Albia Dugger Miami Dade College Cecie Starr Christine Evers Lisa Starr Chapter 42 Ecosystems (Sections )

42.1 Too Much of a Good Thing Human activities can disrupt nutrient cycles that have been operating since long before humans existed Phosphorus is often a limiting factor for aquatic producers, and sudden addition of phosphorus (eutrophication) causes algal blooms that cloud water and threaten aquatic species eutrophication Nutrient enrichment of an aquatic ecosystem

Experiment: Phosphorus Enrichment

Fig. 42.1, p. 709 nitrogen, carbon, phosphorus added nitrogen, carbon added Experiment: Phosphorus Enrichment

42.2 The Nature of Ecosystems In ecosystems, organisms and their environment interact through a one-way flow of energy and a cycling of nutrients Ecosytems require ongoing inputs of energy (open systems) Nutrients taken up by producers are returned to the environment by decomposers, then taken up again

Energy Flows, Nutrients Cycle Light energy that enters the system returns to the environment as heat Nutrients are continually recycled

Fig. 42.2, p. 710 heat energy Consumers animals; fungi; heterotrophic protists, bacteria, and archaeans materials cycling Producers plants; photosynthetic protists and bacteria energy in chemical bonds light energy Energy Flows, Nutrients Cycle

Producers plants; photosynthetic protists and bacteria light energy Fig. 42.2, p. 710 heat energy Consumers animals; fungi; heterotrophic protists, bacteria, and archaeans materials cycling energy in chemical bonds Stepped Art Energy Flows, Nutrients Cycle

ANIMATION: One-way energy flow and materials cycling To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

Primary Producers and Production An ecosystem runs on energy captured by primary producers primary producer (autotroph) An organism that obtains energy and nutrients from inorganic sources to build organic compounds primary production Rate at which producers capture and store energy Varies by ecosystem, season, and nutrient availability

The Roles of Consumers Consumers are described by their diets: Herbivores (plants) Carnivores (animal flesh) Parasites (tissues of a living host) Omnivores (plants and animals) Detritivores (detritus) Decomposers (waste and remains)

Key Terms consumer Organism that obtains energy and carbon by feeding on tissues, wastes, or remains of other organisms detritivore Consumer that feed on small bits of organic material decomposer Organism that feeds on biological remains and breaks organic material down into its inorganic subunits

Energy Flow and Nutrient Cycling Heat energy is not recycled: Energy captured by producers is converted to bond energy in organic molecules, and released by metabolic reactions that give off heat Nutrients are recycled: Producers take up inorganic molecules (nutrients) from the environment to form organic molecules Decomposers break down organic molecules and return nutrients to the environment

ANIMATION: The role of organisms in an ecosystem To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

ANIMATION: Food chain To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

42.3 Food Chains Food chains describe how energy and materials are transferred from one organism to another food chain Description of who eats whom in one path of energy in an ecosystem – transfer of energy to higher trophic levels trophic level Position of an organism in a food chain

A Food Chain First trophic level (primary producer): Autotroph (grass) converts light to chemical energy Second trophic level (primary consumer): Grasshopper eats grass Third trophic level (second-level consumer): Bird eats grasshopper Fourth trophic level (third-level consumer): Coyote eats bird

A Food Chain

Fig. 42.3, p. 711 First Trophic Level Primary producer Second Trophic Level Primary consumer Third Trophic Level Second-level consumer Fourth Trophic Level Third-level consumer big bluestem grass grasshopper coyote sparrow A Food Chain

Fig , p. 711 A Food Chain

Fig , p. 711 A Food Chain

Fig , p. 711 A Food Chain

Fig , p. 711 A Food Chain

Food Chain Limits Energy captured by producers usually passes through no more than four or five trophic levels The length of food chains is restricted by the inefficiency of energy transfers Only 5-30% of energy in an organism at one trophic level ends up in tissues of an organism at the next trophic level

42.4 Food Webs Food chains of an ecosystem cross-connect as a food web Food web structure reflects environmental constraints and the inefficiency of energy transfers among trophic levels food web Set of cross-connecting food chains

Types of Food Chains Food webs include two types of interconnecting food chains: grazing food chain Energy transferred from producers to herbivores (grazers) detrital food chain Energy transferred directly from producers to detritivores (worms or insects) Major food chain in land ecosystems

