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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint® Lecture Slides forEssential Biology, Second Edition & Essential Biology with Physiology
Neil Campbell, Jane Reece, and Eric Simon
Presentation prepared by Chris C. Romero
CHAPTER 19CHAPTER 19
Communities and EcosystemsFigures 19.1 – 19.4
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• Some plants recruit parasitic wasps that lay their eggs in caterpillars that eat the plants
• The oceans cover about 75% of Earth’s surface
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• Only a tiny fraction of the sunlight that shines on Earth is converted to chemical energy
• Sunken ships, army tanks, and subway cars are being used as artificial reefs
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• Coral reefs
BIOLOGY AND SOCIETY:
REEFS, CORAL AND ARTIFICIAL
– Are distinctive and complex ecosystems
– Support a diversity of organisms
Figure 19.1
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• Pollution and development
– Can easily degrade coral reefs
• Artificial reefs
– Are being created by humans to help replace those that have been destroyed
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• A community
KEY PROPERTIES OF COMMUNITIES
– Is an assemblage of species living close enough together for potential interaction
Figure 19.2
3
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• The diversity of a community
Diversity
– Is the variety of different kinds of organisms that make up the community
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• The diversity of a community has two components
– Species richness, the total number of different species in the community
– Relative abundance of the different species
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Figure 19.3
Community 1
Community 2
4
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• The prevalent form of vegetation mainly depends on the terrestrial situation
Prevalent Form of Vegetation
• The types and structural features of plants in a community largely determine the kinds of animals that live in the community
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• Community stability
Stability
– Refers to the community’s ability to resist change and return to its original species combination after being disturbed
– Depends on both the type of community and the nature of disturbances
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• The trophic structure of a community concerns the feeding relationships among the various species making up the community
Trophic Structure
Figure 19.4
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• Interspecific interactions are interactions between species
INTERSPECIFIC INTERACTIONS IN COMMUNITIES
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• Interspecific competition
Competition Between Species
– May occur when two or more species in a community rely on similar limiting resources
– May limit population growth of the competing species
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• Russian ecologist G. F. Gause studied the effects of interspecific competition in two closely related species of protists
Competitive Exclusion Principle
P. aurelia
P. caudatum
Separate cultures
Combined cultures
Figure 19.5
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• From his research, Gause concluded that two species so similar that they compete for the same limiting resources cannot coexist in the same place
• Ecologists called this concept the competitive exclusion principle
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• Testing the competitive exclusion principle
Figure 19.6
Ocean
Hightide
Chthamalus
Balanus
Low tide
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• A species’ ecological niche
The Ecological Niche
– Is the sum total of a species’ use of the biotic and abiotic resources in its environment
– Is the species’ ecological role
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• We can now restate the competitive exclusion principle as follows
– Two species cannot coexist in a community if their niches are identical
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• There are two possible outcomes of competition between species with identical niches
Resource Partitioning
– Extinction of one species
– Evolution of one species to use a different set of resources
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• Resource partitioning
– Is the differentiation of niches that enables similar species to coexist in a community
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Figure 19.7
A. ricordii
A. distichusA. aliniger
A. distichus
A. cybotes
A. ricordii
A. insolitus
A. christophei
A. etheridgei
A. christophei
A. etheridgeiA. cybotes
A. distichus
A. insolitus
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• Predation
Predation
– Is when organisms eat other organisms
– Identifies the predator as the consumer and the food species as the prey
– Includes herbivory, the consumption of plants by animals
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• Most predators have acute senses
Predator Adaptations
• Many predators
– Have adaptations such as claws, teeth, fangs, stingers, or poison to help catch and subdue prey
– Are fast and agile
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• Plants have various types of defenses against herbivores
Plant Defenses Against Herbivores
– Chemical toxins
– Spines and thorns
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• Animals can avoid being eaten
Animal Defenses Against Predators
– By using passive defenses such as hiding
– By using active defenses such as escaping or defending themselves
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• Behavioral defenses include
– Alarm calls
– Mobbing
Figure 19.8
10
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• Distraction displays
– Direct the attention of the predator away from a vulnerable prey to another prey that is more likely to escape
Figure 19.9
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• Camouflage, or cryptic coloration
– Is a passive defense that makes a potential prey difficult to spot against its background
Figure 19.10
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• Some animals
– Have mechanical or chemical defenses against predators
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• Animals with chemical defenses are often brightly colored
