e.g., filtering of water by a wetland) Ecological restoration: actual efforts to restore an area Difficult, time-consuming, and expensive WIDELY SEPARATED REGIONS SHARE SIMILARITIES Biome: major regional complex of similar communities recognized by: Plant type Vegetation structure EXAMPLES OF RESTORATION EFFORTS Prairie restoration: replanting native species, controlling invasive species, controlled fire to mimic natural fires The world’s largest project: Florida Everglades Flood control and irrigation removed its water Populations of wading birds dropped 90–95% It will take 30 years and billions of dollars to restore natural water flow ABIOTIC FACTORS INFLUENCE BIOME LOCATIONS The type of biome depends on temperature, precipitation Also air and ocean circulation, soil type Climatographs: a climate diagram showing an area’s mean monthly temperature and precipitation 7 2/2/2015 AQUATIC SYSTEMS HAVE BIOME-LIKE PATTERNS Various aquatic systems comprise distinct communities Coastlines, continental shelves, open ocean, deep sea Coral reefs, kelp forests Some coastal systems (estuaries, marshes, etc.) have both aquatic and terrestrial components Aquatic systems are shaped by Water temperature, salinity, dissolved nutrients Wave action, currents, depth, light levels Substrate type Animals, not plants, delineate marine communities TEMPERATE DECIDUOUS FOREST Deciduous trees lose their broad leaves each fall They remain dormant during winter Mid-latitude forests in Europe, east China, eastern North America Even, year-round precipitation Fertile soils Forests: oak, beech, maple 8 2/2/2015 TEMPERATE GRASSLANDS More temperature difference Between winter and summer Less precipitation supports grasses, not trees Also called steppe or prairie Once widespread, but has been converted to agriculture Bison, prairie dogs, groundnesting birds, pronghorn TEMPERATE RAINFOREST U.S. coastal Pacific Northwest Heavy rainfall Coniferous trees: cedar, spruce, hemlock, fir Moisture-loving animals Banana slug Erosion and landslides affect the fertile soil Most old-growth is gone as a result of logging TEMPERATE RAIN FOREST TROPICAL RAINFOREST Southeast Asia, west Africa Central and South America Year-round rain and warm temperatures Dark and damp Lush vegetation Diverse species But in low densities Very poor, acidic soils Nutrients are in the plants 9 2/2/2015 TROPICAL DRY FOREST Also called tropical deciduous forest Plants drop leaves during the dry season India, Africa, South America, north Australia Wet and dry seasons Warm, but less rainfall Converted to agriculture Severe soil erosion SAVANNA Tropical grassland interspersed with trees Africa, South America, Australia, India Precipitation occurs only during the rainy season Animals gather near water holes Zebras, gazelles, giraffes, lions, hyenas 10 2/2/2015 DESERT Minimal precipitation Sahara: bare, with sand dunes Sonoran: heavily vegetated Temperatures vary widely Day vs. night, seasonally Soils (lithosols): high mineral content, low organic matter Animals: nocturnal, nomadic Plants: thick skins, spines TUNDRA Russia, Canada, Scandinavia Minimal rain, very cold winters Permafrost: permanently frozen soil Residents: polar bears, musk oxen Migratory birds, caribou Lichens, low vegetation, no trees Alpine tundra: on mountaintops 11 2/2/2015 BOREAL FOREST (TAIGA) Canada, Alaska, Russia, Scandinavia A few evergreen tree species Cool and dry climate Long, cold winters Short, cool summers Nutrient poor, acidic soil Moose, wolves, bears, lynx, migratory birds CHAPARRAL Occurs in small patches around the globe Mediterranean Sea, Chile, California, south Australia Densely thicketed, evergreen shrubs Highly seasonal biome Mild, wet winters Warm, dry summers Fire-resistant plants 12 2/2/2015 COMPETITION IS A FORM OF SPECIES INTERACTION WHERE: 20% 20% 20% 20% 20% 20% 1. 2. 3. 4. 5. Both species are harmed One species benefits, but the other is harmed Both species benefit One species invites another to enter a particular area Neither species is particularly affected 1. 