Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 1 Community Biological communities
Document related concepts
Occupancy–abundance relationship wikipedia , lookup
Ecological fitting wikipedia , lookup
Habitat conservation wikipedia , lookup
Island restoration wikipedia , lookup
Overexploitation wikipedia , lookup
Storage effect wikipedia , lookup
Latitudinal gradients in species diversity wikipedia , lookup
Nitrogen cycle wikipedia , lookup
River ecosystem wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Theoretical ecology wikipedia , lookup
Transcript
Community Ecology Biosphere Chapter 54 Population Ecosystem Organism Community 1 Community • 2 Biological communities A biological community refers to all the species that occur together at any particular locality. 3 4 Gleason & Clements Individualistic Holistic Individualistic Holistic 5 6 1 Number of stems per hectare Individual species in a community respond independently to changing environmental conditions. A synchronous change of species in communities exist only when sharp changes of environmental conditions occur. Normal soil 400 Ecotone Serpentine soil Black oak Poison oak Iris Douglas fir Hawkweed California fescue Snakeroot 200 Canyon live oak Collomia Ragwort Yarrow Buck brush 0 Small fescue Fireweed Knotweed Dry Wet Moisture gradient 7 Biodiversity: number & evenness Attributes of ecological communities – – – 8 Biodiversity — The number and evenness of species. kingfisher merganser otter great blue heron dipper garter snake The niche concept— The role of interspecific interactions steelhead roach stickleback water scavenger frog tadpole beetle larva Food web structure — The feeding relationships among species. newt caddis fly larva snail crayfish tuft midge – Succession— The change of communities through time. diatoms 9 Biodiversity measures the number of species and their evenness • blue-green algae green algae 10 Most species in a community are rare Species richness may be equal, but relative abundance may be different. 11 12 2 Exercise: What factors determine the occurrence of a species in a community? Biodiversity: community 1 > 2 kingfisher merganser great blue heron otter dipper garter snake steelhead roach stickleback water scavenger frog tadpole beetle larva snail newt caddis fly larva crayfish tuft midge diatoms 13 First, a species needs to be able to tolerate the local physical-chemical environment. green algae blue-green algae 14 Second, the environment must provide required resources, such as food. + required resources 15 16 A niche ~ the fundamental “niche” + required resources 17 18 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The distribution patterns of Chthamalus & Semibalanus Joseph Grinnell (UC Berkeley) High tide Chthamalus Low tide Semibalanus 19 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Exercise: Is this range the fundamental niche of Chthamalus? How do you know? Joseph H. Connell (UC Santa Barbara) High tide Chthamalus Low tide Semibalanus 21 Results: What does the removal experiment tell you? Let’s do a removal experiment High tide [1] removing Chthamalus … High tide Chthamalus After removing Chthamalus … Chthamalus Low tide Semibalanus 22 Low tide [2] removing Semibalanus … 23 Semibalanus After removing Semibalanus … 24 4 Fundamental vs Realized Niches Realized Niches – High tide Actual niche utilized by an organism is influenced by competition, predation, parasitism, mutualism, etc.. Chthamalus Low tide – Biological interactions change niche space, thus contribute to the structure of a community. Semibalanus Fundamental Realized niches niches 25 Predation often reduces “niche” space ~ the realized “niche” 26 Biotic interactions limiting + required resources 27 28 Exercise: What’d happen if 2 species had overlap niches, e.g. steelhead & roach? Ghost of competition past … Ghost of predation past … The fundamental niche of a species may shift due to consistent biological interactions over evolutionary time scale. Thus, the effects of competition or predation are no longer exist in the present day. kingfisher merganser great blue heron otter dipper garter snake steelhead Species as we see them today are products of biological interactions over evolutionary times. roach water scavenger frog tadpole beetle larva snail newt caddis fly larva crayfish tuft midge diatoms 29 stickleback green algae blue-green algae 30 5 Outcomes of interspecific competition – One species may be driven to extinction (competitive exclusion). When resources are limiting, no two species utilizing the same niche can coexist indefinitely. – one will eventually eliminate the other Or, one or both species has to shift their niches by changing their behavior (resource partitioning). Sometimes, morphology change as well (character displacement) to enhance resource partitioning. 