– This is a caution to predators called warning coloration
Figure 19.11
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• Mimicry
– Is a “copycat” adaptation in which one species mimics the appearance of another
– Is used by some species to gain protection
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• In Batesian mimicry
– A palatable or harmless species mimics an unpalatable or harmful model
Figure 19.12
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• In Müllerian mimicry
– Two or more unpalatable species resemble each other
Figure 19.13
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• Predator-prey relationships
Predation and Species Diversity in Communities
– Can actually preserve species diversity
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• The experiments of Robert Paine
– Removed a dominant predator from a community
– Provided evidence of the phenomenon of predation
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Figure 19.14
WithoutPisaster
With Pisaster(control)
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• Paine’s experiments and others
– Led to the concept of keystone predators
• Keystone predators
– Help maintain species diversity by preventing competitive exclusion of weaker competitors
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• A symbiotic relationship
Symbiotic Relationships
– Is an interspecific interaction in which one species, the symbiont, lives in or on another species, the host
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• Parasitism
Parasitism
– Is a symbiotic relationship in which one organism benefits while the other is harmed
• The parasite
– Obtains its nutrients by living in or on its host organism
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• Natural selection
– Has refined the relationships between parasites and their hosts
– Can rapidly temper host-parasite relationships
Figure 19.15
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• Mutualism
Mutualism
– Is a symbiosis that benefits both partners
Figure 19.16
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• Many mutualistic relationships have evolved from predator-prey or host-parasite interactions
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• The branching of interactions between species makes communities complex
The Complexity of Community Networks
Figure 19.17
WoundingDetection by plant
Release of volatile attractants
Recruitment
Chemical in saliva
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• Disturbances
DISTURBANCE OF COMMUNITIES
– Are episodes that damage biological communities, at least temporarily
– Destroy organisms and alter the availability of resources
– Affect all communities
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• Ecological succession
Ecological Succession
– Is the process of community change
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• In primary succession
– A community arises in a virtually lifeless area with no soil
Figure 19.18, parts 1–3
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• Primary succession from barren soil to a complex community can take hundreds of years
Figure 19.18, parts 4–6
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• Secondary succession occurs where a disturbance has destroyed an existing community but left the soil intact
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• Small-scale disturbances
A Dynamic View of Community Structure
– Often have positive effects on a community
– May create new habitats
Figure 19.19
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• The intermediate disturbance hypothesis
– States that species diversity may be greatest in an area where disturbance is moderate in both severity and frequency
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• An ecosystem
AN OVERVIEW OF ECOSYSTEM DYNAMICS
– Is a biological community and the abiotic factors with which the community interacts
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• Energy flow
– Is the passage of energy through the components of the ecosystem
• Chemical cycling
– Is the use and reuse of chemical elements within the ecosystem
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• Energy
– Flows through an ecosystem when consumers feed on producers
– Cannot be recycled within an ecosystem, but must flow through continuously
Figure 19.20
Light energy
Chemical cycling (C, N, etc.)
Chemical energy
Heat energy
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• Energy flow and chemical cycling
– Depend on the transfer of substances in the feeding relationships, or trophic structure of an ecosystem
• Trophic levels
– Divide the species of an ecosystem based on their main sources of nutrition
• Trophic relationships
– Determine an ecosystem’s routes of energy flow and chemical cycling
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• A food chain
Trophic Levels and Food Chains
– Is the sequence of food transfer from trophic level to trophic level
– May have many levels
Figure 19.21
Carnivore
Carnivore
Carnivore
Herbivore
Plant
A terrestrial food chain
Quaternary consumers
Tertiary consumers
Secondary consumers
Primary consumers
Producers
Carnivore
Carnivore
Carnivore
Zooplankton
Phytoplankton
A marine food chain
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• Herbivores, which eat plants, algae, or autotrophic bacteria, are the primary consumers of an ecosystem
• Above the primary consumers, the trophic levels are made up of carnivores, which eat the consumers from the levels below
– Secondary consumers include many small mammals, such as rodents, and small fishes that eat zooplankton
– Tertiary consumers, such as snakes, eat mice and other secondary consumers
– Quaternary consumers include hawks and killer whales
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• Detritivores, or decomposers
– Derive their energy from the dead material left by all trophic levels
– Are often left off of most food chain diagrams
Figure 19.22
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• The feeding relationships in an ecosystem
Food Webs
– Are typically not as simple as in an unbranched food chain
– Are usually woven into complex food webs
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Figure 19.23
Quaternary,
tertiary,and secondary consumers
Tertiary and
secondary consumers
Secondary and
primary consumers
Primary consumers
Producers (plants)
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• What limits food chains?