Arctic Food Web

Fig. 42.4, p. 712 Detritivores and decomposers (nematodes, annelids, saprobic insects, protists, fungi, bacteria) purple saxifrage This is just part of the buffet of primary producers. Parasitic consumers feed at more than one trophic level. lemming Major parts of the buffet of primary consumers (herbivores) flea erminesnowy owlgyrfalcon A sampling of carnivores that feed on herbivores and one another arctic foxarctic wolfhuman (Inuk) grasses, sedgesarctic willow mosquito Second Trophic Level Higher Trophic Levels volearctic hare First Trophic Level Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig , p. 712 Arctic Food Web

Fig. 42.4, p. 712 lemming Major parts of the buffet of primary consumers (herbivores) Second Trophic Level volearctic hare Stepped Art erminesnowy owlgyrfalcon A sampling of carnivores that feed on herbivores and one another arctic foxarctic wolfhuman (Inuk) Higher Trophic Levels purple saxifrage This is just part of the buffet of primary producers. grasses, sedgesarctic willow First Trophic Level Detritivores and decomposers (nematodes, annelids, saprobic insects, protists, fungi, bacteria) Parasitic consumers feed at more than one trophic level. fleamosquito Arctic Food Web

ANIMATION: Food webs To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

Trophic Interactions in Ecosystems Understanding links in food webs helps ecologists predict how ecosystems respond to change Computer models show that all species in an ecosystem are closely linked by trophic interaction Even in large communities with many species, 95% of species are within three links of one another

A Land Food Web

ANIMATION: Rainforest food web To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

BBC Video: Seed Banks Helping to Save Our Fragile Ecosystem

BBC Video: The Vanishing Honeybee’s Impact on Our Food Supply

BBC Video: What is the Environmental Cost for Your Food?

42.5 Ecological Pyramids Ecological pyramid diagrams illustrate the inefficiency of transfers between trophic levels A biomass pyramid shows amounts of organic material in bodies of organisms at each trophic level at a specific time An energy pyramid shows energy flow through each trophic level in a given interval

Florida Aquatic Ecosystem

Fig. 42.6, p. 713 Florida Aquatic Ecosystem

Fig. 42.6a, p. 713 A Biomass pyramid (grams per square meter) 809 detritivores (crayfish) and decomposers (bacteria) top carnivores (gar and bass) carnivores (smaller fishes, invertebrates) herbivores (plant-eating fishes, invertebrates, turtles) producers (algae and aquatic plants) Florida Aquatic Ecosystem

Fig. 42.6a, p. 713 detritivores (crayfish) and decomposers (bacteria) 5 A Biomass pyramid (grams per square meter) 809 producers (algae and aquatic plants) 11 carnivores (smaller fishes, invertebrates) top carnivores (gar and bass) herbivores (plant-eating fishes, invertebrates, turtles) Stepped Art Florida Aquatic Ecosystem

Fig. 42.6b, p. 713 Florida Aquatic Ecosystem

Fig. 42.6b, p. 713 detritivores + decomposers = 5, carnivores 3, top carnivores 20,810 producers herbivores B Energy flow pyramid (kilocalories per square meter per year) Florida Aquatic Ecosystem

Fig. 42.6b, p. 713 detritivores + decomposers = 5,060 20,810 producers B Energy flow pyramid (kilocalories per square meter per year) 21 top carnivores carnivores 383 3,368 herbivores Stepped Art Florida Aquatic Ecosystem

Food and Energy Feeding a population of meat-eaters requires far greater crop production than sustaining a population of vegetarians A person who eats a plant food gets most of the calories in that food When plant food is used to grow livestock, only a small percentage of the plant’s calories ends up in meat

Key Concepts Organization of Ecosystems A one-way flow of energy and the cycling of raw materials among species maintain an ecosystem Nutrients and energy are transferred in a stepwise fashion through food chains that interconnect as complex food webs

ANIMATION: Energy flow at Silver Springs To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

42.6 Biogeochemical Cycles Elements essential to life move between a community and its environment in a biogeochemical cycle biogeochemical cycle A nutrient moves between environmental reservoirs and in and out of food webs Chemical and geologic processes move elements to, from, and among environmental reservoirs (rocks, sediments, water, atmosphere)

Biogeochemical Cycles

Fig. 42.7, p. 714 Nonliving environmental reservoirs Seawater and fresh water Atmosphere Rocks and sediments Living organisms Biogeochemical Cycles

Key Concepts Biogeochemical Cycles In a biogeochemical cycle, a nutrient moves relatively slowly among its environmental reservoirs The reservoirs may include air, water, and rocks Nutrients moves more quickly into, through, and out of food webs