31 32 Competitive Exclusion Among Paramecium Georgyi F. Gause (Moscow Univ.) Alone Population density – • 200 200 150 P. aurelia Together 100 50 50 0 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P. caudatum P. aurelia 150 100 50 0 50 0 4 8 12 Days 16 20 24 34 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 200 150 200 150 100 0 4 8 12 16 20 24 Days Either way, competition reduce population sizes, thus, change relative abundance and community structure. If competitive exclusion did not occur, resource partitioning must exist. Alone P. caudatum 0 0 4 8 12 16 20 24 Days 0 33 150 100 200 Population density – If niche overlap extensively, then, to coexist, the shared resources must not be limiting. Otherwise, ….. P. caudatum 100 P. bursaria 50 0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 Days Days P. caudatum P. bursaria Together Population density – Principle of Competitive Exclusion 75 Eat bacteria 50 Eat yeasts 25 0 0 4 8 12 Days 16 20 35 36 6 Consequences of long-term competition • Resource Partitioning The fundamental niche of a species may shift under long-term interspecific competition through 2 processes: – Resource partitioning – Character displacement • Species living in the same area (sympatric species), over time, evolve behavioral mechanisms that partition available resources to avoid direct competition. 37 38 Resource Partitioning – the sympatric species have subdivided the niche Robert MacArthur (Princeton Univ.) RESOURCE PARTITIONING OF INSECT-EATING WARBLERS Cape May warbler Bay-breasted warbler Myrtle warbler 39 40 Resource partitioning of insect-eating lizards Character displacement • 41 Sympatric species tend to exhibit greater differences in morphology than allopatric species (species that live apart from each other) to avoid direct competition. 42 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Does the diversification of Darwin’s finches involve resource partitioning & character displacement? Individuals in each size class (%) Character Displacement 50 G. fuliginosa Alone Los Hermanos Islets 25 0 50 Daphne Major Island 25 0 50 G. fortis Alone San Cristobal and Floveana Islands 25 0 G. fuliginosa and G. fortis Sympatric 7 9 11 13 15 Finch beak depth (mm) 43 44 Exercise: Use an analogy to describe “niche” to your friend. Mode of interspecific competition • kingfisher merganser otter great blue heron dipper garter snake steelhead roach stickleback water scavenger frog tadpole beetle larva snail newt • caddis fly larva crayfish tuft midge diatoms green algae Exploitative competition – e.g. Paramecium compete for food – the 2 species consume shared resources – The 2 species don’t need to see each other Interference competition – e.g. barnacles compete for space – the 2 species fight over resources (space) – there are face-to-face confrontations blue-green algae 45 Exploitative competition – Hey, don’t drink too fast ! 46 Interference competition – Hey, you pinch my straw ! 47 48 8 Kangaroo rats and other desert rodents Number of other rodents Removal experiments are the strongest tests of the existence of interspecific competition Kangaroo rats removed Kangaroo rats present 15 10 5 0 1988 1989 1990 49 Exercise: So, how does competition affect community structure? Detecting Interspecific Competition • 50 Negative effects of one species on another do not automatically indicate competition. kingfisher – Presence of one species may attract a predator that consumes both, causing one species to have a lower population size than the other. (apparent competition) merganser great blue heron otter dipper garter snake steelhead roach stickleback water scavenger frog tadpole beetle larva newt snail caddis fly larva crayfish tuft midge diatoms 51 Predation also affects community structure. kingfisher merganser green algae blue-green algae 52 Exercise: What’d happen to the community when heron reduce roach? otter great blue heron kingfisher dipper garter snake merganser great blue heron otter dipper garter snake steelhead roach stickleback water scavenger frog tadpole beetle larva newt steelhead caddis fly larva snail roach stickleback water scavenger frog tadpole beetle larva crayfish tuft midge snail newt caddis fly larva crayfish tuft midge diatoms green algae blue-green algae diatoms 53 green algae blue-green algae 54 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Number of individuals Predators reduce the population size of prey, and often induce top-down trophic cascades. Trophic cascades are a key feature in community dynamics. Paramecium 1200 We will talk about it in ecosystem ecology. 800 Didinium 400 0 1 2 3 4 5 6 7 Days 55 Coevolution 56 Plant defenses against herbivores -- Morphological defenses The interdependent evolution of two or more species. Particularly, “arms races” between predators and prey drive evolutionary changes and remarkable adaptations in both predator and prey species, and promote species diversity. 