ENERGY FLOW IN ECOSYSTEMS
– How do lessons about energy flow apply to human nutrition?
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• Biomass
Productivity and the Energy Budgets of Ecosystems
– Is the amount of organic material in an ecosystem
• An ecosystem’s primary productivity
– Is the rate at which plants and other producers build biomass
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• Productivity of different ecosystems
Figure 19.24
Open ocean
(a) Percentage of Earth’s surface area
(b) Average net primary productivity (g/m 2/yr)
(c) Percentage of Earth’s net primary productivity
Continental shelfExtreme desert, rock, sand, iceDesert and semidesert scrub
Tropical rain forestSavannaCultivated landBoreal forest (taiga)Temperate grasslandWoodland and shrublandTundraTropical seasonal forestTemperate deciduous forest
Temperate evergreen forestSwamp and marshLake and streamEstuaryAlgal beds and reedsUpwelling zones
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• When energy flows as organic matter through the trophic levels of an ecosystem, much of it is lost at each link in a food chain
Energy Pyramids
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Figure 19.25
Plant material eaten by caterpillar
100 kilocalories (kcal)
50 kcalFeces
15 kcal
Growth
35 kcalCellular respiration
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• An energy pyramid
– Is a diagram that represents the cumulative loss of energy from a food chain
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Figure 19.26
Tertiary consumers
Secondary consumers
Primary consumers
Producers
10 kcal
100 kcal
1,000 kcal
10,000 kcal
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• The dynamics of energy flow apply to the human population
Ecosystem Energetics and Human Nutrition
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• Eating producers instead of consumers requires less photosynthetic productivity and reduces the impact on the environment
Figure 19.27
Secondary consumers
Primary consumers
Producers
Human vegetarians
Corn
(a)
Humanmeat-eaters
Cattle
Corn
(b)
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• Ecosystems
CHEMICAL CYCLING IN ECOSYSTEMS
– Depend on a recycling of chemical elements
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• Biogeochemical cycles
The General Scheme of Chemical Cycling
– Are chemical cycles in an ecosystem that involve both biotic and abiotic components
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• Three key points to biogeochemical cycles
– Each circuit has an abiotic reservoir
– A portion of chemical cycling can rely completely on geological processes
– Some chemicals require processing before they are available as inorganic nutrients
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• Generalized scheme for biogeochemical cycles
Figure 19.28
Consumers
Producers
Detritivores
Nutrients available to producers
Abioticreservoir
Geologic processes
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• A chemical’s specific route through an ecosystem varies with the particular element and the trophicstructure of the ecosystem
Examples of Biogeochemical Cycles
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Figure 19.29a
CO2 in atmosphere
Burning
Wood and fossil fuels
Cellular respiration
Higher-level consumers
Decomposition
Detritivores
Photosynthesis
Producers
Primary consumers
Detritus
(a) The carbon cycle
• The carbon cycle
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Figure 19.29b
Denitrifying bacteria Assimilation
by plants
Nitrogen (N 2) in
atmosphere
Amino acids and proteins in plants and
animals
Detritus
Detritivores
Nitrogen-fixing bacteria
in root nodules of legumesDecomposition
Nitrogen fixation Nitrogen-
fixingbacteriain soil
Ammonium (NH4
+ )Nitrifying bacteria
Nitrates (NO3
– )
• The nitrogen cycle
(b) The nitrogen cycle
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Figure 19.29c
• The phosphorous cycle Uplifting
of rockPhosphates
in rock
Weathering of rock
Phosphatesin organic
compoundsConsumers
Producers
Rock
Precipitated (solid)
phosphatesPhosphates in solution
Phosphatesin soil
(inorganic)
Detritus
Detritivoresin soil
(c) The phosphorus cycle
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• The water cycle
Figure 19.29d
Precipitation over the sea
(283)
Solar heat
Water vapor over the sea
Oceans
Net movement of water vapor by wind (36)
Evaporation from the sea (319)
Evaporation and transpiration (59)
Water vapor over the
land
Precipitation over the land (95)
Surfacewater and
groundwater
Flow of water from land to sea
(36)
(d) The water cycle
27
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• Biomes
BIOMES
– Are the major types of ecosystems that cover large geographic regions of the Earth
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How Climate Affects Biome Distribution
• Because of its curvature, Earth receives an uneven distribution of solar energy
Low angle of incoming sunlight
Sunlight directly overhead
Low angle of incoming sunlight
Atmosphere Figure 19.30
