Transcript Slide 1
Chapter 37 Communities and Ecosystems PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Lecture by Brian R. Shmaefsky Copyright © 2009 Pearson Education, Inc. COMMUNITY STRUCTURE AND DYNAMICS Copyright © 2009 Pearson Education, Inc. 37.1 A community includes all the organisms inhabiting a particular area Biological community – An assemblage of populations living close enough together for potential interaction – Described by its species composition Boundaries of the community vary with research questions – Can be a pond – Can be the intestinal microbes of a pond organism Copyright © 2009 Pearson Education, Inc. 37.2 Interspecific interactions are fundamental to community structure Interspecific interactions – Relationships with other species in the community Interspecific competition – Two different species compete for the same limited resource – Squirrels and black bears – Compete for acorns Copyright © 2009 Pearson Education, Inc. 37.3 Competition may occur when a shared resource is limited Ecological niche – Sum of an organism’s use of biotic and abiotic resources – Interspecific competition occurs when the niches of two populations overlap Competition lowers the carrying capacity of competing populations Copyright © 2009 Pearson Education, Inc. 37.3 Competition may occur when ……. Interspecific competition between orange-crowned warbler and Virginia’s warbler Copyright © 2009 Pearson Education, Inc. 37.4 Mutualism benefits both partners Reef-building corals require mutualism – Photosynthetic dinoflagellates – Live in the cells of each coral polyp – Produce sugars used by the polyps – Provide at least half of the energy used by the coral animals Video: Clownfish and Anemone Copyright © 2009 Pearson Education, Inc. 37.5 EVOLUTION CONNECTION: Predation leads to diverse adaptations in prey species Predation benefits the predator but kills the prey Prey adapt using protective strategies – Camouflage – Mechanical defenses – Chemical defenses Video: Seahorse Camouflage Copyright © 2009 Pearson Education, Inc. 37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants Herbivory is not usually fatal – Plants must expend energy to replace the loss Plants have numerous defenses against herbivores – Spines and thorns – Chemical toxins Copyright © 2009 Pearson Education, Inc. 37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants Herbivores and plants undergo coevolution – A change in one species acts as a new selective force on another – Poison-resistant caterpillars seem to be a strong selective force for Passiflora plants Copyright © 2009 Pearson Education, Inc. Eggs Sugar deposits 37.7 Parasites and pathogens can affect community composition A parasite lives on or in a host from which it obtains nourishment – Internal parasites include nematodes and tapeworms – External parasites include mosquitoes and ticks Pathogens are disease-causing parasites – Pathogens can be bacteria, viruses, fungi, or protists Copyright © 2009 Pearson Education, Inc. 37.7 Parasites and pathogens can affect community composition Non-native pathogens can have rapid and dramatic impacts – American chestnut devastated by chestnut blight protist – A fungus-like pathogen currently causing sudden oak death on the West Coast Non-native pathogens can cause a decline of the ecosystem Copyright © 2009 Pearson Education, Inc. 37.8 Trophic structure is a key factor in community dynamics Trophic structure – A pattern of feeding relationships consisting of several different levels Food chain – Sequence of food transfer up the trophic levels Copyright © 2009 Pearson Education, Inc. 37.8 Trophic structure is a key factor in community dynamics Producers – Support all other trophic levels – Autotrophs – Photosynthetic producers – Plants on land – Cyanobacteria in water Copyright © 2009 Pearson Education, Inc. 37.8 Trophic structure is a key factor in community dynamics Consumers – Heterotrophs – Primary consumers – Secondary consumers – Tertiary consumers – Quaternary consumers Detritivores and decomposers – Derive energy from dead matter and wastes Video: Shark Eating a Seal Copyright © 2009 Pearson Education, Inc. Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Grasshopper Plant A terrestrial food chain Primary consumers Zooplankton Producers Phytoplankton An aquatic food chain Mouse Secondary consumers Herring Grasshopper Primary consumers Zooplankton Producers Phytoplankton Plant A terrestrial food chain An aquatic food chain Snake Tertiary consumers Tuna Mouse Secondary consumers Herring Grasshopper Primary consumers Zooplankton Producers Phytoplankton Plant A terrestrial food chain An aquatic food chain Trophic level Hawk Quaternary consumers Killer whale Snake Tertiary consumers Tuna Mouse Secondary consumers Herring Grasshopper Primary consumers Zooplankton Producers Phytoplankton Plant A terrestrial food chain An aquatic food chain 37.9 Food chains interconnect, forming food webs Food web – A network of interconnecting food chains Copyright © 2009 Pearson Education, Inc. Quaternary, tertiary, and secondary consumers Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (plants) 37.11 Keystone species have a disproportionate impact on diversity Keystone species – A species whose impact on its community is larger than its biomass or abundance indicates – Occupies a niche that holds the rest of its community in place Copyright © 2009 Pearson Education, Inc. Keystone Keystone absent 37.12 Disturbance is a prominent feature of most communities Disturbances – Events that damage biological communities – Storms, fire, floods, droughts, overgrazing, or human activity – The types, frequency, and severity of disturbances vary from community to community Copyright © 2009 Pearson Education, Inc. 37.12 Disturbance is a prominent feature of most communities Communities change drastically following a severe disturbance Ecological succession – Colonization by a variety of species – A success of change gradually replaces other species Copyright © 2009 Pearson Education, Inc. 37.12 Disturbance is a prominent feature of most communities Primary succession – Begins in a virtually lifeless area with no soil Secondary succession – When a disturbance destroyed an existing community but left the soil intact Copyright © 2009 Pearson Education, Inc. Annual Perennial plants plants and grasses Shrubs Softwood trees Hardwood such as pines trees Time 37.13 CONNECTION: Invasive species can devastate communities Introduction of rabbits in Australia Copyright © 2009 Pearson Education, Inc. 600 Km Australia Key Frontier of rabbit spread Origin: 1860 ECOSYSTEM STRUCTURE AND DYNAMICS Copyright © 2009 Pearson Education, Inc. 37.14 Ecosystem ecology emphasizes energy flow and chemical cycling Ecosystem – All the organisms in a community as well as the abiotic environment Components of ecosystems – Energy flow – Passage of energy through the ecosystem – Chemical cycling – Transfer of materials within the ecosystem Copyright © 2009 Pearson Education, Inc. 37.14 Ecosystem ecology emphasizes energy flow and chemical cycling A terrarium has the components of an ecosystem Copyright © 2009 Pearson Education, Inc. Chemical cycling Energy flow Chemical energy Light energy Heat energy Chemical elements Bacteria and fungi 37.15 Primary production sets the energy budget for ecosystems Primary production – The amount of solar energy converted to chemical energy – Carried out by producers – Produces biomass – Amount of living organic material in an ecosystem Copyright © 2009 Pearson Education, Inc. 37.15 Primary production sets the energy budget for ecosystems Primary production of different ecosystems Copyright © 2009 Pearson Education, Inc. Open ocean Estuary Algal beds and coral reefs Desert and semidesert scrub Tundra Temperate grassland Cultivated land Boreal forest (taiga) Savanna Temperate deciduous forest Tropical rain forest 0 500 1,000 1,500 2,000 2,500 Average net primary productivity (g/m2/yr) 37.16 Energy supply limits the length of food chains A pyramid of production – Illustrates the cumulative loss of energy transfer in a food chain Copyright © 2009 Pearson Education, Inc. Tertiary consumers 10 kcal Secondary consumers 100 kcal Primary consumers 1,000 kcal Producers 10,000 kcal 1,000,000 kcal of sunlight 37.17 CONNECTION: A production pyramid explains why meat is a luxury for humans The dynamics of energy flow apply to the human population Copyright © 2009 Pearson Education, Inc. Trophic level Secondary consumers Human meat-eaters Human Primary consumers vegetarians Producers Corn Cattle Corn 37.18 Chemicals are cycled between