2. 3. 20% 20% 20% 20% 4. WHICH STATEMENT IS FALSE ABOUT TROPHIC LEVELS? 5. 1 20% 1. 2. 3. 4. 5. Autotrophs (plants) occupy the first trophic level Detritivores consume waste products or dead bodies Biomass and energy increase going up the food chain There are fewer predator species than prey species in an area Food webs leave out many species interactions 2 3 20% 20% 4 20% 1. 2. 3. WHICH OF THE FOLLOWING IS NOT AN EXPLOITATIVE INTERACTION? 2 3 4 2 3 4 5 20% Predation Herbivory Parasitism Competition All of these are exploitative interactions 1 1 5 One species preys on mice during the day, another species preys on mice during the night One species is chased out of an area by another species A prey species becomes more vulnerable to a predator A pine tree evolves thicker pinecones to reduce consumption by squirrels A host becomes resistant to a parasite 20% 20% 20% WHICH OF THE FOLLOWING IS AN 4. EXAMPLE OF RESOURCE PARTITIONING? 5. 1 2 3 20% 4 20% 5 5 13 2/2/2015 20% 1. 20% 1. 2. 3. 4. The slopes of a newly formed volcanic island Wetlands in Texas, following Hurricane Rita A receding glacier Vegetation growing in a newly exposed lake bed Secondary succession would not occur in any of these areas 20% 20% 20% 20% 2. 3. SECONDARY SUCCESSION WOULD TAKE PLACE5. ON WHICH OF THE FOLLOWING? 1 2 3 4 20% 2. 3. 4. 5. 20% 20% 5. 5 20% 20% Remove exotic species from an area Introduce native species to a newly reforested area Plant trees in a logged forest Replace topsoil and plant grasses on an old coal mining site A restoration ecologist would do all of these 1 20% 3 4 2 2. 3. 4. 5. 3 4 4 5 20% b) c) 20% 20% d) e) WOULD YOU BE WILLING TO DECREASE THE AMOUNT OF MEAT YOU CONSUME (I.E., EAT LOWER ON THE FOOD CHAIN) TO SAVE ENERGY AND DECREASE YOUR ECOLOGICAL FOOTPRINT? 1. 2 3 20% 20% Tropical rainforest Temperate grasslands Temperate rainforest Taiga Tundra 1 20% 5 WHICH BIOME IS FOUND IN THE COASTAL PACIFIC NW OF THE U.S., HAS HEAVY RAINFALL; CEDAR, SPRUCE, AND HEMLOCK 20% 20% 20% 20% 20% TREES; AND MOISTURE-LOVING ANIMALS? 1. 2. 3. 4. 5. 20% Tropical rainforest Temperate grassland Chaparral Taiga Tundra a) 2 20% WHICH BIOME DOES NOT HAVE ENOUGH PRECIPITATION TO SUPPORT TREES, IS ALSO CALLED STEPPE OR PRAIRIE, AND HAS BEEN CONVERTED TO AGRICULTURE? a) b) c) d) e) 1 20% WHAT4. IS THE BEST DEFINITION OF INVASIVE SPECIES? WHICH OF THE FOLLOWING ACTIVITIES WOULD A RESTORATION ECOLOGIST DO? 1. Any species that occurs naturally in an area Any species that arrives in an area from somewhere else An exotic species that spreads widely and changes a community A native species that spreads widely and changes a community A species that is not alien or exotic to an area 5 Yes, if the extra food were sent to countries with starving people Yes, because it would help protect the environment I don’t eat meat now No, I don’t see the need to eat lower on the food chain No, I won’t get enough protein if I don’t eat meat 1 20% 20% 2 3 20% 4 20% 5 14 2/2/2015 ALTHOUGH MUSTANGS ARE NOT NATIVE TO THE UNITED STATES, THEY EXIST IN SEVERAL WESTERN STATES ON FEDERALLY 1. AsLAND. an exotic species, they should OWNED AS AN INTRODUCED immediately be removed and adopted SPECIES,orWHAT SHOULD BE DONE WITH killed 2. Although they are an exotic species, THEM? they are part of our heritage and 20% should be allowed to stay They have been here so long that we should just leave them alone Many countries eat horseflesh, so we should round them up and export them to horse-eating countries It doesn’t matter; it’s not that important 3. 4. 5. 1 20% 2 20% 3 20% WHAT DOES THIS FIGURE ILLUSTRATE? 20% 4 1. A predator–prey cycle 2. Competitive exclusion 3. Resource partitioning 4. Succession 5. Mutualism 20% 20% 20% 20% 20% 5 1 2 3 4 5 In this climatograph for Odessa, Ukraine, in the grassland biome, certain months are depicted in yellow. These show: 1. 2. 3. 4. 5. 20% 1 Cold winters Hot winters Dry seasons Wet seasons Cool summers 20% 2 20% 3 20% 4 20% 5 15