LINCOLN v DAYLIGHT CHEMICAL, et al. - 42.1 - - 031111761227.42.1
Chapter 42 Ecosystems (Sections 42.1 - 42.6)
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Transcript of Chapter 42 Ecosystems (Sections 42.1 - 42.6)
Albia Dugger • Miami Dade College
Cecie StarrChristine EversLisa Starr
www.cengage.com/biology/starr
Chapter 42Ecosystems
(Sections 42.1 - 42.6)
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; photosyntheticprotists and bacteria
energy in chemical bonds
light energy
Energy Flows, Nutrients Cycle
Producers plants; photosyntheticprotists 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
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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
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ANIMATION: Food chain
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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. 42.3.1, p. 711
A Food Chain
Fig. 42.3.2, p. 711
A Food Chain
Fig. 42.3.3, p. 711
A Food Chain
Fig. 42.3.4, 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, sedges arctic willow
mosquitoSecond TrophicLevel
Higher Trophic Levels
vole arctic hare
First Trophic Level
Arctic Food Web
Fig. 42.4.1, p. 712
Arctic Food Web
Fig. 42.4.2, p. 712
Arctic Food Web
Fig. 42.4.3, p. 712
Arctic Food Web
Fig. 42.4.4, p. 712
Arctic Food Web
Fig. 42.4.5, p. 712
Arctic Food Web
Fig. 42.4.6, p. 712
Arctic Food Web
Fig. 42.4.7, p. 712
Arctic Food Web
Fig. 42.4.8, p. 712
Arctic Food Web
Fig. 42.4.9, p. 712
Arctic Food Web
Fig. 42.4.10, p. 712
Arctic Food Web
Fig. 42.4.11, p. 712
Arctic Food Web
Fig. 42.4.12, p. 712
Arctic Food Web
Fig. 42.4.13, p. 712
Arctic Food Web
Fig. 42.4.14, p. 712
Arctic Food Web
Fig. 42.4, p. 712
lemming
Major parts of the buffet of primary consumers (herbivores)
Second TrophicLevel
vole arctic 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, sedges arctic 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
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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
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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) 1.5
11
37
5
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)
809producers (algae and aquatic plants)
11carnivores (smaller fishes, invertebrates)
top carnivores (gar and bass) 1.5
37herbivores (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 = 5,06021carnivores
3,368
383
top carnivores
20,810producers
herbivores
B Energy flow pyramid (kilocalories per square meter per year)
Florida Aquatic Ecosystem
Fig. 42.6b, p. 713
detritivores + decomposers = 5,060
20,810producers
B Energy flow pyramid (kilocalories per square meter per year)
21top carnivores
carnivores383
3,368herbivores
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
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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