57 Plant defenses against herbivores -- secondary compounds 58 Some herbivores can breakdown secondary compounds Mustard oils – cabbages – cabbage butterfly 59 60 10 Herbivores make use of secondary compounds Herbivores make use of secondary compounds Cardiac glycoside – milkweed – Monarch butterfly 61 Chemical defenses Prey defenses against predators • Chemical defenses • Morphological defenses – Cryptic (camouflage) coloration. – Warning (aposematic) coloration. – Mimicry 62 63 Camouflage! Can you see them? 64 Warning! Dare you eat them! 65 66 11 Batesian mimicry is where a harmless species mimics a harmful one. Danaus plexippus Müllerian mimicry is where two or more unpalatable species resemble each other. Limenitis archippus 67 68 In addition to competition, predation & herbivory, there are other types of species interactions Müllerian mimicry & Batesian mimicry 69 70 Commensalism Cannibalism Epiphytes 71 Barnacles on whales 72 12 Mutualism Parasitism -- ectoparasites 73 Parasitism -- endoparasites 74 Insect Parasitoid 75 Parasites with complex life cycles often manipulate host behavior 76 Mutualism turns parasitism 77 78 13 What’d happen to ants if you removed rodents? Interactions Among Ecological Processes • • Predation may reduce competition Parasitism may alter competition Indirect effects – Presence of one species may affect a second species through interactions with a third species. – Ants Rodents + + – – Large seeds 79 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 60 Small seeds 80 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ComplexArt) indirect interaction Fig. 54.23(TE Fig. 54.22(TE Art) Number of ant colonies • Rodents removed Rodents not removed – Ants 40 Rodents 20 – + + – Oct 74 May 75 Sep 75 May 76 Aug 76 Jul 77 Sampling periods Large seeds Small seeds 81 Keystone species 82 A tidal pool community A species whose absence would bring about a significant change in the community. Top predators in a community are often keystone species (e.g. sea stars affect the diversity of tidal pool communities). 83 84 14 After sea star removal Before After 85 86 Exercise: Who do you think is the keystone species in this community? Sea stars as a keystone species kingfisher merganser great blue heron otter dipper garter snake steelhead roach stickleback water scavenger frog tadpole beetle larva newt snail caddis fly larva crayfish tuft midge diatoms 87 Ecosystem engineering green algae blue-green algae 88 Succession Some keystone species modify their habitats to produce a particularly strong effect on community structure, e.g. beavers. • Biological communities change with time, usually, but not necessarily, from a simple to a more complex structure. – – 89 primary succession secondary succession 90 15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Soil nutrients change as succession progress Primary succession - occurs on bare substrates 300 Year 1 Glacial retreat Nitrogen (g/m2) 250 Year 100 Year 200 c 200 Nitrogen in forest floor 150 100 b 50 a Year 1 Pioneer mosses 91 Nitrogen in mineral soil Year 100 Year 200 Invading Alder Spruce alders thickets forest Secondary succession occurs where an existing community has been cleared, but the soil is left intact. Primary succession - occurs on bare substrates 93 94 Why succession occurs? • • • 92 Why succession occurs? Pioneer species are able to tolerate harsh conditions during early succession. • Seed dispersers also aid the succession process Settled species alter the habitat which facilitate the invasion of subsequent colonizers. The habitat may be further altered that inhibit the growth of original colonizers. 95 96 16 Marine and island communities are subject to disturbance by tropical storms. Most communities are in a state of nonequilibrium owing to frequent disturbances 97 We often think that disturbances have a negative impact on communities, but some communities are maintained by disturbance. 98 Species number Exercise: Do disturbances increase or decrease species diversity in a community? How? ? Disturbance 99 Exercise: What factors influence the biodiversity of this community? Intermediate disturbance theory 100 Communities experiencing moderate levels of disturbance will have greater species richness than communities experiencing either smaller or larger levels of disturbance. simultaneous successional stages dominant competitors kept at bay kingfisher merganser great blue heron dipper garter snake steelhead roach stickleback water scavenger frog tadpole beetle larva snail newt caddis fly larva crayfish tuft midge diatoms 101 otter green algae blue-green algae 102 17 Causes of biodiversity, so far Biosphere Physical-chemical environment Biological interaction Disturbance Others? Population Ecosystem Organism Community 103 104 Dynamics of Ecosystems Ecosystem ecology Chapter 55 • • Chapter 55 An ecosystem includes all the organisms living in a particular place, and the abiotic environment in which they interact. Ecosystem ecology is about … – Biogeochemical cycles of chemical elements through ecosystems. – Energy flows through ecosystems (a one-way process). 