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• Heated by the direct rays of the sun, air at the equator rises, then cools, forms clouds, and drops rain
Cloud formation and rain
Ascending moist air releases moisture
Descending dry air
Descending dry air
TropicsTemperate zone
Temperate zone Figure 19.31
28
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• Proximity to large bodies of water and the presence of landforms such as mountain ranges also affect climate
Wind direction
Pacific Ocean
East
Coast Range
CascadeRange
Figure 19.32
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• The distribution of terrestrial biomes depends largely on climate
Terrestrial Biomes
• If the climate in two geographically separate areas is similar, the same type of biome may occur in them
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• Most biomes
– Are named for major physical or climatic features and for their predominant vegetation
Figure 19.33
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Figure 19.34a
• Tropical forest
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Figure 19.34b
• Savanna
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• Desert
Figure 19.34c
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• Chaparral
Figure 19.34d
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Figure 19.34e
• Temperate grassland
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Figure 19.31f
• Temperate deciduous forest
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Figure 19.34g
• Coniferous forest
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• Tundra
Figure 19.34h
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• Aquatic biomes
Freshwater Biomes
– Occupy the largest part of the biosphere
32
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• Standing bodies of water
Lakes and Ponds
– Range from small ponds to large lakes
Figure 19.35a
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• In lakes and large ponds
– The communities are distributed according to the depth of water and its distance from shore
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• The photic zone
– Includes the shallow water near shore and the upper stratum of water away from shore
– Is named because light is available for photosynthesis
33
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• The aphotic zone
– Is deeper, where light levels are too low to support photosynthesis
• The benthic zone
– Is the bottom of all aquatic biomes
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• Rivers and streams
Rivers and Streams
– Are bodies of water flowing in one direction
– Support quite different communities of organisms than lakes and ponds
Figure 19.35b
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• Marshes, ponds, and other wetlands
– Are common in downstream areas
Figure 19.35c
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• Human activities have affected many streams and rivers
Figure 19.36
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• Oceans
Marine Biomes
– Cover about 75% of the planet’s surface
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• Estuaries
Estuaries
– Are areas where a freshwater stream or river merges with the ocean
– Are one of the most biologically productive environments on Earth
Figure 19.37
35
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• Marine life is distributed according to
Major Oceanic Zones
– Depth of the water
– Degree of light penetration
– Distance from shore
– Open water versus bottom
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• Oceanic zones
Figure 19.38
Intertidal zone
Continental shelf
Benthic zone (seafloor)
Photiczone
Aphoticzone
Pelagic zone
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• The intertidal zone
– Is the area where land meets water
– Includes organisms adapted to attach to rocks or vegetation or to burrow
Figure 19.39
36
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• The pelagic zone
– Is the open ocean
– Contains phytoplankton and zooplankton
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• The benthic zone
– Is the ocean bottom or seafloor
– May include hydrothermal vent communities
Figure 19.40
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• Coevolution
EVOLUTION CONNECTION:
COEVOLUTION IN BIOLOGICAL COMMUNITIES
– Describes adaptations of two species that are closely connected
37
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• Coevolution of a plant and insect
Figure 19.41
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EcosystemLight
Energy flow Producers Consumers Decomposers
Heat
Chemical cycling
(biotic abiotic)
• An Overview of Ecosystem Dynamics
SUMMARY OF KEY CONCEPTS
Visual Summary 19.1
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• Trophic Levels and Food Chains
Visual Summary 19.2
Autotrophs Heterotrophs
Light
Producer
Energy and chemicals
Herbivore (primary
consumer)
Carnivore (secondary consumer)
Detritus
Detritivore(decomposer)
Organic and
inorganic compounds
38
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• Energy Pyramids
Visual Summary 19.3
Approximately 90% loss of energy at each trophic level
Energy