organic matter and abiotic reservoirs Ecosystems are supplied with a continual influx of energy – Sun – Earth’s interior Life also depends on the recycling of chemicals – Organisms acquire chemicals as nutrients and lose chemicals as waste products Copyright © 2009 Pearson Education, Inc. 37.18 Chemicals are cycled between organic matter and abiotic reservoirs Biogeochemical cycles – Cycle chemicals between organisms and the Earth – Can be local or global Decomposers play a central role in biogeochemical cycles Copyright © 2009 Pearson Education, Inc. Consumers 3 2 Producers Decomposers 1 Nutrients available to producers Abiotic reservoir Geologic processes 4 37.19 The carbon cycle depends on photosynthesis and respiration Carbon is the major ingredient of all organic molecules The return of CO2 to the atmosphere by respiration closely balances its removal by photosynthesis The carbon cycle is affected by burning wood and fossil fuels Copyright © 2009 Pearson Education, Inc. CO2 in atmosphere 5 Burning 3 Cellular respiration Photosynthesis 1 Higher-level consumers Wood and fossil fuels Primary consumers Wastes; death Decomposers (soil microbes) Plants, algae, cyanobacteria 4 Detritus 2 Plant litter; death 37.20 The phosphorus cycle depends on the weathering of rock Organisms require phosphorus for nucleic acids, phospholipids, and ATP – Plants absorb phosphate ions in the soil and build them into organic compounds – Phosphates are returned to the soil by decomposers – Phosphate levels in aquatic ecosystems are typically low enough to be a limiting factor Copyright © 2009 Pearson Education, Inc. 6 Uplifting of rock 3 Weathering of rock Runoff Phosphates in rock Animals Plants 1 Assimilation 2 Phosphates in solution Detritus Phosphates in soil (inorganic) 5 Rock Precipitated (solid) phosphates Decomposition Decomposers in soil 4 37.21 The nitrogen cycle depends on bacteria Nitrogen is an essential component of proteins and nucleic acids Nitrogen has two abiotic reservoirs – Air – Soil Nitrogen fixation converts N2 to nitrogen used by plants – Carried out by some bacteria and cyanobacteria Copyright © 2009 Pearson Education, Inc. Nitrogen (N2) in atmosphere 8 Animal Plant 6 Assimilation by plants Organic compounds Nitrogen fixation Death; wastes 5 Denitrifiers Organic compounds 3 Nitrates in soil (NO3–) Nitrogen-fixing bacteria in root nodules Detritus Free-living nitrogen-fixing bacteria and cyanobacteria Decomposers 4 1 Nitrifying bacteria 7 Decomposition Ammonium (NH4+) in soil Nitrogen fixation 2 37.22 CONNECTION: Ecosystem alteration can upset chemical cycling Chemical cycling in an ecosystem depends on – The web of feeding – Relationships between plants, animals, and detritivores – Geologic processes Altering an environment can cause severe losses in chemical cycling – Erosion – Acid rain Copyright © 2009 Pearson Education, Inc. 80.0 60.0 Deforested 40.0 20.0 4.0 3.0 Completion of tree cutting Control 2.0 1.0 0 1965 1966 1967 1968 37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems Major changes in terrestrial ecosystems disrupt chemical cycling These changes can increase nutrients in aquatic ecosystems – Algal and cyanobacteria blooms – Eutrophication Copyright © 2009 Pearson Education, Inc. 37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems The most serious current threats – Acid precipitation – Changes in land use – Climate warming Video: Cyanobacteria (Oscillatoria) Copyright © 2009 Pearson Education, Inc. Producer Herbivore (primary consumer) Energy flow Chemical cycling Decomposers Carnivore (secondary consumer) Ecosystems involve the processes of (a) (b) in which in which makes a chemical elements (c) one-way trip from solar energy to chemical energy to heat is are from converted by incorporated by (d) (e) to chemical into energy of components of organic molecules detritivores return elements to which pass through (f) You should now be able to 1. Describe the characteristics of a community 2. Explain how interspecific interactions affect the dynamics of populations 3. Describe the trophic structure of a community 4. Explain how species diversity is measured 5. Describe the role of environmental disturbance on ecological succession 6. Explain energy and nutrient cycling in ecosystems Copyright © 2009 Pearson Education, Inc.