105 Eugene Odum (Univ. of Georgia) 106 Biogeochemical Cycles • • • • 107 The water cycle The carbon cycle The nitrogen cycle The phosphorus cycle 108 18 Physical processes move elements around Biological processes move elements around Feeding Photosynthesis Decomposition 109 110 The water cycle Biogeochemical Cycles • • • • The water cycle The carbon cycle The nitrogen cycle The phosphorus cycle Ice Organisms 111 112 Reservoirs of water The Water Cycle • • Atmosphere By area, oceans receive ¾ and lands ¼ of precipitation. Both lands and oceans evaporate much of water back to the atmosphere. Ice On lands, transpiration from plants account for 90% of water back to the atmosphere. Organisms 113 114 19 Water cycling processes Groundwater • Ice • Organisms Groundwater (stored in aquifer) is the largest reservoir of water on lands. It is recharged via percolation of rainfall and water seeps down from lakes and streams through soil, very slowly. The flow is also very slow. 115 116 Mining and pollution of groundwater • • Deforestation breaks the local water cycle • Human mine groundwater, thus many underground aquifers have much higher withdraw rates than recharge rates. Agriculture will be in trouble. Pesticides, herbicides, and fertilizers accumulate in groundwater are virtually impossible to be removed (b/c slow turnover rate). Yet, groundwater supplies about 50% of drinking water (in U.S.). • In forest ecosystems, plants take up much moisture and transpire it back into the atmosphere, forming clouds. When forests are cut down, water drains from the local area instead of forming clouds. The lack of rains further prevents reforestation, and may create semi arid desert (positive feedback). 117 Deforestation also causes erosions 118 Biogeochemical Cycles • • • • 119 The water cycle The carbon cycle The nitrogen cycle The phosphorus cycle 120 20 The carbon cycle Carbon Cycle • • Carbon cycle is based on CO2 which makes up 0.03% of the atmosphere, dissolved in water, and those C locked up in organic compounds (live or dead organisms) and sediment (carbonates). Most organic compounds formed as a result of CO2 fixation (photosynthesis). About 70% of CO2 in the atmosphere is fixed by photosynthesis annually. 121 122 Reservoirs of Carbon Carbon Cycle • • Carbon in the ecosystems cycles through photosynthesis and respiration processes. Most organic compounds are ultimately broken down, and C is released back into the atmosphere. Under natural condition, photosynthesis and respiration are proximately balanced. But we have been tipping the balance. 123 124 Carbon cycling processes Tipping the balance • 125 Increasing fuel consumption, and deforestation by burning are liberating carbon at an increasing rate. 126 21 Green house effects CO2 and global warming 127 128 The nitrogen cycle Biogeochemical Cycles • • • • The water cycle The carbon cycle The nitrogen cycle The phosphorus cycle 129 130 Nitrogen-fixing symbionts The Nitrogen Cycle I • • Only a few kind of prokaryotes can fix atmospheric nitrogen into forms that can be used for biological processes. Only symbiotic bacteria fix enough nitrogen to be of major significance Nitrogen fixation: N2+ 3H2 Æ 2NH3 • • 131 Nitrogen fixation: N2+ 3H2 Æ 2NH3 Nitrogen-fixing bacteria form symbiotic relationship mainly with the roots of legumes (the pea family). 132 22 Reservoirs of nitrogen The Nitrogen Cycle II • After organisms die, nitrogen in organisms become soil nitrates through 2 processes carried out by decomposers. Organisms • • Ammonification – NH4+ (ammonium) are released during the metabolic processes of decomposers. Nitrification -- NH4+ are converted by bacteria into NO2- (nitrite) and NO3- (nitrate) which can be taken up by regular plants. 133 Nitrogen cycling processes The Nitrogen Cycle III • • 134 Nitrogen fixed in soil (NO3- , nitrate) may return to atmosphere through Denitrification, carried out by bacteria under anaerobic condition. Feeding Denitrification: Bacteria get O2 from NO3- and release N2 or N2O back to the atmosphere. 135 Tipping the balance • 136 Eutrophication The use of fertilizers, thus large amount of nitrogen, in agriculture alter the natural cycles of nitrogen. 137 138 23 Phosphorus Cycle Biogeochemical Cycles • • • • The water cycle The carbon cycle The nitrogen cycle The phosphorus cycle 139 The Phosphorus Cycle • • 140 Reservoirs of phosphate Organisms The largest reservoir of phosphates exist in rocks. Phosphates weather from rocks and soils into water. They may enter plants and animals, or are transported to oceans and accumulate in sediments. 141 Sediments & up-welling • 142 Guano deposits The nitrates and phosphates locked up in sediments, particularly those in the deep ocean floor, can be brought back only by up-welling. 