Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Chapter 37 Communities and Ecosystems Lecture by Brian R. Shmaefsky

Copyright © 2009 Pearson Education, Inc. COMMUNITY STRUCTURE AND DYNAMICS

Copyright © 2009 Pearson Education, Inc 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.  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 37.2 Interspecific interactions are fundamental to community structure

Copyright © 2009 Pearson Education, Inc 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.  Interspecific competition between orange-crowned warbler and Virginia’s warbler 37.3 Competition may occur when …….

Copyright © 2009 Pearson Education, Inc 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 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 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.  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 37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants

Eggs Sugar deposits

Copyright © 2009 Pearson Education, Inc 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.  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 37.7 Parasites and pathogens can affect community composition

Copyright © 2009 Pearson Education, Inc 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.  Producers –Support all other trophic levels –Autotrophs –Photosynthetic producers –Plants on land –Cyanobacteria in water 37.8 Trophic structure is a key factor in community dynamics

Copyright © 2009 Pearson Education, Inc.  Consumers –Heterotrophs –Primary consumers –Secondary consumers –Tertiary consumers –Quaternary consumers  Detritivores and decomposers –Derive energy from dead matter and wastes 37.8 Trophic structure is a key factor in community dynamics Video: Shark Eating a Seal

Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain

Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton

Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton Secondary consumers Mouse Herring

Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton Secondary consumers Mouse Herring Snake Tuna Tertiary consumers

Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton Secondary consumers Mouse Herring Snake Tuna Tertiary consumers Hawk Killer whale Quaternary consumers Trophic level

Copyright © 2009 Pearson Education, Inc Food chains interconnect, forming food webs  Food web –A network of interconnecting food chains

Producers (plants) Primary consumers Secondary and primary consumers Tertiary and secondary consumers Quaternary, tertiary, and secondary consumers

Copyright © 2009 Pearson Education, Inc 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

Keystone absent

Copyright © 2009 Pearson Education, Inc 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.  Communities change drastically following a severe disturbance  Ecological succession –Colonization by a variety of species –A success of change gradually replaces other species Disturbance is a prominent feature of most communities

Copyright © 2009 Pearson Education, Inc.  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 Disturbance is a prominent feature of most communities

Time Shrubs Annual plants Perennial plants and grasses Softwood trees such as pines Hardwood trees

Copyright © 2009 Pearson Education, Inc CONNECTION: Invasive species can devastate communities  Introduction of rabbits in Australia

Key Frontier of rabbit spread Origin: Km Australia

Copyright © 2009 Pearson Education, Inc. ECOSYSTEM STRUCTURE AND DYNAMICS

Copyright © 2009 Pearson Education, Inc 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.  A terrarium has the components of an ecosystem Ecosystem ecology emphasizes energy flow and chemical cycling

Energy flow Light energy Chemical energy Chemical elements Heat energy Bacteria and fungi Chemical cycling

Copyright © 2009 Pearson Education, Inc 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.  Primary production of different ecosystems Primary production sets the energy budget for ecosystems

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 Average net primary productivity (g/m 2 /yr) 1,000 1,500 2,5002,000

Copyright © 2009 Pearson Education, Inc Energy supply limits the length of food chains  A pyramid of production –Illustrates the cumulative loss of energy transfer in a food chain

1,000,000 kcal of sunlight 10 kcal 100 kcal 1,000 kcal 10,000 kcal Producers Primary consumers Secondary consumers Tertiary consumers

Copyright © 2009 Pearson Education, Inc CONNECTION: A production pyramid explains why meat is a luxury for humans  The dynamics of energy flow apply to the human population

Producers Primary consumers Secondary consumers Human meat-eaters Cattle Corn Human vegetarians Trophic level

Copyright © 2009 Pearson Education, Inc 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.  Biogeochemical cycles –Cycle chemicals between organisms and the Earth –Can be local or global  Decomposers play a central role in biogeochemical cycles Chemicals are cycled between organic matter and abiotic reservoirs

Consumers Geologic processes Producers Decomposers Nutrients available to producers Abiotic reservoir

Copyright © 2009 Pearson Education, Inc The carbon cycle depends on photosynthesis and respiration  Carbon is the major ingredient of all organic molecules  The return of CO 2 to the atmosphere by respiration closely balances its removal by photosynthesis  The carbon cycle is affected by burning wood and fossil fuels

Photosynthesis Decomposers (soil microbes) Cellular respiration Detritus Plants, algae, cyanobacteria Primary consumers Higher-level consumers Burning CO 2 in atmosphere Plant litter; death Wastes; death Decomposition Wood and fossil fuels

Copyright © 2009 Pearson Education, Inc 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

Animals 1 Plants Detritus Decomposers in soil Decomposition Phosphates in rock Weathering of rock Runoff Assimilation Phosphates in solution Phosphates in soil (inorganic) Precipitated (solid) phosphates Rock Uplifting of rock

Copyright © 2009 Pearson Education, Inc 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 N 2 to nitrogen used by plants –Carried out by some bacteria and cyanobacteria

Nitrogen (N 2 ) in atmosphere 8 Plant Animal Assimilation by plants Organic compounds Organic compounds Death; wastes Denitrifiers Nitrates in soil (NO 3 – ) Detritus Decomposers Decomposition Nitrifying bacteria Ammonium (NH 4 + ) in soil Nitrogen fixation Nitrogen fixation Nitrogen-fixing bacteria in root nodules Free-living nitrogen-fixing bacteria and cyanobacteria

Copyright © 2009 Pearson Education, Inc 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

Deforested Completion of tree cutting Control Nitrate concentration in runoff (mg/L)

Copyright © 2009 Pearson Education, Inc 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.  The most serious current threats –Acid precipitation –Changes in land use –Climate warming TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems Video: Cyanobacteria (Oscillatoria)

Decomposers Producer Energy flow Chemical cycling Herbivore (primary consumer) Carnivore (secondary consumer)

chemical elements Ecosystems involve the processes of in which makes a from are incorporated by is converted by to chemical energy of into components of detritivores return elements to which pass through one-way trip solar energy to chemical energy to heat organic molecules (a)(b) (c) (d)(e) (f)

Copyright © 2009 Pearson Education, Inc. 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