143 144 24 Tipping the balance • Eutrophication Three times more phosphates than crops required are added to agricultural lands each year. 145 146 Exercise: What would happen to nutrient cycles after deforestation? When the watershed is intact … The amounts of nutrient inputs from rains and snows are about equal to the amounts that flow out. • When the forest is cut down … • Hubbard Brook Experimental Forest The nutrient inputs from rains drain from the local area. 147 Consequences of deforestation Nutrients cycle, but energy doesn’t 80 Concentration of nitrate (mg/l ) 148 40 4 Deforestation 2 0 1965 1966 1967 1968 149 150 25 Energy flows through ecosystems Different types of producers – – Photo-autotrophs – CO2+ H2O Æ C6H12O6 (Energy provided by solar energy) Chemo-autotrophs– CO2 or CH4 Æ Æ Æ C(H2O)n (Energy provided by H2S+ O2 Æ Energy) 151 Trophic level refers to the feeding level of an organism Different types of consumers – – – 152 Primary consumers – herbivores, grainivores, frugivores, “Higher” consumers – carnivores, insectivores, parasites, Detritivores -- break down dead organic material Scavengers – Vultures and crabs Decomposers – Bacteria and fungi 153 154 Primary Productivity • • Green plants capture about 1% of the solar energy that falls on their leaves. In a given area during a given period of time … – Gross primary productivity (GPP) is the total organic matter produced by producers. – Net primary productivity (NPP) is the amount of organic matter produced that is available to consumers. – Biomass is the total mass of all organisms. Primary productivity of various ecosystems. 155 156 26 Primary productivity of various ecosystems. Low Exercise: Why do they have different NPP ? High 157 158 Primary Productivity We did not talk about the material covered in the following 20 slides. But they will show up in the final examine. • • • The productivity in a given area is ultimately determined by the amount of energy it receives. Thus, NPP often increases as the growing season lengthens. In aquatic ecosystems, light and nutrients limit primary production. In terrestrial ecosystems, temperature, moisture, and nutrients limit primary production. 159 160 On a local scale, nutrients in the soil can play key roles in limiting primary production. Not all NPP is consumed • • • 161 NPP not consumed will eventually become available to decomposers. And, not 100% of the NPP consumed by herbivores is assimilated Herbivores assimilate about 20% of consumed biomass; carnivores 5%. On average, 10% of consumed biomass is assimilate by consumers. 162 27 ~10% assimilation from one level to the next The assimilation by consumers is only ~10% 17% Growth = assimilation 33% Cellular respiration 50% Feces = heat loss 163 Exercise: Why most food chains contain less than 4 trophic levels? Primary producer Primary consumer Secondary consumer 164 Diminishing energy due to heat loss Primary producer Tertiary consumer Primary consumer Secondary consumer Tertiary consumer One-way energy flow 165 166 Energy availability (NPP) affects the length of a food chain. Diminishing energy due to heat loss Fig. 54.1 167 168 28 Ecological Pyramids Exercise: Why are top predators rarer than lower consumers? Moving up a food chain, you generally find fewer individuals, lower total biomass, and lower total energy at each successive trophic level. 169 Pyramid of numbers 1 11 170 Pyramid of biomass Decomposer (5 g/m2) Carnivore Herbivore Second-level carnivore (1.5 g/m2) First-level carnivore (11 g/m2) 4,000,000,000 Herbivore (37 g/m2) Photosynthetic plankton Photosynthetic plankton (807 g/m2) 171 Here is a good reason to be a vegetarian Pyramid of energy Decomposer (3890 kcal/m2/yr) 172 First-level carnivore (48 kcal/m2/yr) Herbivore (596 kcal/m2/yr) Photosynthetic plankton (36,380 kcal/m2/yr) 173 174 29 Trophic cascade Three-level top-down cascade Trout – Invertebrate -- Algae • The effect of one trophic level flows up or down to other levels. Top-down effects – Bottom-up effects – 175 No Trout No Trout 176 Algae-eating insect Algae (g/m2) Algae Exercise: Fish added No fish added In a imaginary state, people love to hunt – deer hunting. They hate the wolves that take “their” deer. Wolves are bad. So they do everything to get rid of wolves. 200 100 0 60 50 40 30 20 10 0 5000 4000 3000 2000 1000 0 What would happen if wolves disappeared? before after fish addition 177 Sand County Almanac 178 Bottom-up effects Three levels By Aldo Leopold I have lived to see state after state extirpate its wolves. I have watched the face of many wolfless mountain, and seen the south-facing slopes wrinkle with a maze of new deer trails. I have seen every desuetude, and then to death. I have seen every edible tree defoliated to the height of a saddle horn. Increase the amount of light, increase predator biomass 179 Predator biomass Damselfly nymph 300 Vegetation biomass Herbivore biomass Predatory fish Chironomids Damselflies (number/g algae) (number/m2) Four-level top-down cascade Amount of light 180 30 Bottom-up effects Four levels Exercise: Why are there portions of the curves where vegetation biomass does not increase as productivity increases? Increase productivity, increase food-chain length Productivity 181 Productivity 182 31
